Neurons

Question 1

Outline the types of neurons

Answer 1

Sensory
Relay
Motor

Question 2

Outline the structure of a neuron

Answer 2

Cell body includes nucleus, containing genetic material of cell
Branchlike structures called dendrites protrude from cell body - these carry nerve impulses from neighbouring neurons towards cell body

Axon carries impulses away from cell body down length of neuron
Axon covered in fatty layer of myelin sheath protecting axon & speeds up electrical transmission of impulse

If MS was continuous it would have reverse effect & slow down electrical impulse
Thus, MS segmented by gaps called nodes of Ranvier, these speed up transmission of impulse by forcing it to ‘jump’ across gap along axon

At end of axon = terminal buttons that communicate with next neuron in chain across synapse

Question 3

Where are neurons located?

Answer 3

Cell bodies of motor neurons in CNS but long axons form part of PNS
Sensory neurons located outside CNS, in PNS in clusters called ganglia
Relay neurons make up 97% of all neurons & most found within brain & visual system

Question 4

Outline the process of electrical transmission

Answer 4

When neuron = resting state Inside of cell = negatively charged comapred to outside
When neuron activated by stimulus, inside of cell becomes positively charged for split second causing action potential to occur
This creates an electrical impulse that travels down axon towards end of neuron

Question 5

Outline synaptic transmission

Answer 5

Neurons communicate with each other within groups called neural networks
Each neuron separated by synapse (tiny gap)
Signals within neurons = transmitted electrically//Signals between = chemically
When electrical impulse reaches end of neuron (presynaptic terminal) it triggers release of NT from tiny sacs called synaptic vesicles

Neurotransmitters (NT) = chemicals that diffuse across synapse & taken up by postsynaptic receptor site on dendrites of next axon of neuron in chain
Here, chemical message converted back to electrical impulse & transmission begins again
Only 1 direction of travel as NT released from presynaptic neuron terminal & received by postsynaptic neuron

NT have either inhibitory/excitatory effect on neighbouring neuron
E.g. serotonin causes inhibition in receiving neuron, resulting in neuron being more negatively charged & less likely to fire & vice versa

Whether a postsynaptic neuron fires is decided by process of summation
Excitatory & inhibitory influences summed: if net effect = excitatory more likely to fire