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Chapter - 45: Endocrine System & Hormones
Transcript of Chapter - 45: Endocrine System & Hormones
Exocrine glands have specific DUCTS that carry the secreted substances onto body surfaces or into body cavities There are many types of signaling molecules, including: Hormones, Local Regulators, Neurotransmitters, and Pheromones Hormones are secreted into extracellular fluids by endocrine cells which reach target areas via the bloodstream (or hemoglyph).
Some are found in organs that are part of other organ systems.
They serve a range of functions, including: maintaining homeostasis; mediating responses to environmental stimuli; and regulating growth, development, and reproduction.
For example they coordinate responses to stress & dehydration. Local Regulators are secreted molecules that act over short distances and reach their target cells solely by diffusion.
Local regulators play roles in many processes, including blood pressure regulation, nervous system function, & reproduction.
They function in the paracrine and autocrine signaling. Paracrine targets nearby cells autocrine acts upon the secreting cell itself.
Cytokines are local regulators HORMONES LOCAL REGULATORS Overview Hormone: a molecule secreted to communicate regulatory messages throughout the body Hormones only elicit responses from target cells; this is because target cells have specific receptors for that particular hormone The human body has two long-distance regulating systems; the endocrine system and the nervous system Endocrine system: involves chemical signals by hormones Nervous system: involves chemical signals by neurotransmitters Concept 45.2 Negative feedback and antagonistic hormone pairs are common features of the endocrine system Negative feedback loop: where the response to a stimuli reduces the process which originally stimulated it Insulin: a hormone secreted by Beta cells (β) which triggers the uptake of glucose from the blood glucagon: a hormone secreted by Alpha cells (α) which promotes the release of glucose into the blood Diabetes mellitus: condition where blood glucose levels rise but cells still can't take enough up; this causes fat to become the main substrate for cell respiration Type 1 diabetes: (insulin dependent) destroys the body's ability to produce insulin; correlated with onset as a child Type 2 diabetes: (non-insulin dependent) failure of target cells to respond normally to insulin, correlated with obesity and onset as an adult due to dietary habits NEUROTRANSMITTERS & NEUROHORMONES Transmit information by neuron
Communicate with target cells at specialized junctions called synapses
Neurons secrete neurotransmitters at these synapses, which diffuse a short distance to bind to receptors on the target cells
Important for sensation, memory, cognition, and movement
In neuroendocrine signaling neurosecretory cells (specialized neurons typically found in the brain) secrete molecules (neurohormones) from nerve cell endings through the bloodstream
ADH(vasopressin) is a hormone critical to kidney function and water balance (Recall Ch. 44) PHEROMONES Pheromones are chemicals that are released into the external environment.
Mark trails that lead to food, define territories, warn of predators, and attract potential mates.
Queen bees release the Queen Mandibular Phermone (QMP) that ensures that the queen is the only reproductive female in the hive by affecting the reproductive systems of worker bees. It's also an attractive signal and when it's lacking robber bees come.
Endocrine: Fluids to anywhere
Paracrine: Local, neighbors
Autocrine: Local, self
Synaptic: Neurons across synapses to target
Neuroendocrine: Neuron across synapse to bloodstream to targets (anywhere) Secreted molecules vary based on type and location of the cells involved.
Hormones are ALSO divided based on structure and pathway for synthesis Three main groups: Polypeptides (proteins and peptides), amines, & steroids.
These 3 groups are split into 2 classes of hormones Water Soluble Lipid Soluble
Receptors located INSIDE target cells.
Proven by rat estrogen experiment. Only accumulate in the cells of tissue that are responsive.
Receptors located on the SURFACE of target cells.
Hypothesized and then proven by Horowitz at Davis with frog melanocyte-stimulating hormone. Y? Think about the cell membrane.
Lipid soluble diffuse through the lipid bilayer and reach the inside of the cell.
Water Soluble are unable to pass through the bilayer and are forced to hang around the outside. WATER SOLUBLE Secreted via exocytosis, travel freely through the bloodstream, and bind to cell surface signal receptors.
Can lead to either changes in cytoplasmic function or gene expression.
Examples: Melanocyte-stimulating hormone in frogs. Controls location of pigment granules in skin cells. Epinephrine, insulin. LIPID SOLUBLE Diffuse across the membranes of endocrine cells and travel through bloodstream to transport proteins. When they diffuse into target cells they bind to intracellular signal receptors.
Trigger changes in gene transcription.
Examples: Estradiol, cortisol Epinephrine is secreted by your adrenal glands. It then reaches the liver cells. Once that happens it binds to a G coupled receptor in the plasma membrane which triggers a cascade of events involving the synthesis of cAMP as a second messenger. cAMP activates protein kinase A which leads to activation of an enzyme required for glycogen breakdown and inactivation of an enzyme required for glycogen synthesis.
In the end the liver releases glucose into the bloodstream which provides you with the fuel needed to deal with the situation. The hormone (in this case steroid) activates the receptor, which directly triggers the cell's response.
It binds to the receptor, forming a hormone-receptor complex.
The receptor portion then interacts w/ DNA or the binding protein, stimulating transcription.
Following the translation of the mRNA it is secreted and transported in the blood.
Fun fact: Vitellogenin is the steroid. It's used in the reproductive system to make egg yolks. Yay. Hormones can have several different effects. This is possible because of the variety of target cells. Target cells can differ in the molecules that receive or produce the response to the hormone. If the cells differ the tissues differ, which varies their responses because of the difference in their receptors or signal transduction pathways. Local Regulators are cool They're super fast even though they use the same pathways as hormones. Nitric Oxide (NO) is a nitrogen double bonded to oxygen.
When the level of oxygen drops NO is synthsized and released. NO activates an enzyme which relaxes the neighboring smooth muscle tissue which improves blood flow to tissues. It produces erections by increasing blood flow.
NO is usually highly reactive&toxic, and normally reacts & breaks down within a few seconds.
Viagra is able to interfere with the breakdown of NO, which leads to sustained erections.
Prostaglandins are another type of local regulator. Named such because they were first found in prostate gland secretions that contribute to semen. In females it causes contractions, fever, inflammation, and the intensification of pain. However, they also regulate the aggregation of platelets which is rather important.
Fun fact: Aspirin inhibits prostaglandin synthesis. The End Presentation by Your mum likes this Concept 45.3 The Endocrine and Nervous Systems act individually and together in regulating animal physiology Signals from the nervous system initiate and regulate endocrine signaling Example: Caterpillar development The signals that control development originate in the brain Neurosecretory cells produce a peptide (PTTH) that causes the release of another chemical (Ecdysone) Ecdysone is what promotes the molting and allows the butterfly to metamorphize Corpata Allata secretes a third signalling molecule, juvenile hormone, that determines when metamorphosis takes place by maintaining larval characteristics Hypothalamus is very important Plays a central role in both Endocrine AND Nervous systems RECEIVES information from nerves and in response INITIATES the appropriate endocrine signaling. Hypothalamus Pituitary Gland Posterior Pituitary - grows towards the mouth, stores & secretes 2 hormones made by the Hypothalamus Anterior Pituitary - grows upward towards the brain. Hormones released by the hypothalamus regulate secretion of hormones by anterior pituitary AO- Posterior Anterior - More of them - FLAPGAT or FLAT GAP Growth Hormone (GH)
Folicle Stimulating Hormone (FSH)
and Luteinizing Hormone (LH)
Thyroid Stimulating Hormone (TSH)
T3 and T4
Estradiol Anterior Pituitary Regulated by Hypothalmic Hormones.
Stimulates growth and metabolic functions. Regulated by Hypothalmic Hormones.
Stimulates milk production & secretion. Lactin-Milk Regulated by Hypothalmic Hormones.
Stimulates production of sex cells.
FSH- ova & sperm, LH - ovaries and testes.
FSH - fish, swimming, sperm. LH - Lord, anyone who addresses themself as "lord" Regulated by Hypothalmic Hormones.
Stimulates the thyroid gland. Pancreas Regulated by Glucose in blood.
Lowers blood glucose level. Think diabetes. Thyroid Regulated by Glucose in blood.
Raises glucose level. Opposite of Insulin oxytocin is a hormone under positive regulation; when it's stimulated it's response is to activate the stimulus again Tropic Hormones: Hormones that regulate functions of endocrine cells/glands LH and FSH: regulate activities of male and female gonads ACTH: regulates production and secretion of steroid hormones PTH (parathyroid hormone) and calcitonin are two antagonistic controllers of blood calcium levels causes mineralized matter in bones to decompose and release Ca 2+ 2+ 2+ stimulates reabsorption in kidneys of Ca promotes the conversion of vitamin D to an active hormone that stimulates uptake of Ca glucocorticoids are effective in treating arthritis because of their anti-inflamatory effects, but their long term effects can disrupt normal metabolic activities Regulated by TSH.
Stimulates and maintains metabolic processes. Regulated by Ca in blood.
Lowers blood calcium levels. Regulated by Nervous System.
Raises blood glucose level; increases metabolic activities;
constricts certain blood vessels & Regulated by FSH and LH.
Promotes development and maintenance of male secondary characteristics (eg. voice) Adrenal Medulla Gonads Parathyroid Adrenal Cortex A type of glucoprotein, it raises blood glucose level and is regulated by ACTH.
It is released by the body as a reaction to stress. They elevate blood pressure and prepare the body for a fight or flight response. Regulated by FSH and LH.
Stimulates growth of reproductive organs;
Promotes development of secondary characteristics.
Regulated by Ca in blood.
Raises blood calcium level Stimulates cells in the kidneys to reabsorb sodium and water, raising blood pressure and volume Breaks down muscle proteins and converts them to glucose which is then released into the blood. HORMONES ENDOCRINE Lipid Soluble Water Soluble