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ANSC 312 - Repro Physiology > Midterm 2 - Lecture 15 > Flashcards

Midterm 2 - Lecture 15 Flashcards

1
Q

GnRH

A

Source: Hypothalamus
Target: Gonadotroph cells in anterior pituitary
Action: Release FSH & LH

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2
Q

FSH

A

Source: Gonadotroph cells in anterior pituitary
Target: Sertoli cells in testes
Action: Maintenance of spermatogenesis and Stimulate androgen binding protein (ABP) production

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3
Q

LH

A

Source: Gonadotroph cells in anterior pituitary
Target: Leydig cells in testes
Action: T4 production

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4
Q

What are Leydig cells the equivalent of?

A

Follicular theca interna cells

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5
Q

What are Sertoli cells the equivalent of?

A

Follicular granulosa cells

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6
Q

T4

A

Source: leydig cells (testis)
Target: hypothalamus, reproductive tract, muscle
Action: male sexuality
- increase sexual behaviour and characteristics
- decrease GnRH production
- increase spermatogenesis
- increase muscle development
- cause accessory sex glands to develop

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7
Q

Androgen Binding Protein (ABP)

A

Source: sertoli cells (testes)
Target: N/A
Action: binds T4 in seminiferous tubules to stimulate spermatogenesis

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8
Q

Inhibin

A

Source: sertoli cells (testes)
Target: gonadotroph cells (anterior pituitary)
Action: inhibits FSH secretion

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9
Q

What are all reproductive fxns ultimately controlled by?

A

positive and negative feedback

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10
Q

Positive effects of male endocrinology

A
  • GnRH stimulates FSH & LH production by Ant Pit
  • LH stimulates T4 production by the Leydig cells
  • FSH stimulate sertoli cells to produce ABP and Inhibin
  • ABP binds T4 in the seminiferous tubules and T4 stimulates spermatogenesis
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11
Q

Negative effects of male endocrinology

A
  • T4 inhibits GnRH production by the hypothalamus
  • inhibin inhibits FSH production by the Anterior Pituitary
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12
Q

Male Hormonal Cycle

A

Hypothalamus has no surge center
- discharges GnRH in frequent pulses or bursts
- GnRH pulses last for a few moments and occur several times a day
- LH and FSH surges induced by GnRH pulses
- T4 surges induced by LH: continual T4 stimulation is needed for spermatogenesis

*cycle occurs over a few hours

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13
Q

Puberty

A

the process of acquiring reproductive competence

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14
Q

What are the pubescent processes in the male?

A
  • behavioral traits expressed
  • ejaculation
  • spermatozoa present in ejaculate
  • adequate sperm production to accomplish fertilization
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15
Q

What is the limiting factor to the onset of puberty?

A

Hypothalamus!
- onset of puberty requires secretion of GnRH at frequency and quantities appropriate to stimulate gonadotropin (FSH & LH) release by the ant pit at levels adequate to support gametogenesis
- in the male, onset of puberty occurs due to decreased hypothalamic sensitivity to negative feedback of T4

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16
Q

5 endocrine steps leading to puberty in the male

A
  1. increase in GnRH pulse amplitude and frequency drives an increase in LH and FSH
  2. Leydig and Sertoli cells mature in response to the increase in LH and FSH but T4 remains basal
  3. when T4 production increases, LH and FSH decrease (implies GnRH pulse decrease)- due to negative feedback T4 by hypothalamus
  4. T4 continues to increase from Leydig cells in response to LH
  5. T4 “builds” to adult levels (also GnRH pulse amplitude and frequency)
17
Q

Cattle age of puberty

A

7-18 months

18
Q

Sheep age of puberty

A

6-9 months

19
Q

Swine age of puberty

A

3-8 months

20
Q

Horse age of puberty

A

13-18 months

21
Q

Dog age of puberty

A

5-12 months

22
Q

Cat age of puberty

A

8-10 months

23
Q

Factors affecting onset of puberty

A
  • plane of nutrition
  • rate of growth
  • exposure to environmental cues
  • genetic background
24
Q

Environmental conditions that affect male puberty

A

Photoperiod - seasonal breeders
- sheep, goats, horses
- T4 levels and testes size vary with season

Social Contact (male-female, male-male)
- not well understood

25
Q

Early onset of puberty in males

A

Reduce generation interval and advance genetic improvement
- reduction in age of puberty would result in genetically superior males producing semen earlier and longer
- limit “down-time” waiting for the onset of puberty
- applicable to sires used in AI studs

ANSC 312 - Repro Physiology (21 decks)

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