Puberty Flashcards
Describe puberty.
The PROCESS of a male or female to be able to complete reproduction successfully.
What is required for pubertal onset in mammals?
Development of specific hypothalamic neurons to release GnRH at the correct frequencies.
What can gonadotropins promote?
Gametgenisis, steriodogensis, and development of reproductive tissues
What three things can puberty be influenced by?
Genetics, Reaching proper body size and exposure to certain stimuli
List and describe the three puberty definitions in the female.
1) Age at first estrus-Usually not followed with ovulation.
2) Age at first ovulation- Determined by palpation, ultrasonography but must be frequently observed.
3) Age when a female can support pregnancy without deleterious effects
List and describe the four puberty definitions in the male.
1) Age when behavioral traits are shown (mounting, erection)
2) Age at first ejaculation
3) Age when spermatozoa appear in the ejaculate
4) Age when the ejaculate has a threshold number of sperm.
List the average ages for each species to reach puberty.
Cattle- 11 months
Sheep- 7 months
Pig- 7 (male) 6 (female)
Horse- 14 (male) 18 (female)
Which species is most aware of the daylight when reaching puberty?
Sheep are very aware and the length of day will greatly affect their puberty time.
What is the number one attribute contributing to puberty?
Both male and female must have hypothalamic GnRH neurons capable of releasing pulses of GnRH
What are some metabolic signals that could affect the threshold body size for puberty?
- Leptin-produced from fat, keeps us from eating
- Insulin-store sugar
- NPY
- IGF-I
List four external or social factors affecting puberty.
Season, Photoperiod, presence of the male, Rearing density
Describe rearing density.
Giving pigs proper room. Not too crowded yet being around plenty of other pigs.
What will the anterior pituitary produce before puberty when stimulated with GnRH
LH and FSH
How will prepubertal animals respond to exogenous FSH and LH?
Produces follicules and estradiol
When does development of the hypothalamus occur?
Gradually as the animal grows
What causes the preovulatory LH surge at puberty?
Preovulatory GnRH surge
Describe how frequency of GnRH is controlled
-Pulse Generator which reads internal signs (nutrients, serum E2)
and External Signals (day length and presence of opposite sex)
Where is the pulse generator at?
Preoptic area and anterior hypothalamus
What is the Gonadostat Theory of Puberty?
As puberty approaches there is a decrease in the sensitivity to the negative feedback efforts of E2.
The hypothalams is inherently which gender?
female
Which gender has a surge center?
Female because she doesn’t produce testosterone
What must happen to testosterone to defeminize the hypothalamus.
It must be converted to E2
Why is E2 prevented from crossing the blood brain barrier?
It is attached to alpha-fetoprtein that is too large to cross.
What converts the testosterone to E2 after crossing the BBB?
aromatase enzyme
What is the fundamental difference in endocrine profiles from a postpubertal male and female?
The LH does not surge in the male but surges for the female at estrus
What are two important factors in regulating age of pubertal onset?
Age and amount of body fat
How is environmental information received?
sensory neurons in the optic and olefactory systems, processed by the CNS and delivered as neural inputs to the GnRH neurons
List three female species and their season of birth that will affect their age of puberty.
Sheep-Spring lambs reach puberty in half the time 5-6 months
Cows-Fall heifers will reach puberty sooner
Pigs-Fall born reach puberty faster
