MODULE 5: Endocrinology Flashcards
Types of Hormones
Polypeptides:
- ribbon structures
- chain of aa’s
- e.g. insulin
- hydrophilic
Steroids:
- 4 ring structure
- all come from cholesterol
- e.g. cortisol
- hydrophobic
Amines:
- small modification of aa
- e.g. adrenaline and thyroxines
- some hydrophilic some hydrophobic
Receptor Location
- varies with hormone type
- hydrophilic –> receptor in plasma membrane
- released via exocytosis
- float through blood stream and find target cell
- identify and bind to target cell surface receptor
- lipidphilic –> receptor in cytoplasm or nucleus
- diffuses through membrane
- attaches to transport proteins to travel through blood
- diffuses through target cell membrane and binds to intracellular receptor, forming hormone-receptor complex
Negative Feedback Loop
- restore homeostasis
Stimulus –> endocrine gland –> hormone –> target tissue –> response
neg feedback = reduce stimulus
pos feedback = reinforce stimulus
Hormone Cascade Pathway
- sensory neuron detects stimulus
- causes endocrine gland to secrete hormone into blood vessel via neurosecretory cell
- hormone finds target cell and binds to activate production of another hormone
- hormones reach body tissues to produce response
- negative feedback loop stops hormone production to restore homeostasis
Hormone Cascade Pathway (Cold)
- hypothalamus detects cold
- hypothalamus secretes thyrotopin-releasing hormone
- anterior pituitary secretes thyroid-stimulating hormone
- thyroid gland secretes thyroid hormone
- thyroid hormone increases cellular metabolism –> increases body temp
Blood Glucose Levels: After a Meal
- homeostasis: blood glucose level ~ 90mg/100mL
- stimulus: blood glucose level rises after eating meal
- beta cells of pancreas release insulin into blood
- –> body cells take up more glucose || liver takes up glucose and stores as glycogen
- –> blood glucose level declines
- –> homeostasis
Blood Glucose Levels: Missing a Meal
- homeostasis: blood glucose level ~ 90mg/100mL
- stimulus: blood glucose level declines after missing a meal
- alpha cells of pancreas release glucagon into blood
- –> liver breaks down glycogen into glucose
- –> blood glucose level rises
- –> homeostasis
Diabetes Mellitus
Type 1:
immune system destroys pancriatic beta cells
Type 2:
insulin deficiency of reduced response of target cells due to change in insulin receptors
Blood Pressure
- normal blood pressure and volume
- blood pressure and volume drops (dehydration/blood loss)
- sensors in JGA detect decrease
- JGA releases renin
- liver –> angiotensinogen –> angiotensis I –> angiotensis 2
- arterioles constrict and increase blood pressure || adrenal gland secretes aldosterone to increase Na+ and H2O absorption in distal tubes to increase blood volue
- normal blood pressure and volume
Endocrine Glands in Human Brain
- hypothalamus and pituitary gland
- posterior pituitary: extension of neural tissue (dry)
- anterior pituitary: many different kinds of cells, containing lots of capillaries (rich/pink)
Posterior Pituitary Hormones
ADH —> kidney tubes
Oxytocin —> mammary glands and uterine muscles
Hypothalamus secretes oxytocin which is released through posterior pituitary gland
Anti Diuretic Hormone (ADH)
- short polypeptide hormone
- ADH attaches to kidney cell via GPCR
- takes up water from urine via aquaporin channel
- transports water to blood stream to reduce blood osmolarity
- negative feedback loop
Diabetes Insipidus
- mutations that prevent ADH production or inactive ADH receptor gene
- mutations in squaporin gene
- severe consequences: dehydration, solute imbalances (because increase urine volume)
- alcohol can also inhibit ADH release
Portal Circulation
network of capillaries, portal vessels, another network of capillaries
Anterior Pituitary Hormone
- contains lots of blood vessels (pink)
- portal circulation
- regulated by hypothalamus
- hypothalamic hormones travel through portal circulation
- can be stimulating or inhibiting (lots of different cells)
- has tropic and non-tropic effects (some both: growth hormone)