The process of synaptic transmission, including reference to neurotransmitters, excitation and inhibition

Question 1

What is a synapse?

Answer 1

The area between the axon of one neuron and the cell body or dendrite of another.

Question 2

what is synaptic transmission

Answer 2

Synaptic transmission is the process of transmitting messages from neuron to neuron, as the electrical impulse (‘action potential’) cannot pass through the gap between a neuron and the neuron/muscle it is communicating with.

Question 3

what are Neurotransmitters

Answer 3

Neurotransmitters are chemical messengers that carry signals across the synaptic gap to the receptor site on the postsynaptic cell.
Neurotransmitters can be classified as either excitatory or inhibitory in terms of their action.

Question 4

Examples of neurotransmitters:

Answer 4

serotonin, dopamine, GABA

Question 5

Evidence for the effect of neurotransmitters on behaviour:

Answer 5

Abnormal levels of neurotransmitters have been implicated in mental illnesses, for example, a lack of serotonin is thought to be a contributing factor to depression.
As such, the drug-based treatments (e.g. SSRI’s) for serotonin focus on increasing the availability of the neurotransmitter in the brain.As this can have a positive effect in the reduction of depressive symptoms we can conclude that neurotransmitters do have an effect on behaviour.

Question 6

process of synaptic transmission

Answer 6

1)Vesicles transport neurotransmitters down the axon towards the presynaptic terminal.

2)Nerve impulses/action potentials cause vesicles to fuse with the presynaptic membrane and release neurotransmitters into the synaptic space, a process known as exocytosis

3)Neurotransmitters diffuse across the synaptic space and bind to receptor sites on the postsynaptic neuron, where they have either an excitatory or inhibitory effect.

4)Neurotransmitters separate from receptor sites and are reabsorbed into the presynaptic neuron via transporter sites and recycled

Question 7

look at labelled diagram of synaptic transmission

Answer 7

..

Question 8

Excitatory

Answer 8

Excitatory neurotransmitters such as noradrenaline are the nervous system’s ‘on-switches’ and increase the likelihood that an excitatory signal is sent to the postsynaptic cell, which is then more likely to fire an impulse (e.g. increased heart rate due to activation of the muscles by noradrenaline). They therefore trigger nerve impulses in the receiving neuron and stimulate the brain into action e.g. dopamine.

Question 9

Inhibitory

Answer 9

Inhibitory neurotransmitters such as serotonin and GABA are the nervous system’s ‘off-switches’ and decrease the likelihood that a neuron will fire an impulse, they are generally responsible for calming the mind and body, by balancing mood and inducing sleep, for example, and as such filter out unnecessary excitatory signals

Question 10

what is Summation

Answer 10

Summation is the process that determines whether or not an action potential will be triggered by the combined effects of excitatory and inhibitory signals.

Question 11

what is the net effect

Answer 11

If the net effect on the post synaptic neuron is excitatory (i.e. more excitatory neurotransmitters e.g. dopamine have bound to receptor sites on the post-synaptic neuron), the neuron will be more likely to fire an impulse.

If the net effect on the post synaptic neuron is inhibitory (i.e. more inhibitory neurotransmitters e.g. serotonin have bound to receptor sites on the post-synaptic neuron), the neuron will be less likely to fire an impulse.