Endo 5 Flashcards
1
Q
Where are the adrenal glands located?
A
- superior poles of kidneys
- one on left and one on right
- yellow in colour because there is a lot of cholesterol here to make lipophilic hormones
2
Q
What are the three layers of the cortex?
A
- zona glomerulosa
- zona fasciculata
- zona reticularis
- from superficial to deep, they are responsible for salt, sugar, and sex
3
Q
What is the deepest layer of the adrenal gland?
A
- adrenal medulla
- releases catecholamines into the blood during sympathetic response
- cells are modified post ganglionic neurons of sympathetic nervous system
4
Q
What is the function of the zona glomerulosa?
A
- primary product is aldosterone
- aldosterone is a mineralocorticoid
- corticosteroid responsible for minerals, in particular sodium potassium balance
- talks to kidneys in the tubules when it is creating filtrate and signals for sodium to come back into the body
- water follows it so helps to maintain electrolyte and fluid balance in body
- adjusts blood pressure and blood volume
- release controlled by renin-angiotensin-aldosterone (RAA) pathway
5
Q
How is aldosterone release regulated?
A
- RAA pathway by negative feedback
- stimulus: decrease in blood pressure (directly related to dehydration, Na deficiency, hemorrhage, decrease in blood volume)
- sensed by juxtaglomerular cells in kidneys
- they release renin which goes into circulation and renin works on angiotensinogen (made by liver, but it’s inactive until you break it up) and turns it into angiotensin 1
- angiotensin 1 circulates until it passes capillary beds in lungs where endothelial cells have ACE (angiotensin converting enzyme)
- ACE turns it into angiotensin 2
- angiotensin 2 releases aldosterone so kidneys reabsorb sodium in filtrate and retain water to boost blood volume and pressure
- angiotensin 2 also constricts vascular smooth muscle so blood pressure goes up
- once BP goes up, feeds back on JG cells and stops renin release
6
Q
What is the function of the zona fasciculata?
A
- secretes glucocorticoids (stress hormones)
- main effect on glucose homeostasis and promote hyperglycemia
- includes cortisol, cortisone, corticosterone
- glucocorticoids have the following effects: promote protein breakdown in tissues (mostly lean muscle), enhance lipolysis in adipocytes, promote glucose formation using proteins that have been broken down and fats (liver makes new glucose)
- puts it into circulation to get to tissues
- promotes resistance to stress to mobilize energy stores
- suppresses non essential things in body: anti-inflammatory and immunosuppressive (when people are stressed and release cortisol, become susceptible to colds/infections)
- suppresses other non essential functions: growing/repairing tissues
7
Q
How is cortisol release controlled?
A
- controlled by HPA axis
- in hypothalamus, low cortisol or stressors (blood glucose, pH, something external, perceived threat, thoughts/emotions) will signal for corticotropin releasing hormone (CRH)
- CRH travels down pituitary portal system to ant pituitary where adrenocorticotropic hormone is released (ACTH)
- gets to adrenal cortex and causes release of cortisol
- cortisol will give various tissue effects
- elevated cortisol inhibits release of ACTH and CRH
- BUT as long as stressors are present, this will trump everything
- in adrenal medulla, get release of catecholamines as well
8
Q
What is the function of the zona reticularis?
A
- secretes androgens
- main one is DHEA (dehydroepiandrosterone)
- in post pubertal males, adrenal androgen secretion is less than testicular androgen production (in form of testosterone)
- in females, adrenal androgens contribute to libido (has effects on hypothalamus) and some are converted to estrogens by other tissues (peripheral conversion)
- menopause occurs when ovaries stop producing follicles/generating estrogen but there are still androgens being made to adrenal cortex that get converted to estrogens so there is still some source of estrogen in body
9
Q
How is release of androgens controlled?
A
- CRH released from hypothalamus
- ACTH release from ant pituitary
- stimulates reticularis to release androgens
- accounts for 5% of androgens in body
- no negative feedback
- cortisol is the hormone that is shutting this system down by negative feedback
10
Q
What is the function of adrenal medulla?
A
- modified sympathetic ganglia (post ganglionic neurons of symp nervous system)
- turn into epithelial cells
- put product into bloodstream
- direct neuronal connection during symp response and catecholamine release right into blood
- nerve impulses to sympathetic centres in spinal cord then to splanchnic nerve which innervates medulla
- mostly secretes epinephrine (20% norepinephrine)
- EP stimulates alpha and beta receptors (alpha get vasoconstriction, beta increases rate of contraction of heart)
- NE preferentially stimulates alpha 1
11
Q
How does the stress response occur?
A
- Alarm phase (fight or flight): EP released from adrenal medulla, cortisol released from adrenal cortex (mediated by sympathetic nervous system and at same time adrenal cortex releases cortisol- this takes minutes-hours to have effects)
- Adaptation: cortisol is elevated while adapting to stressors (lipolysis, protein, catabolism, gluconeogenesis), can adapt to the stress (cope with it and this system will shut off- a lot of it is perceived stress) or resist (maintain heightened energy state), cortisol suppresses functions that are non essential in a fight or flight response (eg. SLUDD, reproduction, growth, immunity)
- Exhaustion: can lead to illness/death if you can’t eliminate or cope with the stressor
12
Q
What are stressors?
A
- thoughts, emotions (limbic system feeds down to hypothalamus)
- somatosensations (pain stimulates hypothalamus)
- hot or cold environments
- toxins, infections
- hemorrhage (decrease in BP)
- drop in blood glucose levels
- anything else that disrupts homeostasis (eg. acid-base)
13
Q
What are eustressors? What are distressors?
A
- good stress; helps body prepare for a challenge
- distressors: promote exaggerated stress response that does not go away and becomes detrimental and alters homeostasis (can lead to illness)
- force hypothalamus to respond
- eg. chronic pain, dented family car, etc.
14
Q
What is a short term vs long term stress reponse?
A
15
Q
What are causes of adrenal gland diseases?
A
- largely due to insufficient or excess cortisol
- less common are disorders of aldosterone hypersecretion or medullary hypersecretion (releasing too many catecholamines all the time)
24
Q
What occurs to create hypersecretion of androgens?
A
- cholesterol is used to make intermediates and same enzyme converts those to aldosterone and cortisol
- issue in congential adrenal hyperplasia is that enzyme gene is mutated
- get lots of androgens
- deficiency drives pituitary to produce more ACTH
