Download Nervous System 1

Nervous System
Learning Outcomes
• Understand the role of the Nervous System
• Understand what Stimuli, Receptors and Effectors are
• Understand what the role of Motor and Sensory
Neurons are.
• Understand the role of Axons and Impulses.
•
•
•
•
•
•
•
Nervous System
Things are happening round you all the time. You have to detect
and respond to many changes. But how does your body do this
Your body responds to changes in ways
Nervous system
Hormonal system
Your nervous system sends electrical messages along your nerves
to and from different parts of your body.
Your hormonal system sends chemical messages around your body
in the blood.
The electrical messages and the chemical messages tell your body
what to do.
Getting a reaction
• All our reactions happen in the same way. There are always
• Stimuli
• Receptors
• Effectors
• Stimuli are changes that can be detected
• Receptors detect the changes
• Effectors bring about the responses
 What happens if you sit down on a drawing pin?
 The stimulus is the drawing pin
 The receptors are the pain receptors
 Your response is to get up quickly
 The Chain of events is:
Stimulus
Receptor
Coordinator
Effector
Response
The coordinator is the part of the body that decides what to do
What do you think the coordinator is in our example?
Your Nervous System
• The nervous system control your actions. It coordinates
different parts of your body so that they work together and
are able to bring about the correct responses
• Your nervous system coordinates your muscles, so that you
can walk, run, write, read etc
• When you smile the nervous system coordinates the
muscles in your face
• Your nervous system also coordinates things that you don’t
even think about, like swallowing, blinking and breathing.
The Central
Nervous System
is connected to
different parts of
the body by
Nerves.
Each Nerve is
made up of lots of
Nerve Cells or
Neurons
Sense Organs are
our receptors.
They send
messages to the
Central Nervous
System telling it
what has
happened.
These messages
are sent along
Sensor Neurons
The main parts of the
nervous system are
the Brain and the
Spinal Cord.
Together they are
called the Central
Nervous System.
The Brain is protected
inside the skull
The Spinal Cord is
protected inside your
Backbone
Muscles and Glands are
our different
effectors. The Central
Nervous System sends
messages telling them
what to do.
These messages are
sent along Motor
Neurons
Sensory
Neuron
Motor
Neuron
The messages that Nerves carry are called Nerve Impulses. They carry
electrical signals. They pass very quickly along the Axon of the Neuron
An Impulse travels along the Axon like a train along a track.
Each one is separate from the next. They travel along one after the other.
Some Axons have a fatty sheath around them. This insulates the Axon and
makes the Impulse travel along faster.
Coordination
What is the
Stimulus?
What is the
Response?
Which parts are the
Receptors, the
Effector and the
Coordinator?
Your Nervous
System helps you
react to different
situations.
Synapses
• The end of one neuron is not connected to the next. There
is always a small gap between them. The gap is called a
synapse.
• When an impulse reaches the end of an axon, a chemical is
produced. The chemical diffuses across the gap. It starts off
an impulse in the next neuron .
• Only one end of a neuron can make this chemical. So
synapses make sure an impulse can only travel in one
direction.
• Synapses have two other functions:
 A Resistor- it may take a number of impulses before enough
chemical is made to start the impulse in the next neuron.
 A Junction Box- One neuron may pass on its impulse to a
number of other neurons.
• Our synapses are easily affected by drugs. Some drugs can
block them. Others can make them work too quickly. Alcohol
is thought to affect synapses in the brain. This can slow
down people’s reactions.
Reflex arcs
• What happens when you touch a hot object?
• You take your hand away from a hot object very fast. You do it automaticallywithout thinking. Why do you think this is?
• Many reflexes protects you. They happen very quickly, so you don't harm
yourself.
• The following diagram shows a picture of a reflex arc.
What’s going on!
Stimulus
Receptor
Sensory Neuron
Relay Neuron
Motor Neuron
The stimulus is the flame
The receptor is the heat sensor in the
skin
Passes along an impulse to the CNS
In the spinal cord the impulse is passed on to the
relay neuron, it’s part of the co-ordinator
This passes the impulse onto the effector
The motor neuron carries the impulse to a muscle in the arm. The muscle is
the Effector.
The muscle contracts to remove the hand from the hot object. This action is a
Response.
H/W: 17th/1
Draw a diagram
of a neurone
(motor, relay or
sensory), and
label it’s cellular
components.