2. summation At Synapses

Question 1

What does summation mean ?

Answer 1

Where the total sum of lots of smaller impulses triggers an action potential

Question 2

What happens if the stimulus is weak?

Answer 2

Only a small amount of neurotransmitters will be released from a neurone into synaptic cleft

Might not be enough to excite post synaptic membrane to threshold even and stimulate action potential

Question 3

Summation at synapse

Answer 3

When effect of neurotransmitters released from many neurones (or 1 neurone that’s stimulates a lot of times in short space of time) is added together

It means synapses accurately process information finely tuning response

Question 4

Name 2 types of summation

Answer 4

Spatial

Temporal

Question 5

What is spatial summation ?

Answer 5

Where 2 or more presynaptic neurones release their neurotransmitters at same time onto same postsynmatic neurone

Small amount of neurotransmitter released from each neurone can be enough altogether to reach threshold in post synaptic neurone and trigger actuonpoetbuao

Question 6

What can offset spatial summation reaching threshold ?

Answer 6

If some neurones release inhibitory neurotransmitters then the total affect of all neurotransmitters will be no action potential

Question 7

What is temporal summation ?

Answer 7

Where 2 or more nerve impulses arrive in quick succession from same presynaptic neurone - has to be quick of the neurotransmitter will be removed from cleft before its reaches high level to trigger action potential

This makes action potential more likely because of more neurotransmitters being released into synaptic cleft

Question 8

What is a neuromuscular junction

Answer 8

Specialised cholingeric synapse between motor neurone and muscle cell

Use neurotransmitters acetylcholine which binds to cholingeric receptions called nicotinic cholingeric receptors

Question 9

What are the similarities between neuromuscular junctions and cholingeric synapses?

Answer 9

Both release ACh from vesicles

ACh then diffuses acrosss synaptic cleft

Binds to cholingeric receptors on post synaptic membrane

Generates action potential if threshold is achieved

Ach broken down by enzymes acetylcholinsterase

Question 10

What are differences between neuromuscular junctions and cholingeric synapses ?

Answer 10

At neuromuscular junctions ;
•post synaptic membrane has lots of food that form clefts that store AChE
•postsynptic membrane has more receptors than others
•ach is always exicitory so when motor neuron fires action potential it normally triggers response in muscle cell - not always the cause dor other synapses