Lecture 2 The Pituitary Gland Flashcards by Jessica Eze

Name the principal organisers of the endocrine system

Hypothalamus and Pituitary

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Name the structure that connects the hypothalamus to the pituitary gland

Infundibulum

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What is the posterior portion of the pituitary gland

An extension of the neural tissue

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What is the anterior portion of the pituitary gland

True endocrine gland of epithelial origin

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What is the function of the Hypothalamus

Integration centre for endocrine systems

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Where is the Hypothalamus located

Base of the brain, below the thalamus

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Where is the pituitary gland loctaed

In a pocket in the sphenoid bone, directly below the hypothalamus

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Name external stimuli that effects the hypothalamus

Cold
Stress
Metabolic demand
Hydration status
Exercise
Day/Night
Menstrual cycle
Sleep
Breastfeeding
Pregnancy
Puberty

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Name functions affected by the pituitary gland

Adrenal
Thyroid
Gonadal
Lactation
Parturition
Growth
Water balance
Metabolism

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What type of hormones do both the anterior and posterior pituitary release

Trophic and non-trophic

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All hormones released by the hypothalamus are____

Neurohormones

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All hormones released by the posterior pituitary gland are ____

Neurohormones (from hypothalamus)

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All hormones released by the anterior pituitary gland are ___

Endocrine hotmones

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Define Trophic Hormones

Neurohormones secreted into capillaries traveling to anterior pituitary and govern the release of secondary hormones

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Define Non-trophic Hormones

Neurohormones produced in the hypothalamus and travel to posterior pituitary via axons where they are released into the blood

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Name 5 hypothalamic “releasing hormones”

– Thyrotropin Releasing Hormone (TRH)/(TSH)
– Corticotropin Releasing Hormone (CRH)
– Growth Hormone Releasing Hormone (GHRH)
– Gonadotropin Releasing Hormone (GnRH)
– Prolactin Releasing Hormone (PRH)

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Name 2 hypothalamic “inhibiting hormones”

– Growth Hormone Inhibiting Hormone (GHIH) aka somatostatin

– Dopamine aka Prolactin Inhibiting Hormone (PIH)

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All hypothalamic hormones are peptides except_____

Dopamine

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PRH causes the release of what anterior pituitary hormone

Prolactin–> Breast

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TRH causes the release of what anterior pituitary hormone

TSH–> Thyroid gland

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CRH causes the release of what anterior pituitary hormone

ACTH–> Adrenal Cortex

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GHRH causes the release of what anterior pituitary hormone

GHIH inhibits what anterior pituitary hormone

GnRH causes the release of what anterior pituitary hormone(s)

FSH and lSG (Gonadotropins)–> endocrine cells of gonads

PIH inhibits the release of what anterior pituitary hormone

Prolactin

What is the Hypothalamus-hypophyseal portal system

Network of tiny vessels which transfer trophy hormones from hypothalamus to anterior pituitary

The anterior pituitary is connected to the hypothalamus via

Capillary portal system (hypothalamic-hypophyseal portal system)

What is the anterior pituitary sometimes called

Adenohypophysis | Makes up 2/3rds of the gland

What is the posterior pituitary gland sometimes called

Neurohypophysis | Makes up 1/3rd of the gland

What is the function of the Pars intermedia

* Stimulates production of melanin (MSH) | * Sits between anterior and posterior pituitary

Describe the short feedback loop

Trophic hormone has negative feedback on Hypothalamus

Describe long feedback loop

End hormone from endocrine gland acts on anterior pituitary gland and hypothalamus

Name the 2 peptide neurohormones released from the posterior pituitary

 Vasopressin (aka anti-diuretic hormone; ADH)- maintains water balance, increase water retention  Oxytocin- uterine contraction and lactation

Where are the posterior pituitary peptide neurohormones synthesised

Magnocellular neurons

What is the main function of vasopression

Regulates water balance

What triggers vasopressin

Increase in plasma osmolarity | Decrease in plasma volume/blood pressure

Site/mode of action of vasopression

Kidney collecting ducts- water reabsorption | Vascular smooth muscle- increase blood pressure

What is the main function of oxytocin

Milk ejection and uterine contraction

What triggers the release of oxytocin

Labour (baby's head against cervix), Suckling

Site/mode of action of oxytocin

Milk duct smooth muscle- contracts muscle, ejecting milk | Uterine smooth muscle- child birth

Define hyposecretion

too little hormone secreted- disorders at any level of pituitary access

Define hypersecretion

too much hormone secreted

Define hypo responsiveness

reduced response of the target cell

Define hyperresponsiveness

increased response of the target cell

What are primary disorders

those in which the defect is in the cells that secrete the hormone (end hormone)- most common

What are secondary disorders

those in which there is too little or too much trophic hormone from pituitary

Wha are tertiary disorders

relate to hypothalamic defects

What does hyporesponsiveness relate to

alterations in receptor for hormone, disordered post-receptor events or failure of metabolic activation of hormone, (where this is required for function).

What could be the cause of hyper responsiveness

: could be due to permissive effects e.g. Thyroid hormone ++ adrenaline mediated lipolysis

prolonged exposure to low hormone plasma leads to

Up-regulation of receptor number (increase tissue sensitivity)

Prolonged exposure to high hormone plasma leads to

Down regulation of receptor umber (decrease tissue sensitivity)

Define permissive effects

the presence of one hormone enhances the effect of another eg epinephrine causes only modest lipolysis in adipose tissue, but when thyroid hormones are also present, greatly increased lipolysis occurs. TH  synthesis of receptors for epinephrine on adipocytes. TH itself has no effect on lipolysis but is permissive to epinephrine.

Define Antagonistic effects

The presence of one hormone reduces the effect of another e.g. Growth hormone impairs glucose uptake in response to insulin by decreasing the number of insulin receptors on muscle and adipose tissue.