Posterior Pituitary Gland

Question 1

Posterior Pituitary Gland Formation

Answer 1

The substance of the post. pit. gland is formed by the terminal parts of neurons that originate in a specific nucleus of the hypothalamus

Question 2

Posterior Pituitary Gland Function

Answer 2

The post. pit. gland STORES two specific hypothalamic hormones that only use the posterior as their doorway to the systemic circulation
Post. Pit Gland DOES NOT MAKE HORMONES

Question 3

Posterior Pituitary Hormones General

Answer 3

There are only 2 of them: Antidiuretic hormone/vasopression and oxytocin
Made in the hypothalamus
Not much overlap in function
What are referred to as “posterior pituitary hormones” are really two particular hypothalamic hormones

Question 4

Posterior Pituitary Hormone Targets

Answer 4

Target peripheral body tissues
Since the hormones are released directly into the blood there’s no need for releasing or inhibiting hormones because there is a tissue bridge

Question 5

Antidiuretic hormone/ Vasopressin

Answer 5

ADH=AVP- same hormone with two names because it has 2 different target tissues with 2 different tissue specific effects (regulation of blood pressure)

Question 6

ADH/AVP Endpoints

Answer 6

1. Regulation of body fluid volume and osmolarity

2. Contribution to blood pressure regulation

Question 7

ADH Activity

Answer 7

Water retention by kidneys

Making renal collecting ducts permeable to water

Question 8

AVP Activity

Answer 8

Contraction of arteriolar smooth muscle

Question 9

Regulation of ADH secretion

Answer 9

Negative feedback via two different control loops

1. Osmolar control loop
2. Blood volume control loop

Question 10

Osmolar control loop steps

Answer 10

1. Hypothalamus senses increased serum osmolarity
2. Hypothalamus signals ADH/AVP from posterior pituitary
3. ADH exerts its effects
4. Blood osmolarity decreases
5. Hypothalamic osmoreceptors sense normalized osmolarity
6. ADH release stopped (negative feedback)

Question 11

Blood volume control loop steps

Answer 11

1. Decrease in blood pressure stimulates low-pressure receptors in cardiac atria, carotid sinus and aortic arch
2. AVP/ADH is released in response to the above
3. AVP causes arteriolar smooth muscle contraction
4. Increased blood pressure is sensed
5. AVP release stopped (negative feedback)

Question 12

Diabetes Insipidis

Answer 12

Disorder of ADH secretion
Complete/partial failure of either ADH secretion (central nervous system) or responsiveness of renal tubules to ADH
Either one makes kidney unable to recover water
Diabetes= increased urination
Insipidous= ADH failure

Question 13

Syndrome of inappropriate ADH secretion

Answer 13

SIADH
Disorder of ADH secretion
Excretion/inappropriate ADH secretion so can’t excrete water
Causes water retention and water intoxication (extremely difficult to treat)
NOT Caused by excessive H2O intake

Question 14

Oxytocin Endpoints

Answer 14

1. Stimulation of Milk EJECTION (production=prolactin)- letting milk out of mammary gland that’s already been made
2. Stimulation of uterine contraction
3. Promotion of pair bonding and maternal behavior (males to females and mom to baby)
4. Importance in social grooming related to group bonding

Question 15

Oxytocin Activity

Answer 15

Contraction of mammary myoepithelial cells
Contraction of uterine smooth muscle
Develops and maintains the pair bond and maternal care
Importance in social grooming

Question 16

Oxytocin regulation of secretion

Answer 16

Uses a POSITIVE FEEDBACK systems
Signals originate at periphery and signals are SENSORY from target organ (neural-touch related signals)
2 separate control loops depending on which organ is involved (mammary or uterine regulation)

Question 17

Mammary regulation of oxytocin secretion

Answer 17

1. Large conditioned aspect to control oxytocin release as related to the mammary gland (ex. conditioned response- baby pushes on teat, stimulates milk letdown)
2. Teat or mammary gland stimulation relayed to hypothalamus
3. Hypothalamus release oxytocin which travels through the blood
4. Myoepithelial cells have receptors for oxytocin, they contract, contractile cells push milk out, milk ejection occurs
5. Continued suckling causes continued oxytocin release
6. Positive feedback lost when infant stops suckling

Question 18

Uterine regulation of oxytocin secretion

Answer 18

1. Oxytocin stimulates uterine contraction
2. Uterine contraction stretches uterine cervix
3. Stretch sensed and transmitted to hypothalamus
4. Hypothalamus secretes more oxytocin in response (more contraction, more stretch etc.)
5. Cycle continues until fetus is expelled (positive feedback)
6. With loss of cervical stretch, oxytocin release stops