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Receptors, effectors and the CNS
Receptors are groups of specialised cells which can detect energy changes
in the environment and turn them into electrical impulses. Receptors are
often located in the sense organs ear, eye, skin etc with each organ
having receptors sensitive to particular kinds of stimulus.
Sense organ Receptors sensitive to
Skin pressure, pain, temperature
Tongue chemicals in food
Nose chemicals in the air
Ears sound and position of the head
When a receptor is stimulated it sends a signal to the central nervous
system or CNS in humans, the brain and spinal cord. The CNS processes
the information coming in and sends signals back to the effector organs
which enact the body's response to the stimulus.
An effector organ is any organ which has an effect for example, a muscle
contracting to move your arm, a muscle squeezing saliva out of your salivary
gland or even an endocrine gland squirting a hormone into your blood.
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All the electrical signals on which the nervous system depends are transmitted by
another group of specialised cells called nerve cells or neurones. There are
three different types of neurones with slightly different functions:
1. Sensory neurones carry signals from sense organs to the spinal cord
2. Relay neurones carry messages from one part of the CNS to another
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The signals processed by the CNS can result in two different types of action.
They may be passed to the higher centres of the brain and result in a conscious
act. This is a voluntary action.
But if the safety of the organism demands a very quick response, the signals
may be passed directly, via a relay neurone, to a motor neurone for instant,
unthinking action. This is a reflex action.…read more