The Nervous System

• The two parts of the nervous system are the Central Nervous System (made up of the brain and spine) and the Peripheral Nervous System.
• A neurone is a long cell that carries electrical signals.
• In between two neurones there is a synapse which carries the signal chemically to the next neurone where the electrical impulse continues.
• The receptor detects changes in our environment.
• An effector then responds in a suitable way.
• Sense organs contain special cells called receptor cells.
• Those special cells detect the stimuli.
• Sense organs and what stimuli they detect:

  Ears - sound

  Eyes - Light

  Skin - Temperature, pressure & pain

  Nose - chemicals in the air.

  Tongue - chemicals in your mouth ( food + drink)
• The effectors are the muscles and glands.
• A reflex action is a quick reaction that does not require a signal to the brain.
• The 3 features of a reflex action:

  -Rapid

  -Automatic

  -Protective
• The reason why reflex actions are much faster than a normal reaction is because a message does not have to be sent to the brain.
• The nerve pathway that follows a reflex action called a reflex arc.
• 7 Components of a reflex arc:

  Stimulus

  Receptor

  Sensory Neurone

  Relay Neurone

  Motor Neurone

  Effector

  Response

  (between the neurones there are synapses)
• A with drawl action is moving body part away from stimuli.
• The blinking reflex protects us from the environment. (dust in the air)
• The hole in the eye that allows light into the eye is called the pupil.
• The coloured part of the eye is called the iris.
• When we are in the presence of bright light the pupil will constrict to protect your eye.
• When we are in the presence of dim light our pupil will dilate to allow us to see.
• The coordinator in the body is the CNS (brain + spinal cord).