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IGCSE: Biology- Coordination
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IGCSE: Biology- Triple award Coordination revison notes. Covers all content, course summary
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CoordinationLiving organisms are sensitive to their surroundings - one of the 8 life processes.
A change in the environment is called a stimulus - this could be internal (such as blood glucose levels) or
external - such as a temperature change. Organisms can respond to these changes.
The nervous system consists of
neurons & the CNS.
The central nervous system (CNS)
consists of the brain and spinal cord.
The CNS coordinates a response
between receptors and effectors.
Sensory
neurons carry
the impulse
from the
receptor to the
CNS.
Relay neurons
relay the
impulse around the CNS.
Motor neurons carry the impulse from CNS to the effector.
An effector brings about a response to a stimuli. An effector
may either be:
- A muscle - contract to bring about movement
- A gland - secrete hormones
HOW IT WORKS:
1. Receptors detect a stimulus and convert its energy into an impulse
2. Sensory neurons transmit this electrical impulse to the CNS
3. Impulse transmitted through CNS by a relay neurone & CNS coordinates a response
4. Impulse transmitted to effector along a motor neurone
5. Effector brings about the response
A synapse is a gap between 2 neurons.Instead of electrical impulses, chemicals called neurotransmitters diffuse
across the synapse. And generate a new electrical impulse for the next neuron.
Reflexes are automatic responses to stimuli, designed to protect us from harm. They do not involve the
conscious part of the brain, and are rapid (very fast).
, REFLEX ARC:
1. Receptors detect stimulus
2. Impulse sent along sensory neurone
3. To CNS / Spinal cord
4. Impulse passed on to relay neurone (across a synapse)
5. Impulse passed on to motor neurone (across a synapse)
6. Motor neurone transmits impulse to the effector (a muscle)
7. Muscle contracts to move hand away.
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