The Human Nervous System
Key Words
The Nervous System - detects and reacts to stimuli.
Stimuli - changes in the envrionment.
Receptors - cells that detect stimuli.
Effectors - respond to nervous impules and bring about a change.
Central Nervous System (CNS) - received information from the receptors and then coordinates a response.
Neurones - transmit information very quickly to and from the brain.
Sensory neurones - carry information as electrical impulses from the receptors to the CNS.
Motor Neurones - carry electrical impulses from the CNS to the effectors.
Synapse - the connection between two neurones.
Reflexes - rapid, automatic responses to certain stimuli that don't involve the conscious part of the brain.
Reflex arc - the passage of information in a reflex from receptor to effector.
Relay neurones - connect sensory neurones to motor neurones.
The brain - part of the central nervous system contains:
- Cerebral cortex - responsible for things like consciousness, intelligence, memory and language.
- Medulla - controls unconscious activites like breating and heartbeat.
- Cerebellum - responsible for muscle coordination.
Magnetic resonance imaging (MRI) scan - produce  a very detailed picture of the brain's structures.
Sclera - tough, supporting wall of the eye.
Cornea - transparent outer layer found at the front of the eye. It refracts light into the eye.
Iris - contains muscles that allow it to control the diameter of the pupil and therefore how much light enters the eye.
Lens - focuses the light onto the retina.
Retina - contains receptor cells sensitive to light intensity and colour.
Ciliary muscles & Suspensory ligaments - controls the shape of the lens.
Optic nerve - carries impulses from the receptors on the retina to the brain.
Long-sighted - people are unable to focus on near objects.
Short-sighted - people are unable to focus on distant objects.
Contact lenses - think lenses that sit on the surface of the eye and are shaped to compensate for the fault in focusing.
Laser eye surgery - corrects bad eyesight by vaporising tissue with a laser which changes the shape of the cornea.
Replacement lens surgery - the lens is replaced with a clear plastic one to correct bad eyesight.
Also see Light, Hormonal coordination, Homeostasis
PRACTICAL
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Links for Learning
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Bitesize: The Human Nervous System.
Bitesize: Coordination and control, the Brain.
Learn Do Jo: Brain and Neuropsychology.
Moodle: The structure of the Brain.
The Student Room: The nervous system and the eye.
S Cool: The eye.
Bitesize: The eye.
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