The Pituitary Gland and the Hypothalamus Flashcards by Zain Aslam

What is the hypothalamus and the pituitary gland known as?

Principle organisers of the endocrine system

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How is the hypothalamus and pituitary connected?

Via the pituitary stalk called the infundibulum

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Is hypothalamic communication to the Pit. Gland neural or endocrine?

Both - neural to posterior gland and endocrine to anterior gland = neuroendocrine function

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Where is the Pit gland?

In a pocket in the sphenoid bone directly below the hypothalamus

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What types of hormone do the hypothalamus and pit gland release?

Trophic and non-trophic

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What is a trophic hormone? Give an example of when oit is used?

A hormone that governs the release of another hormone

Neurohormones secreted into capillaries and traveling to the anterior pit. gland governing release of AP hormones

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Give an example of non-trophic hormones.

Neurohormones made in hypothalamus and travel via hypothalamic axons to the posterior Pit. gland

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All hormones released by the posterior pit. gland are…

Neurohormones from hypothalamus

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All hormones released by the AP gland are…

Classic endocrine hormones

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What do all hypothalamic trophic hormons bind to? What does this binding do?

Receptors on the AP gland which inhibit or stimulate hormone release

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Name the 5 hypothalamic releasing hormones and what they do.

Stimulate AP to release hormones

Thyrotropin releasing hormone - TRH

Corticotropin releasing hormone - CRH

Growth Hormone Releasing Hormone - GHRH

Gonadotropin Releasing Hormone - GnRH

Prolactin Releasing Hormone - PRH

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Name the hypothalamic inhibiting hormones.

Growth hormone inhibiting hormone - GHIH

Prolacting inhibiting hormone - PIH

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What is growth hormone inhibiting hormone also known as?

Somatostatin

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What is prolactin inhibiting hormone?

Dopamine

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What type of hormone class are all the hypothalamic hormones?

All are peptide BESIDES dopamin/prolactin inhibiting hormone which is an amine

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What is the hypothalamo-hypophyseal portal system?

A network of vessels which transfer trophic hormones from hypothalamus to the AP

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What is needed to maintain control of the hypothalamo-hypophyseal portal system?

Small numbers of neurosectretory neurons

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How does the H-H portal system work?

Hormones are released from the neurosecretory neurons at the median eminence and travel via capillaries to the AP gland

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Does the H-H portal system encompass a short or long system - what significance does this have?

Short - leads to a rapid and dynamic response

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What is a hypophysiotropic hormone?

Hormones made by endocrine cells in the hypothamalus and released at the capillary bed called the median eminence and transported to the AP gland

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What type of tissue is the AP and the PP glands?

AP - true endocrine

PP - neuroendocrine

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What is the origin of both glands

AP - epithelial

PP - neural tissue

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How are both glands connected to the hypothalamus?

AP - via capillary portal system called the hypothalamo-hypophyseal system

PP - neural connection

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What is the AP gland also called?

Adenohypophysis

What does the PP gland secrete?

Neuro hormones made in the hypothalamus

What is the PP gland also called?

Neurohypophysis

How much of the pituitary does each gland make up?

AP - 2/3s | PP- 1/3

What are the 6 hormones released from the AP gland?

Thyroid stimulating hormone - TSH Adrenocorticotrophic hormone - ACTH Follicle stimulating hormone - FSH Luteinising Hormone - LH Growth Hormone - GH Prolactin

5 of the 6 hormones released by the AP gland have trophic functions- which one is not trophic and what does it do?

Prolactin - direct stimulation of milk production during lactation

What is another name for Thyroid stimulation hormone? And what does it do?

Thyrotrophin - Leads to thyroid hormone release

What is another name for adrenocotricotrophic hormone and what does it do?

Corticotrophin - Acts on adrenal cortex to stimulate cortisol release

What is another name for follicle stimulating hormone and luteinising hormone?

Gonadotrophins - act on gonads leading to regulation of reproductive function (non-trophic action of the hormone) and sex hormone release (trophic)

What does growth hormone do?

Acts on liver to release IGF-1* (trophic action) Directly stimulates tissue metabolism (non-trophic)

What does 3 integration centers does feedback control involve?

Hypothalamus AP gland Target endocrine cell

What acts as the neg. feedback signal?

The hormone itself

How does the neg. feedback work?

The hormone fees back to inhibit hormone secretion

What is a long-loop feedback?

When the hormone feeds back from the endocrine target

What is a short-loop feedback?

When the feedback is from the AP to the hypothalamus

Purpose of feedback systems?

Link levels of sequential hormones together and maintains plasma conc within correct range

What hormones does the PP gland store and release?

Vasopressin | Oxytocin

What is another name for vasopressin?

ADH - Anti-diuretic hormone

Where are ADH and oxytocin synthesised?

In magnocellular neurons which have their cell bodies in specific areas of the hypothalamus

How do these hormones get from the hypothalamus to the PP gland?

Axons project down the infundibulum to the PP gland, they don't synspase but their terminals end on capilaries - The hormones travel down this route and are stored in the terminals until the nerve is stimulated and they are released directly into blood stream into PP gland

ADH and oxytocin behave as what type of hormones?

Peptide

Function of ADH?

Regulate water balance

What triggers ADH release?

Increased plasma osmolarity | Decreased plasma volume/BP

What is the site of action for ADH and what is its mode of action?

Site - kidney collecting ducts Mode - increase water re absorption and increase BP

Function of oxytocin?

Milk ejection and uterine contraction

What triggers oxytocin release?

Labour - babies head against cervix | Suckling

Site and mode of action for oxytocin for milk production?

Site - milk duct, smooth muscle Mode - contracts muscle which ejects milk

Site and mode of action for oxytocin for labour

Site - uterine smooth muscle | Mode - Child birth

What is hyposecretion?

Too little

Hypersecretion?

Too much

Hyper/Hypo-responsiveness means?

Reduced or increased response of target cell

1* disorders are what...?

Those in which the defect is in the cells that secrete the hormone

2* disorders?

Where there is too little or too much trophic hormone from pituitary causing hormone to be too high or too low

3* disorders?

Relate to hypothalamic defects

What can cause hyporesponsiveness?

Alterations in receptors for the hormone Disordered post-receptor events Failure of metabolic activation of hormone (Still a prehormone/prepro)

What can cause hyper-responsiveness

Permissive effects