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HL Bio > 6.6 hormones, homeostasis, reproduction > Flashcards

6.6 hormones, homeostasis, reproduction Flashcards

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1
Q

what are hormones?

A

chemical messengers which bind to receptors to trigger responses in target cells

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2
Q

what is homeostasis?

A

the ability of an organism to monitor and maintain a dynamically stable internal environment within physiological limits

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3
Q

why must glucose levels be regulated?

A

high levels of glucose in the blood can damage cells

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4
Q

which hormones regulate blood glucose levels?

A

insulin + glucagon

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5
Q

insulin and glucagon are released from ________

A

the islets of Langerhans

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6
Q

_______ is released when blood glucose concentration increases

A

insulin

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7
Q

what hormone is secreted when blood glucose decreases?

A

glucagon

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8
Q

insulin is released by…

A

beta cells

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9
Q

what are the cells that secrete glucagon?

A

alpha cells

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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
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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
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12
Q

insulin and glucagon are __________ hormones

A

antagonistic

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13
Q

what is the type of diabetes that occurs during childhood?

A

type 1 IDDM

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14
Q

type 2 NIDDM caused by… (2, short)

A
  • a failure to respond to insulin production
  • the down-regulation of insulin receptors
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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
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16
Q

how is type 1 diabetes mellitus managed?

A

through insulin injections to regulate blood glucose

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17
Q

how is type 2 diabetes mellitus managed?

A

through controlling diet and lifestyle

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18
Q

what are symptoms of diabetes? (3, short)

A
  • glucose in urine
  • high blood glucose
  • frequent urination
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19
Q

what part of the body secretes thyroxin?

A

the thyroid gland

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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
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21
Q

what are 2 functions of thyroxin?

A
  • controls basal metabolic rate
  • controls energy production
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22
Q

what is the detector and the control in the regulation of body temperature?

A

detector: thermoreceptors
control: thermostat in hypothalamus

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23
Q

how does thyroxin control body temperature? (short)

A

by controlling the basal metabolic rate

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24
Q

how does thyroxin increase body temperature? (short)

A
  • it incrs basal metabolic rate
  • incr metabolic activity -> incr production of heat
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25
Q

goitre, the enlarging of the thyroid gland, is caused by…

A

iodine deficiency

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26
Q

why must body temperature be regulated?

A

for efficient enzymatic activities

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27
Q

when body temperature rises, what happens? (4)

A
  • 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
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28
Q

what happens when body temperature decreases?

A
  • 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
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29
Q

what cells secrete leptin?

A

adipose tissue

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30
Q

how is fat stores regulated? (short)

A

adipose cells produce leptin which suppresses appetite

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31
Q

why are obese people less likely to recognise when they are full? (short)

A
  • their bodies are constantly producing higher levels of leptin
  • progressively become desensitised to leptin
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32
Q

why are leptin injections ineffective for obese people?

A

their bodies are unresponsive to leptin

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33
Q

the gland that produces melatonin is…

A

the pineal gland

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34
Q

what does melatonin control?

A

circadian rhythmns

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35
Q

what cells detect light?

A

ganglion cells in the retina

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36
Q

the ________________ nucleus of the __________ regulates the release of melatonin

A

suprachiasmatic nucleus, hypothalamus

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37
Q

what do the ganglion cells detect?

A

ocular light exposure

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38
Q

upon detecting ocular light exposure, the ganglion cells send signals to…

A

the suprachiasmatic nucleus in the hypothalamus

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39
Q

melatonin is secreted in response to…

A

period of darkness

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40
Q

ocular light exposure ______ the secretion of melatonin

A

inhibits

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41
Q

how can one counter jet lag?

A

take prescribed doses of melatonin at predetermined times

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42
Q

which is the sex-determining region on the Y chromosome?

A

gene SRY

43
Q

the SRY protein is also known as the…

A

testis-determining factor (TDF)

44
Q

how does the SRY gene cause the growth of testes?

A

it codes for TDF which causes embryonic gonads to form into testes

45
Q

in fetuses, testosterone triggers…

A

the prenatal development of male genitalia

46
Q

what are some male secondary sexual characteristics that develop during puberty? (2/3)

A
  • sperm production
  • growth of testes
  • deepening of voice
47
Q

what forms due to the lack of TDF results in the formation of?

A

ovaries

48
Q

what triggers the prenatal development of female genitalia?

A

estrogen

49
Q

which part secretes estrogen for the prenatal development of female genitalia?

A

ovaries

50
Q

what are some female secondary sexual characteristics that develop during puberty? (2/3)

A
  • breasts development
  • pubic hair
  • hip widening
51
Q

label a front view diagram of the male reproductive system

A

-

52
Q

what is the function of the seminal vesicle?

A
  • 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
Q

which part transports semen from the testes to the urethra?

A

vas deferens/sperm duct

54
Q

what is the function of the prostate gland?

A
  • secretes thin fluid that reduces viscosity of semen -> enhance sperm motility
  • alkaline medium -> counteracts acidic environment in vagina
55
Q

the Cowper’s gland produces…

A
  • alkaline fluid to neutralise any acid in urethra
  • flush out pathogens
  • lubricant for intercourse
56
Q

the epididymis ______ sperm until ejaculation

A

stores

57
Q

what is the function of the scrotum?

A

it holds testes outside the body at lower temp for optimal sperm production

58
Q

what is the role of the testes?

A

produces sperm and testosterone

59
Q

what is the role of the penis in sexual intercourse?

A

contains erectile tissue that enlarges and becomes hard -> allows for the penetration of the vagina for semen to be ejaculated near the cervix

60
Q

the urethra _______ the semen from the prostrate gland to the outside of the body via the ______

A

conducts, penis

61
Q

label a side view diagram of the male reproductive system

A

-

62
Q

label a front view diagram of the female reproductive system

A

-

63
Q

what is the function of the ovary?

A

produces ova, estrogen and progesterone

64
Q

where is the site of fertilisation?

A

the oviduct

65
Q

which part of the oviduct collects ovum at ovulation?

A

fimbriae

66
Q

what is the function of the oviduct?

A
  • site of fertilisation
  • cilia in the oviduct transport embryo to the uterus
67
Q

the role of the cervix is to…

A
  • 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
Q

the vagina __________ penis to ____________ during intercourse

A

stimulates, ejaculate

69
Q

where is the embryo embedded during pregnancy?

A

the endometrium

70
Q

what is the function of the uterus? (3 short)

A
  • it receives the embryo which gets embedded into its endometrium
  • protects the fetus
  • nourishes fetus w O2, food -> removes waste products
71
Q

what is the role of the vulva?

A
  • it protects interal genitalia
  • contains urethra opening for passing urine
72
Q

label a side view diagram of the female reproductive system

A

-

73
Q

how long is a menstrual cycle?

A

~28 days

74
Q

the menstrual cycle is controlled by __________ and _________ feedback

A

-ve, +ve

75
Q

what are the hormones involved in the menstrual cycle?

A

FSH, LH, estrogen, progesterone

76
Q

what are the key events in the menstrual cycle?

A
  1. follicular phase
  2. ovulation
  3. luteal phase
  4. menstruation
77
Q

what hormone causes the maturation of the follicle?

A

FSH

78
Q

what hormone inhibits the development of other follicles?

A

estrogen

79
Q

what produces estrogen in the follicular phase?

A

follicles

80
Q

what occurs in the follicular phase? (5)

A
  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
Q

what triggers the release of the ovum from the mature follicle?

A

surge in LH

82
Q

what occurs during ovulation? (1)

A
  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
Q

after the ovum is released what happens to the follicles? (short)

A

follicular cells are transformed into the corpus luteum

84
Q

what hormone stimulates the formation of the corpus luteum?

A

LH

85
Q

what is the effect of progesterone on the endometrium?

A

it thickens and maintains the endometrium in preparation for pregnancy

86
Q

what secretes progesterone?

A

the corpus luteum

87
Q

how long does the corpus luteum “live”?

A

12 days

88
Q

the inactive corpus luteum is the corpus ________

A

albicans

89
Q

what happens during the luteal phase? (6)

A
  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
Q

what are the process involved in IVF (short)

A
  1. usage of drugs -> down regulation of menstrual cycle
  2. use of hormones -> induce superovulation
91
Q

what kind of people would seek IVF? (2 for female, 2 for male)

A
  • blocked oviduct
  • no ovulation
  • erectile dysfunction
  • low sperm count
92
Q

why are drugs used in IVF

A

to downregulate or stop menstrual cycle

93
Q

how do the drugs stop the menstrual cycle?

A

it inhibits the pituitary gland from secreting FSH and LH

94
Q

how is superovulation induced?

A

through injections of relatively high conc of FSH over 10-12 days

95
Q

____ is a substitute for LH

A

human Chorionic Gonadotropin (hCG)

96
Q

hCG in IVF causes the follicles to ________ and eggs to be _______

A

mature, released

97
Q

how is the egg retrieved during IVF?

A

via aspiration w a needle and an ultrasound to guide into a test tube

98
Q

what does the sperm collected from the male donor undergo?

A

it is processed to concentrate it

99
Q

in IVF, sperm and egg are incubated at ___ºC

A

37

100
Q

how many cells must an embryo have for it to be implanted?

A

~8

101
Q

what instrument is used for the implantation of embryos?

A

a catheter

102
Q

what are the processes in IVF? (9)

A
  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
Q

what was Aristotle’s theory on reproduction?

A

‘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
Q

what did Harvey discover?

A
  • 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)

HL Bio (53 decks)

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