Estrous Cycle

Question 1

Estrus

Answer 1

heat

period of time when the female is sexualy receptive

standing heat= period of time when the female stands to be mated

Question 2

Monoesterous

Answer 2

one estrous cycle per year

wolves, foxes, bears and dogs

Question 3

Polyestrous

Answer 3

repeated estrous cycles are uniformly distributed throughout the year

cattle, swine, rodents

Question 4

seasonally polyestrous

Answer 4

repeated estrous cycles for a portion of the year

horses, sheep, goats and cats

Question 5

Diestrus

Answer 5

period of sexual quiescence separating phases of the estrous cycle in polyestrous animals

characterized by the activity of the CL which produces progesterone

Question 6

Anestrus

Answer 6

period when female does not exhibit estrous cycles

ovaries are relatively inactive: no preovulatory follicles or CL

Question 7

what causes anestrus

Answer 7

season, lactation, presence of offspring, pregnancy, stress and disease

Question 8

Hormones

Answer 8

estrus- estrogen
diestrus- progesterone
anestrus-none?

Question 9

Day 0 of estrus cycle

Answer 9

the estrous cycle begins and ends with estrus and/or ovulation

day of ovulation, or first day of estrus (species variations)

Question 10

estrous cycle events

Answer 10

ovarian and behavioral

Question 11

Ovarian events

Answer 11

follicular phase and luteal phase

Question 12

Follicular phase

Answer 12

follicles are the dominant ovarian structure

20% of the estrous cycle

primary reproductive hormone is estradiol (E2)

Question 13

Luteal phase

Answer 13

period from ovulation until CL regression

80% of the estrous cycle

primary reproductive hormone is progesterone (P4)

Question 14

PGF 2a

Answer 14

causes progesterone to decrease and luteolysis to occur

Question 15

Bovine estrous cycle phases

Answer 15

proestrus
estrus
metestrus
diestrus

Question 16

Proestrus

Answer 16

early follicular phase

female attracts male but does not allow mating

Question 17

Estrus

Answer 17

follicular phase

period of sexual receptivity and mating

Question 18

Metestrus

Answer 18

early luteal phase

female is no longer receptive

Question 19

Diestrus

Answer 19

luteal phase

the female refuses the male

Question 20

Mare estrous cycle

Answer 20

2 stages only, estrus and diestrus

Question 21

endocrine events

Answer 21

proestrus- transition from progesterone dominance to estrogen dominance
estrus- estrogens
metestrus- transition from estrogen dominance to progesterone dominance
diestrus- period of maximum luteal function (progesterone)

Question 22

Estrogen

Answer 22

positive feedback on surge center in hypothalamus

negative feedback on anterior pituitary (LH and FSH)

Question 23

inhibin

Answer 23

negative feedback on anterior pituitary (LH and FSH), to decrease FSH secretion

released by follicle

Question 24

GnRH

Answer 24

produce in hypothalamus

acts on the pituitary to release FSH and LH

Question 25

FSH

Answer 25

released from the anterior pituitary acts on the ovary to produce follicles

Question 26

Estradiol (E2)

Answer 26

released by the follicle, acts on brain to produce estrous behavior triggers LH release presence of low P4 (+ feedback)

Question 27

LH

Answer 27

luteinizing hormone, formation of the CL released from anterior pituitary, selection and maturation of follicles LH surge to induce ovulation

Question 28

LH surge

Answer 28

occurs at day 0/estrus

Question 29

Induced ovulator

Answer 29

camelid and queen (cat) copulation necessary for ovulation

Question 30

Luteal phase

Answer 30

P4 and prostaglandin

Question 31

Progesterone

Answer 31

P4 secreted by CL, responsible for maintaining pregnancy inhibits release of LH

Question 32

Prostaglandin F2a

Answer 32

released by myometrium, lyses the CL (luteolysis) progesterone falls and animal returns to estrus

Question 33

types of cyclicity

Answer 33

Polyestrous, seasonally polyestrous and monestrous

Question 34

Photoperiod

Answer 34

amount of daylight controls when animal will cycle lack daylight increases melatonin secretion by pineal gland melatonin acts on hypothalamus to either increase or decrease report hormones short day breeders will cycle during fall/winter (ewe, doe) long day breeders will not cycle during fall/winter (mare)

Question 35

Short day breeder

Answer 35

decreased light, increase melatonin and increase ovarian activity increased melatonin increases GnRH-cyclicity with increased daylight decrease GnRH

Question 36

Long day breeder

Answer 36

decreased light, increase melatonin, and decrease ovarian activity, decrease GnRH secretion-anestrus with increased daylight increase GnRH

Question 37

Estrous cycle summary

Answer 37

physiologic events that occur between successive periods of sexual receptivity (estrus or heat) and/or ovulation 2-4 stages, spontaneous and induced ovulates cyclicality of some females is affected by the amount of daylight