6.2 Nervous System

Question 1

importance of reflex actions

Answer 1

protect from danger and prevent tissue damage

helps maintain posture

automatic reaction

Question 2

how calcium ions are involved in synaptic transmission (2)

Answer 2

nerve impulse causes calcium to enter presynaptic membrane

this causes vesicles to fuse with the membrane and release the neurotransmitter

Question 3

why is it important that nuerotransmitters are transported blackout of synapses (2)

Answer 3

if not removed the neurotransmitter will keep binding to receptors

therefore would keep causing action potentials

Question 4

describe the sequence of events leading to the release of acetylcholine and its binding to the postsynaptic membrane (4)

Answer 4

action potential arrives at presynaptic membrane

calcium enters presynaptic knob

vesicles fuses with membrane

acetycholine diffuses across synaptic cleft

Question 5

when a nuerone transmits a series of impulses, its rate of o2 consumption increases. Expain why (3)

Answer 5

more respiration to produce more ATP

respiration uses up o2

ATP required for active transport of ions

Question 6

explain what causes the conduction of impulses along a non myelinated axon to be slower than along a myelinated axon (3)

Answer 6

none myelinated means whole membrane is depolarised

when myelinated depolorisation only at nodes

so impulses can jump node to node

Question 7

describe the sequence of events involved in transmission across a cholinergenic synapse (5)

Answer 7

depolarisation of presynaptic membrane

calcium channels open and calcium ions enter synaptic knob

calcium ions caused synaptic vesicles to move to the pre synaptic membrane and release acetylcholine (neurotransmitter)

acetylcholine diffuses across synaptic cleft

acetylcholine attatches to receptors on postsynaptic membrane

sodium ions enter post synaptic nuerone leading to depolorisation

Question 8

synapses are uni-directional explain how acetylcholine contributes to a synapse being uni-directional (2)

Answer 8

acetylcholine only released on presynaptic membrane

receptors for acetylcholine to bind to only on post synaptic membrane

Question 9

suggest two advantages of simple reflexes (2)

Answer 9

1. quicker process therefore more effective
2. does not need to be learnt