Nervous Coordination

Question 1

What is a synapse?

Answer 1

The gap between 2 neurons

Question 2

Function of a synapse

Answer 2

To transfer impulses across neurons

Question 3

Steps of a synapse functioning

Answer 3

An action potential arrive at the presynaptic knob.

Ca+ ion channels open and ions diffuse into the presynaptic knob.

Vescicules containing neurotransmitters fused with presynaptic membrane. Causing neurotransmitters to be released into the synapse.

Neurotransmitters diffuse down conc gradient across cleft towards postsynaptic neuron.

Neurotransmitters bind to receptors which have a complimentary structure.

Na+ ion channels on post-synaptic membrane open and so ions diffuse in. Above threshold, an action potential is triggered.

Neurotransmitters degrae and released from receptors. Channels close and resting potential restored.

Question 4

Why is the impulse / neurotransmitter unidirectional?

Answer 4

Neurotransmitters and vesicules found in the presynaptic knob.

Receptors only on postsynamptic membrane.

Question 5

Neurotrasmitter and enzyme in cholergenic synapse

Answer 5

Neurotransmitter - Acetylcholine

Enzyme - Acetylcholine esterase

Question 6

What is summation?

Answer 6

Build up of transmitters in the synapse to help generate an action potential.

Question 7

Why is summation required sometimes?

Answer 7

Some action potentials do not result in a sufficient concenrtations of neurotransmiteers for a sufficient opening of Na channels for an action potential to be triggered.

Question 8

Spatial summation

Answer 8

Many different presynaptic neurones collectively trigger a new action potential by combining neurotransmitters they release to exceed threshold on a postsynaptic.

Question 9

Temporal summation

Answer 9

One neurone releases neurotransmitter repeatedly over a short period of time to add up to enough to exceed the threshold.

Question 10

What is an inhibitory synapse?

Answer 10

A realising of neurotransmitter which makes the postsynaptic membrane less likely to trigger an action potential.

Question 11

How does inhibtory synapse reduce action potentials?

Answer 11

Hyperpolarisation.

Membrane is more negative and below resting potential so needs more sodium ions for an action potential.

Question 12

Where are synapses located?

Answer 12

At the end of axons

Question 13

Process of inhibitory synapse

Answer 13

Neurotransmitters bind to Cl- ion channels causing them to open and move into the postsynaptic neurone.

K+ channels open and K+ move into the postsynaptic neurone.

Question 14

Differences between cholergic and neuromuscular synapses

Answer 14

Neurone to neurone/effecter vs motor neurone to muscle fibre

Neurones motor, sensory or relay vs only motor neurones

Excitatory or inhibitory vs only excitatory

Question 15

Similarities between cholergic and neuromuscular synapses

Answer 15

Neurotransmitter transported by diffusion.

Receptors cause a reflux of Na+ when neurotransmitter binds.

Use a Na+ / K+ pump to repolarise the axon.

Use enzymes to break down neurotransmitters.