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Regulatory Systems: Hormones & Homeostasis - Coggle Diagram
Regulatory Systems: Hormones & Homeostasis
Overview of the Endocrine System
A system of glands that secrete hormones directly into the bloodstream to regulate body functions.
Maintains homeostasis, regulates growth, metabolism, reproduction, and stress responses.
Hormone Effects and Regulation
Agonists
Compounds that mimic the action of natural hormones.
Example: Synthetic estrogen in birth control.
Antagonists
Compounds that block hormone action.
Example: Beta-blockers inhibit epinephrine effects.
Inhibition
Hormone decreases the activity of target cells.
Example: Somatostatin inhibits growth hormone.
Down-Regulation
Decrease in receptor number due to high hormone levels, reducing sensitivity.
Example: Insulin resistance in Type 2 diabetes.
Stimulation
Hormone increases the activity of target cells.
Example: TSH stimulates thyroid hormone release
Up-Regulation
Increase in receptor number due to low hormone levels, enhancing sensitivity.
Example: Increased oxytocin receptors during labor.
Major Endocrine Glands and Hormones
Pancreas
Location: Behind stomach.
Hormones:
Insulin → Lowers blood glucose by promoting uptake.
Glucagon → Raises blood glucose by stimulating glycogen breakdown.
Gonads
Testes (Male):
Hormone: Testosterone.
Function: Sperm production, secondary sex traits.
Ovaries (Female):
Hormones: Estrogen, Progesterone.
Function: Egg development, menstrual cycle, pregnancy support.
Pineal Gland
Function: Regulates circadian rhythms and sleep-wake cycles.
Hormone: Melatonin.
Location: Deep in brain.
Parathyroid Glands
Location: Behind thyroid.
Hormone: PTH (Parathyroid Hormone).
Function: Raises blood calcium by stimulating bone breakdown and increasing calcium absorption.
Thymus
Location: Upper chest, behind sternum.
Hormone: Thymosin.
Function: Promotes T-cell development for immune response.
Adrenal Glands
Location: On top of kidneys.
Adrenal Cortex:
Cortisol → Manages stress and metabolism.
Aldosterone → Regulates sodium and water balance.
Adrenal Medulla:
Epinephrine & Norepinephrine → Activate fight-or-flight response.
Hypothalamus
Location: Inferior medial brain region.
Function: Regulates pituitary gland via releasing/inhibiting hormones.
Hormones
GHRH → Stimulates GH.
GHIH → Inhibits GH.
TRH → Stimulates TSH.
CRH → Stimulates ACTH.
GnRH → Stimulates FSH & LH.
PRH → Stimulates prolactin.
PIH (dopamine) → Inhibits prolactin.
Pituitary Gland
Location: Below hypothalamus, in sphenoid bone.
Posterior Pituitary Hormones:
Oxytocin → Stimulates uterine contractions and bonding.
ADH → Promotes water retention in kidneys.
Anterior Pituitary Hormones:
GH → Stimulates growth and metabolism.
TSH → Stimulates thyroid hormone production.
ACTH → Stimulates adrenal cortex to release cortisol.
FSH & LH → Regulate reproductive processes.
Prolactin → Stimulates milk production.
Thyroid Gland
Location: Neck, below larynx.
Hormones:
T3 & T4 → Regulate metabolism and energy usage.
Calcitonin → Lowers blood calcium by inhibiting bone resorption.
Comparison
Slower but longer-lasting effects than the nervous system
Communication Pathways
Endocrine Signaling
Hormones are secreted directly into the bloodstream and travel to distant target cells to regulate physiological processes.
Example: Insulin from the pancreas affects glucose uptake in muscles.
Exocrine Signaling
Substances are secreted through ducts to external or internal surfaces.
Example: Salivary glands secrete saliva into the mouth.
Paracrine Signaling
Chemical signals affect nearby cells without entering the bloodstream.
Example: Growth factors influencing neighboring cells during wound healing.
Autocrine Signaling
Cells release signals that act on themselves, often for self-regulation.
Example: Immune cells releasing cytokines that act on themselves.
Neuroendocrine Pathway
Neurons release hormones into the bloodstream.
Example: Hypothalamus releasing TRH to stimulate pituitary.
Types of Chemical Messengers
Neurotransmitters
Chemical messengers released by neurons to transmit signals across synapses.
Example: Dopamine, serotonin.
Hormones
Steroids: Lipid-soluble hormones derived from cholesterol.
Examples: Cortisol, estrogen.
Polypeptides: Chains of amino acids.
Examples: Insulin, growth hormone.
Amines: Derived from amino acids like tyrosine.
Examples: Epinephrine, thyroxine.
Other Hormone-like Compounds
Includes prostaglandins and nitric oxide, which act locally to regulate physiological functions.
Hormone-Receptor Interactions
Water-Soluble Hormones
Bind to receptors on the cell membrane and activate signal transduction pathways using second messengers like cAMP.
Example: Epinephrine.
Lipid-Soluble Hormones
Pass through the cell membrane and bind to intracellular receptors, directly influencing gene expression.
Example: Testosterone.
Overview of the Urinary System
The urinary system removes waste and excess substances from the blood and helps maintain the body's fluid and electrolyte balance by producing and excreting urine.
Organs Involved
Kidneys
Filter blood, remove waste, regulate water and salt balance, produce hormones.
Nephron Structure and Function
Nephron: Microscopic functional unit of the kidney (~1 million per kidney).
Parts
Renal Corpuscle:
Glomerulus
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Proximal Convoluted Tubule (PCT):
Reabsorbs glucose, amino acids, ions, and water.
Example: 65% of sodium and water reabsorbed here.
Loop of Henle:
Descending limb: Permeable to water → water reabsorbed.
Ascending limb: Impermeable to water → salts reabsorbed.
Establishes osmotic gradient (countercurrent multiplier).
Distal Convoluted Tubule (DCT):
Fine-tunes ion balance and pH via secretion and reabsorption.
Responsive to aldosterone.
Collecting Duct:
Final concentration of urine.
Responsive to ADH for water reabsorption.
Delivers urine to renal pelvis.
Papillary Duct:
Collects urine from multiple nephrons → minor calyx → renal pelvis.
Kidney Processes
Filtration
Occurs in glomerulus.
Blood pressure forces plasma into Bowman's capsule.
Example: Removal of urea, excess ions, and water.
Reabsorption
Occurs in PCT, Loop of Henle, DCT.
Nutrients and water reabsorbed into blood.
Example: Glucose reabsorbed in PCT; water reabsorbed in descending limb.
Secretion
Active transport of waste into tubules.
Example: Hydrogen ions secreted to regulate blood pH.
Excretion
Urine expelled via ureters → bladder → urethra.
Ureters
Muscular tubes that carry urine from kidneys to bladder.
Bladder
Hollow organ that stores urine until excretion
Urethra
Tube that releases urine from the bladder to the outside.
Other Excretory Organs
Skin: Excretes salts and water via sweat.
Lungs: Excrete carbon dioxide.
Excretion vs. Elimination:
Excretion
Removal of metabolic waste (e.g., urea).
Elimination
Removal of undigested food (via digestive tract—not considered excretion).
Nitrogenous Waste
Source
Breakdown of proteins and nucleic acids during metabolism.
Types
Ammonia (NH₃): Highly toxic; requires large amounts of water to excrete—used by aquatic animals.
Urea: Less toxic; soluble in water—used by mammals.
Uric Acid: Least toxic; excreted as paste—used by birds and reptiles.
Why It Matters:
Nitrogenous waste must be removed to prevent toxicity.
Example: Bird droppings contain uric acid, which is corrosive to car paint.
Osmoregulation
Definition: Regulation of water and solute concentrations to maintain internal balance.
Osmosis: Movement of water across membranes from low to high solute concentration.
Example: Salt on a slug draws water out, dehydrating it.
Osmolarity:
Solute concentration in a solution (measured in milliosmoles per liter, mOsm/L).
Strategies
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Adaptations in Other Animals
Vampire Bats: Excrete dilute urine while feeding (to reduce weight), then concentrate urine later.
Birds/Reptiles: Excrete uric acid as paste to conserve water.
Freshwater Fish/Amphibians: Excrete large volumes of dilute urine to eliminate excess water.
Marine Fish: Drink seawater and excrete concentrated urine; use gills to excrete salt.
Countercurrent Multiplier System
Location: Loop of Henle.
Function: Creates osmotic gradient in renal medulla.
Mechanism:
Descending limb loses water.
Ascending limb pumps out salts.
Gradient allows collecting duct to reabsorb water efficiently.
Hormonal Regulation
Antidiuretic Hormone (ADH)
Produced by hypothalamus, released by posterior pituitary.
Triggered by high blood osmolarity or dehydration.
Increases water reabsorption in collecting ducts.
Effect: Concentrated urine, reduced water loss.
ADH blockers: Cause increased urination and dehydration
Renin-Angiotensin-Aldosterone System (RAAS)
enin-Angiotensin-Aldosterone System (RAAS)
Triggered by low blood pressure or low sodium.
Renin (from kidneys) → activates angiotensin → stimulates aldosterone (from adrenal cortex).
Aldosterone increases sodium reabsorption → water retention → raises blood pressure.
Effect: Restores blood volume and pressure.
Erythropoietin (EPO)
Produced by kidneys in response to low oxygen levels.
Stimulates red blood cell production in bone marrow.
Clinical use: Treat anemia in kidney disease.
Calcitriol (Active Vitamin D)
Synthesized in kidneys from vitamin D precursors.
Enhances calcium absorption in intestines.
Effect: Maintains bone health and calcium balance.