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Bio 20 - Teacher: The Circulatory System
Meaghan McKenzieon 23 June 2013
Transcript of Bio 20 - Teacher: The Circulatory System
Transports gases (respiratory system), nutrients (digestive system), and waste products (excretory system).
Regulates internal temperature and transports hormones.
Protects against blood loss from injury (platelets) and against disease causing microbes or toxic substances (white blood cells).
Pumping blood through the body
Keeping oxygen-rich blood separate from oxygen-poor blood
Ensuring that blood only flows in one direction through the body
Atria (plural):2 small chambers where the blood enters the heart (atrium - singular)
Ventricles: 2 large chambers where the blood is pumped to the body/lungs
Septum: thick, muscular wall that separates the atria and ventricles
Valves: prevent backflow of the blood inside the heart
Vena cavae (s: vena cava): carry oxygen-poor blood from the body to the heart.
Pulmonary Arteries: carry oxygen-poor blood from the heart to the lungs.
Pulmonary Veins: carry oxygen-rich blood from the lungs to the heart.
Aorta - carries oxygen-rich blood from the heart to the body
What is it?
Cardiac muscle that pumps blood
About the size of two fists
Located slightly to the left of the middle of your chest
Major Blood Vessels
arteries = away from heart
What is Blood Pressure?
SA Node (sinoatrial): Stimulates the atria of heart to contract simultaneously. Known as the pacemaker of the heart - sets the pace for cardiac activity.
AV node (atrioventricular): transmits electrical signal through a bundle of fibers called the bundle of his
Perkinje fibers: fast conducting fibers that stimulate the muscles of the ventricles to contract.
**Why can't the heart have one signal to contract?
Pressure exerted by the blood when the heart contracts.
Blood fills the atria.
Pressure exerted by the blood vessels when the heart relaxes.
Blood fills the ventricles
The Heart Beat
The stimulus that triggers a heartbeat is an electrical signal that originates from within the heart itself:
Records the electrical activity of the heart.
Blood Pressure: blood exerting pressure on vessel walls.
Two types of pressure:
Systolic: maximum pressure when ventricles contract. (S=squeeze)
Diastolic: Lowest pressure before the ventricles contract again.
AV valves are closed (prevents blood backflow into the atria).
SL valves are open (blood is squeezed into arteries).
AV valves are open (blood is squeezed from atria into ventricles).
SL valves are closed (prevents blood from flowing into arteries).
Blood pressure is measured by a sphygmomanometer (has a blood pressure cuff.
Healthy blood pressure for a student is about 120/80mm Hg and below.
Blood pressure is measured in millimeters of mercury (e.g.120/80 mm Hg) for systolic/diastolic.
There are three kinds of blood vessels:
carry the blood away from the heart
Return the blood to the heart.
where the exchange of nutrients,gases, and wastes takes place.
Are HIGHLY ELASTIC:
Expand as blood surges through when ventricles contract.
Snap back into shape when ventricles relax.
Grow a Heart!
Not as elastic as arteries.
Contain valves to keep blood flowing in right direction. (Veins have Valves). Works against gravity.
+ Skeletal Muscle (contracting walls of veins) + Valves (preventing backflow)
= the flow of blood in veins.
Walls are a SINGLE layer of cells.
Usually only ONE blood cell at a time flows through.
The cells that make up living tissues are a distance of 1-3 cell widths from a capillary.
Why do you think that this is necessary?
Blood flow is slower in capillaries = allows time for diffusion.
Direction of diffusion is determined by the material's concentration gradient.
Why do you think that the muscular walls of the atria might not be as thick as the walls of the ventricles?
Which of the ventricle walls do you suppose might be thicker?
This action keeps blood flowing in the right direction. Also provides additional pumping motion.
Your pulse is an artery!
The amount of blood pumped by the heart (L/min).
Indicates the level of oxygen delivered to the body and the amount of related muscle performance.
= heart rate x stroke volume
Heart rate: beats per minute (average person 70 beats/min)
Stroke volume: the volume of blood entering/leaving the ventricles (average person 70mL)
Average cardiac output: 4900ml/min
Most fit: Have a low resting heart rate and a high stroke volume => heart is very efficient
Regular cardiovascular exercise will increase the stroke volume and enlarge the ventricular chambers.
Blood vessels carry blood along 3 different pathways:
Pulmonary pathway (to the lungs)
Systemic pathway (to the body)
Coronary pathway (to the heart)
Cardiovascular Disorders and Treatments
General term to describe several conditions.
The walls of the arteries thicken and lose some of their elastic properties.
Arteries become harder.
Most common type of arteriosclerosis.
Build-up of plaque (fatty deposits, calcium, and fibrous tissues) on the inside of artery walls.
Blood flow is decreased, blood pressure is increased.
May lead to chest pain (angina), blood clots, shortness of breath, heart attack, or heart failure.
Reduce the risk of developing this condition:
Eat a diet low in saturated fats/high in fruits and veggies
anti-blood clotting medicine (e.g. Aspirin)
medicine to break down clots
angioplasty (force open the artery by inflating a tiny balloon)
stent (permanent metal tube - holds the vessel open)
Use arteries or veins from other parts of the body to bypass clots
Creates a new pathway around a blocked vessel in the coronary pathway.
Due to valves not opening/ closing properly.
Can be heard using a stethoscope = whooshing/ rasping sound
Congenital defects - present since birth.
Acquired defects - arise later in life.
Sometimes called a connective tissue because it links all the cells and organs in the body.
Considered a tissue even though it appears to be fluid.
Consists of 2 distinct elements:
Fluid - plasma: water + dissolved gases, proteins, sugars, vitamins, minerals, hormones, and waste products.
55% of blood.
Solid - the "formed portion": red blood cells, white blood cells, and platelets.
45% of blood.
Red Blood Ce s
Also called erythrocytes (red cell).
Biconcave disk; has no nucleus.
Specialized for oxygen transport.
Contains hemoglobin pigments.
A respiratory pigment that contains iron.
Around 250 000 000 pigments/RBC
Chemically binds with oxygen.
Oxygen is released in capillaries and it diffuses into cells.
Small amount of carbon dioxide is also carried.
Condition where there are too few RBC's or too little pigment inside the RBC's.
= Reduced amount of oxygen carried to the body.
May be caused by dietary deficiency.
White Blood Cells
Also called leucocytes (white cell)
About 1% of blood volume
% may double when body is fighting disease.
All WBC's have nuclei.
3 Groups of WBC's:
consist of: neutrophils, basophils, and eosinophils
Can leave the bloodstream.
May become further specialized as macrophages, which destroy invaders.
Granulocytes and monocytes are both found in circulating blood.
Both engulf (eat) and destroy invaders.
Fragments of cells that form when large cells in the bone marrow break apart.
Contain NO nucleus. Break down quickly in blood.
Play a key role in clotting blood, preventing excessive blood loss.
Involved in a complex cascade of cellular events triggered by injury.
Fibrin is insoluble.
Forms a mesh of strands around the injured area, trapping escaping blood cells and forming the clot.
Collecting platelets rupture and release chemicals that combine with other blood components to produce thromboplastin (enzyme).
In presence of Ca2+ ions, thromoplastin catalyzes the reaction that turns prothrombin (plasma enzyme produced by the liver) into thrombin.
Thrombin then catalyzes the reaction that turns fibrinogen into fibrin.
Besides carrying the formed portion of the blood, plasma contains proteins, nutrients, ions, waste products, and gases, such as carbon dioxide.
Carbon dioxide dissolves in the plasma (which is mostly water):
- forms carbonic acid inside red blood cells
- forms bicarbonate ions in plasma.
*these two act as a buffer to keep the blood at the right pH.
Carbon dioxide is carried from tissues to the lungs for gas exchange.
Transport (exchange in capillaries):
absorbs nutrients (e.g. glucose/amino acids) that are made available by digestion (small intestines) or synthesized by cells.
removes waste products of cellular processes (e.g. uric acid, carbon dioxide).
Blood is important for transporting materials, sending messages, and regulating heat and concentration of substances in the body.
Blood serves as a medium for conveying chemical messengers (hormones) from their origins to their targets.
Hormones play a central role in regulating and coordinating the internal systems of the body.
the body would be unable to respond effectively to fluctuations in its external or internal environment.
Chemicals released by damaged blood vessels attract platelets to the site.
Maintaining homeostasis is another important function of blood, especially in relation to temperature regulation.
Temperature regulation: balance heat production with heat loss.
Blood coming from the interior of the body is usually warmer than the skin.
As more blood passes by the skin, more heat is lost.
Rate of heat loss depends on the difference in temperature between the skin and the external environment.
The greater the heat gradient, the faster the heat is lost through the skin.
Body gets too warm = get rid of excess heat to maintain constant internal temperature.
Heat comes from cellular respiration and muscular activity.
Nervous system causes blood vessels to dilate = increased amount of blood flow to skin
= increased amount of heat that can be lost from the skin.
Vasodilation - skin will look more red.
Sweating is one way for the body to get rid of excess heat - the evaporation of water from the skin takes energy.
Dehydration can be a serious problem, especially with fevers.
When the external temperature is cold, heat energy needs to be conserved.
Blood vessels near the surface of the skin will contract.
This reduces the amount of heat that is dissipated from the skin.
too high - vasodilation
too low - vasoconstriction
Exercise - vasodilation
increased blood flow to muscles (containing glucose and O2)
Alcohol and nicotine promote vasodilation.
Counter-current heat exchange helps the body reuse heat in the blood.
Deep arteries and veins, which lie adjacent to one another, exchange heat so that the blood is warmed going back to the body core.
Insufficient amount of blood clotting proteins in the blood.
Constant danger of bleeding to death from minor injuries.
Treatment: injections containing the missing clotting factor.
*Prominent in European royalty - the "Royal Disease"
Cancer of the white blood cells.
2 main types:
Too many leucocytes, which are immature and unable to fight infection.
Crowd out RBC's, causing anemia and fatigue
similar symptoms to myeloid
cancer of the lymphocytes
Acute - symptoms appear suddenly, death follows quickly
Chronic - may go undetected for years (don't die right away)
Treatment - blood transfusions, chemotherapy, and bone marrow transplants (very painful, last resort)
Capillaries are present in networks, or "beds", throughout the body.
About 1 billion capillaries in the human body.
The blood flow through a capillary bed can be "turned on or off" depending on whether the nearby cells need nutrients.
Sphincters close to allow the blood to bypass these capillaries.
Happens during digestion.
- lower in capillaries than in arteries
- a little higher in capillaries than in veins (veins have the lowest pressure).
- blood travels from high => low pressure, = flows in one direction.
-decreases the further the blood is from the heart.
The exchange of materials between blood in a capillary and the fluid surrounding the individual cells in the body takes place across the wall of the capillaries.
The cells of the body are constantly bathed in a liquid called interstitial fluid (or extracellular fluid - ECF).
Any material changes must pass through this fluid.