IGSCE Biology – 2j: Coordination and Response
The Nervous System
o We have a nervous system in order that we can detect and respond to changes in
our environment.
o This is also known as the stimulus (stimuli pl).
Parts of the Nervous System
o The nervous system is comprised of three parts.
o The brain and the spinal cord are the nervous system – it processes information.
o The peripheral/spinal nerves make up the peripheral nervous system – it connects
the central nervous system to receptors and effectors.
Sense Organs
o Nose – it detects smell and is sensitive to chemicals.
o Ear – it detects sound and is sensitive to vibrations.
o Skin – it detects touch and temperature and is sensitive to pressure and heat.
o Eye – it detects sight and is sensitive to light.
o Mouth – it detects taste and is sensitive to chemicals.
Nerves and Neurones
Nerves
o Information from receptors pass along the sensory neurone to the brain (e.g., a
nasty smell from the nose).
o The brain interprets the information given and then coordinates a response.
o Charged particles (electrical impulses) then travel down the motor (effector)
neurones to the muscle glands (e.g., turn head away from smell).
Motor Neurone
o Motor neurones carry impulses from the brain (central nervous system) to effectors
which can be muscles or glands.
o They have a long fibre (axon) which is insulated by a fatty sheath and tiny branches
(dendrons) which branch further as dendrites at each end.
, Sensory Neurone
o Sensory neurones carry impulses from sensory receptors to the spinal cord and brain
(central nervous system).
o Sensory neurones are different to motor neurones in the fact that their cell body is
apart from the neuron itself.
Relay Neurone
o Relay neurones carry impulses from one part of the central nervous system to
another.
Reflexes and Synapse
Reflexes
o Reflexes are responses that are designed to reduce damage or injury.
o They must be extremely rapid.
o In order to be rapid, there is a reflex arc which means that the impulse goes straight
back out of the central nervous system to the effectors.
The Journey of an Impulse
o An electrical impulse passes from the sensory receptor (nerve ending), along the
sensory neurone to the spinal cord.
o The impulse then passes to a relay neurone and straight back along a motor neurone
to the effector organ (muscle).
o The time between the stimulus and the reflex action is as quick as possible – it allows
you to react to stimuli without thinking about it.
Synapses
The Nervous System
o We have a nervous system in order that we can detect and respond to changes in
our environment.
o This is also known as the stimulus (stimuli pl).
Parts of the Nervous System
o The nervous system is comprised of three parts.
o The brain and the spinal cord are the nervous system – it processes information.
o The peripheral/spinal nerves make up the peripheral nervous system – it connects
the central nervous system to receptors and effectors.
Sense Organs
o Nose – it detects smell and is sensitive to chemicals.
o Ear – it detects sound and is sensitive to vibrations.
o Skin – it detects touch and temperature and is sensitive to pressure and heat.
o Eye – it detects sight and is sensitive to light.
o Mouth – it detects taste and is sensitive to chemicals.
Nerves and Neurones
Nerves
o Information from receptors pass along the sensory neurone to the brain (e.g., a
nasty smell from the nose).
o The brain interprets the information given and then coordinates a response.
o Charged particles (electrical impulses) then travel down the motor (effector)
neurones to the muscle glands (e.g., turn head away from smell).
Motor Neurone
o Motor neurones carry impulses from the brain (central nervous system) to effectors
which can be muscles or glands.
o They have a long fibre (axon) which is insulated by a fatty sheath and tiny branches
(dendrons) which branch further as dendrites at each end.
, Sensory Neurone
o Sensory neurones carry impulses from sensory receptors to the spinal cord and brain
(central nervous system).
o Sensory neurones are different to motor neurones in the fact that their cell body is
apart from the neuron itself.
Relay Neurone
o Relay neurones carry impulses from one part of the central nervous system to
another.
Reflexes and Synapse
Reflexes
o Reflexes are responses that are designed to reduce damage or injury.
o They must be extremely rapid.
o In order to be rapid, there is a reflex arc which means that the impulse goes straight
back out of the central nervous system to the effectors.
The Journey of an Impulse
o An electrical impulse passes from the sensory receptor (nerve ending), along the
sensory neurone to the spinal cord.
o The impulse then passes to a relay neurone and straight back along a motor neurone
to the effector organ (muscle).
o The time between the stimulus and the reflex action is as quick as possible – it allows
you to react to stimuli without thinking about it.
Synapses
