The Nervous System (Biology GCSE)


Uploaded by freeeschool on 04.09.2012

Transcript:
GCSE Biology – The Nervous System
Hello! Welcome to a video about the Nervous system. We are going to look at what the nervous
system is and how it can help to cause responses to the environment.
It starts off with the overall job of the nervous system is to detect stimuli in order
to coordinate responses and behavior. By the word “stimuli”, this word stimuli here
is plural and in singular, it is stimulus. By stimuli, we mean changes in the environment.
What we mean in changes in the environment, it is actually linked to your five senses.
The way we detect changes in the environment are through our five senses. Those are through
the sense of smell which are chemicals in the air; the sense of touch which is not just
the finger there. It is actually all over our body. Our skin is the organ that will
give you the sense of touch. We have chemicals that we detect for taste. We have light senses
in our eyes or light receptors in our eyes so that we can detect or see things. We have
sound receptors which help us to hear. We often forget that also in our ear, we have
structures that help us with our balance. They help us detect position so that we can
keep balance. That’s one that is often forgotten; but that’s also found within the ear.
The next thing that I want to look at really is the overall structure of the nervous system.
We have two parts to it. One major part of it is called the Central Nervous system. The
central nervous system consists of the brain and the spinal cord. The spinal cord is the
stick cord coming from the base of the brain and these other parts coming from the spinal
cord are other nerve cells or bundles of nerves coming either from the central nervous system
or going to the central nervous system. But the central nervous system often abbreviated
to CNS is the brain and the spinal cord.
Around that are the types of nerves which work in order to detect the stimuli in the
environment and to bring about the response. We are going through how that works now.
To start us off with we have receptor cells or receptors that are found in our sense organs.
For example, if you hear a sound, that will be detected by a sound receptor in your ear
and that will then send a signal from the ear to the central nervous system. That is
sent by a special type of nerve or special type of neuron called a sensory neuron. That
sends a signal from the receptor to the central nervous system.
From the central nervous system, we have another type of neuron or another type of nerve which
is called a motor neuron and that will send a signal from the central nervous system to
this thing called an effector. An effector is basically either a muscle or a gland and
that effector will then bring about the response.
If you were to hear a loud sound, it would go through this whole system and your response
would be perhaps to cover your ears or to duck or something like that. This whole system
is designed to detect the change and respond to it.
Now, in the central nervous system, there is also another type of neuron and that is
called a relay neuron. The job of the relay neuron is really to take the signal from a
sensory neuron and transfer it to the motor neuron. That’s an overall view of how the
nervous system works.
It is probably worth mentioning at this point that this section here is called a synapse.
That’s basically a junction between one neuron and another. The way that works there
is that we have instead of an electrical signal, so this is an enlarged version of this area
here, instead of electrical signal that we have that goes along the sensory neuron, the
relay neuron and the motor neuron, we actually have a chemical signal that is passed from
one neuron to another like so. So the chemical signal will be passed from one neuron to another. That actually works across
the little gap that we see here in this whole structure called a synapse.
Now, let’s have a look at an actual example of how this might work. I’m going to use
the example of a runner waiting on the starting blocks. That runner is waiting for a sound
which would be the sound of the gun firing and the response that he will make is to start
running. What you should be able to do is to describe the pathway in which this happens.
To start off, we have the bang from the starter pistol. That will be detected by your sound
receptors in your ears. That signal will be then sent along a sensory neuron along the
central nervous system, along a motor neuron and then to your effector. The effector in
this case would be muscles in the legs, a variety of different muscles but it will be
muscles and the response will then be to start running.
You should be able to describe this whole sequence of events for a whole range of different
examples. Another example might be for you to say that you smell some food at lunchtime.
The stimulus here would be chemicals in the air which would be smell that you would detect.
The message will go along the sensory neurons and the central nervous system, motor neurons
and the actual fact for that example would probably be glands in your stomach which would
then start producing digestive juices. That’s another example of how that might work.
There is the whole system simplified for you a little bit. As I said, you should be able
to talk about this whole system, this whole sequence of events for a whole range of different
examples.
[end of audio – 06:16] GCSE Biology – The Nervous System
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