(nervous system) synaptic transmissions

Question 1

neural networks

Answer 1

neurons communicate with each other within groups

Question 2

synapse

Answer 2

junction where 2 neurones meet

Question 3

which signals are transmitted electrically v. chemically across a synapse

Answer 3

electrically = signals within neurons
chemically = signals between neurons

Question 4

neurotransmitters

Answer 4

chemicals that are released from synaptic vesicle into synapse of neurons

Question 5

when are neurotransmitters released

Answer 5

when the electrical impulse reaches the end of the neuron (presynaptic terminal) & triggers release from synaptic vesicles

Question 6

what do neurotransmitters affect

Answer 6

transfer of impulse to another nerve/muscle

Question 7

once neurotransmitters cross the synapse, what are they taken up by

Answer 7

postsynaptic receptor site on dendrites of next neuron

Question 8

what happens at the postsynaptic receptor site

Answer 8

chemical message converted back to electrical impulse & process of transmission begins again

Question 9

what does a synapse consist of

Answer 9

• presynaptic knob
• synaptic cleft
• postsynaptic membrane

Question 10

describe cholinergic synapses

Answer 10

synapses that use acetylcholine (ACh) as a neurotransmitter

Question 11

describe the steps of transmission at a synapse

Answer 11

1. impulse arrives at end of presynaptic neurone
2. vesicles move towards (and fuse with) presynaptic membrane - this releases neurotransmitters into synaptic cleft
3. neurotransmitters diffuse across synaptic cleft down conc. gradient
4. neurotransmitters attach to receptors on postsynaptic membrane
5. triggers impulse which travels along postsynaptic neurone
6. neurotransmitters are recycled/destroyed once impulse is sent

Question 12

describe the process of reuptake

Answer 12

when neurotransmitters are ‘taken back up’ into terminal buttons of neurons

Question 13

when does an action potential occur

Answer 13

when a neuron sends information down an axon (away from cell body)

Question 14

what is the action potential

Answer 14

explosion of electrical activity - means some event (stimulus) causes resting potential to move forward

Question 15

what 2 types of effect can neurotransmitters have

Answer 15

excitatory or inhibitory

Question 16

what’s an excitatory neurotransmitter

Answer 16

they make it more likely next neuron will fire due to the neuron becoming more positively charged eg. adrenaline

Question 17

what’s an inhibitory neurotransmitter

Answer 17

they make it less likely the next neuron will fire due to the neuron becoming more negatively charged eg. serotonin

Question 18

what does normal brain function depend on

Answer 18

regulated balance between excitatory & inhibitory influences

Question 19

describe summation

Answer 19

• excitatory & inhibitory influences are summed
• if net effect on post synaptic neurone is inhibitory, neuron will be - less likely to ‘fire’
• if net effect is excitatory, neuron will be more likely to fire
• thus, action potential of postsynaptic neuron is only triggered if sum of excitatory/inhibitory signals at any one time reaches the threshold