Synapses 1 Lecture

Question 1

Outline the general journey of information across a neuron

Answer 1

Information arrives at the cell body via dendrites where it is assimilated and processed → processed info is digitised and transmitted along the axon → at the end of the axon the information is passed to the target (muscle/neuron) via nerve terminal.

Question 2

What is a synapse?

Answer 2

A junction between two cells where electrical changes in one cell cause a signal to be passed to another usually via a chemical neurotransmitter.

Question 3

How long is the synaptic cleft?

Answer 3

Around 20nm

Question 4

What is neurdomodulation?

Answer 4

Activity at synapses can be modulated - a slower timescale than normal neurotransmission and affects the excitability of the pre- and post synaptic cell using modulation of endogenous systems.

Question 5

What happens to resting membrane potential during synaptic transmission?

Answer 5

It fluctuates.

Question 6

How are neurotransmitters released?

Answer 6

The release of neurotransmitters is quantal - the neurotransmitter is released in packets from a single vesicle at a time - the more vesicles released, the stronger the signal at the post synaptic membrane.

Question 7

What are the 3 sub divisions of synaptic activity?

Answer 7

Presynaptic activity, postsynaptic activity, neurotransmitter inactivation

Question 8

Describe the presynaptic mechanism of axonal transport

Answer 8

Small-molecule transmitters - enzymes are synthesised in the cell body, and transported slowly along the axon, used to synthesise and package neurotransmitters and then released.

Peptide-transmitters - Neurotransmitter precursors synthesised in the cell body, microtubules guide molecular motors e.g dynein, which move these vesicles along.