Unit 9- Synapse

Question 1

What is the purpose of neurotransmitters and name 2

Answer 1

• as action potentials cannot cross the synapse so the nerve impulse are carried by neurotransmitters instead
• noradrenaline and acetyl choline

Question 2

How do synapses work?

Answer 2

1- action potential arrives at presynaptic knob
2- calcium channels in in PreSK open so calcium ions diffuse into the cell down the conc gradient
3- this causes synaptic vesicles to fuse with the preSK cell membrane releasing the neurotransmitter by exocytosis
4- neurotransmitter diffuses across synaptic cleft
5- neurotransmitter binds to receptors on post synaptic membrane causing ion channels to open causing a local depolarisation in post synaptic membrane called the post synaptic potential which may set up an action potential

Question 3

How are the neurotransmitters removed from the cleft and where do they end up?

Answer 3

• enzymes break down the neurotransmitters in the post synaptic membrane, the products the diffuse back across the cleft to be absorbed (endocytosis) and resynthesised in presynaptic neurone
• proteins in the presynaptic neurone membrane actively transport whole neurotransmitters back into presynaptic membrane

Question 4

What is the enzyme that reads down acetyl choline called?

Answer 4

Acetylcholinesterase

Question 5

What different types of ion channel synapses are there?

Answer 5

• excitatory ion channel synapses

- inhibitory ion channel synapses

Question 6

What happens at an excitatory ion channel synapse?

Answer 6

• The neuroreceptors on the post synaptic cell membrane are Sodium channels
• when the channels open positive Na+ diffuse ions diffuse into, causing local depolarisation
• this is called excitatory postsynaptic potential (EPSP)
• so the PD is closer to the threshold potential
• action potential is more likely to happen

Question 7

What happens at an inhibitory ion channel synapse?

Answer 7

• the neuroreceptor on post synaptic nicely membrane are chloride channels
• when the channels open ions diffuse in causing local hyperpolarisation
• called inhibitatory postsynaptic potential
• an action potential is less likely to happen as the PD is further away from the threshold

Question 8

Give 2 typical neurotransmitters that cause an excitatory postsynaptic potential?

Answer 8

Ecetylcholine and glutamate

Question 9

Give a neurotransmitter that causes an inhibitory postsynaptic potential:

Answer 9

Glycine or GABA

Question 10

What nervous system is acetyl choline found?

Answer 10

-parasympathetic autonomic system

Question 11

What pat of the nervous system is noradrenaline found?

Answer 11

• sympathetic autonomic nervous system

Question 12

what is the spatial summation?

Answer 12

• this is the sum of all the post synaptic potentials from different synapses from all the dendrites

Question 13

whats is the temporal summation?

Answer 13

• the sum of a sequence of post synaptic potentials at 1 single synapse in a time period

Question 14

when will an action potential occur? and what is this process called?

Answer 14

when the grand post synaptic potential is above the threshold potential
- this is called summation or synaptic integration

Question 15

-what is the grand post synaptic potential?

Answer 15

• the sum of all the excitatory and inhibitory post synaptic potentials across all the cells synapses

Question 16

what is axon convergence?

Answer 16

when the post synaptic neurone has many inputs but only 1 output through its axon

Question 17

how may chemical affect the synapse? 3

Answer 17

• affect the amount of neurotransmitter synthesises
• block or stimulate neurotransmitter release
• inhibit or mimc enzymes
• block calcium channels
• block neurotransmitter binding to receptors
• block neurotransmitter reuptake

Question 18

how does nicotine affect the synapse?

Answer 18

• affects peripheral nervous system
• has similar structure to acetyl choline, so binds to acetyl choline receptors on post synaptic membrane
• this causes the release or adrenaline, dopamine and endorphins
• result: increased heart rate and blood pressure and feeling happy

Question 19

what way does adrenaline affect the body?

Answer 19

• triggers fight or flight response in sympathetic nervous system
• increase heart rate and blood pressure

Question 20

how do endorphins and dopamine affect the brain?

Answer 20

dopamine- leads to feeling of pleasure

endorphins- cause feeling of pleasure but leads to withdrawals and addiciction

Question 21

how does cobra venom affect the synapse and body?

Answer 21

• binds irreversibly to acetyl choline receptors
• this prevents the binding of acetyl choline
• post synaptic membrane is not stimulated to depolarise
  causing paralysis or death if nerves that stimulate breathing muscles are affected

Question 22

how does lidocaine affect the synapse and body?

Answer 22

• blocks voltage gated dependent Na+ channels in post synaptic membrane
• Na+ cannot enter the cell when neurotransmitter binds
• action potential cannot form in the post synaptic cell
  acts as an anaesthetic preventing impulses from being conducted