Help
Options
Didn't know it?
click below
click below
Knew it?
click below
click below
Don't Know
Remaining cards (0)
Know
retry
shuffle
restart
0:00
Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.
Normal Size Small Size show me how
Normal Size Small Size show me how
Repro 11-12
Neuroendocrine behaviour and puberty
| Question | Answer |
|---|---|
| Endocrine glands in cattle | hypothalamus pituitary gonads (ovaries, testes) |
| Endocrine signalling | endocrine autocrine paracrine neurohormone |
| Hypothalamus | region at base of the brain neuroendocrine gland mediates hormonal and environmental influences on reproduction |
| Neuroendocrine gland | in the hypothalamus hormones released from terminals of axons into blood vessels that feed into anterior pituitary secretes GnRH |
| GnRH secretion | pulsatile release crucial pulse frequency determines pattern of FSH and LH secretion two systems regulate female gonadotropins |
| Systems regulating female gonadotropins | tonic/episodic system surge system (produces LH surge before ovulation) |
| Pituitary gland | consists of anterior pituitary and posterior pituitary |
| Anterior pituitary | releases FSH, LH, prolactin controlled by hypothalamic neurohormones via portal system |
| Posterior pituitary | stores and releases oxytocin |
| FSH | follicle stimulating hormone |
| LH | luteinising hormone |
| Female gonads (ovaries) | theca cells are stimulated by LH to produce androgens and progesterone Granulosa cells stimulated by FSH to produce oestrogen |
| Male gonads (testes) | leydig cells stimulated by LH to produce testosterone Sertoli cells stimulated by FSH to support spermatogenesis |
| Oestrogen function | behaviour follicle development positive feedback at high levels |
| Progesterone function | pregnancy maintenance negative feedback |
| Testosterone function | libido spermatogenesis secondary sex characteristics |
| Prostaglandin | produced by uterus causes luteolysis triggers CL regression |
| Negative feedback (hormone feedback loops) | testosterone, oestradiol, progesterone inhibit GnRH lowers FSH and LH |
| Positive feedback (hormone feedback loops) | high sustained E2 in females triggers LH surge Feedback ensures balance in reproductive cycle and prevents overstimulation |
| Environmental influences on Reproduction | stress nutrition daylight/photoperiod metabolic state |
| Luteolysis | regression of CL |
| Components of luteolysis | functional regression: loss of progesterone secretion structural regression: physical breakdown of luteal tissue |
| Puberty | the ability of the animal to produce gametes and reach reproductive competence |
| When does puberty occur? | when GnRH neurosecretory activity increases |
| Female puberty definition | age at first behavioural oestrus (heat) age at which the female can support a pregnancy |
| Male definition of puberty | age when behavioural traits first expressed (mounting/erection) age at first ejaculation age when ejaculate contains threshold for spermatozoa fertilisation |
| Puberty timing | varies widely between species, breed, sex, growth rate and environment |
| Key mechanisms involved (neuroendocrine control of puberty) | reduced sensitivity to oestradiol negative feedback decline in oestradiol receptor-positive neurons in the hypothalamus increased kisspeptin neuron activity stimulating GnRH neurons |
| GnRH pulsatility triggers (neuroendocrine control of puberty) | increased LH surges follicular growth oocyte maturation first ovulation |
| Factors affecting puberty | nutrition breed differences photoperiod social interactions (male exposure advances puberty) stress and environmental conditions |
| Silent ovulation | first ovulation often occurs without behavioural oestrus CL forms; progesterone primes brain for later normal oestrus cycles |
| Oestrus cycle purpose | synchronise ovulation and receptivity with optimal embryo survival environment |
| Oestrus categories | polyestrous seasonally polyestrous monoestrus |
| Proestrus | begins after CL regression and ends at onset of estrus, period of follicle growth |
| Oestrus | period of sexual receptivity "heat" |
| Metestrus | early postovulatory period, CL begins to develop |
| Diestrus | begins approx 4 days after ovulation and ends with regression of CL |
| Stages of oestrus cycle | Proestrus oestrus metestrus diestrus |
| seasonal polyestrous cycles | only occur during certain times of the year |
| long day breeders cycle | breed when day length increases eg horses |
| short day breeders cycle | breed when day length decreases eg sheep |
| Monoestrus | one cycle per year oestrus periods last for several days eg dogs |
| Polyestrous | regularly occurring oestrus cycles throughout the year eg cattle and swine |
| Ovulation | release of egg from ovary occurs near the end of the oestrus period varies between species |
| before ovulation | egg cell contained in a follicle |
| during ovulation | follicle breaks, releasing egg into oviduct if sperm present, egg may become fertilised |
| after ovulation | CL forms on ovary and releases progesterone if egg not fertilised, CL does not grow, allowing another follicle to grow and another oestrus period to occur |
| Progesterone functions | prepares uterus for embryo implantation stops other eggs from forming maintaining pregnancy mammary gland development |
| Cow gestation | 283 days |
| Cow oestrus | 10-26 hours 18 hour average |
| Cow oestrus cycle | 18-24 days 21 day average |
| Cow ovulation | 4-16 hours post oestrus |
| Sheep gestation | 150 days |
| sheep oestrus | 20-42 hours 30 hour average |
| sheep oestrus cycle | 15-18 days 17 day average |
| sheep ovulation | 12-18 hours post oestrus |
Created by:
sakelleher29
Popular Agriculture sets