Synapse

Question 1

What is the difference between chemical and electrical synapses?

Answer 1

electrical is when the current flows directly through gap junctions whereas in chemical, a chemical travels through the cleft

Question 2

Chemical synapses occur between neurons and?

Answer 2

other neurones, muscle cells, gland cells

Question 3

Describe the events at a chemical synapse

Answer 3

1. An arriving action potential depolarises the axon terminal membrane of a presynaptic neurone.
2. Depolarisation of the axon terminal membrane opens voltage-gated calcium ion channels, and calcium ions (Ca2+ ) enter the cytosol of the axon terminal. This results in ACh release from the synaptic vesicles by exocytosis.
3. ACh diffuses across the synaptic cleft and binds to receptors on the postynaptic membrane. Cation (Na+, K+) channels open, producing a graded depolarisation due to Na+ inflow.

Question 4

What are a few transmitters?

Answer 4

Acetylcholine. (ACh), GABA, dopamine, serotonin, endorphins, substance P, glutamate

Question 5

What are 3 methods of neurotransmitter removal?

Answer 5

re -uptake by pre synaptic neuron, often recycled and used again

diffusion - passive process, can’t be used in situations with high frequency AP

enzymatic destruction - enzymes breakdown neurotransmitters

Question 6

What are excitatory neurotransmitters?

Answer 6

Transmitter causes depolarisation increasing cell activity

Question 7

What are inhibitory neurotransmitters?

Answer 7

Transmitter causes hyperpolarisation which decreases cell activity

Question 8

What is a EPSP?

Answer 8

An excitatory postsynaptic potential, is a graded depolarization caused by a neurotransmitter at the postsynaptic membrane.

An EPSP results from the opening of chemically gated ion channels in the plasma membrane that lead to membrane depolarization.

Question 9

What is summation?

Answer 9

A post-synaptic cell will ‘fire’ only if it receives sufficient excitation to drive the MP beyond threshold
This occurs when it receives many excitatory inputs (and few inhibitory inputs) within a short time period

Question 10

What is convergence?

Answer 10

each neuron receives many inputs from other cells

Question 11

What is divergence?

Answer 11

each neuron then synapses with many other cells

Question 12

What is a motor end plate?

Answer 12

synapse between a motor nerve and a muscle fibre

Question 13

What does the action potential create at a motor end plate?

Answer 13

muscle contraction

Question 14

What neurotransmitter is used at neuromuscular junctions?

Answer 14

acetylcholine

Question 15

What enzyme breaks down acetylcholine?

Answer 15

acetyl cholinesterase

Question 16

How can drugs affect synapses?

Answer 16

they can block the synapses by affecting the synthesis, release, action, second message system, and inactivation of the transmitter

Question 17

What does botox (botulinum toxin) do?

Answer 17

prevents the release of transmitter from motor nerves

Question 18

How do beta-blockers affect synaptic activity?

Answer 18

they prevent receptors being stimulated by neurotransmitters by binding to receptors