The Nervous system

Summary

The nervous system and hormones enable us to respond to external changes. They also help us to control conditions inside our bodies. Hormones are used in some forms of contraception and in fertility treatments.  

You should be able to:

■ evaluate the benefits of, and the problems that may arise from, the use of hormones to control fertility, including In Vitro Fertilisation (IVF)

Key terms

Central nervous systemBrainSpinal cordStimulus / stimuli (plural)ReceptorImpulseNeuronesNerveSensory neuroneRelay neuroneMotor neuroneEffectorSynapseReflex actionMuscle

The Nervous System

• Brain• Spinal cord• Nerves

• Enables you to control your body

• Gives you feedback about the world

What does it do?

What are its component parts?

Look away if you’re squeamish…

A dissected brain, spinal cord and sections of major nerves.

The Cells of the Nervous System - Neurones

The route impulses take

Receptors in the eyes are sensitive to ___________________Receptors in the ears are sensitive to ___________________Receptors in the ____________ are sensitive to changes in positionReceptors in the _____________ and ___________ are sensitive to chemicals that enable us to taste and smellReceptors in the skin are sensitive to t________________, p_______________ and p_______

The route impulses take

Effectors –

Sensory neurone

Motor neurone

Relay neurones (in brain or spinal cord)

The SpineYou don’t need to know any of these little details – just remember that the spinal cord carries messages to and from the brain.

Left: sensory neurone

Right: motor neurone

Above: Sensory NeuroneBelow: Motor Neurone

Diagrams and Drawings in Biology

Nerves – bundles of neurones

Close-up of a nerve

Single neurones in cross-section

How Impulses Pass from Neurone to Neurone – the Synapse

Synapses

A Neuro-Chip

Reflex Reactions – bypassing the brain for extra speed

Reflex Reactions

Can you think of any?

• Startle reflex – moving away, contraction of arm and leg muscles, blinking, breathing changes

• Withdrawal reflex – moving away from potentially harmful influences (e.g. high temperature)

• Iris reflex – pupil becomes smaller in bright light

Knee Jerk Reflex

Why the knee jerk reflex?

• This reflex is quite useful for walking. Every time you put weight on your foot, your muscles contract to support you. Without this reflex, we would all look silly staggering around, having to consciously think about working our muscles for each step, but with the muscles reacting too hopelessly late to be useful. Chewing gum at the same time would be out of the question.