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55 Cards in this Set
- Front
- Back
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what is a myelin sheath made from? |
lipid and protein |
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what is a reflex arc? |
A reflex arc is a pathway along which impulses are transmitted from a receptor to an effector without involving conscious regions of the brain |
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what is reflex action? |
fast automatic response to a stimulus that is not voluntary |
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what is white and grey matter in the spinal cord? |
white matter mostly consist of axons, grey matter has mostly cell bodies |
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describe the pathway of a reflex arc of nerve impulses when u sense pain |
receptor for pain-> sensory neurone -> dorsal root of spinal nerve -> cell body of sensory neurone -> intermediate neurone -> ventral root of spinal nerve -> motor neurone -> effector |
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What is a resting potential? what is the typical value? |
It is the potential difference between the inside of a resting axon and the outside, -60mV and -70mV |
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the resting potential is maintained and produced by what? |
Na+-K+ pumps in the cell membrane using ATP, 3NA+ out for every 2 K+ in so axon cytoplasm more negative |
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what is depolarisation in the cell? |
charge in the cell become less negative |
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what is the threshold voltage for an action potential? |
-60mV to -50mV , below this no action potential would occur |
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describe how action potentials are generated |
there are sodium and potassium channels( voltage gated channels) resting potential channel close electric current cause voltage gated channels in the cell membrane of axon to open , allow N+ diffuse in due to higher conc outside than inside, depolarisation cause more channel to open, -50mV cause more channel to open,reach +30mV positive feedback |
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how does depolarisation occur? |
after 1ms of action potential, na+ channel close and K+ channel open, so Na+ stop diffusing in and K+ diffuse out from higher conc to lower conc, return to -70mV |
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what is refractory period? |
when sodium ion voltage gated channels are shut tight and cannot be stimulated because it is recovering from the previous action potential |
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what are the 3 consequences of refractory period? |
action potentials are discrete events, do not merge there is a minimum time between action potentials occurring at any one place on a neurone length of refractory period determines the frequency at which impulses are transmitted along neurones |
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what is the difference between the action potentials of strong and weak stimulus ? |
stronger stimulus have greater frequency , more action potentials in more neurones |
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how does diameter of axon affect the speed of the impulse? |
greater diameter result in greater speed |
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what is saltatory conduction? |
when action potential jump from one node of ranvier to the next because the myelin sheath does not allow K+ and na+ to flow |
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how does receptor cells work? |
they are transducers, they convert energy in one form ex.light to an electrical impulse |
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describe how chemoreceptors in taste buds detect salt |
they are influenced by sodium ions, the ions diffuse thru a selective channel protein in cell membrane of microvilli , increase in +ve charge is called receptor potential, if stimulation is sufficent then voltage gated calcium ion channel open , ca ions enter n lead to exocytosis of vesicle with neurotransmitter |
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what is a cholinergic synapse? |
it is a synapse that uses acetylcholine as it's transmitter substance |
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describe what happens in he synaptic transmission of a cholinergic synapse. |
1)action potential arrives which stimulates voltage gated channels for calcium ions to diffuse in cytoplasm of presynaptic neurone. 2)calcium ions cause vesicles with Ach to move to presynaptic membrane to fuse and release it 3)upon release Ach diffuse across synaptic cleft 4)Ach molecules bind to receptors in postsynaptic membrane , causing sodium ion channel to open 5)sodium ion diffuse in and depolarises the membrane. |
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how is Ach broken down and reformed? |
Ach breaks down into choline and acetate with enzyme acetylcholinesterase thru hydrolysis, in synaptic cleft there is the enzyme. choline and acetyl coenzyme a form Ach in presynaptic neurone |
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synapses slow down rate of transmission of nerve impulse between neurones so why have neurones? give 4 reasons |
1) synapses ensure one way transmission 2) synapses allow integration of impulses 3) synapses allow interconnection of nerve pathways 4) synapse are involved in memory and learning |
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what are the thick and thin filaments in myofibrils made of? |
thick filaments are made of myosin and thin ones made from actin |
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what causes the stripes in myofibril? |
darker stripes have thick filaments,A band lighter parts have thin filaments,I band darkest part is when thick n thin overlap |
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what is the purpose of m line and z line |
m line provides attachment for myosin filament z line provide attachment for actin filaments |
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what do you call the part between two z lines? |
a sarcomere |
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how does muscle contract? |
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equation for releasing ATP from creatine phosphate and regeneration of creatine phosphate and what happens and when there is no ATP left? |
creatine phosphate + ADP --> creatine + ATP creatine + ATP --> creatine phosphate + ADP if no atp is left to regenerate creatine phosphate then it is converted to creatine and excreted in urine |
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what is a gland? |
A gland is a group of cells that produces and releases one or more substances in a process known as secretion. |
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where are harmones insulin,ADH , adrenaline and glucagon produced? |
endocrine glands |
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what harmones are lipid soluble? |
steroid harmones |
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when does ovulation take place? |
when there is a surge in LH and FSH, but mostly LH |
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what happens in uterine cycle? |
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how does venus fly trap close so rapidly? |
due to release of elastic tension of the cell walls |
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what are two adaptations of Venus fly traps to avoid closing unnecessarily and wasting energy ? |
1)stimulation of a single hair does not trigger closure 2)there are gaps between the hairs so small insects can crawl out so they do not waste energy on a small meal. |
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what is the value for threshold voltage? |
-60mV to -50 mV |
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what happens when chemoreceptors in taste buds detect sweet? |
cells that are sensitive to sweet have receptor proteins that stimulate G protein to activate enzyme to produce cyclic AMP , which acts as a secondary messenger to activate a cascade to amplify the signal leading to the closure of K channels , this causes depolarisation of the membrane. |
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how is repolarisation and depolarisation achieved in plants? |
depolarisation is caused by outflow of negatively charged chloride ions, repolarisation is caused by outflow of positively charged potassium ions |
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how is a venus fly trap stimulated and closed? |
the defelction of sensory hairs would activate calcium ions channels at the base of hair. calcium ions open to allow ions to flow in to generate receptor potential, if two of these hairs are stimulated within a period of 20 to 35 sec,an action potential would travel along the trap. if it is longer, the time interval restarts |
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how do venus fly traps close so rapidly? |
due to release of elastic tension in cell walls |
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plant growth occurs at meristems ex.roots n shoot tips, what are the 3 growth stages and which is auxin involved in ? |
1)cell division by mitosis 2)cell elongation by absorption of water 3)cell differentiation auxin is involved in growth by elongation |
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how to auxins work in elongation growth? |
binding of auxins to auxin receptor protein causes ATPase to pump H+ ions across the cell surface membrane from cytoplasm into cell wall. in cell wall there is expansins which are activated by decrease in pH. expansins loosens the linkage between microfibrils by disrupting non covalent interactions between microfibirls. to allow them to briefly slide past one another without losing overall strength of cell wall when water enters K+ channel also open so it flows in the cytoplasm n decrease water potential so h20 enter thru aquaporin. |
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what does Gibberellin do? how does it cause seed germination by regulating genes? |
it regulates genes involved in synthesis of amylase. it destroys della proteins which are transcription inhibitors , so it increases the transcription of amylase |
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what is the gap of the synaptic cleft ? |
20nm |
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name 2 neurotransmitters that all nervous system use, and name 2 neurotransmitters that the brain uses |
all nervous system, noradrenaline and acetylcholine brain, dopamine and glutamic acid |
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what does the progesterone do after ovulation? |
it inhibits the anterior pituitary gland from secreting more LH and FSH |
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what hormone stimulates anterior pituitary gland to release LH and FSH? |
gonadotrophin releasing hormone ( GnRH) |
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name the 3 phases in menstrual cycle |
follicular ovulatory luteal |
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role of sertoli cell |
provide nutrient for spermatid protect sperm from attack from immune system regulation of sperm production |
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stages of an action potential and which channels open? |
depolarisation= upwards part of action potential, sodium channel opens, passive influx of sodium repolarisation= passive efflux of K+ , k channel open restoration of membrane potential, more negative hyperpolarization= outward movement of K+, overshoots, K+ channels doesnt close fast enough, but Na-K+ acts to restore to be depolarised refractory period= voltage gated na+ channels close |
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discuss biological,social and ethical implications of contraceptive pill |
bio neg-rise in blood pressure nausea,increased risk of breast cancer increase STD bio pos- no menstruation, reduced risk of developing ovarian cyst , reduced risk of uterine infection social,ethical neg- more marriage breakdown, single parent families, increase promiscuity , religious objection social, ethical pos-reduction in unwanted pregnancies women have control over their fertility |
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describe and explain structural features of wind pollinated plant |
lost of pollen is made pollen is small, aerodynamic easily carried by the wind , more chance of pollination anthers are loosely attached long filaments sticks out to release pollen into the air stigmas hang out so they are exposed stigmas are feathery, to catch pollen no petals no nectar, so no energy is wasted |
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outline technique in IVF |
the women is given a hormone treatment to superovulate, to stimulate follicle production, then the oocytes is harvested and semen is collected from a man, then the sperm is activate. sperm can be collected from the sperm bank or a sperm donor. then the sperm is added into a petri dish with the female oocyte, then it is mixed. 2-3 days to allow fertilisation to occur. then the embryo is added into the uterus, hormones given to prepare the uterine lining |
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difference of male and female gametogenesis? |
female gametogenesis begins before birth and male begins at puberty, female 1 ovum and male 4 spermatids female meiosis is interrupted and male meiosis continuous process, female fertilisation needed to complete meiosis, greater number of gametes produced in males, males can produce gametes to a greater age |
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how does venus fly trap respond to touch? |
mechanical energy is converted into electrical energy so the sensory hair will respond to touch cell membrane will depolarise if at least two hairs are touched within 35 secs action potential will occur action potential will spread over the lobe to the hinge cells H+ will be pumped out into cell walls cell wall loosens, links are broken calcium pectate dissolves Ca2+ enters the cells, cell expand and become turgid change from convex to concave traps shut in 0.3s, loss of elastic tension |
