Reproduction: Hypothalamus and Pituitary

Question 1

When and how does oxytocin affect the female?

Answer 1

During parturition, acts on myometrium to induce contractions. Acts on endometrium to stimulate production of prostaglandins which also induce contractions.

During labor: stimulation of cervix initiates Ferguson reflex in which large amount of oxytocin is released into circulation. Also released to brain of mother

Lactation: milk-ejection reflex

Question 2

What role does prolactin play?

Answer 2

Stimulates mammary gland development and milk production.

• Hypothalamus tonically suppresses secretion, mediated by dopamine
• Estrogen is positive control for synth and secretion

Question 3

What role does GnRH play?

Answer 3

Drives release of LH and FSH

Question 4

How is GnRH secreted?

Answer 4

In a pulsatile fashion (continuous secretion causes down-regulation and halted response to GnRH)

Question 5

What can affect the release of GnRH?

Answer 5

Can be modulated by NMs

• -Inhibitory: GABA, 6-endorphin, dopamine
• -Stimulatory: Glutamate, Noradrenaline, Neuropeptide Y

Signals from the Environment: seasonal changes, other individuals, food, stress (high cortisol)

Sensory cues: pheromones

Tactile cues: vaginal stimulation (cats and rabbits), association with a mate and nesting, reduced suckling (decreases lactational anestrus in beef cows)

Question 6

True or false: LH and FSH are released separately and independently?

Answer 6

True

Question 7

How can GnRH control LH and FSH despite different release patterns?

Answer 7

Its pulsatility differentially affects the secretion, but activin and inhibin also regulate secretion of FSH but not LH

High GnRH pulses=release of LH
Low GnRH pulses=release of FSH

Question 8

In general, which gonadotropin is more tightly controlled by GnRH?

Answer 8

LH