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Biology Mark scheme flashcards > the nervous system > Flashcards

the nervous system Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Explain why there is a difference in colour between grey and white matter (1)

A

grey matter contains cell bodies

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2
Q

What is the name given to the cells which partially cover neurones (1)

A

shwaan cell

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3
Q

What is the name given to the material which the cells produce to cover the axon (1)

A

myelin

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4
Q

What is the function of this material in the conduction of an action potential (2)

A
  • insulates the axon
  • allows saltatory conduction/ impulse jumps from node to nod
  • so speeding up the transmission of the action potential/ increase speed of conduction
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5
Q

Multiple scleropsis is a progressive, degenerative disease of the nervous system in which myelin sheath is destroyed. Symptoms include increasing muscle weakness and loss of vision suggest an explanation for these symptoms (2)

A
  • impulses cannot jump from node to node/ saltatory conduction is stopped/ local circuits are too short/ voltage gate Na+ channels between nodes of ranvier
  • so action potential cannot be generated/ speed of conduction is reduced/ action potential does not reach destination
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6
Q

Suggest a possible medical treatment for multiple sclerosis (1)

A
  • remyelinate the axon
  • use of stem cells
  • make the membrane add Na+ channels in bare areas
  • prevet further ddemyelination
  • immune suppressants/inhibitory frugs
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7
Q

Give two ways in which the nerve net differes from the nervous system of a vertebrate (2)

A
  • responds to limited number of stimuli
  • cannot detect source of stimulus/ impulse passes in all directions
  • number of effectors is mall
  • no CNS
  • action potential can be carried in more than one direction along a neurone
  • one type of cell/ unmyelinatied / slower response
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8
Q

Describe how the resting potential is maintained in the neurone (3)

A
  • sodium potassium pump
  • ATP/active transport
  • 3Na+ out and 2K+ in
  • organic anions negative charged molecules/ proteins
  • -70mv potential difference across membrane
  • membrane leakage more permeable to K+ than Na+
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9
Q

What is taking place at -70mv
an at +40mv (5)

A

-70mv
* threshold reached
* sodium voltage gated channels open
* sodiums ion diffuse into cytoplam
* depolarised
+40mv
* sodium voltage gated channels close
* potassium voltage gated channels open
* potassium diffuses out
* sodium/ potassium pumps
* repolarised

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10
Q

Multiple sclerosiss is caused by the immune system destroying th myelin sheath of nerones. Explain why this condiytion leads to the slowing down of the transmission of a nerve impulse (3)

A
  • myelin sheath electrical insulation
  • ions exchange only at nodes of ranvier/ depolarisation only at nodes
  • action potential jumps from one node of ranvier to next
  • saltatory conduction
  • if no myelin sheath local circuits
  • altatory conduction must faster than local circuits
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11
Q

Suggest the ways in which chemicals could increase activity of the nervous system (2)

A
  • mimic action of normal transmitters/ bind to receptors
  • prevents breakdown of transmitter
  • stimulate release of transmitters
  • reduce threshold for excitation of posst synaptic membranes
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12
Q

Suggest ways that chemical can decrease actviity in the nervous system (2)

A
  • block receptors on posty synaptic membrane
  • prevent Ca2+ being released
  • prevent exocytosis
  • prevents recycling of neurotransmitter /active tranport back across presynaptic membrane
  • raises threshold
  • changes shape of neurotransmitter
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13
Q

Name the cell that forms myelin sheath (10

A

schwaan cell

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14
Q

Explain in terms of movement of ions what causes the rise of membrane potential from -70mv to 40mv (2)

A
  • voltage gated sodium channels open/ increase in sodium ion permeability
  • sodium ions diffuse/flood/rush/sudden influx in
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15
Q

state the name given to the name to the rapid fall in membrane potential (1)

A

repolarisation

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16
Q

Suggest how cardiac muscle fibres would respond when the voltage across the membrane rises (1)

A

contraction

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17
Q

The cardiac muscle fibres used to obtain the oscilloscope trace where obtained from a frogs heart. Consider the ethics of killing a frog to obtain cardica muscle fibre one argument in favour and one against (2)

A
  • frog has a right to life / suffering/ pain/distres/ harm of frogs/ frogs are scarce in the wild
  • benefits to medicine/ health of the heart
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18
Q

What units is membrane potential (1)

A

mv

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19
Q

What units is time (1)

A

ms

20
Q

What is represented by -55mv (1)

A

threshold potential

21
Q

When a person touches a hot object with their finger they will move away from the heat. State the advantage to humans of having this type of response to an external stimulus (1)

A

protecting/ prevents damage/injury/harm

22
Q

What is the name given to the type of nervous system in a cnidarian (1)

A

nerve net

23
Q

Explain why the non myelinated neurones of cnidarians result in slower impulses than mammals (2)

A
  • impulse must pass along whole length of the neurone/membrane/axon
  • mammals have meyli/nodes which cause saltatory conduction
24
Q

Explain the toxic effects of organophosphates (5)

A
  • aceytlcholine is normally hydrolysed/ broken down by acetylcholinesterase
  • organophosphates prevent the breakdown of acetylcholine
  • acetylcholine remains bound to receptors on posty synaptic membrane
  • so synaptic transmission/action potentials continue to be generated
  • sustained contraciton of muscle
  • uncontrolled ocntractions of diaphragm/intercostal muscles intefere with breathing
25
Q

psychoactive drugs can affect synaptic transmission in a number of different ways suggest some different mechanisms by which psychoactive drugs could decrease the rate of synaptic transmission (4)

A
  • some drugs prevent synthesis/resynthesis of neurotransmitter
  • blocking Ca2+ uptake
  • some drugs inhibit release/exocytosis of neurootransmitters
  • some drug block receptors in post synaptic membrane preventing neurotransmitters biding to them
  • sodium ion channels change shape
  • faster reabsorption of neurotransmitter
  • hyperpolarisation of posty synaptic membrane
26
Q

Impulses are transmitted throguh the nuerone as a wave of action potentials. Explain how the movement of ions result in the generation of an action potential (4)

A
  • sodium ions channels open
  • sodium ions (rusn in / influx)
  • threshold reached/ exceeded
  • charge changes to become positive inside axon and negative outside axon
27
Q

Give two reasons shown on the diagram whcih would prevent the nerve impulse travelling in the opposite direction (2)

A
  • synaptic vesicles only on presynaptic membrane side of synapse
  • refractory period/ hyperpolarisation
28
Q

Explain what would happen to the rate of transmission of the never impulse if the myelin was damaged (2)

A
  • slow down
  • saltatory conduction would ot take place/ local circuit shortened
29
Q

Curare is a poisonous plabts which causes muscle paralysis by acting on the post synaptic membrane preventing transmission fo the nerve impule across muscular joing suggest and explain how curare may prevent the transmission of the impulse across the neuromuscular junction (3)

A
  • curare has a complementary shape binds to receptors of synaptic membrane
  • prevents transmitter substance / acetylcholine binding
  • Na+ gated channels remain close/no active potential/ Na+ oion do not move in
30
Q

Motor neurones have only a single dendrite true of false (1)

A

false

31
Q

Suggest why curare aplant poison causing muscle paralysis have no effect on the contraction of muscles of the heart (1)

A

different tranmitter used to trigger contraction of the heart / adrenalin used/ heart is myogenic

32
Q

Motor neuorne have many axons true or false

A

false

33
Q

dendrties recieve and intergrate impules true of false (1)

A

true

34
Q

dendrites of motor neurone are rarely myelinated true of false (1)

A

true

35
Q

What is a reflex actions (2)

A
  • rapid reaction/ response to a stimulus
  • automatic/involuntary/not under concious control/brain not involved
36
Q

Describe how a resting potential is maintained in a neurone (2)

A
  • Na+ sodium ions are activley removed / pumped out/ faster than K+ ions are moven in
  • K+ diffuse out more rapidly that Na+
  • sodium potasssium pumps pump 3Na=out and 2K+ in
37
Q

Describe how the potential across the membrane is reversed when an action potential is produced (2)

A
  • sudden change/increase in permeability of the membrane to Na+/ sodium gates/ channels open
  • sodium ions diffue in down a concentration gradient
38
Q

Suggest an explanation for the increase in speed of conduction as axon diameter increases (2)

A
  • speed of transmission depends on resistane of axon
  • larger diameter of the axon the less the resistance
  • increased diameter increased surface area over which exchange of ions take place
39
Q

Explain wh a myelinated axon uses less ATP to transmit a nerve impulse than a non myelinate axon of the same diameter (2)

A
  • ATP is required for active transport/ ref of sodium potassium pumps
  • Na+ ions activvley moved out only at nodes in myelinated
  • Na+ activley moved out along whole length of axon in nin myelinated
40
Q

Explain giving two reasons why nerve impulses can only travel in one directions (2)

A
  • sensitvity of the nerrve membrane lost during depolarisation/refractory period
  • in synapses transmitter substances diffuse from knob to post synaptic membrane
41
Q

From which type of biological molecules are pumps and channels and the bilayer made up of (2)

A
  • pumps and channels - proteins
  • bilayers - phospholipids
42
Q

How is the resting potential bought about (2)

A
  • sodium and potassium pump
  • 3Na + out and 2K+ in
  • K channels open
  • less permebale to Na+
43
Q

How is depolarisation bought about (2)

A
  • impulse opens Na+ channel
  • Na+ ions rush in / sudden increase in permeability to Na+
44
Q

Explaij how impulses are transmitted across a synapse (3)

A
  • transmitter substances synthesised in synaptic knob
  • impulse causes secretory vesicle to migrate to presynaptic membrane / Ca2+ rush in
  • vesicle fuses with membrane discharges transmitter substance /exocytosis
  • diffusion of transmitter substance across cleft
  • transmitter binds to post synaptic membrane / stimulates depolarisation / reference to receptors
45
Q

Describe the function of acetylcholine at a synapse (5)

A
  • acts as a neurotransmitter/ transmits impulse across synapse
  • synaptic vesicles fuse with pre synaptic membrane
  • released aceytlcholine diffuses across synpatic cleft
  • attatched to receptor sites on posty synaptic membrane
  • sodium channels open and Na+ ions diffuse in
  • membrane is depolarised
  • action potential is generated
46
Q

Explain how substance secreted by schwaan cells and their arrangement along the neurone affect the speed of transmission of a nerve impulse (4)

A
  • myelin inhibits movement of ions from axon/insulates axon / prevent depolaisation
  • gaps between shwaan cells called nodes of ranvier
  • no myelin present in nodes
  • depolarisation only posible at nodes of ranvier / action potential can only form at nodes where there ins no myelin/ channels can only open/close in the nodes
  • action potential jumps from one node to next/saltatory conduction/lengthens local circuits
  • nerve impule transmission is faster

Biology Mark scheme flashcards (12 decks)

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