Animal Reproduction Flashcards
What is a hormone?
Endogenous substance released into circulation. It has a high affinity and specificty of binding to specific target cells and initiates a biological response.
What are the different mechanisms of hormone release?
Endocrine
Neuroendocrine
Paracrine
Neurocrine
Autocrine
What kind of control is reproduction under?
Nervous and endocrine.
What are the two types of reflexes seen by neural control?
Simple neural reflex (does not go passed the spine)
Neuroendocrine reflex (goes up to the hypothalamus to release hormone from adenohypophysis)
Describe the hypothalamus - hypophyseal portal system.
Cells in the hypothalamus release GnRH into the hypothalamic portal system.
GnRH goes directly to adenohypophysis and acts on gonadotropes.
Adenohypophysis releases FSH and LH
FSH and LH travels to ovaries and testes
There is also feedback inhibition by the hormones produced at the testes/ovaries.
Which type of control is longer lasting? Neural or endocrine?
Endocrine. It is also slower.
What hormones are relased by the hypothalamus?
GnRH
The pituitary gland releases _____.
FSH
LH
Prolactin
Oxytocin
What hormones do the ovaries release?
Testes?
Ovary: Estradiol, progesterone, inhibin, testosterone, relaxin.
Testis: testosterone, inhibin, estradiol
What hormones are released by the placenta?
Progesterone
Estradiol
hCG
eCG
Oxytocin
PGF2-a
What hormones are derived from cholesterol?
Progesterone, testosterone, estradiol
What hormones are glycoproteins?
FSH, LH, TSH
What hormones are peptides?
GnRH
Prostaglandins are released by the _____. What happens upon adminsitration of prostaglandins during pregnancy?
uterus
Abortion
Describe the mechanism of action of protein hormones.
Activate protein kinase A via cAMP and GPCR.
cAMP activates it by stimulating regulatory subunit and catalytic subunit.
Eventually leads to the construction of new proteins for reproduction.
Describe the mechanism of action of steroid hormones.
Diffuse through the plasma and nuclear membranes of the target cell.
Bind to nuclear receptor
mRNA production is triggered and protein synthesis begins
What factors determine the magnitude and duration of action of hormones?
Pattern and duration of secretion
Half-life
Receptor density
Affinity receptor-hormone
What are the general hormone secretion pattersn?
- Episodic: hormones under nervous control. Released in sudden bursts or pulse.
- basal: hormone stays low but fluctuates with low amplitude pulses.
- Sustained: e.g. steroids. levels remain high in a steady fashion for long period (days/weeks)

How can hormones be measured?
Blood, saliva, urine, lymph, tear, feces
Radioimmunoassay and ELISA
Hypothalamic Hormones ——> Pituitary
CRH
TRH
GnRH
ACTH
TSH
FSH & LH; Growth hormone
What are the two antagonists released by the hypothalamus? What do they act on?
SS inhibits growth hormone
Dopamine (DA) inhibits prolactin.
What is puberty?
The process to reach reproducte competences.
The requirement is adequate GnRH to stimulate gonadotrophin release from gonadotroph cells.
The most important driver for puberty onset is the ability of presynaptic neurons to provide information to GnRH neurons.
Figure: Two hypothalamic centers are present:
1) Surge center: increases GnRH secretion; not active prior to puberty.
2) Tonic center: gives a basal GnRH release; active prior to puberty.

What is the best definition of puberty in the female?
Age on which female can support gestationwithout deleterious effect.
Age at first estrous (heat)/ovulation is not good definition because ovulation is silent and not easily determined.
What is the best definintion of puberty in the male?
Age when the ejaculte contain a number of spermatozoa able to produce fertilization.
May also be definied as the age when spermatozoa appear in the ejaculate or age at first ejaculation.






