Hypothalamus & pituitary (lecture 26) Flashcards by Phoebe Snow

What is the hypothalamus composed of?

nervous tissue - neurones

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What is the pituitary composed of?

Anterior and posterior lobes

also known as the hypophysis

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What is the anterior pituitary composed of?

True endocrine tissue
Known as the andenohypophysis

Originates from Rathke’s pouch

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What is the posterior pituitary composed of?

Made of neurones
Known as the neurohypophysis

Consists of axons & nerve endings of neurones whose cell bodies reside in the hypothalamus

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What is the hypothalamic-pituitary axis also known as?

The hypothalamohypophyseal

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What is the hypothalamus?

The region of the brain which plays a key role in homeostasis

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Structure of the posterior pituitary?

Stalk links hypothalamus to the posterior pituitary
Cell bodies of the neurones are in the paraventricular & supraoptic nuclei
The neurones are called the magnocellular neurones
Nerve terminals are in the posterior pituitary
Hormones are synthesised & taken down the axon to be stored in the nervous hermerals in the posterior pituitary before being released into the blood circulation

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Structure of the anterior pituitary?

Connected to hypothalamus by pituitary stalk 
Parvocellular neurones (red) are in the hypothalamus – cell bodies &amp; nerve terminals are both in the hypothalamus 
Release products (neuropeptides) into the blood – portal blood supply that carries blood from hypothalamus down pituitary stalk to anterior pituitary 
Hormones act on the cells in the anterior pituitary which release a hormone into circulation

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What do hypothalamic hormones do?

release hypothalamic hypophysiotropic hormones into the portal circulation & act upon the anterior pituitary

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What is TRH?

Thyrotropin-releasing hormone

Hypothalamic hormone
Stimulating hormone

Stimulates TSH & prolactin release

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What is GnRH?

Gonadotrophin-releasing hormone

Hypothalamic hormone
Stimulating hormone

Stimulates FSH & LH release

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What is CRH?

Corticotrophin-releasing hormone

Hypothalamic hormone
Stimulating hormone

Stimulates ACTH & prolactin release

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What is GHRH?

Growth hormone-releasing hormone

Hypothalamic hormone
Stimulating hormone

Stimulates GH release

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What is growth hormone-release inhibiting hormone?

Also called somatostatin

Hypothalamic hormone
Inhibitory hormone

Inhibition of GH release, also of gastin, VIP, glucagon & insulin

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What is dopamine?

Hypothalamic hormone
Inhibitory hormone

Inhibits prolactin release

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What do posterior pituitary hormones do?

Hormones produced in the magnocellular neurones of the hypothalamus & stored in the posterior pituitary prior to release

Released on demand

What is oxytocin?

Posterior pituitary hormone

Uterine smooth muscle contraction
Breast myoepithelial contraction

What is ADH?

Antidiuretic hormone

Posterior pituitary hormone

Water retention by the kidneys

What do anterior pituitary hormones do?

Release hormones into systemic circulation

Release controlled by hypothalamic hypophysiotropic hormones in portal hypophyseal vessels

What is TSH?

Thyroid stimulating hormone
Anterior pituitary hormone

Released by thyrotrophs

Stimulates thyroid hormone release

What is FSH?

Follicle stimulating hormone
Anterior pituitary hormone

Released by gonadotrophs

Stimulate sex steroid production

What is LH?

Luteinizing hormone
Anterior pituitary hormone

Released by gonadotrophs

Stimulate sex steroid production

What is ACTH?

Adrenocorticotropic hormone
Anterior pituitary hormone

Released by corticotrophs

Stimulates corticol release

What is GH?

Growth hormone
Anterior pituitary hormone

Released by somatotrophs

Stimulates growth

What is prolactin?

Anterior pituitary hormone Released by lactotrophs Stimulates milk production

What is the structure of growth hormone?

191 amino acid peptide hormone synthesised by somatotrophs in the anterior pituitary

How does growth hormone work?

Released in response to growth hormone-releasing hormone (GHRH) from the hypothalamus Release inhibited by growth hormone-inhibiting hormone (somatostatin) from the hypothalamus Stimulates growth, cell reproduction & regeneration Functions of growth hormone can be direct or indirect via insulin-like growth factor 1 (IGF-1)

Acute metabolic actions of GH? (direct actions)

Release fatty acids from adipose tissue & enhances their conversion to acetyl-CoA – promotes muscle growth Reduced glucose metabolism & uptake into cells, especially the liver Increased gluconeogenesis in the liver Increased production of insulin-like growth factor (IGF-1)

Long term effects of GH via IGF-1? (indirect effects)

Growth promoting action on bone, epiphyseal cartilage, soft tissue, gonads, viscera Promotes amino acid uptake & protein synthesis Insulin-like endocrine effects on tissue

What is hypo-pituitary dwarfism?

Under functioning of the pituitary (less GH)

What is pituitary giantism?

Excessive GH secretion in early life

What is acromegaly?

Excessive GH secretion in adulthood