The central nervous system

The central nervous system is made up of the brain and spinal cord.

And the peripheral nervous system is made up of nerves and receptors.

The CNS is made up of neurons that coordinate the messages traveling through the nervous system.

The three types of cells, neurons are:

  • The sensory neuron
    Transmit impulses inwards from sense organs to the CNS

  • Motor neurone
    Transmitting impulses from the CNS to muscles and glands elsewhere in the body

  • Relay neurone
    Transmit the electrical impulses generated by the stimuli to other nerves.

Continuing our studies of the nervous system, here it’s a video showing a reflex act.

stimulus → receptor → sensory neurone → relay neurone → motor neurone → effector → response

In this case, the stimulus is the temperature, the receptors are the thermal receptors in your skin, the effectors are the muscle contraction, the response when the arm bends and the coordinator is the spinal cord.

Biology activity pag. 177

In our biology class, we have been studying coordination and response.


a) In which direction does this synapse allow a nerve impulse to travel?

The nerve impulse travels from the left to he right as the vesicles release the neurotransmitter into the synaptic cleft. Then the neurotransmitters attached to the receptor moleculed in the relay neurone.

b) Describe the roles of the parts labelled A and B in transmitting a nerve impulse from one neurone to the next.

The vesicles contain the neurotransmitters.

The receptors receive the neurotransmitters and trigger a nerve impulse in the relay neurone until it reaches the next synapse.

c) Suggest the role of the mitochondria shown in the diagram.

The mitochondria is where respiration takes place and where energy is released for the neurone to transmit nerve impulses and then the receptors.