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Hormonal regulation of the cycle
The oestrous cycle requires hormonal control.
Which are the hormones in charge of this regulation?
GnRH ultimately controls reproduction
GnRHGonadotropin Releasing Hormone is secreted by the hypothalamus causing the release of FSH and LH. is synthesised and released by the neurons of the hypothalamusThe part of the brain that lies below the thalamus, forming the major portion of the ventral region of the diencephalon and controls autonomic nervous activities and part of the hormonal system. in the form of pulses or surges. Each secretion of GnRHGonadotropin Releasing Hormone is secreted by the hypothalamus causing the release of FSH and LH. provokes production and secretion of FSHFollicle Stimulating Hormone: responsible for the growth of ovarian follicles. and LHLuteinising hormone: responsible for the final maturation of the follicle and ovulation. by the anterior pituitaryGland located at the base of the brain just below the hypothalamus. It is divided into an anterior lobe, and a posterior lobe. The anterior lobe or adenohypophysis secretes FSH and LH, prolactin, growth hormone GH, TSH and ACTH. The posterior lobe secretes oxytocin and vasopressin. gland.
- FSHFollicle Stimulating Hormone: responsible for the growth of ovarian follicles. acts specifically upon the small follicles in the ovaries to stimulate their growth.
- Storage levels of FSHFollicle Stimulating Hormone: responsible for the growth of ovarian follicles. are low in the short-term. In fact, 50% of FSHFollicle Stimulating Hormone: responsible for the growth of ovarian follicles. produced is released each day during the cycle.
- LHLuteinising hormone: responsible for the final maturation of the follicle and ovulation. acts upon the dominant follicleSmall secretory or excretory cavity. Ovarian follicles grow until ovulation or female gamete emission. to provoke final maturation.
- The LHLuteinising hormone: responsible for the final maturation of the follicle and ovulation. surge enables ovulationExpulsion of an ovum from the ovary in female animals..
- The storage of LHLuteinising hormone: responsible for the final maturation of the follicle and ovulation. is prolonged during the cycle. 70% of LHLuteinising hormone: responsible for the final maturation of the follicle and ovulation. secreted is released during the pre-ovulatory rise.
- InhibinHormone secreted by the follicles (or Sertoli cells in the male) that selectively inhibits FSH secretion. selectively stops the release of FSHFollicle Stimulating Hormone: responsible for the growth of ovarian follicles. without affecting LHLuteinising hormone: responsible for the final maturation of the follicle and ovulation. production.
The main intrinsic factors are the ovarian hormones
ProgesteroneSteroid hormone secreted by the corpus luteum of the ovary which has the property of making the endometrium suitable for implantation, maintenance and development of the fertilized egg. (Progesterone also results in multiple activities for the endometrium, myometrium, cervix, vagina and udder.). It inhibits GnRH secretion by feedback action on the pituitary. reduces the secretion of GnRHGonadotropin Releasing Hormone is secreted by the hypothalamus causing the release of FSH and LH., which results in low frequencies of LHLuteinising hormone: responsible for the final maturation of the follicle and ovulation. discharge, thus preventing ovulationExpulsion of an ovum from the ovary in female animals..
Positive feedback:
During the follicular phase, the increase in oestradiolSteroid hormone (derived from sterols, polycyclic alcohols complex) mainly secreted by the female ovary. Its increase is involved with ovulation. levels has a positive feedback effect on the secretion of GnRHGonadotropin Releasing Hormone is secreted by the hypothalamus causing the release of FSH and LH..
Negative feedback:
Constant levels of oestradiolSteroid hormone (derived from sterols, polycyclic alcohols complex) mainly secreted by the female ovary. Its increase is involved with ovulation. have a negative feedback effect on FSHFollicle Stimulating Hormone: responsible for the growth of ovarian follicles. production, causing atresiaParticular form of aplasia: refers to an ovarian follicle that has not completed its final phase of growth and maturation, thus evolving to regression. of the follicular wave in progress and delaying the arrival of a new wave of follicles.
Associated with progesteroneSteroid hormone secreted by the corpus luteum of the ovary which has the property of making the endometrium suitable for implantation, maintenance and development of the fertilized egg. (Progesterone also results in multiple activities for the endometrium, myometrium, cervix, vagina and udder.). It inhibits GnRH secretion by feedback action on the pituitary., oestradiolSteroid hormone (derived from sterols, polycyclic alcohols complex) mainly secreted by the female ovary. Its increase is involved with ovulation. has a negative feedback effect on the secretion of GnRHGonadotropin Releasing Hormone is secreted by the hypothalamus causing the release of FSH and LH., inhibiting FSHFollicle Stimulating Hormone: responsible for the growth of ovarian follicles. and LHLuteinising hormone: responsible for the final maturation of the follicle and ovulation..
Such is the case in the luteal phase.
The oestrous cycle is also influenced by external factors.
The hypothalamusThe part of the brain that lies below the thalamus, forming the major portion of the ventral region of the diencephalon and controls autonomic nervous activities and part of the hormonal system. is also influenced by environmental factors such as light, nutrition of the animal or the stimulus of suckling in beef cows.
The hypothalamusThe part of the brain that lies below the thalamus, forming the major portion of the ventral region of the diencephalon and controls autonomic nervous activities and part of the hormonal system. is also influenced by environmental factors such as light, nutrition of the animal or the stimulus of suckling in beef cows.