Week 3

Question 1

What is the function of the hypothalamus?

Answer 1

-Works to regulate homeostasis -It is the relay station between the nervous and endocrine system -Controls the sex drive and sexual behaviours -Controls emotions and behaviour patterns -Controls the sleep-awake cycle

Question 2

What hormones are produced by the hypothalamus?

Answer 2

The hypothalamus will synthesise and produce hormones for the posterior pituitary which are ADH (also known as Vasopressin) and Oxytocin. For the anterior pituitary it will produce the tropic hormones TRH, CRH, GnRH, and GHRH

Question 3

What are the actions of ADH?

Answer 3

It has two main functions. -It causes water re-absorption in the nephrons in the kidney. -Can cause smooth muscle contraction and vasoconstriction which raises the blood pressure

Question 4

What are the actions of oxytocin?

Answer 4

-It will stimulate milk ejection by contracting the myoepithelial cells in the mammary gland -Can cause the uterus to contract during child birth -Can cause sexual arousal and produce nurturing feelings

Question 5

Describe negative feedback.

Answer 5

This is where the end product of a process will reduce the stimuli for the same process. Effectively reducing the production of the end product

Question 6

Describe positive feedback

Answer 6

This is where the end product of a process will increase the stimuli for the same process.

Question 7

What is another names for the anterior and posterior pituitary?

Answer 7

Anterior - adrenohypophysis Posterior - neurohypophysis

Question 8

What are the two types of neurons that mediate the endocrine function in the hypothalamus?

Answer 8

Magnocellular Parvocellular

Question 9

What are the two magnocellular neurons?

Answer 9

The paraventricular and the supraoptic

Question 10

What is the location of the pituitary?

Answer 10

It is inferior to the hypothalamus and lies in a depression in the base of the skull called the sella turica

Question 11

What is the embryonic origin of the anterior and posterior pituitary and relate to their function.

Answer 11

Posterior pituitary: From the hypothalamus or more specifically the 3rd ventricle of the cerebrum. As it is from neural origin it is a neural endocrine gland. Anterior pituitary: from cells of the roof of the embryonic oral cavity, more specifically Rathke’s pouch. It is from a vascularised place and thus is an endocrine organ.

Question 12

Where do the neurons of the anterior pituitary release their hormones?

Answer 12

They release them into the median eminence

Question 13

What are the two classes of hypothalamus regulatory hormones?

Answer 13

-Releasing hormones which will stimulate the secretion of one or more hormones -Inhibiting hormones which prevent the synthesis and secretion of hormones

Question 14

What is the name of the blood supply in the anterior pituitary?

Answer 14

The hypothalamic-hypophyseal portal vessels

Question 15

Describe the blood supply to the anterior pituitary

Answer 15

The superior hypophyseal artery which supplies the primary capillary plexus. This then leads into the long hypophyseal portal veins to the secondary capillary plexus before the hormones are released into a vein

Question 16

What is the term used to describe the hormones that are released into the median eminence?

Answer 16

Hypophyseotropic hormones

Question 17

What is the action of TRH?

Answer 17

Stimulates secretion of TSH by thyrotropes

Question 18

What is the action of GnRH?

Answer 18

Stimulates the secretion of FSH and LH by gonadotropes

Question 19

What is the action of CRH?

Answer 19

Stimulates secretion of ACTH by corticotropes

Question 20

What is the action of GHRH?

Answer 20

Stimulates the secretion of GH by somatotropes

Question 21

What is the action of GHIH? (also known as somatostatin)

Answer 21

Inhibits the secretion of growth hormones by somatotropes

Question 22

What is the action of PIH?

Answer 22

Inhibits the synthesis and secretion of prolactin by lactotropes

Question 23

What types of hormones is CRH? (protein, peptide, catecholamine, etc.)

Answer 23

Peptide

Question 24

What type of hormones is TRH? (protein, peptide, catecholamine, etc.)

Answer 24

Peptide

Question 25

What type of hormone is GHRH? (protein, peptide, catecholamine, etc.)

Answer 25

Peptide

Question 26

What type of hormone is GnRH?(protein, peptide, catecholamine, etc.)

Answer 26

Peptide

Question 27

What type of hormone in somatostatin? (protein, peptide, catecholamine, etc.)

Answer 27

Peptide

Question 28

What types of hormone is Dopamine? (protein, peptide, catecholamine, etc.)

Answer 28

Catecholamine

Question 29

What is the mechanism of action of CRH?

Answer 29

- It binds to a G-protein coupled receptor on the cell membrane of corticotrophs - this wil activate the second messenger cAMP - this then activates protein kinase A (PKA) to activate Ca2+ channels to increase intracellular calcium - this leads to the exocytosis of ACTH

Question 30

What hormones does TRH stimulate?

Answer 30

TSH (both alpha and beta subunits) and prolactin

Question 31

What is the mechanism of action of TRH?

Answer 31

- It binds to a G-protein coupled receptor - This activates teh second messenger pathway of DAG/IP3 - this leads to protein phosphorylation and a rise in intracellular Ca2+ - this stimulates thyrotropes to syntheisze and release TSH

Question 32

What is the mechanism of action for GHRH?

Answer 32

- binds to a G-protein coupled receptor - thsi stimulates adenylyl cyclase to activate the second messenger cAMP - cAMP causes an increase in gene transcription and synthesis of GH - this causes the Ca2+ channels to open causing a rise in intracellular calcium which stimulate the release of GH through expcytosis

Question 33

What is the mechanism of action for GnRH?

Answer 33

- binds to a G-protein coupled receptor - this activates phosphlipase C causing activation of the DAG/IP3 pathway - this in turn causes a relase of Ca2+ from intracellular stores triggering an exocytosis of LH and FSH

Question 34

What is the mechanism of action for somatostatin?

Answer 34

- Binds to a G-protein coupled receptor and activates Gαi - this inhibits adenylyl cyclase which decreases the cytosolic calcium - this decreases the cells responsiveness to GHRH

Question 35

If a somatotroph is exposed to both GHRH and GHIH which hormone will prevail?

Answer 35

The inhibitory action of GHIH is stronger than that of GHRH

Question 36

Which posterior neuron primarily secretes ADH and which one primarily secrets Oxytocin?

Answer 36

ADH is mainly from the supraoptic nuclei Oxytocin is mainly from the paraventricular nuclei Although both classes of neurons can secrete both, these are the ones the primarily secrete

Question 37

What are neurophysins?

Answer 37

They are parts of the precursor molecules for ADH and Oxytocin

Question 38

What is the precursor for ADH? (what is the name of the neurophysin)

Answer 38

Prepropressophysin

Question 39

What is the precursor for oxytocin? (name the neurophysin)

Answer 39

Prepro-oxyphysin

Question 40

What is the name of the flow that pulls the hormones down the neuron to the endings in the posterior pituitary?

Answer 40

Axoplasmic Flow

Question 41

What stimulates the release of Oxytocin?

Answer 41

The main ones are breast-feeding and childbirth (dilation of the cervix) Others include, suckling, sight/smell/sound of baby, orgasm.

Question 42

What is the mechanism of action for Oxytocin?

Answer 42

- Binds to G-protein coupled receptor - triggers phosphlipase C - Causes formation of IP3 and the release of Ca2+ stores in the cell - the increase of Ca2+ activates calmodulin which results in contraction of smooth muscle (either of the myoepithelial cells of the uterine smooth muscles)

Question 43

What hormone will cause an increase in the number of Oxytocin receptors?

Answer 43

Estrogen

Question 44

What is the target tissue for ADH?

Answer 44

The nephron in the kidneys and vascular smooth muscles

Question 45

What will stimulate the release of ADH?

Answer 45

- increased plasma osmolarity (dehydration) - Decreased ECF volume - Angiotensin II - Pain - Nausea

Question 46

What are the name of the receptors for ADH in the kindney and in the smooth muscle?

Answer 46

Kidney - V2 receptor Muscle - V1 receptor

Question 47

What is the mechanism of action of ADH on V2 receptors?

Answer 47

- binds to a GPCR - activates cAMP - causes insertion of water channels into the luminal membrane

Question 48

What is the mechanism of action of ADH on V1 receptors?

Answer 48

- binds to GPCR - activates IP3/Ca2+ which produces contraction of smooth muscles and constriction of arteries

Question 49

What does Somatostatin inhibit:

Answer 49

Growth Hormone TSH (inhibited by somatostatin analog: Octreotide acetate/octreotide)