Lecture: Physiology of the Pituitary and Adrenal Glands Flashcards

1
Q

Where does the glandular tissue of the anterior pituitary arise from?

A

invagination of pharangeal epithelial tissue

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2
Q

Where does the posterior pituitary arise from?

A

Out growth/extension of the hypothalamus

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3
Q

Where are the hormones that are released from the posterior pituitary synthesised?

A

Magnocellular neurons from the Supraoptic Nucleus and Paraventricular Nucleus.

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4
Q

What hormones are released from the PP?

A

ADH (SON)

Oxytocin (PVN)

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5
Q

What stimulates glandular tissue in AP to release hormones?

A

Neurohormones from hypothalamus carried by capillaries - hypophysal portal vein to stimulate glandular tissue

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6
Q

What cell types is the PP primarily comprised of?

A

The posterior pituitary is comprised primarily of glial-like
cells called pituicytes – these cells do not secrete hormones. Hormones of the posterior pituitary are secreted by magnocellular neurons - cell bodies in the PVN and SON of the hypothalamus. The hormones are synthesized in the cell bodies and transported down the nerve axons into the posterior pituitary

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7
Q

What stimulates oxytocin release?

A

Positive feedback loop. Suckling, sensory stimulation areola,

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8
Q

Function of oxytoxin?

A
  1. Milk ejection – contracts myoepithelial cells that surround
    the mammary alveoli
  2. Hastens delivery, promotes delivery of the placenta, reduces
    bleeding – contracts uterine smooth muscle
    (NOT THE PHYSIOLOGICAL TRIGGER FOR PARTURITION)
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9
Q

MOA of oxytocin?

A

via G-Protein coupled receptor; 2nd
messengers: IP3, DAG
IP3 is the chemical mediator that causes the release of calcium.

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10
Q

MOA of ADH?

A
  1. Reabsorption of water in connecting/collecting tubules via V2 rec. -> cAMP -> insertion of aquaporin-2 into the luminal membrane.
  2. Vasoconstriction via V1 rec. -> IP3, DAG -> ↑[Ca2+]i
  3. Increases thirst (via actions on the CNS)
  4. ↑ACTH from anterior pituitary - ↑aldosterone - ↑
    conservation of Na+ and H2O (Note: plasma K+ and angiotensin II are the main regulators of aldosterone secretion)
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11
Q

What stimulates hormone secretion from the anterior pituitary?

A

Hypothalamic releasing/inhibitory hormones enter a portal system and are conducted to the anterior pituitary

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12
Q

Proportion of AP cells made up of thyrotropes?

A

Thyrotropes (3-5%)
Thyroid-stimulating hormone (TSH) (aka thyrotropin)
Target: thyroid
stimulates T3 & T4 secretion

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13
Q

Proportion of AP cells made up of corticotropes?

A

Corticotropes (15-20%)
Adrenocorticotropic hormone (ACTH) (aka corticotropin)
Target: adrenal cortex
stimulates cortisol secretion

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14
Q

Proportion of AP cells made up of somatotropes?

A

Somatotropes (40-50%)
Growth hormone (GH) (aka somatotropin)
Target: bone, tissues, liver
Growth; influences metabolism

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15
Q

Proportion of AP cells made up of gonadotropes?

A

Gonadotropes (10-15%)
Follicle-stimulating hormone (FSH) & Luteinizing hormone (LH)
Target: ovaries & testes sex hormone secretion;
gamete production

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16
Q

Proportion of AP cells made up of lactotropes?

A

Lactotropes (10-15%)
Prolactin (PRL)
Target: mammary glands
Breast growth; milk secretion

17
Q

What do chromaffin cells in adrenal medulla produce?

A

Adrenalin