6.6 hormones, homeostasis, reproduction Flashcards
(104 cards)
1
Q
what are hormones?
A
chemical messengers which bind to receptors to trigger responses in target cells
2
Q
what is homeostasis?
A
the ability of an organism to monitor and maintain a dynamically stable internal environment within physiological limits
3
Q
why must glucose levels be regulated?
A
high levels of glucose in the blood can damage cells
4
Q
which hormones regulate blood glucose levels?
A
insulin + glucagon
5
Q
insulin and glucagon are released from ________
A
the islets of Langerhans
6
Q
_______ is released when blood glucose concentration increases
A
insulin
7
Q
what hormone is secreted when blood glucose decreases?
A
glucagon
8
Q
insulin is released by…
A
beta cells
9
Q
what are the cells that secrete glucagon?
A
alpha cells
10
Q
what are the effects of insulin? (3)
A
- 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
11
Q
what are the effects of glucagon? (3)
A
- 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
12
Q
insulin and glucagon are __________ hormones
A
antagonistic
13
Q
what is the type of diabetes that occurs during childhood?
A
type 1 IDDM
14
Q
type 2 NIDDM caused by… (2, short)
A
- a failure to respond to insulin production
- the down-regulation of insulin receptors
15
Q
what is early onset diabetes mellitus caused by?
A
- the body not producing sufficient insulin
- due to the autoimmune destruction of b-cells
16
Q
how is type 1 diabetes mellitus managed?
A
through insulin injections to regulate blood glucose
17
Q
how is type 2 diabetes mellitus managed?
A
through controlling diet and lifestyle
18
Q
what are symptoms of diabetes? (3, short)
A
- glucose in urine
- high blood glucose
- frequent urination
19
Q
what part of the body secretes thyroxin?
A
the thyroid gland
20
Q
what stimulates the thryoid gland to secrete thyroxin? (3) (hint: start from brain)
A
- 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
21
Q
what are 2 functions of thyroxin?
A
- controls basal metabolic rate
- controls energy production
22
Q
what is the detector and the control in the regulation of body temperature?
A
detector: thermoreceptors
control: thermostat in hypothalamus
23
Q
how does thyroxin control body temperature? (short)
A
by controlling the basal metabolic rate
24
Q
how does thyroxin increase body temperature? (short)
A
- it incrs basal metabolic rate
- incr metabolic activity -> incr production of heat
25
goitre, the enlarging of the thyroid gland, is caused by...
iodine deficiency
26
why must body temperature be regulated?
for efficient enzymatic activities
27
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
28
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
29
what cells secrete leptin?
adipose tissue
30
how is fat stores regulated? (short)
adipose cells produce leptin which suppresses appetite
31
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
32
why are leptin injections ineffective for obese people?
their bodies are unresponsive to leptin
33
the gland that produces melatonin is...
the pineal gland
34
what does melatonin control?
circadian rhythmns
35
what cells detect light?
ganglion cells in the retina
36
the ________________ nucleus of the __________ regulates the release of melatonin
suprachiasmatic nucleus, hypothalamus
37
what do the ganglion cells detect?
ocular light exposure
38
upon detecting ocular light exposure, the ganglion cells send signals to...
the suprachiasmatic nucleus in the hypothalamus
39
melatonin is secreted in response to...
period of darkness
40
ocular light exposure ______ the secretion of melatonin
inhibits
41
how can one counter jet lag?
take prescribed doses of melatonin at predetermined times
42
which is the sex-determining region on the Y chromosome?
gene SRY
43
the SRY protein is also known as the...
testis-determining factor (TDF)
44
how does the SRY gene cause the growth of testes?
it codes for TDF which causes embryonic gonads to form into testes
45
in fetuses, testosterone triggers...
the prenatal development of male genitalia
46
what are some male secondary sexual characteristics that develop during puberty? (2/3)
- sperm production
- growth of testes
- deepening of voice
47
what forms due to the lack of TDF results in the formation of?
ovaries
48
what triggers the prenatal development of female genitalia?
estrogen
49
which part secretes estrogen for the prenatal development of female genitalia?
ovaries
50
what are some female secondary sexual characteristics that develop during puberty? (2/3)
- breasts development
- pubic hair
- hip widening
51
label a front view diagram of the male reproductive system
-
52
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
53
which part transports semen from the testes to the urethra?
vas deferens/sperm duct
54
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
55
the Cowper's gland produces...
- alkaline fluid to neutralise any acid in urethra
- flush out pathogens
- lubricant for intercourse
56
the epididymis ______ sperm until ejaculation
stores
57
what is the function of the scrotum?
it holds testes outside the body at lower temp for optimal sperm production
58
what is the role of the testes?
produces sperm and testosterone
59
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
60
the urethra _______ the semen from the prostrate gland to the outside of the body via the ______
conducts, penis
61
label a side view diagram of the male reproductive system
-
62
label a front view diagram of the female reproductive system
-
63
what is the function of the ovary?
produces ova, estrogen and progesterone
64
where is the site of fertilisation?
the oviduct
65
which part of the oviduct collects ovum at ovulation?
fimbriae
66
what is the function of the oviduct?
- site of fertilisation
- cilia in the oviduct transport embryo to the uterus
67
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
68
the vagina __________ penis to ____________ during intercourse
stimulates, ejaculate
69
where is the embryo embedded during pregnancy?
the endometrium
70
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
71
what is the role of the vulva?
- it protects interal genitalia
- contains urethra opening for passing urine
72
label a side view diagram of the female reproductive system
-
73
how long is a menstrual cycle?
~28 days
74
the menstrual cycle is controlled by __________ and _________ feedback
-ve, +ve
75
what are the hormones involved in the menstrual cycle?
FSH, LH, estrogen, progesterone
76
what are the key events in the menstrual cycle?
1. follicular phase
2. ovulation
3. luteal phase
4. menstruation
77
what hormone causes the maturation of the follicle?
FSH
78
what hormone inhibits the development of other follicles?
estrogen
79
what produces estrogen in the follicular phase?
follicles
80
what occurs in the follicular phase? (5)
1. increased FSH secretion by anterior pituitary
- FSH stimulates maturation of follicle cells in ovaries and secretion of estrogen by follicles
2. estrogen stimulates incr in FSH receptors in follicles -> follicles more receptive to FSH -> secrete even more estrogen -> +ve feedback loop
3. estrogen stimulates the thickening of the endometrium
4. incr conc of estrogen in circulation inhibits FSH secretion -> -ve feedback
- prevent growth of additional follicles
5. 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
81
what triggers the release of the ovum from the mature follicle?
surge in LH
82
what occurs during ovulation? (1)
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
83
after the ovum is released what happens to the follicles? (short)
follicular cells are transformed into the corpus luteum
84
what hormone stimulates the formation of the corpus luteum?
LH
85
what is the effect of progesterone on the endometrium?
it thickens and maintains the endometrium in preparation for pregnancy
86
what secretes progesterone?
the corpus luteum
87
how long does the corpus luteum "live"?
12 days
88
the inactive corpus luteum is the corpus ________
albicans
89
what happens during the luteal phase? (6)
1. the remaining follicular cells are transformed into the corpus luteum under the effect of LH
2. 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
3. incr progesterone promotes the thickening and maintenance of the endometrium -> to prepare for pregnancy
4. 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
5. -ve feedback signals from P+E removed -> FSH level rises again for next menstrual cycle
6. prostaglandins are released by uterus
- for uterine constriction to slough off endometrium
- eliminated fr the body as menstrual blood
90
what are the process involved in IVF (short)
1. usage of drugs -> down regulation of menstrual cycle
2. use of hormones -> induce superovulation
91
what kind of people would seek IVF? (2 for female, 2 for male)
- blocked oviduct
- no ovulation
- erectile dysfunction
- low sperm count
92
why are drugs used in IVF
to downregulate or stop menstrual cycle
93
how do the drugs stop the menstrual cycle?
it inhibits the pituitary gland from secreting FSH and LH
94
how is superovulation induced?
through injections of relatively high conc of FSH over 10-12 days
95
____ is a substitute for LH
human Chorionic Gonadotropin (hCG)
96
hCG in IVF causes the follicles to ________ and eggs to be _______
mature, released
97
how is the egg retrieved during IVF?
via aspiration w a needle and an ultrasound to guide into a test tube
98
what does the sperm collected from the male donor undergo?
it is processed to concentrate it
99
in IVF, sperm and egg are incubated at ___ºC
37
100
how many cells must an embryo have for it to be implanted?
~8
101
what instrument is used for the implantation of embryos?
a catheter
102
what are the processes in IVF? (9)
1. drugs are first used to downregulate or stop the menstrual cycle
- by inhibiting the pituitary gland from secreting FSH and LH
2. 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
3. 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
4. eggs are retrieved via aspiration w a needle and an ultrasound guide into a test tube
5. semen sample is collected from a male and processed to concentrate it
6. 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
7. dish is examined to choose healthiest embryos
8. implantation in uterus via catheter
9. pregnancy test eg. hCG can be used to see if procedure is succcessful
103
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
104
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)
