Neurons and Synaptic transmission

Question 1

explain sensory , relay and motor neurons

Answer 1

Sensory neurons carry messages from the PNS to the CNS and have long dendrites and short axons
Relay neurons connect the sensory neurons to the motor or other relay neurons/ They have short dendrites and short axons.
Motor neurons -connect the CNS to effectors such as muscles and glands They have short dendrites and long axons.

Question 2

Explain the firing of a neuron

Answer 2

When the neuron is in a resting state the inside of the cell is negatively charged compared to the outside. When a neuron is activated by a stimulus, the inside of the cell becomes positively charged for a split-second causing an action potential to occur. This creates an electrical impulse that travels down the axon towards the end of the neuron.

Question 3

Explain excitation and inhibition using an example of each

Answer 3

Neurotransmitters have either an excitatory or inhibitory effect on the neighbouring neuron. For instance, the neurotransmitter serotonin causes inhibition in the receiving neuron, resulting in the neuron becoming more negatively charged and less likely to fire.In contrast, adrenaline causes excitation of the postsynaptic neuron by increasing its positive charge and making it more likely to fire.

Question 4

explain summation

Answer 4

The question of whether a postsynaptic neuron does fire is decided by the process of summation. The excitatory and inhibitory influences are summed : if the net effect on the postsynaptic neuron is inhibitory then the postsynaptic neuron is less likely to fire ; if the net effect is excitatory it is more likely to fire- and momentarily, the inside of the postsynaptic neuron becomes positively charged. Once the electrical impulse is created, it travels down the neuron