5.2.1 - Structure & Function

What is the function of the nervous system?

Allows the body to react to its surroundings and coordinate an appropriate response.

How does a stimulus lead to a response being carried out by the body?

• Stimulus is converted into an electrical impulse by the receptors.

• The electrical impulse passes along sensory neurons to the central nervous system (CNS).

• The CNS coordinates an appropriate response and an electrical impulse is sent along motor neurons to the effector, which carries out the response.

What sequence of events describe how the nervous system works?

stimulus ➝ receptor ➝ coordinator ➝ effector ➝ response

What is a reflex action?

An automatic and rapid response which does not involve any conscious input from the brain.

Why are reflex actions important?

They aid survival by preventing harm to the body.

Describe how a reflex action occurs via a reflex arc.

• The stimulus is detected by a receptor.

• An electrical impulse passes along a sensory neuron to the spinal cord (part of the CNS).

• At a synapse between a sensory neuron and a relay neuron, a chemical diffuses across the gap and stimulates a new impulse which passes along the relay neuron.

• The same process occurs at a synapse between a relay neuron and a motor neuron.

• At the effector, an appropriate response is carried out.

What is the difference between a reflex pathway and a conscious pathway?

• Within a reflex pathway, the coordination center is a relay neuron found in the spinal cord/unconscious parts of the brain.

• In a conscious pathway, the coordination center is in the conscious part of the brain.