How organisms respond to changes in their environment
An animal’s response to a stimulus is coordinated by their central nervous system (CNS).
A stimulus is a change in the environment of an organism.
Animals respond to a stimulus in order to keep themselves in favourable conditions.
Examples of this include:
moving to somewhere warmer if they are too cold
moving towards food if they are hungry
moving away from danger to protect themselves
Animals that do not respond to a stimulus do not survive for long.
An animal’s response to a stimulus is coordinated by their central nervous system (CNS). The CNS consists of the brain and the spinal cord. It gathers information about, and responds to, changes in the environment.
Receptors respond to a stimulus and send impulses along sensory neuronssensory: Sensory neurones carry messages from sense organs into the CNS to the CNS. The CNS coordinates the information and sends impulses along motor neuronsmotor: motor neurones carry messages out of the CNS to effector organs to the effectors, which bring about a response. The sequence is as follows:
Some receptors are found in the skin. Other receptors can form part of complex organs, such as:
The peripheral nervous system (PNS) consists of motor and sensory neurons that carry information from the receptors to the CNS, as well as instructions from the CNS to the effectors.
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