Synapses

Question 1

Synapses?

Answer 1

• Gaps between end of axon of one neuron and the dendrite of another
• Action potentials transmitted as neurotransmitters that diffuse across the synapse

Question 2

Function of synapse?

Answer 2

• action potential arrives at synaptic knob and depolarisation of knob leads to opening of Ca2+ channels and Ca2+ diffuses into synaptic knob
• vesicles containing neurotransmitters move towards and fuse with presynaptic membrane - neurotransmitters released to synaptic gap
• neurotransmitters diffuse down concentration gradient across gap to postsynaptic membrane. Neurotransmitters binds to receptors on surface of post synaptic membrane
• Na+ ion channels on post membrane open and Na+ diffuse in, if enough neurotransmitters, then enough Na+ diffuse in, above threshold, and postsynaptic neuron becomes depolarised
• neurotransmitters degraded and released from receptor, the Na+ channel close and the post neuron re-establishes resting potential. Neurotransmitters transported back to presynaptic neuron where they are recycled

Question 3

Neurotransmitter in Cholinergic synapse?

Answer 3

• acetylcholine
• enzyme breaks acetylcholine back into choline+acetate

Question 4

Summation?

Answer 4

• rapid build-up of neurotransmitters in synapse to help generate an action potential
• spatial summation
• temporal summation

Question 5

Spatial summation?

Answer 5

• many different neurons collectively trigger action potential by combining neurotransmitters they release to exceed threshold value

Question 6

Temporal summation?

Answer 6

• one neuron releases neurotransmitters repeatedly over a short period of time to add up enough to exceed threshold value

Question 7

Inhibitory synapse?

Answer 7

• cause chloride ions to move into postsynaptic neuron and potassium ions to move out
• makes membrane potential decrease to -80mV, hyperpolarisation - action potential unlikely

Question 8

Neuromuscular junction?

Answer 8

• synapse that occurs between a motor neuron and a muscle

Question 9

Similarity between Neuromuscular junction and Cholinergic synapse?

Answer 9

• unidirectional due to neurotransmitter receptors only being on post synaptic membrane

Question 10

Differences between Neuromuscular Junction and Cholinergic synapse?

Answer 10

• NJ only excitatory, CS both excitatory and inhibitory
• NJ connects motor neuron to muscles, CS connects two neurons
• NJ is end point for action potential, CS a new action potential is generated in next neuron