Nervous controlAn overview of how the nervous system worksWAL:

All

Most

How do reflex arcs prevent damage to the body?

What roles do sensory, intermediate and motor neurones play in a reflex arc?

Some

How does a simple reflex arc work?

Today we are covering from the specification:

Pages 144-146 of NT textbook

Nervous organisationThe nervous system has 2 main divisions:

1)The central nervous system (brain and spinal cord)

2)The peripheral nervous system (pairs of nerves that originate from either the brain or spinal cord)

Nervous organisation1) The peripheral nervous system is divided

into:– Sensory neurones

– Motor neurones

Nervous organisation1) The motor nervous system is further divided

into:– Voluntary nervous system,which carries nerve impulses tobody muscles and is undervoluntary control

– Autonomic nervous system,which carries nerve impulses toglands, smooth muscle and cardiac muscle and is

not under voluntary control, that is, it is involuntary (subconscious)

The spinal cordColumn of nervous tissue that runs along the back inside the vertebral column for protection. Emerging at intervals are pairs of nerves.

StimulusHot pan

ReceptorTemperature receptors in skin

Sensory neurone passes impulse to spinal cord

Intermediate neuronein spinal cord links the neurones together

Motor neurone passes impulse from spinal cordto muscle in upper arm

Effector - the muscle in upper arm is stimulated to contract

ResponseDrop saucepanMess on floor!

Task: Measure your reaction time

Any action that makes survival more likely is clearly of value.•Reflexes are important because:

– They are involuntary and therefore do not require the decision making powers of the brain, thus leaving it free to carry out more complex responses.

– Brain is not overloaded with situations in which the response is always the same.

– Some responses are still sent to the brain and can sometimes over-ride the reflex if necessary, why?

Importance of reflex arcs

Any action that makes survival more likely is clearly of value.•Reflexes are important because:

– They protect the body from harmful stimuli.

– They are effective from birth and do not have to be learnt.

– They are fast, because the neurone pathway is short with very few, typically one or two, synapses (which are the slowest link in a neurone pathway). This is important in withdrawal reflexes.

Importance of reflex arcs

Nervous controlAn overview of how the nervous system worksWAL:

All

Most

How do reflex arcs prevent damage to the body?

What roles do sensory, intermediate and motor neurones play in a reflex arc?

Plenary– Write a paragraph with the words voluntary, intermediate,

sensory, motor, reflex arc, stimulus, response

Some

How does a simple reflex arc work?