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2.13 and 2.14 Structure and Function of the Nervous System and the Reflex…
2.13 and 2.14 Structure and Function of the Nervous System and the Reflex Arc
Intro
This electrical impulse travels along cells called sensory neurons to the central nervous system (CNS)
Here, the information is processed and the appropriate response is coordinated, resulting in an electrical impulse being sent along motor neurones to effectors
Receptor cells convert a stimulus into an electrical impulse
The effectors carry out the response (this may be muscles contracting or glands secreting hormones
The nervous system allows us to react to our surroundings, and coordinate actions in
response to stimuli
Automatic Responses
This because the information travels down a pathway called a reflex arc allowing vital responses to take place
This pathway is different from the usual response to stimuli because the impulse does not pass through the conscious areas of your brain
They are important as they prevent the individual from getting hurt
Process
A stimulus is detected by receptors
Impulses are sent along a sensory neuron
In the CNS the impulse passes to a relay neuron
Impulses are sent along a motor neuron
The impulse reaches an effector resulting in the appropriate response
Automatic responses which take place before you have time to think are called reflexes
Examples of reflex arcs are: pupils getting smaller to avoid damage from bright lights, moving your hand from a hot surface to prevent damage
Synapses
When the impulse reaches the end of the first neuron, a chemical called a neurotransmitter is released into the synapse
This neurotransmitter diffuses across the synapse
Synapses are the gaps between two neurons
When the neurotransmitter reaches the second neuron, it triggers the impulse to begin again in the next neuron
Different neurotransmitters have different effects on the frequency and speed of the impulse in the second neuron
Myelin Sheath
The advantage of having nerves surrounded by myelin is that it allows the nerve transmission (or action potential) to travel faster
Myelin is produced by cells called Schwann cells
Some nerves are myelinated, i.e they are surrounded by a myelin sheath