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Adrenal Physiology Flashcards

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1
Q

What does the Yerkes-Dodson curve demonstrate?

A

The relationship between performance and stress levels

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2
Q

True or false: you have two different stress responses for physical vs psychological stressors?

A

False. You only have one generalized stress response

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3
Q

Describe general adaptation syndrome.

A

Nervous and hormonal responses resulting in a state of intense readiness with fuel mobilized for use

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4
Q

Where is the stress response coordinated?

A

Hypothalamus

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5
Q

Describe the short-term stress response. What occurs? What is the result (6)?

A

The hypothalamus directly stimulates the adrenal glands via the SNS, which causes catecholamines (Epi and NE) to be secreted from the adrenal medulla. Results in:

  1. Increased HR
  2. Increased BP
  3. Stimulates glycogenolysis and GNEO
  4. Dilation of bronchioles
  5. Decreased digestive system activity and urine output
  6. Increased metabolic rate
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6
Q

Describe the long-term stress response. What occurs?

A

CRH secreted from the hypothalamus to the anterior pituitary, which secretes ACTH into the blood to stimulate the adrenal cortex to secrete steroid hormones (MCCs & GCCs)

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7
Q

What are the effects of mineralocorticoids (MCCs) after being secreted from the adrenal cortex (2)? Example?

A

Retention of sodium and water by the kidneys

Increases blood volume and pressure

Ex: aldosterone

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8
Q

What are the effects of glucocorticoids (GCCs) after being secreted by the adrenal cortex (3)? Example?

A
  1. Proteins and fats converted to glucose or broken down directly for energy
  2. Increase blood glucose
  3. Suppression of the immune system

Ex: cortisol

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9
Q

Label the following aspects of the adrenal gland:

Adrenal medulla, Zona glomerulosa, Zona reticularis, Zona fasciculata.

A
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10
Q

What hormones are secreted by the four regions of the adrenal gland? (Zona golmerulosa, Zona fasciculata, Zona reticularis, Adrenal Medulla)

A

Zona golmerulosa: Mineralocorticoids

Zona fasciculata: Glucocorticoids

Zona reticularis: Androgens

Adrenal medulla: Stress hormones (Epi/NE)

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11
Q

Where in the cell are Epi and NE synthesized?

A

Cytosol of adrenal medulla cells

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12
Q

Approximately how much of the adrenal gland is composed of cortex vs medulla?

A

80-90% cortex

10-20% medulla

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13
Q

What types of hormones are synthesized by the adrenal cortex vs medulla?

A

Cortex: steroids

Medulla: amines

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14
Q

What is the embryonic origin of the adrenal cortex vs medulla?

A

Cortex: mesoderm

Medulla: neuroectoderm

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15
Q

What is the innervation of the adrenal cortex like compared to the medulla?

A

Cortex: Almost no innervation

Medulla: SNS innervation

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16
Q

How are products stored in the adrenal cortex vs medulla?

A

Cortex: lipid droplets

Medulla: amine granules

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17
Q

Are the adrenal cortex and medulla essential for life?

A

Cortex: essential

Medulla: nonessential

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18
Q

In the adrenal cortex, approximately how much cholesterol is taken up from the diet and how much is synthesized by the body?

A

Diet: ~80% from LDL

De novo synthesis: ~20%

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19
Q

If cholesterol is the starting material for all hormones of the adrenal gland, what determines what cholesterol is synthesized into?

A

Distribution of enzymes across the different cell types.

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20
Q

What enzyme catalyzes the conversion of cholesterol to pregnenolone? What stimulates this enzyme in the ZG, ZF, and ZR?

A

Desmolase

ZG: Ang II

ZF: ACTH

ZR: ACTH

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21
Q

What enzyme is absent in the ZG that prevents pregnenolone from being converted into GCCs or androgens?

A

17-α hydroxylase

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22
Q

What provides negative feedback to the hypothalamus and pituitary to stop the secretion of hormone by the adrenal glands?

A

Cortisol

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23
Q

ACTH is synthesized from what precursor? What else is it a precursor to?

A

Preproopiomelanocortin (POMC)

Also gives rise to α-melanocyte-stimulating hormone (MSH)

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24
Q

What does it mean for cortisol secretion to be pulsatile?

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A

Alternating bursts of modest secretion separated by silent periods of little to no secretion; amount secreted per pulse does NOT vary

25
What does it mean for cortisol secretion to be diurnal? What structure regulates this?
Plasma ACTH and cortisol peak once a day prior to awakening Regulated by the suprachiasmatic nucleus in the hypothalamus (circadian rhythm)
26
How is cortisol transported in the blood?
75% Corticosteroid-binding protein (CBP, transcortin) 15-20% albumin 5% unbound
27
How does the liver inactivate cortisol?
Conjugates with glucuronide or sulfate to increase cortisol solubility, which facilitates excretion by the kidneys.
28
What is the half-life of cortisol?
~70 minutes
29
Describe the mechanism of action of adrenal steroids after it reaches its target cell (4).
1. Steroid diffuses through cell membrane and binds w/ intracellular receptor-HSP complex 2. HSP released 3. Activated receptor has a high affinity for steroid-response elements of DNA and binds to it 4. Once bound, acts as transcription factor
30
Why can't GCCs immediately relieve acute bronchial asthma attacks? What can they be used for though?
Since GCCs activate synthesis of proteins, there is a lag period of about 30 minutes for them to take effect. This is too slow for an asthma attack. Can be used in the prevention of new asthma attacks
31
How long can the effects of GCCs last? Why?
Hours or days Slow turnover of enzymes and proteins
32
What are the four main functions of cortisol?
1. Stimulate GNEO in response to low blood sugar 2. Increase protein and lipid breakdown 3. Anti-inflammatory effects 4. Suppress immune response
33
What enzymes of GNEO are stimulated by cortisol?
Phosphoenolpyruvate carboxykinase (PEPCK) Glucose-6-phosphatase
34
If cortisol is supposed to increase glucose, why does it inhibit insulin-stimulated glucose uptake by muscles and adipose?
To preserve glucose for use by the brain (the brain can't use muscle or fat)
35
Excess cortisol results in fat deposits where?
Face and trunk
36
What tissues are affected by cortisol?
All of them
37
Why can excess cortisol result in muscle weakness?
Cortisol breaks down muscle to increase blood glucose levels
38
What are the effects of cortisol on bones and its associated hormones?
**Increase bone (calcium) reabsorption** Increases PTH secretion Inhibits osteoblasts
39
What three separate conditions make up high-altitude illness? What medication can be used to treat it? How does it work?
1. Acute mountain sickness 2. High altitude cerebral edema 3. High altitude pulmonary edema Treated with dexamethasone (a GCC): reduces "leakiness" of cerebral and pulmonary blood vessels
40
What is the function of cortisol on the cardiovascular system?
**Required for maintenance of normal blood pressure** Permits responsiveness of arterioles to the constrictive action of adrenergic and angiotensin stimulation
41
What effect does cortisol have on the kidneys?
Inhibits secretion and action of ADH (antagonist) Increases GFR and RBF (which increases CO)
42
What effect does cortisol have on the CNS (specifically memory)?
Enhance memory consolidation Impairs memory retrieval
43
What are the effects of cortisol on fetal development (3)?
Facilitates maturation in utero of the CNS, retina, skin, GI tract, and lungs Increases surfactant synthesis (so breathing can occur immediately after birth Maturation of digestive enzymes so the baby can digest milk
44
What is the difference between Cushing's Syndrome and Cushing's Disease?
Syndrome: broad term for hypersecretion of cortisol Disease: Pituitary microadenoma that produces ACTH (does not respond to negative feedback)
45
\_\_\_\_% of Cushing's syndromes are ACTH dependent and \_\_\_\_\_% are ACTH independent.
~85% ACTH dependent ~15% ACTH independent
46
In regard to ACTH depending Cushing's syndromes \_\_% are caused by Cushing's disease, \_\_% by an ACTH secreting ectopic tumor, and _____ can occur but is rare.
80% Cushing's disease 20% ACTH secreting ectopic tumor Rare CRH secreting ectopic tumor
47
What are the potential causes of ACTH independent Cushing's syndrome? (2)
Adrenal tumor Iadogenic
48
What does it mean when Cushing's syndrome is iatrogenic?
Results from treatment of rheumatoid arthritis, allergies, and prevention of transplant rejection
49
What are some of the symptoms of Cushing's syndrome? (Combination of symptoms may vary).
\*Truncal obesity \*Moon face \*Hypertension Skin atrophy Diabetes Gonadal dysfunction \*Muscle weakness \*Increased body hair (hirsutism) and acne Mood changes Osteoporosis
50
If cortisol levels fluctuate throughout the day, how are adrenal diseases (like Cushing's) diagnosed?
24-hour urine analysis Normally \<50mg/24hr
51
Why is DEX a good treatment for hypercortisolism?
DEX has a 25x greater affinity for cortisol's receptors than cortisol itself
52
What is the difference between primary and secondary adrenal insufficiency?
Primary: Autoimmune destruction of adrenal cortex (Addison's disease) Secondary: Lack of ACTH
53
In Addison's disease, what happens to cortisol, aldosterone, adrenal androgen, and ACTH levels?
ACTH increases Cortisol, aldosterone, and adrenal androgen all decrease
54
What are some symptoms of Addison's disease?
\*Hyperpigmentation (especially in traumatized areas of the skin) Weakness Depression Weight loss Hypotension
55
In secondary adrenal insufficiency, what happens to cortisol, aldosterone, androgen, and ACTH levels?
Decreased ACTH and cortisol No change to aldosterone and androgens
56
What are some symptoms of secondary adrenal insufficiency?
Similar to those of Addison's disease WITHOUT hyperpigmentation Mild orthostatic hypotension Poor response to stress
57
What is cosyntropin? What is it used for?
Synthetic ACTH Used in stimulation test for Addison's disease; response means no disease
58
Any enzyme blockage that decreases cortisol synthesis will _____ ACTH and result in _____ \_\_\_\_\_\_\_?
Increase ACTH Adrenal hyperplasia

Physiology (11 decks)

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