ANSC 3600 Exam 2

The uterus of a cow is more or less fused during development compared to that of a sow?

More

Prostaglandin F2 alpha plays a major role in what reproductive process?

Luteolysis

What does LH stimulate to produce testosterone?

Leydig cells

What does FSH stimulate to stimulate sperm production?

Sertoli Cells

Does the male brain defeminize during development because estradiol can cross the blood-brain barrier?

No

It defeminizes due to testosterone crossing the blood-brain barrier

What is the longest phase of the female reproductive cycle?

Diestrus

What would you inject when trying to block the response of a given endogenous hormone?

An antagonist

What elicits a quicker response, neural reflex signaling or neuroendocrine signaling?

Neural signaling has a quicker response

Between neural reflex and neuroendocrine signaling, which involves the interpretation of signals by the hypothalamus?

Neuroendocrine signaling involves hypothalamus interpretation.

Give an example of a reproductive biological activity that is considered a neural reflex response?

Contraction/relaxation of muscles in scrotum

Give an example of a reproductive biological activity that is considered a neuroendocrine response?

Milk let down

Where is the receptor for LH located?

On the target cell membrane

The initial expression of what gene on the Y chromosome causes the cascade of events resulting in the formation of a male gonad?

SRY

What do sertoli cells produce that leads to the regression of the female ducts?

AMH

Is testosterone required for the formation of the accessory sex glands?

Yes

During primordial follicle formation which cell is responsible for directing the assembly?

Primordial germ cells

Descent of the testes occurs from the action of what specialized ligament?

Gubernaculum

What is NOT a reason an animal may be anestrus?

Ovulation

What are reasons an animal would be anestrus?

Out of season

Disease

Pregnancy

Lactation

In a given 12 months what type of estrus animal will ovulate the most times?

Polyestrus

Silent ovulation occurs because the ___ has not been primed with ____

Brain, progresterone

Luteolysis of the CL is a result of what hormone messenger from the uterus?

Prostaglandin F2 alpha

Estrus is caused by ___ from the ___

Estrogen, Dominant follicle

What hormone system does progesterone inhibt?

GnRH from the hypothalamus

What type of cycle does a dog have?

Monoestrus

Which animal is seasonal polyestrus for long days and seasonal for short days?

Mares are long day polyestrus

Small ruminants (ewes and does) are short day polyestrus

What is the final hormone that ends up in the fetal brain to cause the formation of a male brain?

Testosterone

What is a major difference in the nuclei present in the hypothalamus in female and male brains?

Females have tonic and surge centers

Males only have tonic centers

How do surge and tonic centers in male and female brains relate to differences in gamete production?

Having both surge and tonic centers allows females to cycle and enter estrus.

The tonic center provides a constant “drip” of GnRH for males and females but the males will lack the GnRH surge from the surge center than occurs during the follicular phase.

What kind of feedback does estrogen have on the surge center during the follicular phase?

Positive feedback

Threshold E2 induces action potential firing of GnRH neurons from surge center.

What is the relationship between hormones during the follicular phase?

Low P4, high E2

In what instance would the surge center not release GnRH?

When E2 is low there is no GnRH surge

Low estrogen has negative feedback on surge center

During what phase of the estrous cycle is the surge center inactive?

During the luteal phase

High P4, Low E2 = no GnRH surge

How frequently does the surge center “surge”?

Every 21 days

E2 is only high enough for a surge when a dominant follicle is present

Which center is active from birth?

Tonic center

When is the tonic center more active?

During puberty onset and during follicular phase post-puberty onset

What is the hormone for follicle selection?

Inhibin

What effect does inhibin have when it is released?

E2 is decreased, follicles that haven’t reached dominant stage die off due to lack of estrogen.

If there is a decrease in progesterone how does that affect the tonic center?

Decrease negative feedback on tonic GnRH = increase in pulse frequencies

As a follicle reaches dominant status what hormone does it need less of? What hormone does it need more of?

Needs less FSH

Needs more LH

How much GnRH is sent out from tonic center? How often?

5 pg/ml every 1-2 hours

How does the constant pulse of GnRH from the tonic center affect LH and FSH?

Stimulates basal LH needed by theca cells for androgen synthesis

Increases release of FSH needed by granulosa cells for aromatization of androgen to estrogen

What is the overall effect of the tonic center and GnRH?

Lead to increased estrogen production and follicle growth/maturation

Does the hypothalamus have E2 receptors?

No

What are the stages of the follicular phase?

Proestrus and Estrus

What are the stages of the luteal phase?

Metestrus and Diestrus

What stage in the estrous cycle is the longest?

Diestrus

What phase of the estrous cycle is longest?

Luteal phase

What are 3 internal factors that affect hormone action?

Affinity

Receptivity

Agonists/Antagonists

Define Affinity

Strength of bond between hormone and receptor

More affinity = hormone will last longer due to stronger bond

Less affinity = hormone won’t last as long due to weaker bond

Define receptivity

Location and number of receptors available for binding

List the 3 major events cause by the LH surge directly responsible for ovulation:

Hyperemia - increased pressure

Collagenase breaks down follicular wall

Contraction of ovarian smooth muscle

4 phases in order from undifferentiated to differentiated of spermiogenesis:

1. Golgi phase (G)

2. Cap phase (C)

3. Acrosomal phase (A)

4. Maturation phase (M)

Crossing over occurs during synapsis of Meiosis I during a stage termed:

Prophase I

Functions of estrogen during the follicular phase:

Prepare reproductive tract

Enhance estrus behavior

Induce LH surge

Decrease FSH

What is not a function of estrogen during the follicular phase?

Decrease progesterone

What is the concentration of FSH and Estradiol during follicle recruitment?

FSH concentration is high during recruitment

Estradiol concentration is low during recruitment

What is the concentration of FSH and Estradiol during follicle dominance?

FSH is high

Estradiol is low

What happens to granulosa and theca cells following ovulation?

Granulosa cells become small luteal cells

Theca cells become large luteal cells

What are some effects of prostaglandin F2alpha on the CL?

Disrupt local circulatory system

Vasoconstricts arterioles

Causes calcium influx

Inhibits progesterone synthesis

What is not an effect of PGF2 alpha on the CL?

Disrupts cellular gap junctions

Would you see several generations in a cross sections of a seminiferous tubule regardless of where you took it?

Yes

Does GnRH stimulate a pulse of estradiol?

No, it stimulates a pulse of LH/FSH

Type: Neuropeptide hormone

Source: Hypothalamus

Target: Anterior pituitary (gonadotrope cells)

Effect: Release LH

GnRH

Type: Glycoprotein

Source: Gonadotropes on the Anterior pituitary

Target: Sertoli (testes) and granulosa cells (ovarian follicles)

Effect: Sertoli cell function (increase sperm production) + follicle development and estrogen production (increase)

No releasing hormone, but inhibin inhibits it’s release

FSH

Type: Glycoprotein

Source: Gonadotropes on Anterior pituitary

Releasing hormone: GnRH

Target: Leydig (testes) + theca interna (follicles) and luteal cells (CL)

Effect: Stimulates testosterone production (increase), stimulates ovulation, formation of CL and P4 production increase

LH

Type: Glycoprotein

Source: Sertol cells and granulosa cells

Target: Gonadotrope cells of anterior pituitary

Effect: Inhibits FSH

Inhibin

Type: Protein hormone

Source: Anterior pituitary (lactotrope cells)

Target: Mammary gland cells

Effect: Milk synthesis

Prolactin

Type: Protein hormone

Source: Placenta

Target: Mammary gland cells

Effect: Stimulate mammary gland development

Placental Lactogen

Type: Steroid hormone

Source: Granulosa cells, sertoli cells, placenta

Target: Brain, hypothalamus, repro tract

Effect: Sexual behavior, GnRH release, uterine tone and secretions

Estrogen family: Estradiol-17 beta most common

E2

Type: Steroid hormone

Source: CL, placenta

Target: Brain, hypothalamus, repro tract

Effect: Decrease GnRH release, maintain pregnancy

P4

Type:

Source: Leydig, the

Target: Brain, accessory sex glands, seminiferous tubules, granulosa cells

Effect: Behavior, spermatogenesis, secretion of accessory sex glands, substrate for E2

Define glycoprotein hormones

Protein that has been modified with carbohydrates

Glycosylation occurs to extend half life of hormone

What are the different classification methods for hormones?

Structure - protein, steroid, etc.

Source - hypothalamus, anterior/posterior pituitary, gonad, etc.

Target - gonadotrop cells, granulosa cells, etc

Where do protein hormones typically come from?

Brain tissue

Where do steroid hormones typically come from?

The gonads

What kind of phenomenon is the onset of seasonal cyclicity?

Ocular

Through hypothalamus with pineal gland

What type of hormone has a long half life?

Steroid hormones

Ex: Estrogen

What hormones have a short half life?

Protein hormones

Ex: GnRH

What type of hormone acts locally?

Peptide hormones

How is the half life of a hormone determined?

Determined by metabolic clearance rate

How does sustained release work? What hormone commonly utilizes sustained release?

Sustained release is the build up of concentration because the new hormone is released faster than the old hormone is metabolized.

Common with steroid hormone secretion

How does episodic secretion work? What hormones use this method?

Larger, less frequent bursts of hormones

Low frequency, high amplitude

Typical or neural control of release (Ex: Ovulation)

GnRH from the surge center, LH from anterior pituitary (Ovulatory surge)

What pattern of secretion does the tonic center have?

Basal secretion

• Frequent small bursts

• High frequency, low amplitude

• Hormones removed from system rapidly

What is pattern of secretion in hormones?

Where and how hormones are being secreted

What are some neuropeptide hormones?

GnRH (hypothalamus) and Oxytocin (posterior pituitary gland)

What are some glycoproteins?

LH, FSH, Chorionic gonadotropin (early chorionic membrane), Inhibin

What are some steroid hormones?

Estradiol, Progesterone, Testosterone

What can catalytic subunits initiate?

New protein synthesis

Conversion of substrates

What is the process of signal transduction? What is the result?

Reception of hormone/environmental stimulus (at cell wall) → Transduction (relay molecules, in cytoplasm) → Response (activation of cellular responses)

Result is gene-protein expression and release of contents from hormone

What do you call a cell with specific hormone receptors?

Target cells

What is eCG? What did it used to be called?

Equine Chorionic Gonadotropin

Used to be called PMSG - Pregnant Mare Serum Gonadotropin

What is the function of eCG?

Supports CL in 1st trimester of pregnancy in mares

When injected into cattle it acts like FSH

What is hCG?

Human Chorionic Gonadotropin

What does hCG do?

• In humans it supports CL of pregnancy

• Acts like LH in cattle

  • Induces ovulation if dominant follicle is present

  • Support CL if present

Where is hCG found?

In humans and equines

Where is the fetus in contact with the placenta?

The chorionic membrane of the placenta

What hormones does the fetus produce?

Chorionic gonadotropin - early signal that fetus is present

Progesterone - Supports pregnancy (CL), relaxes myometrium

Estrogen - Tense myometrium to push fetus out (late stage of pregnancy)

Placental Lactogen - Start milk production (late stage of pregnancy)