Endocrine 3 - Hypothalamus and Pituitary

Question 1

Paraventricular and supraoptic nuclei are known as _________ neurons that secrete _______ and _______, respectively.

Answer 1

they are known as magnocellular neurons that secrete oxytocin and ADH, respectively.

Question 2

When the stalk between the hypothalamus and pituitary is disrupted, are all posterior hormones lost forever?

Answer 2

No, the anterior ones are, but the neurons to the posterior pituitary will regrow and re-synapse.

Question 3

What are the neurophysin peptides and what do they do?

Answer 3

They are large segments of the precursor peptide of oxytocin and ADH that serve to protect oxytocin and ADH from degradation in the bloodstream.

Question 4

What stimulates ADH release? What does it do?

Answer 4

Low plasma volume or high plasma osmolarity triggers its release. It acts on kidney CD cells to increase H2O permeability –> increased BP and volume.

Question 5

What stimulates oxytocin release? What does it do?

Answer 5

Parturition, orgasms stimulate its release. It acts on the breast and uterus, stimulates smooth muscle contraction.

Question 6

Is ADH release more sensitive to plasma osmolarity, or low pressure/volume?

Answer 6

Osmolarity

Question 7

Are the effects of ADH on urine volume much more sensitive at very low levels of ADH?

Answer 7

Yeah

Question 8

What receptors and 2nd messengers do oxtyocin and ADH use?

Answer 8

7-transmembrane receptors –> G-alpha protein –> cAMP –> insertion of aquaporins in the cell membranes.

Question 9

Name the five anterior pituitary cell types and what each one secretes.

Answer 9

1. Corticotroph –> ACTH
2. Gonadotroph –> LH/FSH
3. Thyrotroph –> TSH
4. Lactotroph –> PRL
5. Somatotroph –> GH

Question 10

Does GH promote tissue growth directly?

Answer 10

Nope.

GH binds to liver cells –> IGF-1 –> tissue growth

Question 11

Why are people taller now? Why are New Guinea highlanders short?

Answer 11

People are taller now because we eat more arginine. New Guinea highlanders have a low affinity GH receptor on liver cells.

Question 12

Is GH-induced lipolysis mediated by IGF-1?

Answer 12

Nope. GH binds directly to adipose cells –> lipolysis

Question 13

What can excess GH do to glucose metabolism?

Answer 13

It makes people insensitive to insulin.

Question 14

During what part of the sleep cycle are GH levels the highest? What about cortisol?

Answer 14

GH levels are highest ~1 hour after going to sleep. Cortisol levels are highest after you wake up (~9-10 hours after going to sleep, cuz you need to mobilize glucose from fasting overnight).

Question 15

Does nipple stimulation increase prolactin production?

Answer 15

In females yeah

Question 16

What are the three glycoprotein hormones of the anterior pituitary? What do they all have in common? What differentiates them from each other?

Answer 16

TSH, LH, FSH

They all have a common alpha chain, but the beta chain is what confers specificity and interacts with the receptor.

Question 17

What three things are derived from POMC?

Answer 17

1. ACTH
2. alpha-MSH
3. beta-Endorphin

Question 18

Where is somatostatin made and what does it do?

Answer 18

Made by delta cells in the GI tract as well as in the hypothalamus. It inhibits secretion of GH and TSH.

Question 19

Where does CRH come from and what does it do?

Answer 19

Hypothalamus, stimulates release of the POMC-derived hormones (a-MSH, B-Endorphin, ACTH)

Question 20

Where does TRH come from and what does it do?

Answer 20

Hypothalamus, stimulates release of TSH and prolactin

Question 21

Where does dopamine come from and what does it do?

Answer 21

Hypothalamus, inhibits release of prolactin.

Question 22

Define the following feedback loops: ultrashort, short, long.

Answer 22

Ultrashort is when the tissue that releases a hormone is negatively regulated by that exact hormone.

Short is when the immediate target tissue’s product downregulates the initial source (when AP hormones feedback on the hypothalamus).

Long is when the final target organ’s products feedback to the upstream organs.

Question 23

What is brain derived neurotrophic factor (BDNF)?

Answer 23

Its made in the hypothalamus and is a negative regulator of food intake.

Question 24

Name a hormone that participates in ultra-short negative feedback.

Answer 24

Somatostatin

Question 25

Is oxytocin associated with social bonding and blah blah?

Answer 25

Yeah

Question 26

Growth hormone:

A. is also known as somatomedin
B. is secreted in response to somatostatin
C. has both anabolic and catabolic actions
D. is related in structure to progesterone
E. enhances insulin action

Answer 26

C. has both anabolic and catabolic actions

Question 27

Preproopiomelanocortin

A. is made by cells in the hypothalamus
B. contains the hormones TSH and LH
C. stimulates the adrenal cortex to make aldosterone
D. is made by cells in the posterior pituitary
E. contains the hormones ACTH and b-endorphin

Answer 27

E. contains the hormones ACTH and b-endorphin

Question 28

GH inhibition of GHRH release is an example of?:

A. short loop negative feedback
B. long loop negative feedback
C. short loop positive feed back
D. long loop positive feedback
E. ultrashort loop negative feedback

Answer 28

A. short loop negative feedback

Question 29

An example of long loop negative feedback is:

A. IGF-1 stimulation of somatostatin release
B. cortisol stimulation of CRH release
C. IGF-1 stimulation of GHRH release
D. prolactin stimulation of dopamine release
E. SST inhibition of TRH secretion

Answer 29

A. IGF-1 stimulation of somatostatin release