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Physiology > Lecture 11: Introduction to Endocrine > Flashcards

Lecture 11: Introduction to Endocrine Flashcards

1
Q

Is the endocrine system under extrinsic or intrinsic control

A

Extrinsic

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2
Q

Endocrinology

A

Study of homeostatic regulation, growth and other activities that hormones accomplish

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3
Q

What is a hormone

A

Chemical messenger released from ductless glands or neurons into the bloodstream

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4
Q

Hormones are very potent in ___ concentrations

A

Low

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5
Q

Describe endocrine signaling

A

Hormone is released from secreting cell into nearby capillary and then travels through larger blood vessels and into capillaries near target and then finally binds to target cells

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6
Q

What is the basic order in HP axis

A

CNS input—> hypothalamus—> pituitary—> everything else

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7
Q

What are two hormones that are exceptions of the hypothalamic control

A

Insulin (blood sugar) and parathyroid hormone (ca2+)

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8
Q

What cells release insulin in response to elevated glucose levels

A

Pancreatic Beta cells

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9
Q

What tissues are exclusive to endocrine function

A

Pituitary, thyroid, parathyroid, and adrenal glands

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10
Q

What are the three different types of hormones

A

Amines, steroids, peptides

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11
Q

What are amines

A

Derived from modification of a single amino acid

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12
Q

What are two examples of amine hormones

A

Epinephrine and thyroid hormones

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13
Q

Where is epinephrine released from and is it polar vs nonpolar and hydrophilic vs hydrophobic

A

Released from adrenal medulla
Polar and hydrophilic

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14
Q

Are thyroid hormones polar vs nonpolar and hydrophilic vs hydrophobic

A

Non-polar and hydrophobic

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15
Q

What are peptides

A

Chains of amino acids

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16
Q

What hormones are derived as a product of gene expression

A

Peptides

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17
Q

Are peptides polar vs nonpolar, hydrophilic vs hydrophobic

A

Polar and hydrophilic

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18
Q

What type of hormones are CRH, ACTH, GH, oxytocin, vasopressin, insulin and glucagon

A

Peptide hormones

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19
Q

Describe peptide hormone synthesis

A

Peptide hormones are synthesized in nucleus as they are a product of gene expression, then sent to golgi for packaging, packed into secretory vesicles and secreted

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20
Q

What is pro-opiomelanocortin (POMC)

A

Precursor peptide to several hormones and signaling molecules

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21
Q

What are propeptide convertase

A

Cleaves the pro hormone (POMC) at specific locations at lysine and arginine junctions

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22
Q

What are the two propeptide convertase

A

PC1 and PC2

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23
Q

PC1 is expressed solely in ____ and produces ____

A

Pituitary corticosteroids and produces ACTH

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24
Q

PC2 and PC1 are expressed in _____, producing ______

A

Melanotrophs, producing alpha-MSH, beta-MSH, Beta-endorphin

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25
___ and ___ are never produced in same cell type
alpha-MSH and ACTH
26
What are the three qualities of steroid hormones
Non-polar, lipophilic and made from cholesterol
27
Steroids are synthesized from cholesterol in what parts of body
Gonads, adrenal cortex, adipose tissue, placenta, and brain
28
Where is cortisol and aldosterone produced
Adrenal cortex
29
Mobilization of cholesterol into cells is mediated by what 3 channels
ACTH, ANG II, and K+
30
What 3 things is cholesterol derived from
1. LDL in diet 2. Hydrolysis of cholesterol esters in vesicles 3. De novo synthesis of acetyl CoA
31
What are the steps of biosynthesis of steroids in the adrenal cortex
1. Cholesterol is transported to mitochondria and localized by steroidogenic acute regulatory protein (STaR) 2. Cholesterol is converted to pregenenolone by cholesterol desmolase (CYP11A1), primarily activated by ACTH 3. Subsequent conversions occur in smooth ER, facilitated by certain enzymes
32
What primarily activates cholesterol desmolase
ACTH
33
All steroids share their initial step of biosynthesis which is
Conversion of cholesterol—> pregnenolone
34
What cells respond to hormones
Cells with receptor for hormone, if no receptor= no response
35
What are hormone receptors
Proteins that bind to the hormone and initiate a cellular repsonse
36
Where in cells are hormone receptors found
1. Cell membranes 2. Cytoplasm 3. Nuclei
37
What types of hormones can bind receptors in cell membranes
Polar hormones- PEPTIDES and epinephrine
38
What types of hormones can bind receptors in cytoplasm and/or cell nuclei
Nonpolar hormones-steroids and thyroid hormones
39
Describe the steps in steroids binding to receptor and producing cellular response
Steroids can cross cell membrane (nonpolar) and bind receptor in cytoplasm—> translocated into nucleus where hormone and receptor act as transcription factor to activate or inhibit gene transcription Biological effect of steroid hormones: gene transcription—> proteins
40
Describe the steps for peptide hormones binding the receptor and producing a cellular response
Peptide binds receptor on cell membrane (polar) activates AC-> cAMP—> activate kinases to phosphorylation of an enzyme Biological effect of peptide hormones: activation of enzymes via phosphorylation
41
What 3 things can stimulate release of hormone
Neural stimulus (ex: increase AP) Another hormone (CRH—>ACTH) Humoral stimuli- change in solute concentration (ex: BG and insulin)
42
What is the main mechanism by which homeostasis is regulated
Negative feedback
43
What is the basic negative feedback loop with HPA axis
Hypothalamus (releasing hormones)—-> anterior pituitary (trophic hormones)—> target organs (adrenals, thyroid)—> hormone and that hormone will have negative feedback on hypothalamus
44
What is the ultrashort negative feedback loop
Releasing hormone (ex: CRH) inhibiting hypothalamus
45
What is the short negative feedback loop
Trophic hormone (ex: ACTH) inhibiting hypothalamus
46
What is the long feedback loop
Hormone released from target organs (ex: cortisol) inhibiting anterior pituitary and hypothalamus
47
What pathway connects the hypothalamus and posterior pituitary
Neural pathway/neurohyophysis
48
What is the neural pathway
Neurons project to neurohyophysis (aka pars nervosa) to release hormones (oxytocin or vasopressin)
49
What pathway connects the hypothalamus and anterior pituitary
Anterior pathway
50
What is the anterior pathway
Releasing hormones are releasing into portal system (from hypothalamus) to release trophic hormones from anterior pituitary
51
In the HPA axis what is the releasing hormone and what is the trophic hormone
Releasing hormone: CRH Trophic hormone: ACTH
52
Which cell type in the anterior pituitary does CRH act on to stimulate ACTH
Corticotropes
53
ATCH targets ___ gland
Adrenal
54
What three kinds of hormones are released from the adrenal gland
1. Glucocorticoids (cortisol/cortisterone) 2. Mineralcorticoids (aldosterone) 3. Weak androgens (androstenedione, DHEA)
55
Where is CRH released from
Paraventricular nucleus in hypothalamus
56
What is the function of CRH in HPA axis
Released from PVN and travels to anterior pituitary via portal blood to stimulate corticotropes and release ACTH
57
What are the 3 functions of ACTH in cortisol regulation of HPA axis
1. Inhibit CRH via short feedback loop 2. Stimulate adrenal growth 3. Transfers cholesterol to mitochondria and activates cholesterol desmolase (CYR11A1) for steroid synthesis
58
What is the function of cortisol in regulating HPA axis
Directly inhibits CRH and ACTH, inhibits ACTH by inhibiting CRH
59
What is the primary effect of cortisol
Increase blood glucose by enhancing glucogenesis in the liver
60
How does cortisol impact protein catabolism
Increase
61
How does cortisol impact protein synthesis
Decreases
62
How does cortisol impact lipolysis of fats
Increases
63
What is the diabetogenic effect of cortisol
Decreases glucose uptake by tissues, and decreases sensitivity to insulin Result: increased BG
64
How does cortisol effect cardiovascular tissue
Maintains normal BP (over time causes hypertension), upregulates alpha-1 adrenergic receptor, enhances vasoconstriction
65
How does cortisol increase cardiac output
Increases ventricular contractions and upregulates alpha-1 adrenergic receptor
66
How does cortisol impact bones
Inhibits synthesis of type I collagen, decrease osteoblasts and decrease Ca2+ absorption
67
How does cortisol effect immune function
Anti-inflammatory effects, decreases PLA, IL-2, histamine, serotonin
68
How does cortisol effect CT and muscle
Inhibits fibroblast proliferation and collagen formation, thin skin, impaired tissue, proteolysis in muscle leading to weakness
69
How does cortisol secretion reflect circadian rhythms
Cortisol levels change throughout the day, increase in AM and decrease throughout the day
70
Cortisol levels are ___ during hunger and stress
Elevated
71
What is Cushing’s syndrome a result of
Due to primary adrenal hyperplasia
72
What are some symptoms in cushing’s syndrome
Hyperglycemia, hypertension, increase protein catabolism, muscle wasting central obesity, thin skin, bruising
73
What are ACTH and CORT levels in patient with Cushing’s syndrome
ACTH is low, CORT is high
74
What is Cushing’s disease a result of
Due to secondary excess ACTH from pituitary or ACTH secreting cells in the lungs
75
What are ACTH and CORT levels in cushing’s disease
ACTH and CORT are both high
76
What is the classic presentation for cushing’s
Abnormal adipose deposits, thinning, bruising of skin, muscle atrophy of legs
77
What is primary adrenocortical deficiency/addison’s disease
Decrease synthesis of all adrenocortical hormones as a result of autoimmune destruction of tissues
78
Loss of cortisol can lead to
Hypoglycemia, muscle weakness, weight loss, and decreased HPA feedback
79
Why is hyperpigmentation a result of decreased cortisol
Lack of negative feedback on HPA leads to increased ACTH secretion, which contains melanocytes stimulating hormone (alpha-MSH)
80
Loss of aldosterone can lead to
Hyperkalemia, hypotension, metabolic acidosis, salt cravings
81
Loss of androgens can lead to
Decreased libido in females
82
How do you test adrenal cortex function
ACTH stimulation test- add exogenous ACTH and measure cortisol levels at t=0 and t=30 minutes
83
What is the expected value after ACTH stimulation test in normal individual vs abnormal
Expect 2x cortisol in normal individual, subnormal responses are diagnostic of primary adrenal insufficiency, adrenals don’t respond to ACTH
84
Where in HPA axis is impacted by primary adrenal insufficiency and what drugs would make the most sense to prescribe to improve condition
Adrenal cortex damaged- does not respond to ACTH Tx: glucocorticoids (pred) and mineralcorticoids (fludrocortisone)

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