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My LCRS - Endocrinology > The Hypothalamo-Adenohypophysial Axis > Flashcards

The Hypothalamo-Adenohypophysial Axis Flashcards

1
Q

Where does the pituitary gland lie in the brain and under which structure?

A

At the base of the brain in the sella turcica

Directly under the hypothalamus

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2
Q

What is the function of the hypothalamus?

A

Regulates the endocrine system

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3
Q

Which ventricle does the hypothalamus lie around?

A

The third ventricle

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4
Q

How do the two lobes of the pituitary gland develop?

A

Anterior (adenohypophysis) - ‘grows up’ and attaches to base of the brain
Posterior (neurohypophysis) - ‘grows down’ and attaches to the anterior lobe, consists mainly of nerve axons and terminals

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5
Q

What is the region between the hypothalamus and the pituitary gland called?

A

Region of median eminence

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6
Q

What are the hypothalamic nuclei?

A

Clusters of nerve cell bodies in the hypothalamus

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7
Q

Two types of neurones in the hypothalamic nuclei?

A

Neurones that pass through the region of median eminence and terminate at the neurohypophysis (posterior pituitary)
Neurones that terminus at the region of median eminence

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8
Q

Artery supplying region of median eminence?

A

Superior hypophysial artery

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9
Q

Process of neurosecretion into the hypothalamo-hypophysial portal system and to target cells?

A

Hypothalamic neurone is activated, hypothalamic neurosecretion occurs
Neurosecretion released into fenestrated primary capillary plexus in the region of median eminence
Neurosecretions travel by long portal veins and secondary capillary plexus to anterior pituitary target cells

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10
Q

What happens when neurosecretions reach the anterior pituitary cells?

A

Stimulates adenohypophysial hormone release into the CAVERNOUS SINUS and then into general circulation via the jugular veins

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11
Q

General process of adenohypophysial hormone production and packaging?

A

Enzymes cleave prohormones to produce bioactive hormone

Hormones stored in secretory granules

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12
Q

2 protein adenohypophysial hormones?

A

Somatotrophin - produced by somatotrophs

Prolactin - produced by lactotrophs

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13
Q

2 glycoprotein adenohypophysial hormones?

A

Thyrotrophin - thyrotrophs

Gonadotrophins (LH and FSH) - gonadotrophs

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14
Q

Polypeptide adenohypophysial hormone?

A

Corticotrophin (ACTH) - corticotrophs

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15
Q

What molecules stimulate and inhibit release of somatotrophin?

A

Somatotrophin releasing hormone - stimulates release

Somatostatin - inhibits release

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16
Q

What molecules stimulate and inhibit release of prolactin?

A

Thyrotrophin releasing hormone - stimulates release

Dopamine - inhibits release

17
Q

What molecule stimulates thyrotrophin release?

A

Thyrotrophin releasing hormone - stimulates release

18
Q

What molecule stimulates LH and FSH (gonadotrophins) release?

A

Gonadotrophin releasing hormone - stimulates release

19
Q

What molecule stimulates corticotrophin release?

A

Corticotrophin releasing hormone - stimulates release

Vasopressin - also stimulates release (secondary)

20
Q

Which tissues do the 5 main adenohypophysial hormones act on?

A 
Somatotrophin - general body tissue, especially liver
Prolactin - breasts (lactating women)
Thyrotrophin - thyroid
Gonadotrophin - testes, ovaries
Corticotrophin - adrenal cortex
21
Q

Effect of somatotrophin binding to receptors on the liver?

A

Release of SOMATOMEDINS (IGF I, IGF II)

22
Q

Effect of somatotrophin binding to general body tissues?

A

Increased growth and development

23
Q

Somatomedin metabolic effects?

A

Amino acid transport into cells
Protein synthesis
Lipid metabolism leading to increased fatty acid production
Insulin resistance - decreased glucose utilisation and increased blood glucose concentration
Increased cartilage growth

24
Q

Which molecules negatively feedback on somatotrophin production?

A

Somatotrophin and somatomedin release both themselves inhibit further somatotrophin production
Somatostatin also inhibits release

25
Q

Somatotrophin releasing hormone stimulates somatotrophin release, what other conditions stimulate its release?

A 
Sleep (stage 3/4)
Stress
Oestrogens
Exercise
Gasting/hypoglycaemia
Amino acids
Ghrelin (from stomach)
26
Q

Prolactin main physiological effect?

A

Breast lactogenesis in lactating women

27
Q

Secondary effects of prolactin?

A

Increased LH receptors in gonads
Increase Na+/water reabsorption
Steroidogenesis
Immunological effects, stimulates T cells

28
Q

What is prolactin release stimulated by and what is the mechanism resulting in release?

A

Suckling stimulates tactile receptors in breast nipple
Afferent signals stimulate release of TRH and inhibit release of dopamine
These increase prolactin release
Prolactin stimulates milk production by endocrine efferent neural pathway
This is an example of a NEUROENDOCRINE REFLEX ARC

My LCRS - Endocrinology (5 decks)

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