Hypothalamus and Pituitary

Question 1

Give 3 examples of biological states which are controlled by the hypothalamus.

Answer 1

Any 3 of:

• Temperature
• Appetite
• Thirst
• Fatigue
• Behaviour
• Circadian rythm
• Blood pressure
• etc.

Question 2

What inputs affect hypothalamic signalling? Give a few examples.

Answer 2

Light, smell, stress, immune system, neural inputs, endocrine inputs, etc.

Question 3

What are the 2 types of hypothalamic output? What differentiates these?

Answer 3

Direct innervation: fast, often for fight/flight response

Neurosecretion: slow, releases hormones which can have varying effect

Question 4

What is the function of hypophysiotropic hormone?

Answer 4

Regulates the release of anterior pituitary hormones.

Question 5

What is the function of thyrotropin-releasing hormone (TRH)?

Answer 5

Stimulates the release of thyroid stimulating hormone (TSH) from the anterior pituitary.

Question 6

What is the function of gonadotropin-releasing hormone (GnRH)?

Answer 6

Regulates luteinizing hormone and follicular stimulating hormone.

Question 7

What is the function of somatostatin?

Answer 7

A general inhibitor. Acts on growth hormone, thyroid stimulating hormone, insulin, glucagon, etc.

Question 8

What is the function of growth hormone-releasing hormone (GHRH)?

Answer 8

Stimulates the release of growth hormone (tropic), and helps growth of somatotrophs (trophic).

Question 9

What is the function of prolactin-inhibiting hormone (PIH)? What is another name for this?

Answer 9

Also called dopamine, it inhibits the release of prolactin.

Question 10

What is the function of corticotropin-releasing hormone (CRH)? What other hormones regulate it?

Answer 10

Regulates adrenocortical function, ACTH release, appetite, and sympathetic NS. Vasopressin positively regulates CRH while oxytocin acts as a negative regulator.

Question 11

What category of cell types secrete growth hormone (GH)? How are they regulated?

Answer 11

Somatotrophs. Inhibited by somatostatin but also have autocrine signalling for negative feedback.

Question 12

What category of cell types secrete prolactin (PRL)?

Answer 12

Lactotrophs.

Question 13

What category of cell types secrete thyroid-stimulating hormone (TSH)?

Answer 13

Thyrotrophs.

Question 14

What category of cell types secrete adrenocorticotropic hormone (ACTH)?

Answer 14

Corticotrophs.

Question 15

What category of cell types release luteinizing hormone (LH) and follicular stimulating hormone (FSH)?

Answer 15

Gonadotrophs.

Question 16

What kind of receptor does gonadotropin-releasing hormone (GnRH) bind to?

Answer 16

GPCRs.

Question 17

What type of GPCR Galpha subtype activates phospholipase C?

Answer 17

Galpha-q.

Question 18

How is the hypothalamic-pituitary-gonadal axis regulated?

Answer 18

The hormone products of the ovaries and the testis act on the hypothalamus and pituitary in a negative feedback loop.

Question 19

Why must gonadotropin-releasing hormone be secreted in pulses?

Answer 19

Otherwise it would lead to the desensitization of luteinizing hormone (LH) and follicular stimulating hormone (FSH).

Question 20

What kind of receptor does corticotropin-releasing hormone (CRH) bind to?

Answer 20

GPCRs.

Question 21

How is the hypothalamus-pituitary-adrenal axis regulated? (Hint: think “short” and “long” feedback)

Answer 21

By negative feedback, either ACTH secreted by the pituitary inhibiting CRH (short) or cortisol secreted by the adrenal gland inhibiting the pituitary (long).

Question 22

How can the negative feedback of cortisol on the release of ACTH from the pituitary have both fast and slow effects?

Answer 22

Fast: non-genomic, activates signalling pathways
Slow: genomic, alters transcription

Question 23

At what point during the day do we experience a peak in cortisol levels?

Answer 23

Immediately prior to waking. Cortisol levels then decline as the day progresses.

Question 24

What factors can influence the timing of the hypothalamus-pituitary-adrenal axis?

Answer 24

Stresses (physical, emotional, chemical) as well as the circadian rhythm.

Question 25

What effect does increased prolactin (PRL) have on the prolactin axis?

Answer 25

Inhibits gonadotropin-releasing hormone, therefore inhibiting ovulation and spermatogenesis (don’t need to get prego if already prego). Also stimulates milk production and breast development.

Question 26

How can prolactin (PRL) production in the anterior pituitary be upregulated?

Answer 26

Breastfeeding causes negative feedback on prolactin inhibitory hormone (aka dopamine) secreted by the hypothalamus. Inhibiting the inhibitor = upregulation!