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Science, Nervous Systems

  • Date Submitted: 11/06/2010 10:46 PM
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Chapter 7 Science Revision
Nerves and reflex actions:
Two main nervous systems, the central nervous system (CNS) and the peripheral nervous system (PNS)
The CNS is made up of the brain and spinal cord
The PNS is made up of the nerves which connect the CNS to other parts of the body
Nerves act as messengers inside the body carrying information from one part of the body to another
Nerves are made up of nerve cells (neurones)
Neurones or nerve cells carry electrical messages called nerve impulses

Motor neurones carry messages from the CNS to muscles or glands
Sensory neurones carry messages from the sense organs to the CNS
Receptors detect changes in the environment
Stimulus is anything that activates a receptor
Types of receptors: Mechanoreceptors- sensitive to touch stimulation, photoreceptors- sensitive to light stimulation in the eye, thermoreceptors- sensitive to changes in heat, chemoreceptors- sensitive to chemicals such as those found in food

Reflex actions are immediate reactions that happen very fast without warning from the brain. An impulse is sent from the pain receptor to the spinal cord and is acted upon immediately then a message is sent to the brain shortly after which registers pain.
When the electrical impulse gets to the end of the axon they release a chemical message called a neurotransmitter into the space between the next neurone, the dendrite of the next neurone then receives the chemical message
The myelin sheath electrically insulates the fibres from one another and increases the speed of the impulse
Groups of receptors form sensory organs
Effectors are muscles and glands where the messages carried by the nerves end up and are carried out and put into “effect”
The parts of the CNS that contain nerve fibres covered in myelin are called white matter
The main part of the brain is grey matter which is mainly made up of cell bodies
Habituation is becoming so used to a stimulus that you stop responding to it. Eg. When you...


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