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Physiology II Exam 2 (Lauren) > L14 Hypothalamus And Pituitary > Flashcards

L14 Hypothalamus And Pituitary Flashcards

1
Q

What hormones are released from the anterior pituitary?

A

Adrenocorticotropic hormone ACTH

Growth Hormone GH

Thyroid stimulating hormone TSH

Prolactin PRL

Luteinizing hormone LH

Follicle stimulating hormone FSH

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2
Q

What hormones are released from the posterior pituitary?

A

Oxytocin OT

Arginine vasopressin AVP aka Antidiuretic hormone ADH

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3
Q

What is another name for antidiruetic hormone ADH?

A

Arginine vasopressin AVP

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4
Q

What are magnocellular neurons?

A

Large neurons that originate in the hypothalamus that project into the posterior pituitary, where they release their hormones into a capillary bed

(The hormones that are produced by the magnocellular neurons are the final product that get released into the blood!)

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5
Q

Where exactly in the hypothalamus do the magnocellular neurons originate?

A

Paraventricular nuclei

Supraoptic nuclei

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6
Q

What hormones are released from the magnocellular neurons?

A

Oxytocin

AVP aka ADH

NP (Neurophysin)

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7
Q

What are the parvicellular neurons?

A

Neurons that originate in the hypothalamus and extend to a capillary bed in the Median Eminence and release Hypothalamic hormones (releasing or inhibitory)

These hormones then travel down blood vessels into the anterior pituitary where they cause the anterior pituitary to release trophic hormones

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8
Q

What hormones are released into the anterior pituitary by parvicellular neurons?

A

CRH

TRH

GnRH

GHRH

SS (Somatostatin)

DA (dopamine)

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9
Q

What hormones are released by the anterior pituitary into the systemic circulation?

A

ACTH

TSH

LH/FSH

GH

PRL

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10
Q

GHRH causes the release of what hormone from the anterior pituitary?

A

GH

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11
Q

TRH causes the release of what hormones from the anterior pituitary?

A

TSH

Prolactin

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12
Q

What effect does somatostatin have on the anterior pituitary?

A

It INHIBITS the synthesis of GH and TSH

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13
Q

GnRH causes the release of what hormones from the anterior pituitary?

A

LH

FSH

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14
Q

CRH causes the release of what hormone from the anterior pituitary?

A

ACTH

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15
Q

PRF (prolactin releasing Factor) causes the release of what hormone from the anterior pituitary?

A

Prolactin lol

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16
Q

What effect does Dopamine have on the anterior pituitary?

A

It INHIBITS prolactin synthesis

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17
Q

Where are ADH and Oxytocin synthesized?

A

In the cell bodies of the magnocellular neurons

Which are located in the supraoptic and paraventricular nuclei

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18
Q

What is the half life of ADH and Oxytocin?

A

Short, about 8 min

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19
Q

ADH and Oxytocin are (steroid/peptide/amine) hormones

A

Peptides

Which means that when they are synthesized, they start as preprohormones that then get cleaved into prohormones (in the ER) and then get converted to hormones (in the Golgi)

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20
Q

What do neurophysins (NP) do?

A

Bind to ADH or Oxytocin and prevent them from leaving the axon of the neuron before it’s ready to be released

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21
Q

Where do neurophysins (NP) come from?

A

They are released when the precursor hormone is cleaved into ADH or oxytocin

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22
Q

There are two kinds of neurophysins: NP-I and NP-II. Which one binds to ADH and which one binds to Oxytocin?

A

NP-I binds to oxytocin

NP-II binds to ADH

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23
Q

As the precursor hormone travels down the hypothalamic-hypophyseal tract (axon of the magnocellular neuron) it gets cleaved into these three things:

A
  1. ADH or Oxytocin
  2. Nurophysin (NP)
  3. A terminal glycoprotein
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24
Q

Central diabetes insipidus happens when there’s not enough ADH reaching the kidney. Why doesn’t the ADH reach the kidney?

A 
The neurophysin (NP-II) that binds to ADH and keeps it from diffusing out of the axon prematurely is defective.
ADH never reaches the circulation
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25
What does oxytocin do to the uterus and the lactating breast?
Uterus: opens cervix and contracts uterus Lactating breast: milk ejection
26
Suckling on a lactating breast (or hearing a baby cry or smelling a baby) will cause the release of what hormone?
Oxytocin | Which will then cause milk ejection from the nipple
27
Stretching of the cervix causes the release of what hormone ?
Oxytocin Which then causes more uterus contraction A POSITIVE FEEDBACK LOOP WHOAAAAAA 🙇‍♀️
28
What the F does oxytocin do in the heart?
The heart synthesizes and has receptors for OT. When OT is released, it causes ANP/BNP to be released from the cardiomyocytes, and the ANP stimulates the release of nitric oxide from vascular endothelium.
29
Is there more oxytocin in the heart’s atria or ventricles?
3-4x more abundant in atria
30
What causes the release of OT from the heart?
Stretch (increased blood volume)
31
In what ways can Oxytocin regulate blood pressure?
1. In peripheral arterioles, it induces nitric oxide release, causing vasodilation 2. In cardiac muscle, it causes the synthesis and release of ANP and NO, causing negative inotropic and chronotropic effects. ANP induces vasodilation of peripheral arterioles. 3. In the kidney, OT stimulates diuresis and natriuresis 4. Decreases CRF which leads to decreased cortisol production= less stress hormone
32
What receptors does ANP bind to?
natriuretic peptide A Receptor (NPR-A)
33
What are the 2 sources of OT that the heart can respond to?
Pituitary Cardiac
34
What effect does OT have on the heart?
Causes nitric oxide synthesis=dilation of coronary vessels Slows heart rate Decreases strength of contraction Increase in glucose uptake
35
Why would we be interested in giving oxytocin to people with prediabetes?
Because OT increases glucose uptake by a GLUT4 mechanism, independent of the insulin pathway
36
What does this professor prefer to call ADH?
AVP
37
What is this professors name
I don’t know
38
Is this professor a serial killer
Probably
39
What causes the release of ADH?
Increase in plasma osmolarity Decrease in blood volume Angiotensin II
40
What effect will dehydration have on AVP/ADH release?
Increase Dehydration causes hypovolemia and increase in osmolarity
41
Where are the osmoreceptors that detect changes in plasma osmolality?
In the anterior hypothalamus and outside the BBB
42
Which happens first: release of AVP/ADH or stimulation of thirst?
Release of AVP
43
What effect does AVP/ADH have on the kidney?
Causes water reabsorption from the distal tubule and collecting duct Results in increased plasma volume and decrease in osmolarity Low urine output
44
Does it take a small or large change in plasma osmolarity to stimulate release of AVP/ADH?
VERY SMALL CHANGE This is a VERY sensitive system
45
A (large/small) change in blood volume will cause the release of ADH/AVP
VERY large blood volume decrease is required 8-10% of blood volume must be lost
46
What happens to GH levels as you age?
Decrease
47
When do GH levels peak?
Puberty
48
With the increase of GH release, the release of _________ also increases
IGF-1
49
What time of day does GH secretion peak?
During sleep
50
Is GH released in a steady stream?>
No, it is released in pulsatile bursts, so hormone levels fluctuate throughout the day, and plasma measurements are not a good reflection of the function of the anterior pituitary
51
Which hormones amplify the secretion of GH in men vs women
Men: testosterone Women: estradiol (premenopausal women have more GH)
52
The pattern and frequency of pulse release is (the same/different) for males and females
The same
53
The principal regulators of GH release are: 1. 2.
1. GH-releasing hormone | 2. Somatostatin
54
Which cells release GH?
Somatotrophs
55
What are the target cells of GH-RH?
Somatotrophs
56
What kind of a receptor does GH-RH bind to on a somatotrophs?
Gα-s Causes increase in cAMP
57
What kind of receptor does somatostatin bind to on somatotrophs?
Gα-i Decrease in cAMP
58
What happens when GH-RH binds to a somatotroph
1. Increased Adenylate cyclase activity 2. Increased cAMP 3. PKA is activated 4. PKA phosphroylates CREB 5. CREB causes the transcription of Pit-1 6. Pit-1 activates the transcription of the GH gene, causing increased GH levels 7. Pit-1 also upregulates the GH-RH receptor on the somatotroph
59
What happens when somatostatin binds to a somatotroph?
Adenylate Cyclase is inhibited =no PKA to phosphorylation CREB, no Pit-1 transcription and no GH transcription
60
What things will stimulate GH release?
Hypoglycemia Decreased FFAs Arginine Fasting/starvation/exercise Stress Sleep Thyroid hormone Androgens Ghrelin
61
What things will inhibit GH release?
Hyperglycemia Increased FFAs Obesity Aging GH IGF-1
62
How does arginine increase GH release?
It suppresses somatostatin release, allowing GH to be secreted unopposed
63
What are the 2 clinical methods of measuring GH status?
1. Arginine | 2. Insulin challenges to induce hypoglycemia
64
True or False: | GH has direct and indirect effects
True
65
The direct effects of GH are mostly __________
Metabolic
66
The indirect effects of GH are mostly ___________
Growth related
67
What 3 ways does GH affect metabolism?
1. Protein anabolism (muscle) 2. Lipolysis in adipose tissue to mobilize lipids for energy during fasting 3. Stimulates hepatic gluconeogenesis (to provide fuel for the brain during fasting)
68
How could over secretion of GH lead to a form of diabetes?
Because it causes lipolysis in adipose tissue,and an increase of FFAs, muscle and adipocytes don’t uptake glucose In addition, it stimulates gluconeogenesis by the liver. Net effect is an increase in glucose and plasma insulin. Because GH antagonizes the action of insulin, this can lead to a diabetogenic effect ******MUST KNOW THIS******
69
Why are GH’s effects on growth called “indirect”
Because GH causes the release of IGF-1 and IGFBP from the liver and IGF-1 is a peptide that actually acts on muscles, tissues, organs and chondrocytes to increase growth
70
IGF-1 is a peptide that should dissolve nicely in the plasma, yet 80% of it is bound to IGFBP! WHY
Becasue it increases the half-life of IGF1, which is important during times of growth
71
What are the effects of GH on growth?
These are actually indirect effects of GH since these are being done by IGF-1: 1. Muscle- increase lean body mass via increased amino acid uptake and protein synthesis 2. Tissues/organs- increased protein synthesis, DNA synthesis, cell size/number 3. Chondrocytes- increase linear growth via increased amino acid uptake, protein synthesis, DNA synthesis, collagen, chondroitin sulfate, and cell size/number
72
Can GH-RH suppress its own release?
Yes | This is an ultrashort feedback loop!
73
How does GH have an ~autocrine~ inhibitory effect on the somatotroph?
GH feeds back to the hypothalamus to suppress GH-RH release
74
What effects does IGF-1 have on GH release
Suppresses GH release directly from the somatotrophs Stimulates somatostatin production to inhibit the synthesis of GH
75
GH levels increase when: Food is abundant and anabolic/growth states are favored Or Food is scarce and catabolic states are favored
BOTH! However, the effects of GH are different
76
When protein and energy intake are ample, what happens to: GH IGF Insulin
GH increases IGF increases due to GH and insulin Insulin increases due to the protein
77
When protein and energy intake are both ample, what happens to: Protein synthesis Growth Caloric storage
Protein synthesis increases Growth increases No change in caloric storage
78
When carbohydrates alone are ingested, what happens to: GH IGF Insulin Protein synthesis Growth Caloric storage
GH decreases IGF no change Insulin increases Protein synthesis no change Growth no change Caloric storage increased (due to insulin)
79
If you drink 2 L of sugary Cola what happens to your IGF levels
No change
80
In the fasted state, what happens to: GH IGF Insulin Protein synthesis Growth Caloric mobilization
GH increases IGF DECREASES Insulin decreases Protein synthesis/growth DECREASE due to no IGF Caloric mobilization increased (gluconeogenesis, lipolysis)
81
Why does IGF1 decrease in the fasted state even though the hypoglycemia increases GH release?
Fasting increases cortisol levels as well, so the GH and Cortisol promote the production of IGF-BPs. The increase of IGF-BP in the plasma limits the bioavailability of IGF1 to the tissues, and growth is diverted
82
What is the difference between hypopituitarism and panhypopituitarism
Hypopituitarism: only GH is deficient Panhypopituitarism: more than one anterior pituitary hormone is deficient
83
What is the most frequent cause of hypopituitarism?
Traumatic injury such as surgery, car accident, or ischemic damage
84
What is it called when there is ischemic damage to the mother’s anterior pituitary during the postpartum period?
Sheehan Syndrome
85
Can GH deficiency result from impairment at any site of the hypothalamus-pituitary-GH-IGF-axis?
Yes
86
What causes dwarfism?
GH deficiency before puberty
87
Why do some people affected by dwarfism appear pudgy?
Loss of GH-induced lipolysis
88
What causes Laron dwarfism?
Genetic defect in the GH receptor. They have high GH levels but do not produce IGFs or IGF-BPs in response to GH. Their hypothalamus-pituitary axis is totally fine, the defect is in the liver
89
What causes African pigmy-ism?
Partial resistance of GH-receptors in the liver leads to low levels of IGF during puberty
90
What causes acromegaly?
GH hypersecretion AFTER the epiphysis close in adults. Usually caused by a tumor of the somatotrophs. IGF levels become very high.
91
What happens to patients who have acromegaly?
They have appositional bone growth and soft tissue deformities Enlarged hands and feet, decreased fat content Slow onset diabetes Prognathism Gynecomastia Lactation (Last two when prolactin and mammosomatotrophs are involved)
92
How is acromegaly treated?
Surgery to remove pituitary tumor Octreotide (somatostatin analogues) Dopamine analogues GH-receptor antagonists if PRL is co-secreted (He didn’t talk about the last two)
93
What causes gigantism?
GH oversecretion before puberty
94
What happens to people with gigantism
Excessive growth in long bones Hyperinsulinemia/diabetes Cardiac enlargement

Physiology II Exam 2 (Lauren) (4 decks)

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