Adrenal Glands Physiology Flashcards
(90 cards)
1
Q
What are the hormones secreted by the zona glomerulosa of the adrenal gland?
A
Mineralocorticoids (aldosterone)
2
Q
What is the function of aldosterone?
A
Potassium, sodium, and water homeostasis
3
Q
What are the hormones secreted by the zona fasciculata of the adrenal galnd?
A
Glucocorticoids (cortisol)
4
Q
What is the function of glucocorticoids like cortisol?
A
Glucose homeostasis plays a role in the metabolism of proteins and lipids and in adaptation to stress
5
Q
What hormones are secreted from the zona reticularis of the adrenal gland?
A
Sex steroids (androgens)
6
Q
What hormones are secreted by the medulla of the adrenal gland?
A
Catecholamines
7
Q
What are examples of catecholamines secreted by the medulla of the adrenal gland?
A
Norepinephrine
Epinephrine
Dopamine
8
Q
What are the three different classifications of the adrenocortical hormones?
A
MIneralocorticoids
Glucocorticoids
Sex hormones
9
Q
What is an example of sex hormones?
A
DHEA –> an androgen (male sex hormone)
10
Q
What type of hormone is aldosterone?
A
A steroid hormone (mineralocorticoid)
11
Q
What regulates aldosterone?
A
Renin-angiotensin system
12
Q
Where is renin secreted and in response to what?
A
Renin is secreted from the kidneys in response to variations in BP and volume and plasma sodium and potassium levels
13
Q
What is the role of renin?
A
Converts angiotensinogen into angiotensin I
14
Q
What type of hormone is cortisol?
A
A steroid horome (glucocorticoid)
15
Q
How are the levels of cortisol regulated
A
They rise and fall naturally through-out the day
16
Q
When are cortisol levels the highest and when are they the lowest?
A
Lowest: late at night
Highest: early in the morning
17
Q
What is DHEA?
A
Precursor for androgen
18
Q
What is the function of DHEA?
A
Produces male hormones in women and female hormones in men to keep the effects of the dominant sex hormones in balance
19
Q
What is the adrenal medulla?
A
A modified sympathetic prevertebral ganglion that releases epinephrine and norepinephrine into the blood in response to sympathetic stimulation
20
Q
What is the functional unit of the adrenal medulla?
A
The chromaffin cell, which functions as an NE cell
21
Q
What does epinephrine activate have an effect on?
A
b-adrenoreceptor and a-adenoreceptors
22
Q
What is the effect of adrenaline on b-adrenoreceptors?
A
Vasodilation
Tachycardia
Insulin resistance
23
Q
What is the effect of the activation of a-adrenoceptors?
A
Vasoconstriction
24
Q
Which catecholamine acts only om the a-adrenoceptor?
A
Noradrenaline
25
What are the effects of androgens when bound to androgen receptors?
Hair (pubic and axillary)
Libido (especially in females)
26
What are the effects of cortisol when bound to glucocorticoid recepors?
Metabolic regulation
Immunomodulation
Cardiovascular regulation
CNS actions
27
What is the effect of b-LPH?
Pigmentation
28
What is the Aldosterone secretion pathway like?
1. Decrease in plasma volume or increase in plasma K+
2. Increase of plasma angiotensin II
3. Increase of adrenal secretion from the adrenal cortex
4. Increase the concentration of plasma aldosterone
29
What is the effect of increased plasma aldosterone on the cortical collecting ducts?
Increased sodium reabsorption --> Decreased sodium excretion
Increased potassium secretion --> Increased potassium excretion
30
What are the regulation of secretion of mineralocorticoids like aldosterone?
1. The levels of potassium and sodium in the blood
2. The RAAS
3. ACTH (to a lesser extent)
31
What regulates glucocorticoids and androgen ?
Regulated by hypothalamic-pituitary system
32
What is the hypothalamic-pituitary system?
A negative feedback system, one of the most important elements of homeostasis, maintains a steady internal biochemical and physiological balance in the body
33
What does the HPA axis regulate?
Adjusts cortisol levels according to the need of the body, under normal and stressed conditions via ACTH
34
Where is ACTH secreted from?
Secreted from the pituitary gland in response to the orders from the hypothalamus and travels in the bloodstream to the adrenal cortex
35
In relation to stress what kind of glands are adrenal glands?
They are anti-stress glands
36
What is the function of the cortisol during stress conditions?
1. Needs to provide more blood glucose
2. Mobilize fats and proteins for a back-up supply of glucose
3. Modify immune reactions, heartbeat, blood pressure, brain alertness and nervous system responsiveness
37
What happens if the cortisol levels cannot rise in response to the needs of the stress?
Maintenance of the body under stress is nearly impossible
38
What is the catecholamine biosynthesis like?
1. L-Tyrosine to L-DOPA (enzyme: Tyrosine hydroxylase)
2. L-DOPA to Dopamine (enzyme: DOPA decarboxylase)
3. Dopamine to Norepinephrine (enzyme: Dopamine β-hydroxylase)
4. Norepinephrine to Epinephrine (enzyme: Phenylethanolamine N-methyltransferase (PNMT))
39
Which is the rate-limiting step of the synthesis of catecholamines?
Conversion of L-Tyrosine to L-DOPA
40
What induces PNMT?
Glucocorticoids
41
What is the mechanism of regulation of secretion of catecholamines?
1. Stress signals stimulate the sympathetic nervous system.
2. Acetylcholine from preganglionic sympathetic neurons binds to nicotinic receptors on adrenal medullary cells, triggering catecholamine release.
42
Where does the regulation of secretion of catecholamines occur?
Mainly in the adrenal medulla and small neuron group and some subtypes of cardiomyocytes
43
What are the actions of aldosterone?
1. Responsible for the regulation of sodium in the distal tubule and cortical collecting duct
2. Affects Na+ reabsorption by sweat, salivary and intestinal cells
3. Stimulates the synthesis of more Na/K ATP
4. Maintains extracellular volume
44
What happens if there is excess of aldosterone?
1. Increase extracellular fluid volume & arterial pressure
2. Small effect on the plasma sodium concentration
3. Causes hypokalemia and muscle weakness
4. Increases tubular hydrogen ion secretion (mild alkalosis)
45
What does deficiency of Aldosterone lead to?
Hyperkalemia and cardiac toxicity
46
What are the actions of cortisol?
1. Increase of protein synthesis in the liver and decrease its synthesis in muscles
2. Increase of protein destruction in muscles
3. Increase of lipolysis
4. Anti-inflammatory function and immunomodulation
5. Cardiovascular regulation (Increase of BP)
47
What are the effects of cortisol on the glucose metabolism?
1. Increase of glycogen synthesis in the liver and decrease of glucose utilization by peripheral tissues
48
What does cortisol work in tandem with?
Insulin from the pancreas to maintain blood glucose levels in the proper balance
49
What are the effects of cortisol on lipid metabolism?
1. Increases lipolysis in adipose tissue
2. Reduces synthesis of triglycerides
50
What is the result of the cortisol effect on the adipocyte tissue?
Redistribution of the fat with a predominance of central obesity and interscapular deposits of fat (Buffalo hump)
51
What is the effect of cortisol on protein and nucleic acid metabolism?
1. Reduction of protein storage in all cells except the liver ones
2. Increases liver and plasma proteins
3. Mobilizes amino acids from nonhepatic cells, thus increasing blood amino acid levels
4. Increased amino acid transport to the liver cells, and decreased transport of amino acids into other cells
52
What are the effects of cortisol on water and electrolyte metabolism?
1. Deficiency of cortisol --> increase in production of ADH
a. Water retention: action on the collecting tubules
b. Decreased GFR --> impaired. water clearance causes water retention in the body
53
What are the effects of cortisol on the immune system?
1. Cortisol suppresses the immune response directly and indirectly by affecting most cells that participate in immune reactions and inflammatory reactions (a powerful anti-inflammatory)
2. Reduces the rate at which lymphocytes multiply and accelerates their programmed cell death to further protect the body from this over-reaction
54
What are strong corticosteroids used with?
Strong corticosteroids are used with all diseases involving inflammatory processes, including auto-immune diseases
55
What are examples of strong corticosteroids?
Prednisone and Prednisolone
56
What are the effects of cortisol on the cardiovascular system?
1. Could control the contraction of the walls of the mid-sized arteries --> increasing the BP
2. Directly affects the heart by regulating sodium and potassium in the heart cells and increasing the strength of contraction of the heart muscle
57
What is the contraction of walls of mid-sized arteries due to cortisol moderated by?
Calcium
58
What are the effects of cortisol on calcium?
1. Decreases the absorption of calcium from the intestine
2. Increases the renal excretion of calcium
59
What are the actions of catecholamines?
1. Glycogen breakdown into glucose --> Increased blood glucose
2. Increased blood pressure
3. Increased breathing rate
4. Increased metabolic rate
5. Change in blood flow --> increased alertness and decreased digestive and kidney activity
60
What are the characteristics of steroid hormones?
1. They are not packaged but synthesized and immediately released
2. All derived from the same parent compound
3. They are lipid soluble and thus are freely permeable to membranes --> not stored in cells
61
What is the parent compound of all steroid hormones?
Cholesterol
62
Where are the enzymes that produce steroid hormones from cholesterol located?
Located in the mitochondria and SER
63
What is the MOA of steroid hormones?
1. Hydrophobic SHsdiffuse to the cytoplasm and bind cytoplasmic or nuclear receptors
2. Receptor-ligand complex migrates to the hormone response element (HRE)
3. Turn on new transcription genes
4. Translation into new proteins
64
What protein carriers are steroids bound to?
1. Albumin
2. Corticosteroid binding globulin (CBG) or transcortin
3. Sex hormone-binding globulin (SHBG)
4. Androgen binding protein (ABP)
65
What are the % boundings of cortisol?
1. 70% is bound to corticosteroid-binding globulin
2. 22% is bound to albumin
3. 8% is free cortisol
66
What are the % boundings of aldosterone?
1. 60% of aldosterone is bound to albumin
2. 10% is bound to CBG
3. A small amount of aldosterone is bound to other plasma proteins
67
Where is CBG/transcortin produced?
In the liver
68
What increases the synthesis of CBG/transcortin?
Estrogens
69
What is the aim of binding hormones to transport proteins?
Protected from catabolism and inactivation
70
What is the function of transport proteins?
They assist in maintaining a level of hormones in circulation
71
How are most hormones catabolized?
By the liver and the kidneys
72
What does inactivation of steroids involve?
Reductions and conjugations to sulfate to increase their water solubility
73
How are conjugated steroid excreted?
70% in the urine
20% in the feces
10% through the skin
74
What is the half life of the steroids which are bound to plasma proteins?
They have long half-lives (hours)
75
What are peptides and catecholamines like?
Water-soluble, they are transported dissolved in plasma
76
What is the half-life of peptides and catecholamines?
Short half-lives (seconds to minutes)
77
Why are the effects of steroid hormones produced more slowly?
They initiate protein synthesis, but their effects are more long-lasting than those produced by other hormones
78
What are the diseases of the adrenal gland?
Cushing's disease
Addison's disease
79
What is Cushing's disease?
Hyper-active adrenal cortex
80
What are the characteristics of Cushing's disease?
1. Rounded face and obesity
2. Thin, frail skin
3. Poor wound healing
81
What is Addison's disease?
Hypo-active adrenal cortex
82
WHat are the characteristics of Addison's disease?
1. Deceased appetite and weight loss
2. Cold intolerance
3. Stress susceptibility
83
What is Cushing's DISEASE?
The result of a pituitary tumor secreting inappropriate ACTH (increased cortisol from PITUITARY)
84
What is Cushing's SYNDROME?
Causes the same symptoms as Cushing's disease, but it is caused by the overproduction of adrenal hormones
85
What could cause Cushing's syndrome?
Glucocorticoid drugs, tumors that produce cortisol or ACTH
86
What are the endogenous causes of Cushing's ?
65% --> pituitary
25% --> adrenals
10 --> ectopic source, non-pituitary, ACTH producing tumor
87
What is the female: male ration of Cushing's?
5:1
88
What is the age group target of Cushing's?
25 to 40
89
How are hormones affected in Addison's disease?
The anterior pituitary produces excessive but INEFFECTIVE amounts of ACTH to the adrenal cortex, thus hindering its ability to produce and release hormones --> Adrenal gland stops eventually producing cortisol
90
