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)
Tropic Hormones
hormones that regulate the function of other endocrine cells or glands
Non-tropic Hormones
targets non-endocrine tissues
Adrenal Gland
- sits atop kidney
- contains adrenal cortex (endocrine)
- inside cortex is adrenal medulla (neural)
Adrenal Cortex
- contains endocrine cells
- releases corticosteroids: mineralcortocoids (aldosteroneO and glucocorticoids (cortisol)
Adrenal Medulla
- modified neural cells
- releases catecholamine (amine hormone): epinephrine (adrenaline) and norepinephrine (noradrenaline)
- trigger fight or flight response
Hypothalamus and Stress
Hypothalamus detects stress and reacts in two ways
1) Autonomic nervous signal to adrenal medulla (short term)
- Adrenal medulla secretes epinephrine and norepinephrine
- Binds to alpha or beta receptor
- In liver: glycogen to glucose
- In smooth muscle: blood vessels dilate to increase flow to skeletal muscle or blood vessels constrict to restrict flow to intestine
2) Neuroendocrine signal (CRH) to anterior pituitary (long term)
- anterior pituitary secretes ACTH
- adrenal cortex releases corticoids
- cortisol enables body to maintains steady supply of blood sugar
Short Term Stress Response
Epinephrine and norepinephrine
1) glycogen broken down to glucose to increase blood glucose
2) increase blood pressure, breathing and metabolic rate
3) change in blood flow patterns leading to increased alertness and decreased digestive, excretory and reproductive system activity
Long Term Stress Response
Mineralocorticoids:
1) retention of Na+ and water by kidneys
2) increases blood volume and pressure
Glucocorticoids:
1) proteins and fats concerted to glucose to increase blood glucose
2) possible suppression of immune system
Components of Homeostatic System
Set point: target value of a parameter
Sensor: perceives changes in some parameter of environment
Integrator: sends instructions to effector based on sensory information
Effector: responds to change in parameter of environment
Adrenocorticotropic hormone (ACTH) triggers the release of _____ in response to stress.
glucocorticoids
_____ are the main male hormones.
Androgens, such as testosterone, are the main male hormones.
What hormone promotes water retention by the kidneys?
antidiuretic hormone (ADH)
A diuretic promotes water loss; thus it makes sense that ADH (secreted by the anterior pituitary) promotes water conservation.
Which hormone opposes the action of parathyroid hormone?
Parathyroid hormone increases blood calcium levels; calcitonin lowers blood calcium levels.
Which hormone stimulates hormone production by the ovaries and testes?
luteinizing hormone (LH) stimulates hormone production by both the ovaries and testes.
Which hormone stimulates milk production?
Prolactin, secreted by the anterior pituitary, stimulates milk production by the mammary glands.
