The Nervous System

• Nervous system


  Made up of neurons (nerve cells), which go to all parts of the body
• Sensory receptors


  • Detect different stimuli, e.g. light, sound, touch, temperature
• Sense organs are what detect stimuli from the environment e.g. nose, tongue, ears
• Receptors in the sense organs are connected to the CNS, which is made up of the brain and spinal chord
• The brain and spinal chord make sense of information sent by the nerves and co-ordinate a reaction
• The skin is a sense organ and its receptor cells are pressure and temperature, the stimulus being pressure and heat
• The tongues receptor cell is taste and the stimulus is from a chemical
• The nose receptor cells are smell and taste and their stimulus are chemicals
• Neurone - 1 nerve cell

  Nerve - A bundle of nerve cells
• Nerve cell diagram

  A) dendrite

  B) nucleus

  C) axon

  D) cytoplasm

  E) cell membrane

  F) nerve ending

  
• Nerve cells have branched dendrites to pick up impulses and transmit them from one nerve into the other
• The fatty sheath insulates the axon of the nerve cell to contain electrical impulses to protect them and allow faster transmission
• • Relay neurons connect the sensory and motor neuron at the CNS
  • Sensory receptors send impulses to the CNS
  • Motor neurons send the impulse to the muscle for them to relax or contract based on the decision of the CNS
• 3 main stages of a nervous response

  • Stimulus - Change in environment e.g. pressure on skin
  • Stimulus detection - Sensory receptors detect stimulus and transmit impulse along the axon
  • Response from effectors - Response signal transmitted along axon of motor neuron to motor end plate, then effectors e.g. muscles, glands
• Each nerve cell

  A) sensory neuron

  B) relay neuron

  C) motor neuton

  
• Synapase is the place where impulses are transmitted between two nerve cells, or between gland or muscle cells