Exam 3: Hormones

GnRH

Gonadotropin-Releasing Hormone

What secretes GnRH?

Hypothalamus

What does GnRH act upon?

Anterior pituitary gland

What does GnRH do?

It is a hypothalamic hormone that provides the positive drive for the secretion of both LH and FSH by the anterior pituitary gland.

LH

Luteinizing Hormone

What secretes LH?

Anterior pituitary gland

What does LH act upon?

Acts upon the ovary

What is 3 things is LH responsible for?

1. induces ovulation (when LH is in peak concentration) and development of the CL

2. Aids in the maturation of the follicle and spermatozoa

3. Stimulates testosterone production in the male

FSH

Follicle Stimulating Hormone

What secreted FSH?

Anterior pituitary gland

What does FSH act upon?

Ovary

Do you need a lot of FSH?

No, FSH is only needed in very small amounts

3 responsibilities of FSH:

1. induces follicular development

2. induces estrogen production

3. stimulates spermatogenesis

What secreted inhibin?

follicle

What does inhibin act upon?

anterior pituitary

Inhibin

A follicular hormone that causes a reduction in FSH production by the anterior pituitary

What secretes estrogen?

Follicle

What 3 things is estrogen responsible for?

1. Estrus

2. influence mobility and secretory function in the reproductive tract

• uterine milk

3. Responsible for early-stage development of the mammary gland

What secreted progesterone?

Corpus Luteum

4 things progesterone is responsible for:

• maintenance of pregnancy

• Final maturation of the mammary gland

• Reduced excitability of smooth muscle fibers

• negative feedback to the hypothalamus

What secretes oxytocin?

Posterior pituitary, corpus luteum

What does oxytocin act upon?

Smooth muscle

What does oxytocin do?

Causes contractions of smooth muscle fibers involved in:

• milk “let down”

• uterine contractions during parturition

• contractions of smooth muscle in the uterus and oviducts during mating

what secretes prostaglandin?

endometrium

= uterine lining

What does prostaglandin act upon?

corpus luteum

3 functions of prostaglandin

produced by the endometrium of the non-pregnant uterus to:

1. cause the regression of the CL

2. cause uterine contractions

3. give pregnant or open signal

What secretes interferon tau?

embryo

What receives interferon tau?

uterus

What does interferon do?

• Blocks the structural and functional regression of the corpus luteum (leuteolysis)

• pregnancy recognition signal in cattle and sheep

Birth marks the termination of _________

pregnancy

What initiated parturition?

The release of the hormone cortisol from the fetal adrenal cortex initiates parturition

Dystocia

Difficult birth

4 causes of dystocia

• females who are too young

• abnormal presentations (baby coming out in the wrong position)

• An abnormally small pelvis in the female

  • Some cattle producers measure the pelvis at 12-15 months of age and cull heifers that are too small

• fetus too large