Posterior Pituitary

Question 1

Characteristics of Posterior pituitary

Answer 1

• Composed of cells called Pituicytes, act as packing and supporting cells
• Stores and releases hormones that were made by the hypothalamus, into capillaries

Question 2

Which hormones does the Posterior Pituitary release and how do they travel to Post Pit

Answer 2

• ADH or vasopressin
• Oxytocin
• Both are polypeptides of 9 AA
• Transported along the Hypothalamo-hypophyseal tract
  
  • Along with carrier protein Neurophysin to nerve endings in post pituitary

Question 3

ADH 2 main effects

Answer 3

• Increases water re-absorption (retention) by distal tubules and collecting ducts of kidneys
  
  • Decreasing osmotic pressure of blood
  • Regulated by cAMP
• Contraction of vascular smooth muscles generalized vasoconstriction
  
  • Regulated by IP3/Ca

Question 4

Control of ADH

Hyperosmolarity of ECF

Answer 4

• Increase in osmotic pressure of ECF (increase in plasma osmolality) (dehydration)
  
  • Stimulates Hypothalamus to inc ADH
  • Leading to reabsorption of water at the collecting ducts of kidneys–> Dilution of ECF

Question 5

Control of ADH

Loss of ECF

Answer 5

• A decrease in blood vol–> increase ADH
  
  • Loss of ECF–> Less pressure in R atrium–> Less nerve impulse to hypothalamus–> Inc ADH–> Inc water absorption by kidneys–> Maintain ECF levels

Question 6

What are 5 other ways ADH levels are affected and whats the response

Answer 6

• Decrease in arterial blood pressure due to decrease in blood volume–> Inc ADH
• Age–> Inc ADH–> Water retention and hypoatremia
• Pain, emotional stress, physical trauma–> Inc ADH
• Drugs–> Inc ADH
• Alcohol–> Dec ADH

Question 7

Hyposecretion of ADH

Answer 7

• Lack of ADH= Diabetes insipidus
• Enormous output of dilute urine
• Intense thirst
• Fluid intake cant be limited
• Causes: head trauma, brain tumor, irradiation of pituitary, infections of CNS (encephalitis, TB, meningitis)

Question 8

Hypersecretion of ADH

Answer 8

• AKA SYndrome of Inappropriate Anti-Diuretic Hor.
• Decrease serum osmolality cause water to move into cells
• Enormous output of dilute urine, intense thirst
• Decrease in salt and thirst cause:
  
  • Weakness, muscle cramps diarrhea
• If Na levels worsen–> Neurological manifestations
  
  • Lethargy, decrease tendon reflexes, stomach cramping, vomitting, coma, seizures

Question 9

Oxytocin made by and function

Answer 9

• Made by paraventricular nucleus of hypothalamus
• Smooth muscle contraction of uterus
• Contraction of mammary glands myoepithelial cells of alveoli and ducts to eject milk(prolactin makes the milk)
• Men- increase ejaculation