Lecture 2 - Hypothalamo-hypophysial axis: Adenohypophysis Flashcards

1
Q

Draw a diagram of Hypotalamo-hypophysial axis

A

Remember: 3rd ventricle Optic chiasma Hypothalamus Mamillary body Adenohypophysis Neurohypophysis

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2
Q

Anterior pituitary (AP) key features:

A

Median eminence Pars tuberalis Pars distalis (Adenohypophysis) Superior hypophysial artery - to medial eminence and causes hypothalamic neurosecretion when activated Primary capillary plexus - neurosecretion collects here Long portal veins - neurosecretion circulates & acts on cells Secondary capillary plexus - neurosecretion circulates & acts on cells Cavernous sinus (out via jugular veins) - release of adenohypophysial hormones

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3
Q

Where is the pituitary gland located?

A

Sella Turcica

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4
Q

What does the median eminence do?

A

It’s a separator of the hypothalamus and pituitary gland

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5
Q

Innervation of pituitary gland

A

Hypothalamic nuclei can send their axons into the posterior PG or their axons stop before the median eminence

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6
Q

What is the name of the adenohypophysis?

A

Pars distalis

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7
Q

List the adenohypophysial cells and their secretions

A

Somatotrophs - somatotrophin Lactotrophs - Prolactin Thyrotrophs - Thyrotrophin (Thyroid stimulating hormone) Gonadotrophs - Gonadotrophin (LH and FSH) Corticotrophs - Corticotrophin (ACTH) Other cells - non defined

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8
Q

What are the general features of adenohypophysial hormones?

A

All made from Prohormones Enzyme cleavage leads to bioactive hormone AH hormones stored in secretory granules Released by exocytosis

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9
Q

What are some specific adenohypophysial hormones?

A

Proteins: Somatotrophin (191 a.a.), Prolactin (199 a.a.) Glycoproteins (all have same alpha subunit of 92 a.a.): TSH (beta 110), LH & FSH (115 beta) Polypeptide: ACTH (39 a.a.)

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10
Q

What are the hyothalamoadenohypophysial hormones and what do they cause?

A
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11
Q

What are the main target cells for adenohypophysial hormones?

A

Somatotrophin - body tissues and MAINLY liver

Prolactin - Breasts

Thyrotrophin - thyroid

Gonadotrophin - Tests and Ovaries

Corticotrophin - Adrenal cortex

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12
Q

What is the mode of action of somatotrophin?

A

Adenohypophysis > Somatotrophin released > Liver and Body tissues > Somatomedins (IGF I, IGF II) > Body tissues - metabolic actions –> GROWTH AND DEVELOPMENT

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13
Q

What metabolic actions are caused by somatotrophin via IGF I (direct and indirect effect)?

A

Stimulation of a.a. into cells Stimulation of protein synthesis Increased cartilaginous growth Stimulation of lipid metabolism > increased FA production Decreased glucose utilisation and increased gluconeogenesis > INCREASED blood glucose conc

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14
Q

How is somatotrophin regulated?

A
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15
Q

What are the effects of prolactin?

A

BREAST LACTOGENESIS Effects on IS (stimulating T cells) Increases LH receptors Pituitary - Decreases LH releases Hypothalamus - Decreases sexual behaviour Renal Na+/Water reabsorption Steroidogenesis

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16
Q

How is the release of prolactin stimulated (regulation)?

A
17
Q

What is the neuroendocrine reflex arc for prolactin?

A