endocrine system

Question 1

endocrine system action

Answer 1

one of 2 communication systems in the body, acts by glands releasing chemicals (hormones) into the blood stream, the hormones come in contact with all of the body tissues but only react with those that contain receptors specific for that hormone. when this happens, it triggers the body to either do something or release a different hormone.

Question 2

how is the amount of hormone released regulated?

Answer 2

positive and negative feedback loops. all hormones have different half-lives or amounts of time they stay present in the blood stream

Question 3

GnRH

Answer 3

triggers the release of hormones affecting the gonads, such as FSH and LH

Question 4

what systems does the endocrine system affect?

Answer 4

the endocrine system effects many different tissues in the cardiovascular, digestive, reproductive and renal systems

Question 5

how is the repro system controlled?

Answer 5

by the fluctuation of hormones triggered by various external and internal stimuli

Question 6

progesterone

Answer 6

pregnancy hormone produced by a corpus luteum, stopped by prostaglandin, trade names=regumate, LAP4

Question 7

estrogen

Answer 7

causes “in heat” behavior, produced by the developing follicle and increases as the follicle grows

Question 8

FSH

Answer 8

stimulates the growth of a follicle, used to get horses to start cycling. governs sperm production in stallions

Question 9

LH

Answer 9

causes ovulation, causes the formation of the corpus luteum in the follicle after the ovulation in mares, stimulates testosterone production in stallions trade names=hCG, deslorelin

Question 10

what type of breeders are horses?

Answer 10

polyestrous seasonal breeders, they have multiple estrus cycles within their breeding season, but will go into a period of anestrous during the off season

Question 11

when do horses birth their young?

Answer 11

in the spring, horses naturally begin cycling in mid to late spring.

Question 12

what induces estrus?

Answer 12

the amount of daylight perceived in the pineal gland

Question 13

pineal gland

Answer 13

when no light is available, the pineal gland produces a hormone called melatonin, preventing the release of GnRH. As day length increases the amount of melatonin produced decreases and the hypothalamus produces more GnRH.

Question 14

what does GnRH act on?

Answer 14

the pituitary gland, stimulating the release of FSH and LH. this happens in both mares and stallions

Question 15

hypothalamus

Answer 15

gland located in the brain, exerts primary control over the so-called sympathetic response of the autonomic nervous system by means of both hormones and nerves. indirectly controls most of the other glands

Question 16

ovaries

Answer 16

found only in females, located in the upper hindquarters. hold and release ova (female gametes) for reproduction. hormones produced by the ovaries include estrogen and progesterone

Question 17

pancreas

Answer 17

located at the small intestine, plays a crucial role in digestion. maintains the body’s sugar level through insulin which removes sugar from the blood and glycogen

Question 18

pituitary

Answer 18

located in the base of the brain stem, “the master gland” because it has a strong influence over growth, over milk production, over adrenal gland production, over the thyroid gland etc.

Question 19

testes

Answer 19

found only in males, part of the external genitalia, produce sperm, hormone produced is testosterone, responsible for muscle growth

Question 20

thymus

Answer 20

located near the lungs, crucial to the immune system because it is essential for the production of both white blood cells and antibodies

Question 21

thyroid

Answer 21

located in the throat, controls the level of certain chemicals or minerals in the blood, especially calcium and regulates metabolism

Question 22

prostiglandin F2alpha

Answer 22

lyses the porous luteum and causes the mare to begin another cycle, causes smooth muscle contractions. trade names=lutalyse, estrumate

Question 23

oxytocin

Answer 23

causes smooth muscle contractions, allows for milk let down, it can also remove fluid from uterus and induce parturition

Question 24

testosterone

Answer 24

promotes muscle growth, increases appetite. can cause aggressive behavior and other major side effects, trade name=equipoise, winstrol/stanozol