Synapses

Question 1

What is a synapse

Answer 1

• Axon of one neurone connects with the dendrite of another or with an effector
• Neuromuscular junction
• Transmit impulses from one neurone to another - neurotransmitter

Question 2

Synaptic cleft

Answer 2

• Gap between neurones

Question 3

Structure

Answer 3

• 20 - 30nm wide = fast
• Presynaptic neurone - releases neurotransmitters from synaptic knob which is the swollen portion of axon
• Postsynaptic neurone

Question 4

Synaptic knob

Answer 4

• Contains many mitochondria and large amounts of RER
• Mitochondria provides ATP + energy for the cell pumps - aerobic respiration - ATP release energy when it is hydrolysed by ATPase
• SER will synthesise lipids and steroids.
• RER will synthesise proteins (neurotransmitters) - transported in lipid vesicles.

Question 5

Transmission of a message not an impulse

Answer 5

• Chemical not electrical impulse

Question 6

Sensory neurone
Synapse
Interneuron
Synapse
Motor neurone

Answer 6

• Electrical impulse
• Neurotransmitter (chemical)
• Electrical impulse
• Neurotransmitter (chemical)
• Electrical impulse

Question 7

Transmission

Answer 7

• Neurotransmitter - presynaptic - stored in synaptic vesicles + released into synaptic cleft = when action potential reaches synaptic knobs
• Neurotransmitter diffuses across synaptic cleft = unidirectional
• Neurotransmitter binds with complementary receptor molecules - post synaptic membrane
  = New action potential
• Neurotransmitter is hydrolysed by enzymes - loses ability to stimulate neurone

Question 8

All or nothing response

Answer 8

• -55 mV - threshold value - impulse transmitted
• If charge is more negative than this = fail AP
• Threshold will only generate one action potential