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IB Biology HL > Regulation and reproduction > Flashcards

Regulation and reproduction Flashcards

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1
Q

What is membrane potential?

A
  • electric charge difference
    • across membrane
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2
Q

What is resting potential?

A
  • imbalance of positive and negative charges across membrane (-70mV)
  • no signal
  • inside negative, outside positive
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3
Q

What causes resting potential?

A
  • inside
    • K+
    • protein anions (-)
  • outside
    • Na+
    • Cl-
  • sodium-potassium pumps (ATP needed)
    • for every 3Na+, 2K+ are pumped
      • more Na+ on the outside
  • leakages
    • voltage gated channels = open at certain electrical potential value
      • closed are leaky
        • more K+ leaks outside
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4
Q

How do voltage-gated channels work?

A
  • Na+
    • open at threshold potential (depolarisation)
    • Na+ in
    • close at action potential
  • K+
    • open at action potential (repolarisation)
    • K+ out
    • close after reaching resting potential again
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5
Q

How is action potential propagated?

A
  • ion movement depolarises one part
    - Na+ inside move from depolarised part to not yet depolarised
    - Na+ outside move the opposite direction
    - difference = -50mV (threshold potential reached)
  • impulse initiated at one terminal
    • passed at other terminal
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6
Q

What is axon hillock?

A
  • junction between cell body and axon
    • plasma membrane composition changes
      • voltage-gated channels
  • initiates electric impulse
    • small amounts of Na+ accumulate there
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7
Q

What is depolarisation?

A
  • Na+ in axon hillock
  • charge grows inside neurone
    • plasma membrane depolarisation
  • threshold potential is reached (-55mV)
    • voltage-gated channels open
      • Na+ inside
        • more Na+ channels open = positive feedback
      • charge changes to 40mV = action potential
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8
Q

What is repolarisation?

A
  • at action potential
    • Na+ closes — K+ open
    • K+ outside
      • charge drops
      • K+ and Na+ at wrong sides
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9
Q

What is hyperpolarisation?

A
  • K+ channels close
    • slow
  • potential inside drops further than resting state
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10
Q

What happens at the absolute refractory period?

A
  • after action potential
    • Na+ channels can’t open
  • no action potential
    • prevents backflow
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11
Q

What happens at relative refractory period?

A
  • hyperpolarisation
    • harder to reach threshold potential
    • stronger stimulus needed (more Na+)
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12
Q

How is action potential propagated forward?

A
  • depolarisation
    • opens channels in next part of axon
      • signal goes forward
  • local currents
    • Na+ inside the cell (depolarised part) move to the polarised part
    • Na+ outside the cell (polarised) moves to depolarised part
      • this prevents signal from going backwards
      • reduces concentration gradient (easier to reach -55mV)
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13
Q

What is myelin?

A
  • coats nerve fibres
  • phospholipid bilayer
    • Schwann cells deposit myelin
      • 20 or more layers
  • gap: node of Ranvier
  • saltatory conduction
    • impulse jumps from node to node
      • quicker
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14
Q

What is a synapse?

A
  • space between the axon terminals of one nerve and dendrites of the other
    • or muscles and glands
  • fluid-filled gap = synaptic cleft (20nm)
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15
Q

How does a signal move?

A
  • neurotransmitters send signals across synapses
    • from signal to receiver cell
      • receptors on post-synaptic cell
    • diffusion
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16
Q

What are the steps of synaptic transmission?

A
  1. impulse propagated along pre-synaptic neuron
    • reaches axon terminal
  2. depolarisation of membrane
    • voltage-gated channels of Ca2+ open
      • Ca2+ inside
  3. Ca2+ influx causes vesicles with neurotransmitters to move
    • fuse with membrane
  4. neurotransmitter is released to synaptic cleft
    • exocytosis
  5. neurotransmitters bind to post-synaptic receptors
  6. Na+ channels open
    • Na+ into the cell
      • threshold potential
  7. neurotransmitter degraded by enzyme or back into pre-synaptic membrane by a transporter or reuptake pump
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17
Q

How are neurotransmitters in axon terminal?

A
  • produced in cell body
    • in vesicles
      • transported to axon terminal
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18
Q

What happens after synaptic transmission?

A
  • vesicles fuse with pre-synaptic membrane
    • enlarged
  • neurotransmitter reuptake
    • endocytosis
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19
Q

What is a motor neurone?

A
  • from central nervous system (CNS) to muscles
    - elongated axon
  • connected to muscle
    • neuromuscular junction
      • chemical synapse
        • neurotransmitter: acetylcholine (cholinergic)
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20
Q

How is acetylcholine produced?

A
  • pre-synaptic cell
    • combining choline (diet) with acetyl group (aerobic respiration)
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21
Q

How does cholinergic synapse work?

A
  • acetylcholine is released after Ca2+ influx
  • ACh binds to Na+ channel receptors
    • threshold potential
    • shortly bounded: only 1 action potential
  • acetylcholinesterase (in synaptic cleft) breaks ACh down into choline and acetate
  • choline is reabsorbed by pre-synaptic neuron
    • back into ACh
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22
Q

How is knowledge about synaptic transmission applied?

A
  • neuronal and mental diseases
    • Selective Serotonin Reuptake Inhibitor (SSRI) = antidepressants
  • neuroactive toxins
    • neonicotinoids (pesticide)
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23
Q

What are neonicotinoids?

A
  • similar to nicotine
  • binds acetylcholine receptors
    • insects
  • acetylcholinesterase doesn’t break it down
    • irreversible
    • paralysis and death
  • not toxic to humans
    • more cholinergic synapses in CNS of insects
    • bind less strongly to receptors
  • imidacloprid = commonly used pesticide
  • harmful for honeybees
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24
Q

What are hormones?

A
  • chemical messengers
    • produced by endocrine glands
  • homeostasic regulation
  • modification of activity of tissues
  • transported by blood
  • slower but long lasting effects
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25
What are the differences between nervous and endocrine system?
- nerve impulse vs chemical messenger - neurons vs blood - fast vs slow - carried to specific cells vs throughout body - muscles / glands vs range of organs affected
26
What are different types of hormones?
~ steroids - receptors in nucleus - action by transcription regulation - affect gene expression - slow > peptides - receptors in plasma membrane - act by signalling cascade - affect chemical processes and gene expression - fast > proteins, glycoproteins, amines or tyrosine derivatives
27
How do steroid hormones work?
- cross through plasma and nuclear membrane - bind to receptors - ex. sex hormones - form receptor-hormone complex - serves as transcription factor (promotion or inhibition) - produced from cholesterol - calciferol: intestinal cell membrane - complex affects expression of calcium transport protein calbindin - absorption of calcium - cortisol binds in cytoplasm and enters nucleus - in liver cell: gluconeogenesis - conversion of fats and proteins into glucose - decreases expression of insulin receptor - in pancreas
28
How do peptide hormones work?
- bind to membrane receptors - triggers cascade reaction, edited by second messengers - hydrophilic so cannot pass the membrane
29
What is an example of second messengers?
- water soluble — spread signal fast - Ca2+ and cyclic AMP (cAMP)
30
How does epinephrine signalling work?
- epinephrine mediates “fight or flight” (first messenger) - supply of glucose (energy) needed - in liver binds to G-protein couple receptor - activation of G-protein - uses GTP as energy to activate enzyme adenylyl cyclase - ATP —> cAMP - cAMP (cyclic adenosine monophosphate) activates protein kinase enzymes - glycogen breakdown and inhibit glycogen synthesis
31
What are the endocrine glands?
- pituitary - pineal - hypothalamus - thyroid - parathyroid - thymus - mammary - adrenal
32
What is the role of hypothalamus?
- combines nervous and endocrine system - control of pituitary gland - secretion of releasing factors - stimulate anterior pituitary gland - carried by portal vein - negative feedback - blood solute high - osmoreceptors in hypothalamus react - ADH secretion - blood solute low - ADH reduced
33
What is the role of pituitary gland?
- anterior pituitary - growths, reproduction, homeostasis - FSH and LH - posterior pituitary - oxytocin and ADH - hormones synthesised in neurosecretory cell in hypothalamus - the end of axons - impulse stimulates secretion
34
What is thyroxin and its function?
- hormone - regulates metabolic rate (especially in liver, muscle and brain) and helps control body temp - as the body cools, more thyroxine is produced - secreted by thyroid gland (neck) - 4 atoms of iodine - deficiency of iodine = no synthesis of thyroxin
35
How is temperature controlled by thyroxin?
- hypothalamus controls blood temperature - decrease = signal to thyroid - metabolic rate in cells increases - more heat
36
What are the results of thyroxin deficiency?
- thyroxine is a hormone regulating metabolism - deficiency => less metabolism - less ATP - imparted muscle work —> fatigue - imparted neural work —> dizziness, forgetfulness, depression, imparted brain development - less heat —> feeling cold - less sugars and lipids used for cellular respiration —> body fat accumulation - iodine deficiency (hypothyroidism = underactive thyroid) - cause of thyroxin deficiency - enlargement of thyroid = goiter
37
How is milk produced and ejected in mammals?
- in mammary glands - prolactin - anterior pituitary - development of mammary glands - milk production - oestrogen and progesterone increases prolactin - inhibits effect of prolactin on milk production - at labour production begins (no oestrogen and progesterone) - oxytocin - release of milk - nursing by infant stimulates prolactin and oxytocin - contraction of surrounding cells - ejection of milk - positive feedback
38
How are growth hormones used by athletes?
- produced in anterior pituitary - targets liver cells - release of insulin-like growth factor - stimulates bone and cartilage growth - increase muscle mass - short burst of strength - banned
39
What is melatonin’s function?
- feeling of drowsiness, drops body temp - pineal gland - controls circadian rhythms - depend on suprachiasmic nuclei (SCN) in hypothalamus - control secretion of melatonin by pineal gland - information about light from retina - concentration decreases at dawn
40
What are the causes of jet lag?
- three or more time zones - difficulty in remaining awake and sleeping through night - fatigue, irritation, headaches - melatonin can be taken
41
What glands exist in pancreas?
- exocrine - digestive enzymes - alkaline solution - endocrine - hormones
42
How is blood glucose level controlled?
- in pancreas - regions of endocrine tissue: islets of Langerhans - set point: 5mmol/L - alpha cells - glucagon - blood glucose levels fall - stimulation of glycogen breakdown into glucose - released into blood - beta cells - insulin - blood glucose levels increase - stimulation uptake of glucose by tissues - skeletal muscle, liver - insulin broken down by cells it acts upon = ongoing secretion
43
What are the types of diabetes?
- type I - early onset - autoimmune (destruction of beta) - no insulin - skinny complexion - type II - insulin signal not received by cells (insulin resistant) - old - associated with obesity - disturbance of glucose homeostasis - bad diet, no exercise
44
What are the treatments for diabetes?
- type I (defects in B cells of pancreas) - insulin injections - before meal - implanted devices - stem cells maybe - type II (insulin resistance) - adjusting diet, exercise
45
What is leptin?
- produced by adipose tissue - glucose uptake - excess of energetic substrates present - appetite control centre in hypothalamus - feeling of satiety - in mice with recessive on alleles no leptin - obesity - objection of leptin decreased mass
46
Why isn’t leptin used to treat obesity?
- skin irritation and swelling - short-lived protein - rare cases of “low leptin” obesity - loss of leptin sensibility is more probable
47
What are the functions of reproductive system?
- gamete production - storage - nourishment - transport - fertilisation - pregnancy
48
What did Harvey do in his experiment?
- “soil and seed” theory by Aristotle - sperm = seed that develops in woman’s uterus with menstrual blood - dissection of deer’s uterus - no foetus shown - hypothesis: foetus development is independent from sex
49
What are the steps of oogenesis?
1. before birth - oogonia formation - meiosis arrested at prophase I - primary oocyte (follicle) 2. after puberty - each month —> oocyte completes meiosis I and starts prophase II - first polar body - secondary oocyte (released at each cycle) - secondary follicle —> mature follicle 3. fertilisation - meiosis II completed - ovum - maturation of gamete
50
What happens to the follicle after releasing of an oocyte?
- degenerating follicle = corpus luteum —> corpus albicans
51
Where does spermatogenesis occur?
- in testes - narrow tubes = seminiferous tubules - outer layer = germinal epithelium - sperm production begins - more mature = closer to lumen - on the wall —> Sertoli cells (large nurse) - small cells in the gaps = interstitial cells (Leydig cells)
52
What are the steps of spermatogenesis?
1. mitosis (puberty) - spermatogonium —> primary spermatocyte 2. meiosis I - primary spermatocyte —> 2 secondary spermatocytes 3. meiosis II - secondary spermatocytes —> 2 spermatids 4. maturation - spermatozoa = sperm
53
How is sex of the embryo determined?
- starting as females - reproductive hormones: oestrogen and progesterone - from ovaries and placenta - SRY (sex-determining region Y) gene on Y chromosome - encoding for TDF (testicle-determining factor) - TDF triggers development of gonads into testes - testes produce testosterone - testosterone : oestrogen ratio high - further development of male parts
54
How does testosterone work in male development?
- pre-natal - gonads —> testes - male reproductive organs - puberty - production of sperm (primary sexual characteristic) - secondary sexual characteristics - enlargement of penis - pubic hair - deepening of voice
55
What causes pre- and post-natal development of females?
- prenatal - oestrogen and progesterone - both sexes - ratio testosterone : oestrogen matters - female genitalia development during foetal development - puberty - enlargement of breasts - pubic hair - underarm hair
56
What are the stages of menstrual cycle?
follicular —> ovulation —> luteal —> menstruation
57
What happens during follicular phase?
- follicles developing into ovary - most developed breaks open —> into oviduct - rest degenerate - uterus walls (endometrium) thicken and repair
58
What happens during luteal phase?
- wall of follicle releasing egg —> corpus luteum - endometrium prepares for embryo - if no, menstruation starts - corpus luteum breaks down
59
What hormones control menstrual cycle?
- pituitary protein hormones - FSH (follicle stimulating) - LH (luteinising hormone) - ovarian hormones - oestrogen - progesterone
60
What are the roles of different hormones in menstrual cycle?
- FSH - peak at the end of mentruation - development of follicles (with oocyte and follicular fluid) - secretion of oestrogen by follicle wall - oestrogen - peak at the end of follicular phase - repair and thickening of endometrium - increases FSH receptors —> follicles more receptive to FSH —> more oestrogen (positive feedback) - high levels —> inhibition of FSH (negative feedback) - LH secretion - LH - sharp peak at the end of follicular phase - completion in meiosis of oocyte - partial digestion of follicle wall = opening at ovulation - development of follicle wall into corpus luteum - secretes oestrogen (positive feedback) and progesterone - progesterone - rise at start of luteal phase - drops back at the end - thickening and maintaining endometrium - inhibits FSH and LH (negative feedback)
61
What are different fertilisation types?
- internal (terrestrial animals) - gametes would dry - close proximity - external - bringing egg into proximity with sperm - risks: predation, temperature, pH - aquatic animals
62
What happens the first stage of fertilisation?
- acrosome reaction - corona radiata = layer of cells closest to zona pellucida - zona pellucida = coat of glycoproteins around egg - acrosome = membrane-bound sac of enzymes - in sperm head - digest zona pellucida and corona radiata (+ flagella action)
63
What happens at stage 2 of fertilisation?
- membrane on the tip of sperm - proteins that bind to egg membrane - first one to get through binds - fusion of membranes - sperm nucleus enters = fertilisation
64
What is the cortical reaction?
- sperm activates egg - cortical granules = vesicles near egg membrane - contents released by exocytosis - digestion of binding proteins - no more binding - zona pellucida hard > prevention of polyspermy
65
What happens at stage 3 and 4 of fertilisation?
- fusion of plasma membrane of oocyte and sperm - sperm DNA into oocyte - meiosis II completed - mature ovum + polar body
66
What happens at stage 5 of fertilisation?
- male and female pronuclei - chromosomal material decondenses - in ovum after meiosis - no distinction in nuclei - DNA replication in pronuclei
67
What happens at stage 6 of fertilisation?
- membranes of pronuclei breakdown - chromosomes condense - mitosis - uses centrioles from sperm
68
What happens during early embryonic division?
- no size change - mitosis (identical cells) - morula formed - 4 days after fertilisation - unqualified division = formation of blastocyst - 5 days after
69
What is a blastocyst?
- unequal mitotic division + migration of cells (making hollow ball = blastocyst) - 7 days —> blastocysts in uterus (125 cells) - moved by cilia in oviduct wall - zona pellucida breaks down - blastocyst needs external source of food - sinks into endometrium = implantation - exchanging materials with mothers blood - placenta formation
70
What is hCG?
- human Chorionic Gonadotropin (hCG) - produced by early embryo and placenta - maintains corpus luteum for first week —> progesterone necessary for endometrial activity - later placenta starts producing progesterone - corpus luteum degrades
71
What is placenta?
- made out of foetal tissue - contact with maternal tissue - placental villus (foetal tissue) - increase with progression of pregnancy (foetus needs food) - maternal blood in inter-villus - small distance between maternal foetal blood - placental barrier = cells between - selectively permeable - foetus also develops amniotic sac - support for foetus
72
What are the hormones released by placenta?
- oestrogen and progesterone - sustaining pregnancy - no corpus luteum - danger of miscarriage in the switch
73
What happens at the end of childbirth?
- progesterone inhibits oxytocin and contractions of myometrium - foetal signal to placenta —> no progesterone - oxytocin - oxytocin —> contraction of muscle fibres —> stretch receptor signal to pituitary gland to increase oxytocin —> more contractions - positive feedback - cervix dilates - uterine contraction burst amniotic sac (water breaking) - uterine contractions push baby
74
How does child labour work?
- head close to cervix - amniotic fluid released - baby into vagina - baby pushed out - umbilical cord cut, breathing - placenta expelled
75
What are the steps of in vitro fertilisation?
- step 1: down-regulation - drug each day –> pituitary stops secretion of FSH and LH - no oestrogen and progesterone - suspension of cycle - intramuscular injections of FSH and LH daily for 10 days - follicle development - higher concentration, more follicles = superovulation - injection hCG to stimulate maturation - micropipette on ultrasound scanner to take eggs - incubated - embryo placed in uterus - extra progesterone as tablet in vagina (uterus lining maintained)

IB Biology HL (14 decks)

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