Synaptic transmission

Question 1

How do chemically gated ion channels work

Answer 1

ACh (Acetyl Choline) binds to closed channel within membrane. This opens the channel and allows Na+ ions into the cell from the cytoplasm. Once ACh is used up the channel closes again

Question 2

Describe the stages at synapse

Answer 2

1- AP reaches triggers that open voltage gated calcium channels
2- Ca+ ions diffuse into axon terminal. This triggers synaptic vesicles to release ACh (exocytosis)
3- ACh binds to sodium ion channels and produces graded depolarization.
4- ACh broken down into choline and acetal by AChE to end depolarization.
5- Axon terminal absorbs choline and uses it to synthesise new ACh

Question 3

How can we be sure Na+ will go through channels

Answer 3

There will be a concentration gradient and attractive forces (-) from the inside of the cell that will ensure that Na+ ions will go into the cell

Question 4

What difference is there between a neuromuscular junction and a neuron junction

Answer 4

Neuromuscular junctions release alot of ACh into the environment to ensure that the message will be received quickly

Question 5

How does ACh relate to the strength of the message

Answer 5

The more ACh that gets released the more Na+ channels will open.

Question 6

Explain EPSP

Answer 6

Excitatory - Chemical stimulus opens ion channels and depolarizes. Stimulus is removed and excess Na+ ions transported out of cytosol to repolarize

Question 7

Explain IPSP

Answer 7

Inhibitory - Chemical stimulus opens potassium ion channels causing hyperpolarization. Chemical stimulus is removed and returns to resting potential.

Question 8

What are EPSP and IPSP

Answer 8

Types of depolarisations (excitatory and inhibitory)

Question 9

How does an AP get over threshold

Answer 9

The summation of the two inputs (EPSP and IPSP)

Question 10

What are the special features of the Neuro Muscular Junction

Answer 10

At the NMJ the synaptic transmission is Excitatory and absolute. No EPSP and IPSP summation

Question 11

What are two ways we can summate an AP to move over threshold

Answer 11

Temporal summation (time)
Spatial summation (space)

Question 12

Describe how temporal summation works

Answer 12

When one stimulus isn’t enough to induce AP. If another stimulus is observed close enough to the first they add together to get over threshold and produce an AP

Question 13

Describe how spatial summation works

Answer 13

If two axons release AP’s close enough together AND close enough together(time) they can also get over threshold to create an AP