Lecture 12 - Adrenal Gland Flashcards
Where is the adrenal gland located and what are the two parts of the gland?
- located right above the kidneys (there is a pair of adrenal glands as there is a pair of kidneys)
two parts made from two tissues:
Adrenal medulla = modified sympathetic ganglia (in the middle)
Adrenal cortex = steroid factory (around the middle)
what is the main catecholamine hormone that is release from the adrenal medulla?
what is the pathway from stimulus to release in blood of this main hormone?
- the adrenal medulla is a neural endocrine tissue
main hormone:
- the main hormone it produces = catecholamine (mainly epinephrine, some norepinephrine and dopamine)
- epinephrine is secreted in sufficient quality to exert effects thus main hormone
how is epinephrine released in the blood?
- stimulus: activation of the sympathetic nervous system (fight or flight system)
- the preganglionic sympathetic neuron extends from the spinal cord to the adrenal medulla
- the chromaffin cells in the adrenal medulla receives this signal and stimulate release of epinephrine in the blood vessels to the target tissues
short term stress:
how does epinephrine mediate the rapid short term stress response in the different organs of our body?
heart, respiratory system, brain, liver/fat, intestine/skin/kidney, muscles
- when we are in this stressful or ‘flight or fight’ situation, our body reacts in many ways and this is due to epinephrine
ex.
- heart: increases force of contraction –> beats faster
- respiratory system: bronchodilator –> dilated lungs give us more oxygen –> breathe faster
- brain: increase alertness
- liver/fat: glucose release/fatty acid release –> energy
- intestine, skin, kidney: muscle relaxation and arteriole contraction –> leads blood into more important organs (digestion in this situation is not important)
- muscle: muscles that are important (legs) contract, important ones constrict (stomach)
how does the epi pen take advantage of the properties of epinephrine to better response to allergens
severe allergic reaction = anaphylactic shock
- this reaction includes: bronchospasm (constriction of airways) –> respiratory failure, and a dangerous decrease in blood pressure
epi-pen counteracts these symptoms by promoting:
- Bronchodilation –> breathe better
- Vasoconstriction (intestine, skin, kidneys) –> moves blood to more important organs
- Vasodilation (skeletal and cardiac muscles) –> brings blood pressure back up
what are the parts of the adrenal gland from the outer layer all the way in and the hormones that each releases?
mention the 3 layers of the adrenal cortex
- Capsule - outer layer
- Adrenal cortex:
(a) zona glomerulosa –> aldosterone (mineralocorticoids)
(b) zona fasciculata –> glucocorticoids (cortisol)
(c) zona reticularis –> sex hormones (androgens) - Adrenal medulla –> catecholamines (epinephrine)
why do different zones in the adrenal cortex release different hormones?
- steroid hormones all start from one precursor –> cholesterol
- the cells in the different zones of the adrenal cortex contain different enzymes, which will effect the precursor and the intermediates into the different types of hormones
memorize the chart of how cholesterol can be changed to the different hormones produced by the adrenal cortex. list the enzymes that facilitate this reaction too
main hormone products: cotrisol, aldosteone, androstendione (sex hormones)
look at notes
androgens: what is the strength of androgens formed in the adrenal gland vs in the reproductive glands?
- reproductive organs are more responsible for creating the sex hormone in males and females
- therefore androgens (sex hormones) that are formed in the adrenal gland (zona reticularis) are very weak (less than 20% activity of testosterone but converted to more potent androgens and estrogens in peripheral tissues)
androgens: what is the role of androgens in female and male children and adults?
- androgens are important in children as their reproductive hormones are not formed fully
- specifically in male prenatal development (in the womb), males respond to the androgens produced in the adrenal cortex to form male structures
- before puberty, these androgens help in both males and females to develop secondary sex characteristics (pubic hair, body odour, acne etc.)
- Adult Men: no physiological role (we will see the testes are more responsible for forming androgens)
- Women: maintain pubic and axillary hair, source of estrogens after menopause (usually ovaries are more responsible for estrogen production)
aldosterone: review when/why aldosterone is secreted (last lecture) and where it is secreted from (this lecture)
- in the zona glomerulosa, we have aldosterone being secreted
- this was talked abt in the last lecture
- stimuli for release = high K+, high osmolarity, low BP
- aldosterone is secreted for Na+ reabsorption (retaining water) and K+ secretion
- some people use a broader term for what the zona glomerulosa secretes: mineralocorticoids
- this is because minerals, like sodium and potassium are effected
cortisol:
- where is it released
- what class of steroids is it a part of
- what control pathway is it involved in
- continuous or interval secretion?
- what is its role?
- Adrenal cortex also secretes
glucorticoids in the zona fasciculata - Cortisol is the main glucocorticoid
- Control pathway of secretion is the hypothalamic-
pituitary-adrenal pathway - Continuous secretion, circadian/diurnal rhythm
- Role in the mediation of long-term stress
long term/ prolonged stress:
how does prolonged stress stimulate the adrenal cortex to release steroid hormones like cortisol? cortisol regulation
- stress stimulates hypothalamus to release CRH (corticotroin-releasing hormone)
- stress –> CRH release in hypothalamus –> anterior pituitary (true endocrine organ) secretes ACTH –> adrenal cortex (target organ) –> stimulates cells here to release cortisol to certain cells in other organs (liver, fat, muscle, bone, lymphocytes) –> increases glucose blood concentration (gluconeogenesis in liver) , decreases immune system (inhibits immune cells creation)
what is the negative feedback loop system in the cortisol regulation pathway
- once sufficient amount of cortisol is released based on target outputs, cortisol sends a negative feedback loop to anterior pituitary (reduces ACTH), also to hypothalamus (reduces CRH)
- negative feedback loops reduces cortisol in the bloodstream
what are the long term stress metabolic effects of cortisol release:
liver, skeletal muscles, adipose tissues, immune system, kidneys, blood vol/ pressure
long term stress responses:
* Cortisol has metabolic effects – primarily catabolic ie. breakdown tissues so we always energy for use:
1. Promotes gluconeogenesis in liver - promoting new glucose for energy
2. Causes breakdown of skeletal muscle proteins – source of amino acids for energy
3. Enhances lipolysis in adipose tissue – breakdown of fat as a fuel
4. Suppresses the immune system
- kidneys: retain sodium and water
- blood vol./ pressure = rise
why is cortisol essential for preventing hypoglycemia?
- Protective effect against hypoglycemia (when you don’t have enough glucose circulating in your bloodstream for your tissues to use as fuel) through
permissive effect
