Synapses

Question 1

What is a synapse

Answer 1

Synapse is where 2 neurones meet

Question 2

What is Synaptic cleft

Answer 2

Synaptic cleft is gap between 2 neurones

Question 3

What are 3 stages leading to nerve impulse passing along post synaptic neurone

Answer 3

3 stages leading to nerve impulse passing along post synaptic neurone are:
Neurotransmitter release
Stimulation of post synaptic membrane
Inactivation of neurotransmitter

Question 4

What is process of nerve impulse passing along post synaptic neurone

Answer 4

Process of nerve impulse passing along post synaptic neurone is:

1) Action potential arrives at presynaptic knob
2) voltage gated Ca+ion channels open
3) Ca+ions enter presynaptic knob (facilitated diffusion)
4) vesicles containing neurotransmitter fuse with membrane (exocytosis)
5) neurotransmitter released and diffuses across synaptic cleft
6) neurotransmitter binds to receptors on post synaptic membrane
7) Na+ ions enter post synaptic neurone
8) post synaptic membrane depolarised, action potential triggered in post synaptic membrane (provided threshold potential is reached)

Question 5

What do excitatory synapses do and how do they do it

Answer 5

Excitatory synapses make post synaptic neurone more likely to reach threshold to generate action potential.
They do this by making post synaptic more permeable to Na+ ions

Question 6

What do inhibitory synapses do and how do they do it

Answer 6

Inhibitory synapses reduce likelihood of action potential in post synaptic neurone by producing hyperpolarisation of membrane.
They do this by: neurotransmitter opening chloride channels, Cl-ions enter post synaptic membrane (facilitated diffusion) making it more negatively charged.

Question 7

Why do impulses travel only in one direction across a synapse

Answer 7

Impulses only travel in one direction across a synapse because:
Neurotransmitters are only found in presynaptic knob
Receptors for neurotransmitters only found in post synaptic membrane

Question 8

What is role of dendrites in stimulation of cells

Answer 8

Role of dendrites on stimulation of cell is:
Action potential causes influx of Ca2+ions, vesicles fuse with pre-synaptic membrane and neurotransmitter is released and attaches to receptors on cell

Question 9

What happens do neurotransmitter after action potential is set up

Answer 9

After an action potential is set up, neurotransmitter is broken down to make receptors available again

Question 10

Where is presynaptic knob

Answer 10

Presynaptic knob is part of presynaptic neurone that bulges out