Homeostasis Flashcards
(24 cards)
hormones responsible for regulating blood glucose concentrations
insulin and glucagon (act principally on the liver)
insulin
when blood glucose levels are high:
- insulin is released from beta cells of pancreas and cause decrease in blood glucose concentration
- may involve stimulating glycogen synthesis in liver
when blood glucose levels are low:
- glucagon is released from alpha cells of pancreas and cause an increase in blood glucose concentration
diabetes
metabolic disorder that results from high blood glucose concentration over long period
- caused by either not producing insulin (type I) or failing to respond to insulin production (type II)
- treated by insulin injections (type 1 only) or by carefulling monitoring and controlling dietary intake (type II)
type I diabetes
- occurs during childhood (early onset)
- does not produce enough insulin
- caused by destruction of b-cells
- insulin injections to regulate
type II diabetes
- adulthood
- does not respond to insulin production
- caused by down-regulation of insulin receptors
- controlled by managing diet
thyroxin
hormone secreted by thyroid gland in response to signals initially derived from hypothalamus. role is to increase basal metabolic rate. consequence of increasing metabolic activity is production of heat, therefore thyroxin helps to control body temp.
leptin
hormone produced by adipose cells that regulates fat stores within body by suppressing appetite. operating causes more adipose cells to form and more leptin is produced, suppressing appetite. obese people become desensitized to the hormone.
melatonin
hormone produced by pineal gland within the brain in response to changes in light.
circadian rhythms
the body’s physiological responses to 24 hours day-night cycle
- driven by internal circadian clock
testosterone
reproductive hormone in males, secreted by the testes.
- responsible for pre-natal development of male genitalia
- sperm production following onset of puberty
- develops secondary sex characteristics
- maintains sex drive
estrogen and progesterone
female reproductive hormones secreted by the ovaries.
- promote pre-natal development of reproductive organs
- develops secondary sex characteristics
- monthly preparation of egg release following puberty (menstrual cycle)
male reproductive system
testis: production of sperm and testosterone
epididymis: site where sperm matures and develops the ability to be motile. mature sperm is stored here until ejaculation
vas deferens: long tube which conducts sperm from testes to prostate gland during ejaculation
seminal vesicle: secretes fluid containing fructose and mucus
prostate gland:secretes alkaline fluid to neutralize vaginal acids
urethra: conducts sperm from prostate gland to outside of body
female reproductive system
ovary: where oocytes mature prior to release, also responsible for estrogen and progesterone secretion
Fallopian tube: transports oocyte to uterus, typically where fertilization occurs
uterus: organ where a fertillized egg will implant and develop
endometrium: mucous membrane lining of uterus, thickens in preparation for implantation or is otherwise lost
vagina: passage leading to uterus which penis can enter
menstrual cycle
recurring changes that occur within the female reproductive system to make pregnancy possible
- pituitary hormones (FSH and LH) are released from anterior pituitary gland and act on ovaires to develop follicles
- ovarian hormones (estrogen and progesterone) are released from ovaries and act on uterus to prepare for pregnancy
key events in menstrual cycle
follicular phase, ovulation, luteal phase, and menstruation
follicular phase
- FSH is secreted from anterior pituitary and stimulates growth of ovarian follicles
- dominant follicle produces estrogen, which inhibits FSH secretion to prevent other follicles growing
- estrogen acts on uterus to stimulate thickening of endometrial layer
ovulation
- midway through cycle, estrogen stimulates anterior pituitary to secrete hormones
- positive feedback results in large surge of luteinizing hormone (LH) and lesser surge of FSH
- LH causes dominant follicle to rupture and release egg
luteal phase
- ruptured follicle develops into a slowly generating corpus lute
- corpus lieu secretes high levels of progesterone, as well as lower levels of estrogen
- estrogen and progesterone act on uterus to thicken endometrial lining
- they also inhibit secretion of FSH and LH, preventing follicles from developing
menstruation
- if fertilization occurs, developing embryo will implant in endometrium and release hormones to sustain the corpus luteum
- if it doesn’t occur, corpus luteum degenerates
- when it degenerates, estrogen and progesterone levels drop and endometrium can no longer be maintained
- layer is eliminated from body as menstrual blood
- cycle can begin again
In vitro fertilization (IVF)
fertilization that occurs outside of body
- down regulation, super ovulation, fertilization, implantation
down regulation
- drugs are used to halt secretion of FSH and LH, which stops secretion of estrogen and progesterone
- by stopping cycle, doctors can take control of timing and quantity of egg production
superovulation
- using artificial doses of hormones to develop and collect multiple eggs from woman
- patient is injected with large amounts of FSH to stimulate development of many follicles
- they are then treated with hCG, a hormone usually produced by developing embryo
- hCG stimulates follicles to mature and egg is collected prior to follicles rupturing
fertilization
- extracted eggs are incubated in presence of sperm sample from male donor
implantation
- 2 weeks prior to implantation, woman begins to take progesterone treatments to develop endometrium
- healthy embryos are selected and transferred into uterus
- multiple embryos are transferred to improve chances of successful implementation
