Synaptic Transmission

Question 1

what is unidirectionality?

Answer 1

• synapses can only pass information in one direction
• presynpaptic neurone to postsynaptic neurone

Question 2

what is spatial summation?

Answer 2

a number of different presynaptic neurones together release enough neurotransmitter to exceed the threshold value of the postsynaptic neurone
- together they trigger a new action potential

Question 3

what is temporal summation?

Answer 3

a single presynaptic neurone releases neurotransmitters many times overy a short period
- if concentration of neurotransmitter exceeds threshold value of postsynaptic neurone
- a new action potential is triggered

Question 4

what are inhibitory synapses?

Answer 4

less likely that a new action potential will be created on the post synaptic neurone

Question 5

what is the process of inhibitions by inhibitory synapses?

Answer 5

• presynaptic neurone releases a neurotransmiter that binds to chloride ion protein channels on the postsynaptic neurone
• neurotransmitter causes the chloride ion protein channels to open
• chloride ions move into the postsynaptic neurone by facilitated diffusion
• binding of neurotransmitters causes the opening of nearby potassium ion protein channels
• potassium ions move out of the postsynaptic neurone into the synapse
• combined effect of negatively charged chloride ions moving in and positively charged potassium ions moving out, makes the inside of postsynaptic membrane more negative and outside more positive
• membrane potential increases to -80mV compared to -65mV at resting potential
• hyperpolarisation happens making it less likely that a new action potential will be created because a larger influx of sodium ions is needed to produce one

Question 6

what are excitatory synapses?

Answer 6

neurotransmitter binds with the receptor proteins and this leads to a new action potential in the postsynaptic neurone

Question 7

what is a cholinergic synapse?

Answer 7

the neurotransmitter is a chemical called acetylcholine