Anatomy and Physiology Mind Map

Connection:

The calcium ions need to be actively pumped across the membranes against the concentration gradient and obtain the differences in calcium in the sacroplasmic reticulum.

Interstitial fluid

Interstitial fluid is a thin layer of fluid which surrounds the body’s cells. It plays an important role in our body and makes almost 40% of the water in our body, accounting for about a sixth of our body weight. Interstitial fluid acts as a kind of fuelling station in terms of nutrients for our cells. Interstitial fluid contains glucose, salt, fatty acids and minerals such as calcium, magnesium and potassium.

The nutrients in interstitial fluid come from blood capillaries. Interstitial fluid can also hold waste

products which result from metabolism. It is the main component of the extracellular fluid,

which also includes plasma and transcellular fluid.

The Nose:

The nose is a structure of the face made of cartilage, bone, muscle, and skin that supports and protects the anterior portion of the nasal cavity. The nasal cavity is a hollow space within the nose and skull that is lined with hairs and mucus membrane. The function of the nasal cavity is to warm, moisturize, and filter air entering the body before it reaches the lungs. Hairs and mucus lining the nasal cavity help to trap dust, mold, pollen and other environmental contaminants before they can reach the inner portions of the body. Air exiting the body through the nose returns moisture and heat to the nasal cavity before being exhaled into the environment.

Exercise:

Exercise increases the rate at which energy is needed from food. This increases the need for both food and oxygen in the body. This is why your pulse rate and breathing rate increase with exercise. Your pulse is just an indication of your heart rate as your arteries expand each time the ventricles pump blood out of the heart. Your heart speeds up to pump extra food and oxygen to the muscles. Breathing speeds up to get more oxygen and to get rid of more carbon dioxide.

Joints:

Multiarticulate

Crosses many joints

Common

Muscle effects every joint it crosses

Fingers and toes

Triarticulate

Crosses three joints

Position of either joint determines the length of the muscle

Alters the force exerted at the other joint

Very Rare

Uniarticulate

Crosses a single joint

Position of the joint determines length of the muscle

Length of the muscle determines force it can exert

Most effective muscles

Crosses two joints

Position of either joint determines the length of the muscle

Alters the force exerted at the other joint

Muscle Tissue

- Skeletal muscle tissue is called "striated" because of its appearance consisting of light and dark bands visible using a light microscope. A single skeletal muscle cell is long and approximately cylindrical in shape, with many nuclei located at the edges of the cell.

Example: Movement of the skeleton under conscious control, including movement of limbs, fingers, toes, neck or movement of tissues of facial expression under conscious control, e.g. ability to smile and to frown.

- Cardiac muscle fibers are striated, branched and have a single central nucleus. These fibers are attached at their ends to adjoining fibers by thick plasma membranes called intercalated discs.

Example: Pumping of blood through the heart: Alternate contraction and relaxation of cardiac muscle pumps

De-oxygenated blood through the Right Atrium and Right Ventricle to the lungs, and

Oxygenated blood through the Left Atrium and Left Ventricle to the aorta, then the rest of the body.

- Smooth muscle is not striated. Smooth muscle fibers are small and tapered - with the ends reducing in size, in contrast to the cylindrical shape of skeletal muscle. Each smooth muscle fiber has a single centrally located nucleus.

Example: Contractions of smooth muscle constrict the vessels they surround. This is particularly important in the digestive system in which the action of smooth muscle helps to move food along the gastrointestinal tract as well as breaking the food down further. Smooth muscle also contributes to moving fluids through the body and to the elimination of indigestible matter from the gastrointestinal system.

Female Cycle:

About every 28 days, some blood and other products of the disintegration of the inner lining of the uterus (the endometrium) are discharged from the uterus, a process called menstruation. During this time a new follicle begins to develop in one of the ovaries. After menstruation ceases, the follicle continues to develop, secreting an increasing amount of estrogen as it does so.

The rising level of estrogen causes the endometrium to become thicker and more richly supplied with blood vessels and glands.

A rising level of LH causes the developing egg within the follicle to complete the first meiotic division (meiosis I), forming a secondary oocyte.

After about two weeks, there is a sudden surge in the production of LH.

This surge in LH triggers ovulation: the release of the secondary oocyte into the fallopian tube.

Under the continued influence of LH, the now-empty follicle develops into a corpus luteum (hence the name luteinizing hormone for LH).

Stimulated by LH, the corpus luteum secretes progesterone which continues the preparation of the endometrium for a possible pregnancy, inhibits the contraction of the uterus, inhibits the development of a new follicle

If fertilization does not occur (which is usually the case), the rising level of progesterone inhibits the release of GnRH which, in turn, inhibits further production of progesterone.

As the progesterone level drops, the corpus luteum begins to degenerate; the endometrium begins to break down, its cells committing programmed cell death (apoptosis);

The inhibition of uterine contraction is lifted, and the bleeding and cramps of menstruation begin.

Connection:

Sensory transduction in the cochlea and vestibular labyrinth depends on fluid movements that deflect the hair bundles of mechanosensitive hair cells. Mechanosensitive transducer channels at the tip of the hair cell stereocilia allow K+ to flow into cells. Ion channels open in response to mechanical stimuli rather than chemical signals. These include the hair cells of the mammalian inner ear .

There are differences in electrical potential and chemical composition between the fluids of the inner ear and the insides of its cells. These electrochemical gradients are the battery providing power to a membrane-based motor essential for hearing. Systematic differences in the strength of the battery predict gradients in motor function within the inner ear.

Connection:

There are six muscles that are present in the orbit (eye socket) that attach to the eye to move it. These muscles work to move the eye up, down, side to side, and rotate the eye.

Sliding Filament:

For a contraction to occur there must first be a stimulation of the muscle in the form of an impulse from a motor neuron (nerve that connects to muscle). The individual motor neuron plus the muscle fibres it stimulates, is called a motor unit.

When an impulse reaches the muscle fibres of a motor unit, it stimulates a reaction in each sarcomere between the actin and myosin filaments. This reaction results in the start of a contraction and the sliding filament theory.

The reaction, created from the arrival of an impulse stimulates the 'heads' on the myosin filament to reach forward, attach to the actin filament and pull actin towards the centre of the sarcomere. This process occurs simultaneously in all sarcomeres, the end process of which is the shortening of all sarcomeres.

Troponin is attached to the protein tropomyosin within the actin filaments. When the muscle is relaxed tropomyosin blocks the attachment sites for the myosin cross bridges (heads), thus preventing contraction. When the muscle is stimulated to contract by the nerve impulse, calcium channels open in the sarcoplasmic reticulum (which is effectively a storage house for calcium within the muscle) and release calcium into the sarcoplasm (fluid within the muscle cell). Some of this calcium attaches to troponin which causes a change in the muscle cell that moves tropomyosin out of the way so the cross bridges can attach and produce muscle contraction.

Connection: Transport

Some nutrients may be able to move across the barrier between the intestine and blood with no help, others need a special structure to help them pass and a third group require energy input to actively move them across the membrane. The mechanism for passive transport is diffusion, where molecules move from an area of higher concentration, the intestine, to an area of lower concentration, the blood, through random movement.

An intestine full of digested food has a high concentration of nutrients. The bloodstream has a low concentration because it has transported the nutrients it carries to other parts of the body. Once there is a concentration gradient to drive diffusion, the nutrients need a path across the membrane. Fats and fat soluble nutrients can move directly across the lipid membrane. Water, gasses, and other very small molecules can diffuse through the pores of the cell. Larger molecules can move through specially designed channels made out of proteins. Glucose, on the other hand, moves through active transport.

Connections:

Endocrine:

In both sexes, the gonads have gametogenic (production of germ cells) and endocrine (secretion of sex hormones) functions. Steroid hormones secreted by the gonads (androgens, principally testosterone, from testes and estrogen and progesterone from ovaries) promote the sex-specific physical characteristics and initiate and maintain reproductive function. Androgens are steroid hormones with masculinizing effects and estrogens are steroid hormones with feminizing effects. Both types of sex hormones are normally secreted in males and females, but there are general differences in hormone concentrations between sexes.

Skeletal and Muscle

Once the reproductive system gonads are “up and running,” they in turn start producing hormones that not only cause maturation of their own system’s accessory organs and help maintain gametogenesis, but also are crucial for the incredible growth spurt that occurs during puberty and converts the child’s body to an adult’s. The most important effects are the anabolic effects exerted on bone and skeletal muscle. The skeleton becomes taller, heavier, and denser, and in females its pelvis is shaped to accommodate birth. All through a woman’s reproductive years, estrogen helps maintain a healthy bone mass. (Its lack is quickly obvious after menopause.) The skeletal muscles, too, increase in size and mass, and become capable of great strength.

Connection: GI

Any body system requires energy. This comes from the food and liquid we ingest. The gastrointestinal system enables the body to digest complex food substances which need to be broken down into simpler forms so that they can be utilised by the body's cells. The gastrointestinal system must also remove waste together with the urinary system. The urinary system is also important for maintaining the correct composition and volume of body fluids including blood.

Re-absorption:

Re-absorption is the movement of water and solutes from the tubule back into the plasma. Re-absorption of water and specific solutes occurs to varying degrees over the entire length of the renal tubule. Bulk re-absorption, which is not under hormonal control, occurs largely in the proximal tubule. Over 70% the filtrate is reabsorbed here.

Many important solutes (glucose, amino acids, bicarbonate) are actively transported out of the proximal tubule such that their concentrations are normally extremely low in the

remaining fluid. Further bulk re-absorption of sodium occurs in the loop of Henle.

Regulated re-absorption, in which hormones control the rate of transport of

sodium and water depending on systemic conditions, takes place in the

distal tubule and collecting duct.

Muscle Spindles

Muscle spindles are sensory receptors that are located in muscle. Their job is to detect changes in muscle length and the speed of change in muscle length.

When muscles lengthen, the spindles are stretched. This stretch activates the muscle spindle which in turn sends an impulse to the spinal cord. This impulse results in the activation of more motor neurons at spinal level that send an impulse back to the muscle.

This impulse tells the muscle to contract with greater force in order to decrease the speed at which the muscle is being stretched.

Mucociliary Escalator

The mucociliary escalator covers from the nose to most of the bronchi, bronchioles It is composed of two basic parts; the mucus-producing goblet cells and the ciliated epithelium.

The cilia are continually beating, pushing mucus up and out into the throat.

The mucociliary escalator is a major barrier against infection. Microorganisms hoping to infect the respiratory tract are caught in the sticky mucus and moved up by the mucociliary escalator.

The cilia act out movements coordinated in direction towards the pharynx. Thereby the viscous film of mucus including its freight is transported off in direction towards the mouth, where it is either swallowed or expelled via coughing.

Meiosis:

Meiosis is a process where a single cell divides twice to produce four cells containing half the original amount of genetic information. These cells are our sex cells – sperm in males, eggs in females. During meiosis one cell? divides twice to form four daughter cells.

These four daughter cells only have half the number of chromosomes? of the parent cell – they are haploid.

Meiosis produces our sex cells or gametes? (eggs in females and sperm in males).

- Interphase: The DNA in the cell is copied resulting in two identical full sets of chromosomes.

Outside of the nucleus? are two centrosomes, each containing a pair of centrioles, these structures are critical for the process of cell division

Prophase I: The copied chromosomes condense into X-shaped structures. Each chromosome is composed of two sister chromatids containing identical genetic information. The chromosomes pair up so that both copies of chromosome 1 are together, both copies of chromosome 2 are together, and so on.The pairs of chromosomes may then exchange bits of DNA in a process called recombination or crossing over. At the end of Prophase I the membrane around the nucleus in the cell dissolves away, releasing the chromosomes.

Metaphase I: The chromosome pairs line up next to each other along the centre (equator) of the cell. The centrioles are now at opposites poles of the cell with the meiotic spindles extending from them. The meiotic spindle fibres attach to one chromosome of each pair.

Anaphase I: The pair of chromosomes are then pulled apart by the meiotic spindle, which pulls one chromosome to one pole of the cell and the other chromosome to the opposite pole. In meiosis I the sister chromatids stay together. This is different to what happens in mitosis and meiosis II.

Telophase I: The chromosomes complete their move to the opposite poles of the cell. At each pole of the cell a full set of chromosomes gather together. A membrane forms around each set of chromosomes to create two new nuclei. The single cell then pinches in the middle to form two separate daughter cells each containing a full set of chromosomes within a nucleus. This process is known as cytokinesis.

Prophase II Now there are two daughter cells, each with 23 chromosomes. In each of the two daughter cells the chromosomes condense again into visible X-shaped structures that can be easily seen under a microscope. The membrane around the nucleus in each daughter cell dissolves away releasing the chromosomes. The centrioles duplicate. The meiotic spindle forms again.

Metaphase II In each of the two daughter cells the chromosomes (pair of sister chromatids) line up end-to-end along the equator of the cell. The centrioles are now at opposites poles in each of the daughter cells.Meiotic spindle fibres at each pole of the cell attach to each of the sister chromatids.

Anaphase II: The sister chromatids are then pulled to opposite poles due to the action of the meiotic spindle. The separated chromatids are now individual chromosomes.

Telophase II and cytokinesis: The chromosomes complete their move to the opposite poles of the cell. At each pole of the cell a full set of chromosomes gather together. A membrane forms around each set of chromosomes to create two new cell nuclei. This is the last phase of meiosis, however cell division is not complete without another round of

cytokinesis. Once cytokinesis is complete there are four granddaughter cells, each with half a set of chromosomes (haploid):in males, these four cells are all sperm

cells. In females, one of the cells is an egg cell while the other three are polar bodies (small cells that do not develop into eggs).

Tissues Connection:

Tunica intima (the thinnest layer): a single layer of simple squamous endothelial cells glued by a polysaccharide intercellular matrix, surrounded by a thin layer of subendothelial connective tissue interlaced with a number of circularly arranged elastic bands called the internal elastic lamina.

Tunica media (the thickest layer in arteries): circularly arranged elastic fiber, connective tissue, polysaccharide substances, the second and third layer are separated by another thick elastic band called external elastic lamina. The tunica media may (especially in arteries) be rich in vascular smooth muscle, which controls the caliber of the vessel. Veins don't have the external elastic lamina, but only an internal one.

Tunica adventitia: (the thickest layer in veins) entirely made of connective tissue. It also contains nerves that supply the vessel as well as nutrient capillaries (vasa vasorum) in the larger blood vessels.

Capillaries consist of little more than a layer of endothelium and

occasional connective tissue.

Antidiuretic

A hormone made by the hypothalamus in the brain and stored in the posterior pituitary gland. It tells your kidneys how much water to conserve. ADH constantly regulates and balances the amount of water in your blood.

Hormones:

Adrenocorticotropic hormone - ACTH - Adrenal gland/cortex

Thyroid-stimulating hormone - TSH - Thyroid gland

Follicle-stimulating hormone and Luteinizing hormone - FSH, LH - Gonads

Growth hormone - GH, STH - Bones and tissues

Prolactin - PRL - Ovaries, mammary glands

Human growth hormone (hGH) travels to skeletal muscles, bones, and the liver to promote overall growth and development. Thyroid-stimulating hormone (TSH) and adrenocorticotropic hormone (ACTH) target the thyroid and adrenal glands, two primary endocrine glands that regulate metabolism for temperature regulation, growth, and stress resistance. Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) stimulate sex cell production and reproductive processes in the gonads, and prolactin (PRL) induces milk production in mammary glands.

integumentary, The hormones of the endocrine system affect the action of melanocytes and apocrine sweat glands. The integumentary system synthesizes vitamin D, which is active in bone formation controlled by the endocrine system.

Long Bones:

Long bones function to support the weight of the body and facilitate movement.

The epiphyseal plate is the area of growth in a long bone. It is a layer of hyaline cartilage where ossification occurs in immature bones. On the epiphyseal side of the epiphyseal plate, cartilage is formed. On the diaphyseal side, cartilage is ossified, allowing the diaphysis to grow in length. The metaphysis is the wide portion of a long bone between the epiphysis and the narrow diaphysis. It is considered a part of the growth plate: the part of the bone that grows during childhood, which, as it grows, ossifies near the diaphysis and the epiphyses.

Growth plates (epiphysis) at either end, havie a hard outer surface of compact bone and a spongy inner known an cancellous bone containing bone marrow. Both ends of the bone are covered in hyaline cartilage to help protect the bone and aid shock absorbtion.

Located in long bones are two distinctions of bone marrow (yellow and red). The yellow marrow has fatty connective tissue and is found in the marrow cavity. During starvation, the body uses the fat in yellow marrow for energy.[8] The red marrow of some bones is an important site for blood cell production, approximately 2.6 million red blood cells per second in order to replace existing cells that have been destroyed by the liver.

Connection:

So, the concentration (or pressure) of O2 in the alveoli must be kept at a higher level than in the blood & the concentration (or pressure) of CO2 in the alveoli must be kept at a lower lever than in the blood. We do this, of course, by breathing - continuously bringing fresh air (with lots of O2 & little CO2) into the lungs & the alveoli.

As the external intercostals & diaphragm contract, the lungs expand. The expansion of the lungs causes the pressure in the lungs (and alveoli) to become slightly negative relative to atmospheric pressure. As a result, air moves from an area of higher pressure (the air) to an area of lower pressure (our lungs & alveoli). During expiration, the respiration muscles relax & lung volume descreases. This causes pressure in the lungs (and alveoli) to become slight positive relative to atmospheric pressure. As a result, air leaves the lungs.

Gross Anatomy

Lymphatic Fluid

Lymph fluid comes from the intestines, where the digestive system produces a fluid called chyle, which is rich in proteins and fats. It also contains many immune cells, particularly lymphocytes, to attack any pathogens. Lymph fluid varies between white and clear in color. Lymph returns proteins and excess interstitial fluid to the bloodstream. Lymph may pick up bacteria and bring them to lymph nodes, where they are destroyed.

The lymphatic system helps maintain fluid balance in the body by collecting excess fluid and particulate matter from tissues and depositing them in the bloodstream. The portion of blood plasma that escapes is called interstitial or extracellular fluid, and it contains oxygen, glucose, amino acids, and other nutrients needed by tissue cells. Although most of this fluid seeps immediately back into the bloodstream, a percentage of it, along with the particulate matter, is left behind. The lymphatic system removes this fluid and these materials from tissues, returning them via the lymphatic vessels to the bloodstream, and thus prevents a fluid imbalance that would result in the organism’s death. The fluid and proteins within the tissues begin their journey back to the bloodstream by passing into tiny lymphatic capillaries that infuse almost every tissue of the body.

Only a few regions, including the epidermis of the skin, the mucous membranes, the bone marrow, and the central nervous system, are free of lymphatic capillaries, whereas regions such as the lungs, gut, genitourinary system, and dermis of the skin are densely packed with these vessels. Once within the lymphatic system, the extracellular fluid, which is now called lymph, drains into larger vessels called the lymphatics. These vessels converge to form one of two large vessels called lymphatic trunks, which are connected to veins at the base of the neck. One of these trunks, the right lymphatic duct, drains the upper right portion of the body, returning lymph to the bloodstream via the right subclavian vein. The other trunk, the thoracic duct, drains the rest of the body into the left subclavian vein. Lymph is transported along the system of vessels by muscle contractions, and valves prevent lymph from flowing backward. The lymphatic vessels are punctuated at intervals by small masses of lymph tissue, called lymph nodes, that remove foreign materials such as infectious microorganisms from the lymph filtering through them.

Movement of Fluid:

Osmotic and Hydrostatic pressures regulate the continuous exchange and mixing of body fluids. Although water moves freely between the compartments along osmotic gradients, solutes are unequally distributed because of their size, electrical charge, or dependence on transport proteins.

In general, substances must pass through both the plasma and interstitial fluid to reach the intracellular fluid. In the lungs, gastrointestinal tract, and kidneys, exchanges between the outside world and the plasma occur continuously. These exchanges alter plasma composition and volume, with plasma serving as the “highway” for delivering substances throughout the body. Compensating adjustments between the plasma and the other two fluid compartments follow quickly so that balance is restored.

The hydrostatic pressure of blood forces nearly protein-free plasma out of the blood into the interstitial space. The filtered fluid is then almost completely reabsorbed into the bloodstream in response to the colloid osmotic pressure of plasma proteins. Under normal circumstances, lymphatic vessels pick up the small net leakage that remains behind in the interstitial space and return it to the blood.

Interstitial fluid and intracellular fluid occur across plasma membranes. Exchanges across the plasma membrane depend on its permeability properties. As a general rule, two-way osmotic flow of water is substantial. But ion fluxes are restricted and, in most cases, ions move selectively, by active transport or through channels. Movements of nutrients, respiratory gases, and wastes are typically unidirectional (both ways). For instance, glucose and oxygen move into the cells and metabolic wastes move out.

Connection:

They use special proteins called opsins, which turn the photons absorbed by the Rods and Cones into specific electrochemical signals that are then sent to the optic nerve and eventually the brain. This process is called Phototransduction and human vision has four essential types of opsin: one for rods and three for the cones. In your photoreceptors (your rods and cones), opsins are coupled with vitamin A (found in carrots). Vitamin A acts as a light absorbing molecule; after absorbing light its molecular structure changes and it separates from the opsin. As this separating occurs, an electrical signal is generated by the opsin in a very complex biochemical process known as the visual cycle.

Bones

Irregular Bones

They primarily consist of cancellous bone, with a thin outer layer of compact bone. They help protect internal organs and the spinal cord

Flat Bones:

The function of flat bones is to protect internal organs such as the brain, heart, and pelvic organs. They are somewhat flattened, and can provide protection, like a shield; they can also provide large areas of attachment for muscles.

Anterior and posterior surfaces are formed of compact bone to provide strength for protection with the centre consisiting of cancellous (spongy) bone and varying amounts of bone marrow. In adults, the highest number of red blood cells are formed in flat bones.

Short Bones:

The carpals in the wrist (scaphoid, lunate, triquetral, hamate, pisiform, capitate, trapezoid, and trapezium)

(calcaneus, talus, navicular, cuboid, lateral cuneiform, intermediate cuneiform, and medial cuneiform)

They consist of only a thin layer of compact, hard bone with cancellous bone on the inside along with relatively large amounts of bone marrow.

Venous Return:

Venous return is influenced

by several factors:

- Muscle contraction.

- Decreased venous compliance.

- Respiratory activity

- Vena cava compression.

- Gravity

Venous return (VR) is the flow of blood back to the heart. Under steady-state conditions, venous return must equal cardiac output (CO) when averaged over time because the cardiovascular system is essentially a closed loop. The circulatory system is made up of two circulations (pulmonary and systemic) situated in series between the right ventricle (RV) and left ventricle. Balance is achieved, in large part, by the Frank-Starling mechanism. For example, if systemic venous return is suddenly increased (e.g., changing from upright to supine position), right ventricular preload increases leading to an increase in stroke volume and pulmonary blood flow. Increased pulmonary venous return to the left atrium leads to increased filling (preload) of the left ventricle, which in turn increases left ventricular stroke volume by the Frank-Starling mechanism. In this way, an increase in venous return to the heart leads to an equivalent increase in cardiac output to the systemic circulation. Hemodynamically, venous return (VR) to the heart from the venous vascular beds is determined by a pressure gradient (venous pressure, PV, minus right atrial pressure, PRA) divided by the venous vascular resistance (RV) Therefore, increased venous pressure or decreased right atrial pressure, or decreased venous resistance leads to an increase in venous return.

Secretion:

Even after filtration has occurred, the tubules continue to secrete additional substances into the tubular fluid. This enhances the kidney's ability to eliminate certain wastes and toxins. It is also essential to regulation of plasma potassium concentrations and pH.

Movement of Nutrients:

Blood flowing in capillaries nourishes body cells with nutrients and oxygen and receives waste materials such as carbon dioxide. Gases, food nutrients, water, and wastes pass back and forth between body cells and the bloodstream across the thin walls of capillaries.

When you begin to digest your food, the arterioles that are connected to capillaries in your intestine open. Blood flows to the intestines and takes up nutrients from your food. When you begin to exercise, the arterioles to your muscles open so the blood can carry nutrients to your muscle cells. When the arterioles going to the muscles open, some arterioles to your intestine close down. Blood moves from your intestines to your muscles carrying the needed nutrients.

Gases (oxygen and carbon dioxide), nutrients, and wastes pass in both directions across capillary walls. Blood flow in capillaries is pushed by the pumping of the heart.

At the arterial end of the capillary, the net filtration pressure is equal to the net hydrostatic pressure minus the osmotic pressure.

The net filtration pressure is 13mm Hg. This causes the fluid to move from the capillary into the interstitial fluid.

At the venous end of the capillary, the net filtration press is equal to the net hydrostatic pressure minus the net osmotic pressure.

The net filtration pressure is -7 mm Hg. This causes fluid to move from the interstitial fluid into the capillary.

Approximately nine-tenths of the fluid that leaves the capillary at its arterial end renters the capillary at the venous end. The one-tenth of the fluid passes into the lymphatic capillaries and returns to the blood stream via the lymphatic system.

Muscle Classification

Heart Conduction

In each cardiac cycle, the heart contracts (systole), pushing out the blood and pumping it through the body. This is followed by a relaxation phase (diastole), where the heart fills with blood . The atria contract at the same time, forcing blood through the atrioventricular valves into the ventricles. Closing of the atrioventricular valves produces a monosyllabic "lup" sound.

Following a brief delay, the ventricles contract at the same time forcing blood through the semilunar valves into the aorta and the pulmonary artery (which transports blood to the lungs). Closing of the semilunar valves produces a monosyllabic "dup" sound. There is a layer of muscle surrounding the arteries and the veins which help contract and expand the vessels. This creates enough pressure for blood to be pumped around the body. Blood vessels are part of the circulatory system, together with the heart and the blood.

Ear

Tendon Reflex

The reflex exam is fundamental to the neurological exam and important to locating upper versus lower motor neuron lesions. It is used to determine the integrity of the spinal cord and peripheral nervous system, and they can be used to detect the presence of a neuromuscular disease.

Connection

Tiny muscles attached to the ossicles contract or relax to attenuate the volume of sounds passing through the middle ear.

Connection:

Cardiac muscle cells or cardiomyocytes (also known as myocardiocytes or cardiac myocytes) are the muscle cells (myocytes) that make up the cardiac muscle (heart muscle). Each myocardial cell contains myofibrils, which are specialized organelles consisting of long chains of sarcomeres, the fundamental contractile units of muscle cells. Cardiomyocytes show striations similar to those on skeletal muscle cells. Cardiomyocytes have a high mitochondrial density, which allows them to produce adenosine triphosphate (ATP) quickly, making them highly resistant to fatigue.

Cardiomyocytes pump rhythmically and involuntarily like smooth muscle; they are connected by intercalated disks exclusive to cardiac muscle . Cardiomyocytes are self-stimulated for a period of time; isolated cardiomyocytes will beat if given the correct balance of nutrients and electrolytes.

Renal

Distal convoluted tubule

Bowman's Capsule

Afferent arteriole

Glomerulus

Efferent arteriole

Proximal convoluted

tubule

Descending loop

Ascending loop

Peritubular capillaries

Loop of Henle

Venules

Collecting Duct

Heart

Reflex

Baroreflex: The baroreflex is the fastest mechanism to regulate acute blood pressure changes via controlling heart rate, contractility, and peripheral resistance.Baroreceptors are mechanoreceptors located in the carotid sinus and in the aortic arch. Their function is to sense pressure changes by responding to change in the tension of the arterial wall. When a person has a sudden drop in blood pressure, for example standing up, the decreased blood pressure is sensed by the baroreceptor as a decrease in tension therefore will decrease in the firing of impulses. This decrease in blood pressure is normally transient and goes unnoticed because the body quickly responds by increasing tone in the vasculature to augment blood pressure through direct arterial constriction as well as increased venous return to the heart (this is a reflex known as the carotid body reflex)

Shape:

- Circular

Concentric circular arrangement of fascicles – form sphincters that enclose an orifice

- Parallel

Fascicles run parallel along muscles longitudinal axis – flat tendons at either end

- Fusiform

Fascicles nearly parallel along muscles longitudinal axis – flat tendons at either end. Belly is wider than the aponeurosis

- Convergent/Triangular

Muscle has a broad origin but fascicles converge on a thick central tendon

- Pennate

Muscles with long tendons, almost as long as the muscle

-Unipennate

Fascicles arranged on one side of the tendon

Connection: Skin

We lose water in sweat, faeces, urine and when we breathe out (on a cold day you can see this water as it condenses into vapour).

For the cells of our body to work properly, it is important that their water content is maintained at the correct level. This means our body must maintain a balance between the water we take in and the water we lose. This is done by the kidneys.

Differences:

Meiosis produces daughter cells that have 1/2 the number of chromosomes as the parent. Go from 2n to 1n.

Daughter cells produced by meiosis are not genetically identical to one another.

In meiosis cell division takes place twice but replication occurs only once

Adrenocorticotropic hormone - ACTH - Adrenal gland/cortex

Thyroid-stimulating hormone - TSH - Thyroid gland

Follicle-stimulating hormone and Luteinizing hormone - FSH, LH - Gonads

Growth hormone - GH, STH - Bones and tissues

Prolactin - PRL - Ovaries, mammary glands

Mitosis:

Mitosis is a process where a single cell divides into two identical daughter cells (cell division). The major purpose of mitosis is for growth and to replace worn out cells.

Interphase DNA in the cell is copied in preparation for cell division, this results in two identical full sets of chromosomes

Prophase The chromosomes condense into X-shaped structures that can be easily seen under a microscope. Each chromosome is composed of two sister chromatids, containing identical genetic information At the end of prophase the membrane around the nucleus in the cell dissolves away releasing the chromosomes.

Metaphase The chromosomes line up neatly end-to-end along the centre (equator) of the cell. The centrioles are now at opposite poles of the cell with the mitotic spindle fibres extending from them. The mitotic spindle fibres attach to each of the sister chromatids.

Anaphase The sister chromatids are then pulled apart by the mitotic spindle which pulls one chromatid to one pole and the other chromatid to the opposite pole.

Telophase At each pole of the cell a full set of chromosomes gather together.

A membrane forms around each set of chromosomes to create two new nuclei.

Connection: Gradients

- Filtration is primarily driven by hydraulic pressure (blood pressure)

- Osmotic sensors in the hypothalamus react to the concentration of particles in your blood. These particles include molecules of sodium, potassium, chloride, and carbon dioxide. When particle concentration is not balanced, or blood pressure is too low, these sensors and baroreceptors tell your kidneys to store or release water to maintain a healthy range of these substances. They also regulate your body’s sense of thirst.

Connection:

A skeletal muscle consists of numerous muscle cells called muscle fibers. Three layers of connective tissues surround these fibers to form a muscle.

- The endomysium is the connective tissue that surrounds each muscle fiber (cell).

- The perimysium encircles a group of muscle fibers, forming a fascicle.

-The epimysium encircles all the fascicles to form a complete muscle.

- A tendon is a cordlike extension of the preceding three linings. It extends beyond the muscle tissue to connect the muscle to a bone or to other muscles.

-An aponeurosis is a flat broad extension of the three muscle linings and serves the same function as a tendon.

- Fascia is a term for a layer or sheet of connective tissue.

- The deep fascia surrounds the epimysium and encloses or lines other nearby structures such as blood vessels, nerves,

and the body wall.

- The superficial fascia (hypodermis or subcutaneous layer) lies immediately below the skin. The superficial fascia

merges with the deep fascia where the surfaces of the skin meet.

Connection: Transport

- Passive transport occurs in the kidney as the small blood capillaries called glomerulus have their waste products removed from the blood. The concentration of nitrogenous waste products in the Bowman's capsule is low and therefore the wastes in the glomerulus diffuse through the glomerular filtration membrane. This occurs without any energy being used up.

- Active transport can be seen in the kidneys, at the reabsorption stage in the nephrons. Along the nephron, a large network of capillaries surround the tubules that carry the waste. Substances that the body needs from the waste that can be re-used are reabsorbed into the blood stream. These substances are usually glucose, amino acids, vitamins, water and more. This reabsorption usually happens in the proximal and distal convoluted tubules and the loop of Henle.

Blood

Pressure

Systolic blood pressure (the upper number) — indicates how much pressure your blood is exerting against your artery walls when the heart beats.

Diastolic blood pressure (the lower number) — indicates how much pressure your blood is exerting against your artery walls while the heart is resting between beats. Typically, more attention is given to systolic blood pressure (the top number) as a major risk factor for cardiovascular disease for people over 50. In most people, systolic blood pressure rises steadily with age due to the increasing stiffness of large arteries, long-term build-up of plaque and an increased incidence of cardiac and vascular disease.

Pulmonary hypertension (PHT) is high blood pressure in the heart-to-lung system that delivers fresh (oxygenated) blood to the heart while returning used (oxygen-depleted) blood back to the lungs. Unlike systemic blood pressure, which represents the force of your blood moving through the blood vessels in your body, pulmonary blood pressure reflects the pressure the heart exerts to pump blood from the heart through the arteries of the lungs. In other words, it focuses on the pressure of the blood flow in your lungs. The lower right heart chamber, the right ventricle, receives oxygen-depleted blood and pumps it to your pulmonary arteries. The blood then travels to your lungs to be oxygenated, and on to the upper left heart chamber, the left atrium. From there, the oxygen-rich blood moves into the lower left chamber, the left ventricle, which pumps blood to the rest of your body through the aorta.

Normal pulmonary artery pressure is 8-20 mm Hg at rest. If the pressure in the pulmonary artery is greater than 25 mm Hg at rest or 30 mmHg during physical activity, it is abnormally high and is called pulmonary hypertension. Heart failure occurs when the heart becomes too weak to pump enough blood to the lungs.

Hormones:

Hormones affect distant cells by binding to specific receptor proteins in the target cell resulting in a change in cell function. When a hormone binds to the receptor, it results in the activation of a signal transduction pathway.

Hormones regulate internal functions from metabolism and growth to sexual development and the induction of birth. They circulate through the bloodstream, bind to target cells, and adjust the function of whole tissues and organs. It starts with the hypothalamus and the pituitary gland. The hormones they release control the secretions of the other endocrine glands and most endocrine functions. Throughout the body, hormones enable reactions to stress and other outside changes and keep regular processes running smoothly.

The hormones dissolve in plasma and travel the circulatory pathways through various body tissues. Only those target cells have receptors for that particular hormone. Some hormones bind to receptors on the surface of target cells. Others enter the cells and bind to receptors in the cytoplasm or nucleus.

Connection: Organ Systems

Gastrointestinal: The digestive and endocrine systems work together, mostly through the pancreas, to produce and disseminate digestive enzymes. The primary role of the endocrine system is to produce important hormones that tell the digestive system when to start digesting food and when to stop.

Skeletal: Growth hormone is essential for normal skeletal growth and maintenance throughout life, whereas thyroid and sex hormones ensure that normal skeletal proportions are established during childhood and adolescence.

Muscular: One way the endocrine system works with the muscles is through the release of glucose. When your muscles need energy, a signal will be sent to your brain to release more insulin from your pancreas, which will create more energy to be available for use.

Glycogen will be pumped out by your liver if you are in need of energy stores. Also read more about the fight or

flight response.

Respiratory: Both the endocrine and respiratory systems are dependent on each other. Adrenalin, which is released by the

adrenal glands, helps to stimulate the respiratory activity. Also, some endocrine hormones have an effect on the

dilation of the alveoli, or the respiratory passages. This can affect the amount of oxygen

that the lungs absorb.

Skeletal System:

Blood Vessels

Five great vessels enter and leave the heart: the superior and inferior vena cava, the pulmonary artery, the pulmonary vein, and the aorta.

The superior vena cava and inferior vena cava are veins that return deoxygenated blood from circulation in the body and empty it into the right atrium.

The pulmonary artery carries deoxygenated blood from the right ventricle into the lungs for oxygenation.

The pulmonary veins carry oxygenated blood from the lungs into the left atrium where it is returned to systemic circulation.

The aorta is the largest artery in the body. It carries oxygenated blood from the left ventricle of the heart into systemic circulation.

They are roughly grouped as arterial and venous, determined by whether the blood in it is flowing away from (arterial) or toward (venous) the heart.

The arteries and veins have three layers, but the middle layer is thicker in the arteries than it is in the veins.

There are various kinds of blood vessels:

Arteries

Elastic arteries

Distributing arteries

Arterioles

Capillaries (the smallest blood vessels)

Venules

Veins

Connection:

The bones in the skeletal system are formed from several different connective tissues. Bone tissue, or osseous tissue, is the major structural and supportive connective tissue of the body. It forms the rigid part of the bones that make up the skeleton.

There are two types of bone tissue; cortical bone and cancellous bone

Cortical bone or compact bone, forms the extremely hard exterior of bones. Cortical bone facilitates bone's main functions: to support the whole body, protect organs, provide levers for movement, and store and release chemical elements, mainly calcium. It much denser than cancellous bone, it is harder, stronger and stiffer than cancellous bone

Cancellous bone is synonymous with trabecular or spongy bone. Cancellous bone has a higher surface area to mass ratio than

cortical bone because it is less dense. This makes it softer, and weaker but more flexible. The greater surface area also

makes it suitable for metabolic activities such as the exchange of calcium ions. It is highly vascular and frequently contains

red bone marrow where haematopoiesis, the production of blood cells, occurs.

Connection:

Alveolus is lined by simple squamous epithelium. This is because it is exceedingly thin which is needed in order to facilitate diffusion of oxygen while still forming an epithelial barrier between the outside air and the internal body fluids. The cells are flat with flattened/rounded nucleus. It is also called pavement epithelium due to its tile-like appearance

Connection:

Auditory processing begins in the cochlea of the inner ear, where sounds are detected by sensory hair cells and then transmitted to the central nervous system by spiral ganglion neurons, which faithfully preserve the frequency, intensity, and timing of each stimulus. During the assembly of auditory circuits, spiral ganglion neurons establish precise connections that link hair cells in the cochlea to target neurons in the auditory brainstem, develop specific firing properties, and elaborate unusual synapses both in the periphery and in the CNS.

Connection: Calcium Ion

Cardiac muscle fibers contract via excitation-contraction coupling, using a mechanism unique to cardiac muscle called calcium-induced calcium release. In cardiac muscle, ECC is dependent on a phenomenon called calcium-induced calcium release (CICR), which involves the influx of calcium ions into the cell, triggering further release of ions into the cytoplasm. The mechanism for CIRC is receptors within the cardiomyocyte that bind to calcium ions when calcium ion channels open during depolarization, releasing more calcium ions into the cell.

Similarly to skeletal muscle, the influx of sodium ions causes an initial depolarization; however, in cardiac muscle, the influx of calcium ions sustains the depolarization so that it lasts longer. CICR creates a "plateau phase" in which the cell's charge stays slightly positive (depolarized) briefly before it becomes more negative as it repolarizes due to potassium ion influx. Skeletal muscle, by contrast, repolarizes immediately.

Parathyroid hormone secreted by the parathyroid gland regulates the resorption of Ca2+ from bone, reabsorption in the kidney

back into circulation, and increases in the activation of vitamin D3 to Calcitriol. Calcitriol, the active form of vitamin D3,

promotes absorption of calcium from the intestines and the mobilization of calcium ions from bone matrix.

Connection: Connective Tissues

Cartilage. A type of connective tissue that covers the surface of a bone at a joint. Cartilage helps reduce the friction of movement within a joint

Synovial membrane. The synovial membrane lines the joint and seals it into a joint capsule. The synovial membrane secretes synovial fluid (a clear, sticky fluid) around the joint to lubricate it.

Ligaments. Strong ligaments (tough, elastic bands of connective tissue) surround the joint to give support and limit the joint's movement.

Tendons. Tendons (another type of tough connective tissue) on each side of a joint attach to muscles that control movement of the joint.

Nervous

System

Intracellular fluid

The intracellular fluid of the cytosol or intracellular fluid (or cytoplasmic matrix) is the liquid found inside cells.

The cytosol is a complex mixture of substances that include proteins, ions, and organelles dissolved in water.

Intracellular fluid is the place where most of the fluid in the body is contained. This fluid is located within the cell membrane and contains water, electrolytes and proteins. Potassium, magnesium, and phosphate are the three most common electrolytes in the ICF.

Eye:

Connection: Organ Systems

Blood and Lymphatics: Endocrine is ductless meaning it just goes into the body via bloodstream/ diffusion.

It uses the blood stream to transport hormones throughout the body. Each hormone effects different tissues and parts of the body, some effect more more than one thing.

Cardiovascular: When the endocrine system releases hormones, the hormones need to be able to travel through the body to get to their target. Many of the endocrine hormones get released into blood, which is part of the cardiovascular system. Some of the hormones in the endocrine system control different levels of substances in the blood, which is needed for homeostasis to occur.

Renal: The adrenal glands, also a part of the endocrine system, secrete a chemical substance; angiotensin- that allows the kidneys to effectively regulate fluids in the body. This process is directly related to blood pressure and the circulatory system.

Valves

The heart consists of four chambers, two atria (upper chambers) and two ventricles (lower chambers). There is a valve through which blood passes before leaving each

chamber of the heart. The valves prevent the backward flow of blood. These valves are actual flaps that are located on each end of the two ventricles (lower chambers of the heart). They act as one-way inlets of blood on one side of a ventricle and one-way outlets of blood on the other side of a ventricle. Each valve actually has three flaps, except the mitral valve, which has two flaps. The four heart valves include the following:

After the left ventricle contracts, the aortic valve closes and the mitral valve opens, to allow blood to flow from the left atrium into the left ventricle. As the left atrium contracts, more blood flows into the left ventricle. When the left ventricle contracts again, the mitral valve closes and the aortic valve opens, so blood flows into the aorta.

Tricuspid valve: located between the right atrium and the right ventricle

Pulmonary valve: located between the right ventricle and the pulmonary artery

Mitral valve: located between the left atrium and the left ventricle

Aortic valve: located between the left ventricle and the aorta

As the heart muscle contracts and relaxes, the valves open and shut, letting blood flow into the ventricles and atria at alternate times.

Connection:

Cardiovascular

The heart pumps blood filled with oxygen through all parts of your body, including the kidneys. The kidneys clean the blood, removing waste products and extra water. Without the kidneys, your blood would have too much waste and water. Without the heart, your kidneys would not have the oxygen filled blood needed to do its many important jobs. Without the help of your kidneys, the heart would be working too hard or would not function at all.

Movement:

Voluntary: Movement of the muscle is under control

Involuntary: Movement is not under control eg cardiac muscle

Skeletal:

Skeletal muscle tissue is the only muscle tissue under the direct conscious control of the cerebral cortex of the brain, giving it the designation of being voluntary muscle. All conscious movements of the body, including movement of the limbs, facial expressions, eye movements, and swallowing are the products of skeletal muscle tissue. Skeletal muscle cells appear to have a striped, or striated, pattern of light and dark regions. These stripes are caused by the regular arrangement of actin and myosin proteins within the cells into structures known as myofibrils. Myofibrils are responsible for the skeletal muscles’ great strength and ability to pull with incredible force and propel the body.

Each skeletal muscle fiber is a single cylindrical muscle cell. An individual skeletal muscle may be made up of hundreds, or even thousands, of muscle fibers bundled together and wrapped in a connective tissue covering. Each muscle is surrounded by a connective tissue sheath called the epimysium. Fascia, connective tissue outside the epimysium, surrounds and separates the muscles. Portions of the epimysium project inward to divide the muscle into compartments. Each compartment contains a bundle of muscle fibers. Each bundle of muscle fiber is called afasciculus and is surrounded by a layer of connective tissue called the perimysium. Within the fasciculus, each individual muscle cell, called a muscle fiber, is surrounded by connective tissue called the endomysium.

Filtration:

Filtration is the movement of water and solutes from plasma to the renal tubule that occurs in the renal corpuscle. 20% of the plasma volume passing through the glomerulus at any given time is filtered. 180 liters of fluid are filtered by the kidneys every day. The entire plasma volume (3 liters) is filtered 60 times a day! Filtration is primarily driven by hydraulic

pressure (blood pressure) in the capillaries of the glomerulus.

This is essential for the kidneys to rapidly remove waste and

toxins from the plasma efficiently.

Connection:

Neurons carry information from one end of the cell to the other by generating and propagating electrical signals.

The potential difference across the neuron cell membrane is the basis for generating electrical signals. Much like a battery, this potential is creating by the uneven distribution of ions on either side of the membrane.

The concentration gradient, or difference in concentration, of different types of ions across the neuron cell membrane. The two major ions that influence potential difference are sodium, which is abundant outside the cell, and potassium, which is abundant inside the the cell. Both of these ions have a charge of +1.

Definitions:

Negative feedback is a reaction that causes a decrease in function. It occurs in response to some kind of stimulus. Often it causes the output of a system to be lessened; so, the feedback tends to stabilize the system.

Homeostasis is the tendency of an organism or a cell to regulate its internal conditions, usually by a system of feedback controls, so as to stabilize health and functioning, regardless of the outside changing conditions

Endocrine is relating to or denoting glands which secrete hormones or other products directly into the blood.

Exocrine relating to or denoting glands which secrete their products through ducts opening on to an epithelium rather than directly into the blood.

Testosterone:

Testosterone is produced by the gonads (by the Leydig cells in testes in men and by the ovaries in women), although small quantities are also produced by the adrenal glands in both sexes. It is an androgen, meaning that it stimulates the development of male characteristics. Present in much greater levels in men than women, testosterone initiates the development of the male internal and external reproductive organs during foetal development and is essential for the production of sperm in adult life. This hormone also signals the body to make new blood cells, ensures that muscles and bones stay strong during and after puberty and enhances libido both in men and women. Testosterone is linked to many of the changes seen in boys during puberty (including an increase in height, body and pubic hair growth, enlargement of the penis, testes and prostate gland and changes in sexual and aggressive behaviour). It also regulates the secretion of luteinising hormone and follicle stimulating hormone. To effect these changes, testosterone is often converted into another androgen called dihydrotestosterone.

In women, testosterone is produced by the ovaries and adrenal glands. The majority of testosterone produced in the ovary is converted to the principle female sex hormone, oestradiol.

Blood:

Blood is essential to life. Blood circulates through our body and delivers essential substances like oxygen and nutrients to the body’s cells. It also transports metabolic waste products away from those same cells.There are four basic components that comprise human blood: plasma, red blood cells, white blood cells and platelets.

Red blood cells represent 40%-45% of your blood volume. They are generated from your bone marrow at a rate of four to five billion per hour. They have a lifecycle of about 120 days in the body.

Platelets are an amazing part of your blood. Platelets are the smallest of our blood cells and literally look like small plates in their non-active form. Platelets control bleeding. Wherever a wound occurs, the blood vessel will send out a signal. Platelets receive that signal and travel to the area and transform into their “active” formation, growing long tentacles to make contact with the vessel and form clusters to plug the wound until it heals.

Plasma is the liquid portion of your blood. Plasma is yellowish in color and is made up mostly of water, but it also contains proteins, sugars, hormones and salts. It transports water and nutrients to your body’s tissues.

Although white blood cells (leukocytes) only account for about 1% of your blood, they are very important. White blood cells are essential for good health and protection against illness and disease.

They flow through the bloodstream and attack foreign bodies, like viruses and bacteria.

They can even leave the bloodstream to extend the fight into tissue.

Sex Hormones:

The sex hormones are estrogen and testosterone. Like all hormones, they are chemical messengers, substances produced in one part of the body that go on to tell other parts what to do. Both women and men produce both estrogen and testosterone, though in different quantities, and both sexes produce less as they age.

As your ovaries ramp up production of one female sex hormone, they simultaneously slow down production of the other; it's a vital seesaw that keeps your reproductive system running. But the happy partnership can be compromised by weight gain, chronic stress, and exposure to toxic chemicals like BPA. And unchecked estrogen levels can tamper with your libido and lead to irritability, migraines, depression, extreme PMS, and a host of reproductive disorders,

Oestrogen and Progesterone

Oestrogen is primarily responsible for the conversion of girls into sexually-mature women.

Development of breasts, further development of the uterus and vagina, broadening of the pelvis, growth of pubic and axillary hair, increase in adipose (fat) tissue, participate in the monthly preparation of the body for a possible pregnancy, participate in pregnancy if it occurs.

Antagonize the effects of the parathyroid hormone, minimizing the loss of calcium from bones and thus helping to keep bones strong.

Progesterone's most important functions is its role in thickening the lining of the uterus each month.

The enriched endometrial lining is prepared to receive and nourish a fertilized egg. If a pregnancy occurs, progesterone is produced in the placenta and levels remain elevated throughout the pregnancy.

Connection:

A motor neuron (or motoneuron) is a neuron whose cell body is located in the spinal cord and whose fiber (axon) projects outside the spinal cord to directly or indirectly control effector organs, mainly muscles The term 'motor neuron' is usually restricted to the efferent nerves that actually innervate muscles (the lower motor neurons). A single motor neuron may innervate many muscle fibres and a muscle fibre can undergo many action potentials in the time taken for a single muscle twitch.

Connection:

They use special proteins called opsins, which turn the photons absorbed by the Rods and Cones into specific electrochemical signals that are then sent to the optic nerve and eventually the brain. This process is called Phototransduction and human vision has four essential types of opsin: one for rods and three for the cones. In your photoreceptors (your rods and cones), opsins are coupled with vitamin A (found in carrots). Vitamin A acts as a light absorbing molecule; after absorbing light its molecular structure changes and it separates from the opsin. As this separating occurs, an electrical signal is generated by the opsin in a very complex biochemical process known as the visual cycle.

Organelles

An organelle is a specialized part of a cell which has a special function. Organisms are composed of cells, and these cells have specific structures within in them that allow them to carry out their functions. These structures are called Organelles Organelles perform different functions within a cell, and this is called the Division of Labour.

- Nucleus –The nucleus contains nearly all of the cell's genetic material as it holds the DNA

- Nucleolus – makes rRNA which is needed to create ribosomes

- Ribosomes – read the DNA and translate it into amino acids to create peptide chains

- Rough Endoplasmic Reticulum – takes the peptide chains and modifies them (e.g. by adding for carbohydrate chains) and transports proteins that are synthesised in the ribosomes

- Smooth ER – makes lipids, carbohydrates and steroid hormones (all other compounds of the cell that aren’t proteins)

- The Golgi Apparatus is a stack of membrane bound flattened sacs, and are responsible for the modification of proteins received from the ER. These proteins are then packaged into the vesicles

- Vesicles – move substances around the cell and instrumental in carry substances to and from the cell surfaceL

- Lysosomes are membrane bound spherical sacs which contain digestive enzymes used to break down materials

- Centrioles – structures from which microtubules arise for the process of cell division/replication

- Microtubules – structural scaffolding for cell support and highways along which vesicles can move

- Cytoplasm – gel like substance mainly water which all structures of the cell sit in

Blood and

Lymphatics

CNS & Afferent - Efferent

Our nervous system is divided into two parts. The central nervous system includes the brain and the spinal cord. The peripheral nervous system consists of a network of neurons, which spans the organs, the muscles and the body. The neurons in both systems work together to help us think, survive and act on the world around us.

Our nervous system has different types of neurons that are constantly at work. Neurons that receive information from our sensory organs (e.g. eye, skin) and transmit this input to the central nervous system are called afferent neurons. Neurons that send impulses from the central nervous system to your limbs and organs are called efferent neurons. Therefore, as the afferent neurons convey the sensory stimulus to the brain (like burning sensation of a candle), the efferent neurons convey the motor stimulus to the muscles.