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ENDO > Week 3 > Flashcards

Week 3 Flashcards

Hypothalamus and Pituitary

1
Q

What is the function of the hypothalamus?

A

-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

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2
Q

What hormones are produced by the hypothalamus?

A

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

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3
Q

What are the actions of ADH?

A

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

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4
Q

What are the actions of oxytocin?

A

-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

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5
Q

Describe negative feedback.

A

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

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6
Q

Describe positive feedback

A

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

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7
Q

What is another names for the anterior and posterior pituitary?

A

Anterior - adrenohypophysis Posterior - neurohypophysis

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8
Q

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

A

Magnocellular Parvocellular

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9
Q

What are the two magnocellular neurons?

A

The paraventricular and the supraoptic

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10
Q

What is the location of the pituitary?

A

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

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11
Q

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

A

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.

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12
Q

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

A

They release them into the median eminence

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13
Q

What are the two classes of hypothalamus regulatory hormones?

A

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

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14
Q

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

A

The hypothalamic-hypophyseal portal vessels

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15
Q

Describe the blood supply to the anterior pituitary

A

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

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16
Q

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

A

Hypophyseotropic hormones

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17
Q

What is the action of TRH?

A

Stimulates secretion of TSH by thyrotropes

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18
Q

What is the action of GnRH?

A

Stimulates the secretion of FSH and LH by gonadotropes

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19
Q

What is the action of CRH?

A

Stimulates secretion of ACTH by corticotropes

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20
Q

What is the action of GHRH?

A

Stimulates the secretion of GH by somatotropes

21
Q

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

A

Inhibits the secretion of growth hormones by somatotropes

22
Q

What is the action of PIH?

A

Inhibits the synthesis and secretion of prolactin by lactotropes

23
Q

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

A

Peptide

24
Q

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

A

Peptide

25
Q

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

A

Peptide

26
Q

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

A

Peptide

27
Q

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

A

Peptide

28
Q

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

A

Catecholamine

29
Q

What is the mechanism of action of CRH?

A
  • 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
30
Q

What hormones does TRH stimulate?

A

TSH (both alpha and beta subunits) and prolactin

31
Q

What is the mechanism of action of TRH?

A
  • 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
32
Q

What is the mechanism of action for GHRH?

A
  • 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
33
Q

What is the mechanism of action for GnRH?

A
  • 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
34
Q

What is the mechanism of action for somatostatin?

A
  • 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
35
Q

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

A

The inhibitory action of GHIH is stronger than that of GHRH

36
Q

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

A

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

37
Q

What are neurophysins?

A

They are parts of the precursor molecules for ADH and Oxytocin

38
Q

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

A

Prepropressophysin

39
Q

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

A

Prepro-oxyphysin

40
Q

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

A

Axoplasmic Flow

41
Q

What stimulates the release of Oxytocin?

A

The main ones are breast-feeding and childbirth (dilation of the cervix)

Others include, suckling, sight/smell/sound of baby, orgasm.

42
Q

What is the mechanism of action for Oxytocin?

A
  • 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)
43
Q

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

A

Estrogen

44
Q

What is the target tissue for ADH?

A

The nephron in the kidneys and vascular smooth muscles

45
Q

What will stimulate the release of ADH?

A
  • increased plasma osmolarity (dehydration)
  • Decreased ECF volume
  • Angiotensin II
  • Pain
  • Nausea
46
Q

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

A

Kidney - V2 receptor

Muscle - V1 receptor

47
Q

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

A
  • binds to a GPCR
  • activates cAMP
  • causes insertion of water channels into the luminal membrane
48
Q

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

A
  • binds to GPCR
  • activates IP3/Ca2+ which produces contraction of smooth muscles and constriction of arteries
49
Q

What does Somatostatin inhibit:

A

Growth Hormone

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

ENDO (10 decks)

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