THE NERVOUS SYSTEM

DR RITA CHAVEZ

MGA

2012

10.1 Nervous control in humans Core IGSE

• Describe the human nervous system in terms of the central nervous system (brain and spinal cord as areas of coordination) and the peripheral nervous system which together serve to coordinate and regulate body functions • Identify motor (effector), relay (connector) and sensory neurones from diagrams • Describe a simple reflex arc in terms of sensory, relay and motor neurones, and a reflex action as a means of automatically and rapidly integrating and coordinating stimuli with responses • State that muscles and glands can act as effectors • Describe the action of antagonistic muscles to include the biceps and triceps at the elbow joint • Define sense organs as groups of receptor cells responding to specific stimuli: light, sound, touch, temperature and chemicals • Describe the structure and function of the eye, including accommodation and pupil reflex

Let’s do this! • Describe the human nervous system in terms of the central nervous system (brain and spinal cord as areas of coordination) and the peripheral nervous system which together serve to coordinate and regulate body functions. • Identify motor (effector), relay (connector) and sensory neurones from diagrams • Describe a simple reflex arc in terms of sensory, relay and motor neurones, and a reflex action as a means of automatically and rapidly integrating and coordinating stimuli with responses • State that muscles and glands can act as effectors

What is the nervous system

made up of?

• The brain

• The spinal cord

• The nerves (neurones)

The central nervous

system (or CNS for short)

is made up of the brain and the spinal cord.

What is the job of the nervous

system?

• Our survival depends on us being

sensitive to our surroundings.

• We need to be able to detect any

changes and be able to respond to

them.

How does our nervous system work then? • Our sense organs contain special receptor cells which will

detect a change in our surroundings (a stimulus)

• The receptor cells will change the stimulus into an electrical impulse which is passed along nerve cells

• The message will usually go to the brain which will then process it

• The brain then sends a message along nerves to an effector organ (usually a muscle or a gland)

• The effector organ will then give a response (e.g. a muscle will move, or a gland will produce a hormone)

Stimulus

Receptor

Sensory neurone

Central

Nervous

system

Motor neurone

Effector

Response

Basic nerve cell structure

3 main types of nerve cells

sensory

neurone relay

neurone

motor

neurone

Sensory neurons

Carries impulses from receptors e.g pain receptors in skin to the CNS( brain or spinal cord)

Relay neuron

Carries impulses from sensory nerves to motor nerves.

Motor neuron

Carries impulses from CNS to effector e.g. muscle to bring about movement or gland to bring about secretion of hormone e.g ADH

Transmission of signals

The Synapse

Synapses • When a nerve ending meets

up with another nerve ending we get a microscopic space

• This space is called a synapse

• The electrical message travelling along a nerve has to cross the synapse as a chemical message

• When the chemical (neurotransmitter) reaches the other nerve ending it causes an electrical impulse to travel along the next nerve cell

Reacting without thinking

• Sometimes a stimulus requires an immediate response. This is called a reflex action.

• It is an involuntary response and we do it without thinking.

• These automatic responses do not have to be learned. They can be very important in preventing injury to ourselves.

A reflex arc

The nerve pathway taken in a reflex action is called a reflex arc. The nervous message goes to the spinal cord, then a message passes from the spinal cord directly to an effector to give an immediate response.

A reflex arc

The knee jerk reflex action Sometimes

called a relay or

Connector neurone

Another reflex action

Examples of responses

Voluntary actions

• Eating a cake

• Riding a bicycle

• Walking

• Playing the piano

• Coming to school

Involuntary actions

• Your heart beat

• Breathing

• Blinking

• Removing hand

from hot object

• Choking

• Salivating

NEXT…..

• Describe the action of antagonistic muscles to include the biceps and triceps at the elbow joint

• Define sense organs as groups of receptor cells responding to specific stimuli: light, sound, touch, temperature and chemicals

• Describe the structure and function of the eye, including accommodation and pupil reflex

What are our sense organs?

The sense organs are:

• The eyes

• The ears

• The nose

• Tongue

• skin

These organs sense:

• Light

• Sound and balance

• Smell

• Taste

• Pressure, pain, temperature

• http://www.youtube.com/watch?v=FR4S1BqdFG4&feature=related

• http://www.youtube.com/watch?v=roKV8XJHXKc&feature=related