6.6 hormones, homeostasis, reproduction Flashcards
what are hormones?
chemical messengers which bind to receptors to trigger responses in target cells
what is homeostasis?
the ability of an organism to monitor and maintain a dynamically stable internal environment within physiological limits
why must glucose levels be regulated?
high levels of glucose in the blood can damage cells
which hormones regulate blood glucose levels?
insulin + glucagon
insulin and glucagon are released from ________
the islets of Langerhans
_______ is released when blood glucose concentration increases
insulin
what hormone is secreted when blood glucose decreases?
glucagon
insulin is released by…
beta cells
what are the cells that secrete glucagon?
alpha cells
what are the effects of insulin? (3)
- increased glucose uptake via facilitated diffusion by liver and muscles
- increased oxidation of glucose for energy in liver and muscles
- increased conversion of excess glucose to glycogen in liver and muscles
- thus blood glucose decreases -> serves as -ve feedback
what are the effects of glucagon? (3)
- break down of glycogen to glucose
- formation of glucose from amino acids
- promotes lipolysis in adipose cells to convert fats to glycogen to be converted to glucose
- thus blood glucose increases -> serves as -ve feedback
insulin and glucagon are __________ hormones
antagonistic
what is the type of diabetes that occurs during childhood?
type 1 IDDM
type 2 NIDDM caused by… (2, short)
- a failure to respond to insulin production
- the down-regulation of insulin receptors
what is early onset diabetes mellitus caused by?
- the body not producing sufficient insulin
- due to the autoimmune destruction of b-cells
how is type 1 diabetes mellitus managed?
through insulin injections to regulate blood glucose
how is type 2 diabetes mellitus managed?
through controlling diet and lifestyle
what are symptoms of diabetes? (3, short)
- glucose in urine
- high blood glucose
- frequent urination
what part of the body secretes thyroxin?
the thyroid gland
what stimulates the thryoid gland to secrete thyroxin? (3) (hint: start from brain)
- hypothalamus secretes thyrotropin releasing hormone (TRH) in response to stimulus
- TRH stimulates anterior pituitary gland to secrete thyroid stimulating hormone (TSH)
- TSH acts on thyroid gland -> stimulating the secreting of thyroxin
what are 2 functions of thyroxin?
- controls basal metabolic rate
- controls energy production
what is the detector and the control in the regulation of body temperature?
detector: thermoreceptors
control: thermostat in hypothalamus
how does thyroxin control body temperature? (short)
by controlling the basal metabolic rate
how does thyroxin increase body temperature? (short)
- it incrs basal metabolic rate
- incr metabolic activity -> incr production of heat
goitre, the enlarging of the thyroid gland, is caused by…
iodine deficiency
why must body temperature be regulated?
for efficient enzymatic activities
when body temperature rises, what happens? (4)
- thermoreceptors detect the change
- thermostat in hypothalamus inhibits thyroxin release from thyroid gland
- reduced metabolism
- reduced respiration in brown adipose tissues
- vasodilation of skin capillaries -> more blood flows to surface of skin -> allow more heat loss
- incr activity of sweat glands -> incr sweating -> heat removed due to latent heat of evaporation
- body temperature decreases -> negative feedback
what happens when body temperature decreases?
- thermoreceptors detect the change
- thermostat in hypothalamus stimulates thyroxin release from thyroid gland
- contraction of skeletal muscles + incr metabolic rate -> shivering to generate heat
- incr respiration of in brown adipose tissues
- less active sweat glands -> minimise sweating
- formation of goose bumps -> hairs on skin erected to trap air for insulation
- body temperature rises -> negative feedback
what cells secrete leptin?
adipose tissue
how is fat stores regulated? (short)
adipose cells produce leptin which suppresses appetite
why are obese people less likely to recognise when they are full? (short)
- their bodies are constantly producing higher levels of leptin
- progressively become desensitised to leptin
why are leptin injections ineffective for obese people?
their bodies are unresponsive to leptin
the gland that produces melatonin is…
the pineal gland
what does melatonin control?
circadian rhythmns
what cells detect light?
ganglion cells in the retina
the ________________ nucleus of the __________ regulates the release of melatonin
suprachiasmatic nucleus, hypothalamus
what do the ganglion cells detect?
ocular light exposure
upon detecting ocular light exposure, the ganglion cells send signals to…
the suprachiasmatic nucleus in the hypothalamus
melatonin is secreted in response to…
period of darkness
ocular light exposure ______ the secretion of melatonin
inhibits
how can one counter jet lag?
take prescribed doses of melatonin at predetermined times
which is the sex-determining region on the Y chromosome?
gene SRY
the SRY protein is also known as the…
testis-determining factor (TDF)
how does the SRY gene cause the growth of testes?
it codes for TDF which causes embryonic gonads to form into testes
in fetuses, testosterone triggers…
the prenatal development of male genitalia
what are some male secondary sexual characteristics that develop during puberty? (2/3)
- sperm production
- growth of testes
- deepening of voice
what forms due to the lack of TDF results in the formation of?
ovaries
what triggers the prenatal development of female genitalia?
estrogen
which part secretes estrogen for the prenatal development of female genitalia?
ovaries
what are some female secondary sexual characteristics that develop during puberty? (2/3)
- breasts development
- pubic hair
- hip widening
label a front view diagram of the male reproductive system
-
what is the function of the seminal vesicle?
- it secretes fluid containing nutrients including fructose sugar for sperm respiration
- fluid also contains prostaglandins for smooth muscle contraction during ejaculation
- mucus to protect sperm
which part transports semen from the testes to the urethra?
vas deferens/sperm duct
what is the function of the prostate gland?
- secretes thin fluid that reduces viscosity of semen -> enhance sperm motility
- alkaline medium -> counteracts acidic environment in vagina
the Cowper’s gland produces…
- alkaline fluid to neutralise any acid in urethra
- flush out pathogens
- lubricant for intercourse
the epididymis ______ sperm until ejaculation
stores
what is the function of the scrotum?
it holds testes outside the body at lower temp for optimal sperm production
what is the role of the testes?
produces sperm and testosterone
what is the role of the penis in sexual intercourse?
contains erectile tissue that enlarges and becomes hard -> allows for the penetration of the vagina for semen to be ejaculated near the cervix
the urethra _______ the semen from the prostrate gland to the outside of the body via the ______
conducts, penis
label a side view diagram of the male reproductive system
-
label a front view diagram of the female reproductive system
-
what is the function of the ovary?
produces ova, estrogen and progesterone
where is the site of fertilisation?
the oviduct
which part of the oviduct collects ovum at ovulation?
fimbriae
what is the function of the oviduct?
- site of fertilisation
- cilia in the oviduct transport embryo to the uterus
the role of the cervix is to…
- during intercourse, direct sperms into the uterus
- during pregnancy, strong muscles at cervix prevent the fetus from falling out
- dilates during birth to provide birth canal
the vagina __________ penis to ____________ during intercourse
stimulates, ejaculate
where is the embryo embedded during pregnancy?
the endometrium
what is the function of the uterus? (3 short)
- it receives the embryo which gets embedded into its endometrium
- protects the fetus
- nourishes fetus w O2, food -> removes waste products
what is the role of the vulva?
- it protects interal genitalia
- contains urethra opening for passing urine
label a side view diagram of the female reproductive system
-
how long is a menstrual cycle?
~28 days
the menstrual cycle is controlled by __________ and _________ feedback
-ve, +ve
what are the hormones involved in the menstrual cycle?
FSH, LH, estrogen, progesterone
what are the key events in the menstrual cycle?
- follicular phase
- ovulation
- luteal phase
- menstruation
what hormone causes the maturation of the follicle?
FSH
what hormone inhibits the development of other follicles?
estrogen
what produces estrogen in the follicular phase?
follicles
what occurs in the follicular phase? (5)
- increased FSH secretion by anterior pituitary
- FSH stimulates maturation of follicle cells in ovaries and secretion of estrogen by follicles
- estrogen stimulates incr in FSH receptors in follicles -> follicles more receptive to FSH -> secrete even more estrogen -> +ve feedback loop
- estrogen stimulates the thickening of the endometrium
- incr conc of estrogen in circulation inhibits FSH secretion -> -ve feedback
- prevent growth of additional follicles
- as dominant follicle matures -> it starts to express LH receptors
- follicle is stimulated by LH to produce estrogen
- estrogen levels peak -> more LH receptors produced by follicle -> more estrogen produced -> +ve feedback
what triggers the release of the ovum from the mature follicle?
surge in LH
what occurs during ovulation? (1)
- at e end of the follicular phase -> LH surge
- this stimulates the completion of the meiosis in the oocyte + partial digestion of follicle wall
- thus the ovum can be released from mature dominant follicle
after the ovum is released what happens to the follicles? (short)
follicular cells are transformed into the corpus luteum
what hormone stimulates the formation of the corpus luteum?
LH
what is the effect of progesterone on the endometrium?
it thickens and maintains the endometrium in preparation for pregnancy
what secretes progesterone?
the corpus luteum
how long does the corpus luteum “live”?
12 days
the inactive corpus luteum is the corpus ________
albicans
what happens during the luteal phase? (6)
- the remaining follicular cells are transformed into the corpus luteum under the effect of LH
- the corpus luteum synthesises and secretes estrogen and high amts of progesterone
- -ve feedback signals to anterior pituitary gland + hypothalamus
- inhibits FSH and LH secretions respectively
- prevents development of any more follicles
- incr progesterone promotes the thickening and maintenance of the endometrium -> to prepare for pregnancy
- corpus luteum has 12-day life span
- if pregnancy does not occur, it will degenerate into inactive structure corpus albicans
- causes conc of progesterone + estrogen to fall
- endometrium disintegrates -> due to no hormonal support
- -ve feedback signals from P+E removed -> FSH level rises again for next menstrual cycle
- prostaglandins are released by uterus
- for uterine constriction to slough off endometrium
- eliminated fr the body as menstrual blood
what are the process involved in IVF (short)
- usage of drugs -> down regulation of menstrual cycle
- use of hormones -> induce superovulation
what kind of people would seek IVF? (2 for female, 2 for male)
- blocked oviduct
- no ovulation
- erectile dysfunction
- low sperm count
why are drugs used in IVF
to downregulate or stop menstrual cycle
how do the drugs stop the menstrual cycle?
it inhibits the pituitary gland from secreting FSH and LH
how is superovulation induced?
through injections of relatively high conc of FSH over 10-12 days
____ is a substitute for LH
human Chorionic Gonadotropin (hCG)
hCG in IVF causes the follicles to ________ and eggs to be _______
mature, released
how is the egg retrieved during IVF?
via aspiration w a needle and an ultrasound to guide into a test tube
what does the sperm collected from the male donor undergo?
it is processed to concentrate it
in IVF, sperm and egg are incubated at ___ºC
37
how many cells must an embryo have for it to be implanted?
~8
what instrument is used for the implantation of embryos?
a catheter
what are the processes in IVF? (9)
- drugs are first used to downregulate or stop the menstrual cycle
- by inhibiting the pituitary gland from secreting FSH and LH
- relatively high conc of FSH is injected over 10-12 days to induce superovulation
- stimulates the development of many follicles in the ovaries
- thus more eggs for harvesting
- when the follicles reach an appropriate size, hCG, a substitute for LH is injected 36 hours before egg collection
- cause the follicles to mature + eggs to be released
- eggs are retrieved via aspiration w a needle and an ultrasound guide into a test tube
- semen sample is collected from a male and processed to concentrate it
- sperms are mixed with the egg in a test tube and incubated for a few days at 37ºC
- allow zygote to develop to ~8 cells
- dish is examined to choose healthiest embryos
- implantation in uterus via catheter
- pregnancy test eg. hCG can be used to see if procedure is succcessful
what was Aristotle’s theory on reproduction?
‘seed and soil’ theory:
- male produces a seed which forms an egg when mixed with menstrual blood
- egg then develops into a fetus inside the mother
what did Harvey discover?
- he debunked Aristotle’s seed and soil theory, that menstrual blood did not contribute to the formation of a fetus (true)
- questioned the direct role of semen in reproduction (false)
