Name: __________________
Grade 11
1
,Have you ever wondered how your body
automatically manages everyday tasks –
breathing, eating, riding a bike, completing
a mathematical problem?
Your nervous system controls the complex
workings of your body in a fast and efficient
way. It allows you to cope with these
routine things, as well as any other
surprises that might come your way.
The nervous system is the body’s control
and communication centre. It provides a
continuous flow of information between the
environment, the brain and different parts
of the body. This enables the body to
function in a systematic and effective way.
Stimuli (singular: stimulus) are physical or
chemical changes in the environment (both
internal or external) that are capable of
causing a response in an organism.
The environment constantly changes and
so we are always exposed to stimuli.
For example, some external stimuli are light and temperature changes, sound etc.
Sometimes the stimuli may be internal, such as blood pressure change, or pH in body
fluids.
2
,STRUCTURE OF A NERVE
Nerves are functional and structural units of the peripheral nervous system (PNS). They
are composed of individual neurons which transmit information between the PNS and the
central nervous system (CNS). Essentially, nerves are bundles of nerve fibres (axons)
surrounded by connective tissue.
Diagram of a nerve
3
, NERVOUS TISSUE
Nervous tissue is comprised of specialised cells called neurons (a nerve cell) and
supporting cells called glial cells (neuroglia). Neurons join end-to-end to form a continuous
conducting tissue that reaches all parts of your body. Neurons carry impulses (these can
be likened to a tiny electrical signal or message). Each impulse carries a different bit of
information and they travel very quickly through the body. Glial cells play a critical role in
making myelin (e.g. Schwann cells) and supporting and protecting the neurons.
Each neuron consists of a cell body from which processes or fibres called axons or
dendrites emerge. These fibres enable a nerve cell to conduct impulses over distances of
anything from millimetres to over a metre. A dendrite conducts impulses towards its cell
body (afferent), while an axon conducts its impulses away from its cell body (efferent).
There are three types of neurons in your nervous system:
• Sensory neuron
• Interneuron (connector neuron)
• Motor neuron
Sensory neuron
Sensory neurons are afferent neurons as they carry the impulse towards the CNS.
Sensory neurons are unipolar (one fibre attached to the cell body)/In a sensory neuron a
cell body has only one outgrowth that immediately divides into two branches, a dendrite
and an axon as seen below.
4
Grade 11
1
,Have you ever wondered how your body
automatically manages everyday tasks –
breathing, eating, riding a bike, completing
a mathematical problem?
Your nervous system controls the complex
workings of your body in a fast and efficient
way. It allows you to cope with these
routine things, as well as any other
surprises that might come your way.
The nervous system is the body’s control
and communication centre. It provides a
continuous flow of information between the
environment, the brain and different parts
of the body. This enables the body to
function in a systematic and effective way.
Stimuli (singular: stimulus) are physical or
chemical changes in the environment (both
internal or external) that are capable of
causing a response in an organism.
The environment constantly changes and
so we are always exposed to stimuli.
For example, some external stimuli are light and temperature changes, sound etc.
Sometimes the stimuli may be internal, such as blood pressure change, or pH in body
fluids.
2
,STRUCTURE OF A NERVE
Nerves are functional and structural units of the peripheral nervous system (PNS). They
are composed of individual neurons which transmit information between the PNS and the
central nervous system (CNS). Essentially, nerves are bundles of nerve fibres (axons)
surrounded by connective tissue.
Diagram of a nerve
3
, NERVOUS TISSUE
Nervous tissue is comprised of specialised cells called neurons (a nerve cell) and
supporting cells called glial cells (neuroglia). Neurons join end-to-end to form a continuous
conducting tissue that reaches all parts of your body. Neurons carry impulses (these can
be likened to a tiny electrical signal or message). Each impulse carries a different bit of
information and they travel very quickly through the body. Glial cells play a critical role in
making myelin (e.g. Schwann cells) and supporting and protecting the neurons.
Each neuron consists of a cell body from which processes or fibres called axons or
dendrites emerge. These fibres enable a nerve cell to conduct impulses over distances of
anything from millimetres to over a metre. A dendrite conducts impulses towards its cell
body (afferent), while an axon conducts its impulses away from its cell body (efferent).
There are three types of neurons in your nervous system:
• Sensory neuron
• Interneuron (connector neuron)
• Motor neuron
Sensory neuron
Sensory neurons are afferent neurons as they carry the impulse towards the CNS.
Sensory neurons are unipolar (one fibre attached to the cell body)/In a sensory neuron a
cell body has only one outgrowth that immediately divides into two branches, a dendrite
and an axon as seen below.
4
