1
Q
what are adrenal glands
A
- small and located at the top of the kidneys
- like pituitary gland, the adrenal glands are essentially two endocrine organs
2
Q
explain the outer and inner layers of the adrenal glands
A
- the outer layers are called the cortex and they secrete several steroid hormones
- the inner layer is called the medulla and it secretes catecholamines
3
Q
explain the adrenal cortex zones
A
can be divided into 3 distinct zones
1. zona glomerulosa
2. zona fasciculata
3. zona reticularis
4
Q
explain the hormones produced in the adrenal cortex
A
- are all steroid hormones and are based on cholesterol as the precursor molecule
- since the different layers of the cortex contain different enzymes involved in hormone synthesis, each zone can produce different hormones
5
Q
what are the 3 categories of adrenal cortex hormones
A
- mineralocorticoids
- glugocorticoids
- sex hormones
6
Q
explain mineralocorticoids
A
- influence mineral (electrolyte) balance
- they are produced mainly in the zona glomerulosa
7
Q
explain glucocorticoids
A
- play a role in glucose, lipid, and protein metabolism
- they are produced mainly in the zona fasciculata and the zona reticularis
8
Q
explain sex hormones
A
identical or similar to those produced in the gonads, are produced in lower quantities in the zona fasciculata and the zona reticularis
9
Q
what are mineralocorticoids
A
- a class of corticosteroids which are produced in the adrenal cortex
- they influence salt and water balances in the body and are considered essential for life
- in the absence of mineralocorticoids, a person would die as quickly as in a matter of days due to circulatory shock
10
Q
what is the major mineralocorticoid produced
A
- aldosterone
- in the absence of aldosterone, extracellular fluid (ECF) volumes drop, causing a decrease in blood pressure that leads to circulatory shock
- aldosterone plays an essential role in electrolyte balance, so its secretion is related to electrolyte concentrations, blood volume, and blood pressure
- it is independent of anterior pituitary control
11
Q
what are aldosterone’s 2 primary stimuli for secretion
A
- activation of the renin-angiotensin-aldosterone system in response to reduced Na+ and a fall in blood pressure
- direct stimulation of the adrenal cortex by increased K+ concentrations
12
Q
what is the primary glucocorticoid
A
- cortisol
- plays a major role in metabolism as well as other important functions
13
Q
explain the metabolic effects of glucocorticoids
A
- in the liver, cortisol stimulates gluconeogenesis, which means that it produces glucose from non-carbohydrate precursors, such as aa
- to obtain these aa, cortisol stimulates protein degradation in muscle
- cortisol inhibits glucose uptake by most tissues, with the brain being the exception, since glucose is the primary fuel source for the brain
- cortisol also breaks down lipid stores (lipolysis) to mobilize free fatty acids that can be used as a fuel source
14
Q
explain the role in adaptation to stress of glucocorticoids
A
- although it is not fully known why, cortisol plays a key role in the adaptation to stress
- a possible explanation for this is that when wounded or under severe stress, eating becomes a low priority
- cortisol causes a shift away from protein and fat stores while increasing carb stores
- this increased availability of glucose ensures adequate brain activity during times of fasting
- the increased levels of aa, free fatty acids, and glucose also provide the building blocks for wound repair if needed
15
Q
what kind of regulation is cortisol secretion
A
cortisol secretion from the adrenal cortex is under negative feedback regulation involving the hypothalamus and anterior pituitary
16
Q
explain cortisol secretion
A
- the hypothalamus releases corticotropin-releasing hormone (CRH), which stimulates the anterior pituitary to release adrenocorticotropic hormone (ACTH)
- ACTH stimulates the adrenal glands to release cortisol
- plasma cortisol feeds back to the hypothalamus and anterior pituitary to reduce CRH and ACTH release
- this negative feedback system keeps cortisol concentrations around its set point
17
Q
what are the 2 influences that help modulate cortisol secretion
A
- cortisol has a diurnal secretion pattern, with the highest levels occurring in the morning, and the lowest levels at night. this diurnal rhythm is intrinsic to the hypothalamus and anterior pituitary control systems
- mental and physical stress can also override the normal patterns of cortisol secretion. stress leads to a large increase in CRH release from the hypothalamus
18
Q
explain male and female sex hormones
A
- androgens are male sex hormones and estrogens are the female sex hormones
- androgens are produced in the testes, (male gonad), while estrogens are produced in the ovaries (female gonad)
- both androgens and estrogens are important for both males and females
19
Q
explain the adrenal cortex and sex hormones
A
- the adrenal cortex secretes low levels of androgens and estrogens
- their release is stimulated by ACTH, which also regulates cortisol secretion, so sex hormone secretion parallels cortisol secretion
- the amount of sex hormones secreted is insignificant compared to those secreted by the gonads
20
Q
what is the most important adrenal cortex sex hormone
A
- dehydroepiandrosterone (DHEA)
- in males it plays little role (due to high levels of testosterone) but in females it has several important physiological effects
- DHEA is important for growth of pubic and armpit hair, enhancement of the growth spurt at puberty, and maintenance of the female sex drive
21
Q
what are the hormones produced by the adrenal medulla
A
- catecholamines are synthesized by the adrenomedullary secretory cells
- once synthesized, epinephrine and norepinephrine are stored in chromaffin granules, which are similar to the NT storage vesicles found in nerve endings
- upon the appropriate stimulation, the chromaffin granules undergo exocytosis to release epinephrine and norepinephrine into the bloodstream
(although 20% of secreted catecholamines are NE, functionally we only consider the actions of E)
22
Q
where are E and NE released from, and what receptors do they bind
A
NE
- predominantly released from nerve endings
- mainly binds a and B1 receptors near postganglionic sympathetic nerve terminals
E
- released from the adrenal medulla
- can reach all of the a and B1 receptors
B2 receptors are exclusively activated by E
23
Q
explain epinephrine
A
- also known as adrenaline
- a hormone and a NT
- normally produced by both the adrenal glands and certain neurons
24
Q
explain the effects of epinephrine on organ systems
A
- in an emergency or stressful situation, the sympathetic nervous system mobilizes adrenomedullary epinephrine system
- this causes an increased heart rate and strength of contraction to increase cardiac output and a generalized vasocontriction to increase TPR and thus BP
- there is a vasodilation in skeletal muscle blood vessels and a dilation of the respiratory airways to increase oxygen intake
- both E and NE decreases digestive activities
25
explain the effects of epinephrine on metabolism
- has effects on carb and fat lipid metabolism
- E increases blood glucose by several mechanisms
- in enhances liver gluconeogenesis (synthesis of new glucose) and glycogenolysis (breakdown of glycogen to release glucose)
- glycogenolysis is also stimulated in skeletal muscles
- E also promotes lipolysis to increase circulating free fatty acids that can be used as an energy source by the heart and skeletal muscles
26
explain the role of sympathetic nervous system and E in producing the integrated stress response
- the sympathetic stress response is essential in that it permits the body to overcome anything from preventing escape from the situation
- the sympathetic nervous system does this in conjugation with the endocrine system by recruiting the release of epinephrine from the adrenal medulla
27
what are the effects of the sympathetic system and E
- increased muscle strength
- increased mental activity
- increased blood pressure
- increased cellular metabolism
- increased blood flow to essential organs and decreased blood flow to non-essential organs
28
explain the role of insulin and glucagon in producing the integrated stress response
- with respect to stress, these two hormones work to the same purpose as cortisol, to increase blood glucose
- increased glucagon secretion will break down glycogen stores to produce glucose and decreasing insulin secretion will reduce the rate at which glucose is removed from circulation
29
explain the role of CRH-ACTH-Cortisol system in producing the integrated stress response
- is the main system involved in the integrated stress response
- cortisol increases blood levels of glucose, free fatty acids, and aa to provide energy substrate to the brain and to facilitate repair of any damaged tissues
- it is also recognized that ACTH may play a role in resisting stress
- during the formation of ACTH from a larger precursor molecule, B-endorphin, a natural morphine-like substance, is also produced and released along with ACTH
- in the case of stress, B-endorphin could act like analgesia int he case of physical injury
30
explain the role of renin-angiotensin-aldosterone system in producing the integrated stress response
- the renin-angiotensin-aldosterone system also plays a role in increasing blood pressure
- during stress, there is an increase in vasopressin and angiotensin II, both of which are vasoconstrictors that can help increase blood pressure in an emergency
31
explain the diagram of integrated stress response
- once the hypothalamus receives input concerning physical and emotional stressors, it activates the sympathetic nervous system, secretes CRH to stimulate ACTH and cortisol release, and triggers the release of vasopressin
- activation of the sympathetic nervous system brings about the secretion of E, which influences pancreatic secretion of insulin and glucagon
32
explain the vasoconstriction effect of integrated stress response
- vasoconstriction due to catecholamine release means less blood flow through kidneys, setting the renin-angiotensin-aldosterone system in motion
- through these mechanisms, the hypothalamus is able to integrate the responses of the sympathetic and endocrine systems in times of stress
33
explain hyperadrenalism
- refers to conditions in which the adrenal glands secrete excessive amounts of the hormones they produce
- there are 3 main patterns of symptoms caused by hyperadrenalism, each is related to its hormone
34
what are the 3 forms of hypersecretion from the adrenal gland
1. cortisol hypersecretion
2. adrenal androgen hypersecretion
3. hyperaldosteronism
35
explain cortisol hypersecretion
- also called Cushings syndrome, cortisol hypersecretion can occur due to overstimulation of the adrenal cortex by CRH nd/or ACTH, adrenal tumours hypersecreting cortisol independent of ACTH, and ACTH-secreting tumours located somewhere other than the pituitary
- it causes an increase of circulating cortisol and subsequent increased plasma glucose
36
what are characteristic physical features of Cushings syndrome
- buffalo hump (redistribution of fat causes increased depositions on the back between the shoulder blades)
- moon face ( cortisol causes excessive oedema in the cheeks)
37
explain adrenal androgen hypersecretion symptoms - adult females
- a woman will develop masculine-like body hair, a condition called hirsutism
- there is usually an increase in male secondary sex characteristics (deepening of voice, more muscular)
- breast size decreases and menstruation may cease
38
explain adrenal androgen hypersecretion symptoms - adult males
little to no effect as the actions of DHEA are minor compared to that of testosterone
39
explain adrenal androgen hypersecretion symptoms - newborn females
- generally exhibit male-type external genitalia
- during development, the clitoris enlarges and takes on a penile-type appearance
40
explain adrenal androgen hypersecretion symptoms - prepubertal males
there is an early development of male secondary sex characteristics called precocious pseudo-puberty
41
explain hyperaldosteronism
- excessive mineralocorticoid secretion can be caused either by an aldosterone-secreting tumour (primary hyperaldosteronism) or by abnormally high activity of the renin-angiotensin-alldosterone system (secondary hyperalsodteronism)
42
what are symptoms of hyperaldosteronism
symptoms are based on the activity of aldosterone and include excessive Na+ retention (hypernatremia), K+ depletion (hypokalemia), and high blood pressure
43
explain adrenocortical insufficiency
- if you were to lose one adrenal gland, the remaining gland would undergo hypertrophy and hyperplasia to increase its hormone secreting capacity
- it takes dysfunction of both adrenal glands to occur before any type of adrenocortical insufficiency manifests
44
explain primary adrenocortical insufficiency (Addisons disease)
- occurs when all layers of the adrenal cortex are under secreting and is often caused by autoimmune destruction of the cortex
- typically both aldosterone and cortisol are deficient
- this condition can be fatal
- patients display hyperkalemia and hyponatremia
- hyperkalemia can affect cardiac volumes, causing hypotension
- the lack of cortisol leads to a poor response to stress and low blood glucose (hypoglycemia) as well as hyperpigmentation of the skin due to excessive ACTH, which rise in an effort to secret more cortisol
45
explain secodnary adrenocortical insufficiency
- occurs if there is a problem in the hypothalamus or anterior pituitary and is characterized by reduced ACTH
- there is a cortisol deficiency but aldosterone levels are unaffected
- symptoms depend on 3 factors: the level of cortisol deficiency, rate of reduction in cortisol levels, underlying health of individual
46
what are common symptoms of secodnary adrenocortical insufficiency
- severe fatigue
- loss of appetite
- weight loss
- nausea
- vomiting
- diarrhea
- muscle weakness
- irratability
- depression
since aldosterone levels tend to be unaffected, low blood pressure and muscle spasms ar enot as likely as they are in primary adrenal insufficiency
PHGY 216
flashcards
Decks in class (34)
# Cards
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Module 1 Section 135
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Module 1 Section 241
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Module 1 Section 342
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Module 1 Section 446
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Module 1 Section 542
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Module 1 Section 641
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Module 2 Section 122
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Module 2 Section 226
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Module 2 Section 328
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Module 2 Section 413
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Module 2 Section 534
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Module 3 Section 117
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Module 3 Section 226
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Module 3 Section 313
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Module 3 Section 419
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Module 3 Section 523
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Module 3 Section 631
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Module 3 Section 725
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Module 4 Section 132
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Module 4 Section 215
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Module 4 Section 322
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Module 4 Section 440
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Module 4 Section 59
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Module 4 Section 640
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Module 5 Section 120
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Module 5 Section 217
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Module 5 Section 323
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Module 5 Section 426
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Module 6 Section 128
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Module 6 Section 220
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Module 6 Section 339
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Module 6 Section 427
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Module 6 Section 535
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Module 6 Section 614
