Nervous system

• Sensory neurone transmits impulse to CNS

  Parallel transmission to brain for sensation/pain perception
• Nervous system

  Brain, spinal cord and nerves that coordinate and regulate body functions

  
• How CNS and PNS work together

  1. Receptor/sense organ detects stimulus and generates nerve impulses

  2. Sensory neurone transmits nerve impulses to relay neurone in CNS across a synapse

  3. Relay neurone transmits nerve impulses to motor neurone across another synapse

  4. Motor neurone transmits nerve impulses to effector (muscles/glands) to carry out response

  
• Voluntary actions


  Activities controlled consciously
• Involuntary actions

  Activities not controlled consciously
• Reflex action

  1. Receptor detects stimulus

  2. Sensory neurone transmits nerve impulses to relay neurone in spinal cord/brain

  3. Relay neurone transmits nerve impulses to motor neurone

  4. Motor neurone transmits nerve impulses to effector (muscles/glands) to carry out response

  
• Neurones

  • Nerve cells that transmit nerve impulses
  • Have cell body, nerve fibres, terminal nerve fibres

  
• Types of neurones

  • Sensory neurones
  • Relay neurones
  • Motor neurones

  
• Synapse


  Junction or connection between two neurones by chemical means through neurotransmitters
• Reflex arc

  Shortest pathway for nerve impulses from receptor to effector

  
• Reflex centers

  Spinal cord and brain
• Brain/cranial reflexes

  • Pupil reflex

  
• Spinal reflexes

  • Knee jerk
  • Touching a hot object
• Voluntary action


  • Picking up a hot pan
• Central nervous system consists of brain and spinal cord
• Peripheral nervous system consists of cranial and spinal nerves, as well as the sense organs
• neurones labelling

  
• Structure of a sensory neurone

  • Circular cell body

  • One long nerve fibre between receptor and cell body

  • One short nerve fibre between cell body and CNS

  
• Structure of a motor neurone

  • Irregular-shaped cell body

  • One long nerve fibre between cell body and effector

  
• cranial reflexes are controlled by the brain
• spinal reflexes are controlled by the spinal cord
• A reflex action is

  • an immediate response to a specific stimulus
  • without conscious control.
  • require sensory neurone
  • initiated at the receptors
  • involve motor neurone and effector muscles
  • involve the transmission of nerve impulses via electrical and chemical signals
• A reflex arc is the shortest pathway by which nerve impulses travel from the receptor to effector in a reflex action.
• cranial nerves:

  • sensory nerves transmit nerve impulses from receptors to brain
  • motor nerves transmit nerve impulses from brain to effectors
• spinal nerves:

  • sensory nerves transmit nerve impulses from receptors to spinal cord
  • motor nerves transmit nerve impulses from spinal cord to effectors
• sensory neurone transmits nerve impulses from the receptors to the central nervous system.
• motor neurone transmits nerve impulses away from the central nervous system to the effectors.
• relay neurone transmits nerve impulses within the central nervous system.
• voluntary action is

  • controlled by our will
  • does not require a stimulus
  • initiated at brain
  • does not require sensory neurone
  • slower response than reflex
• Compare and contrast between hormonal and nervous control

  Similarity:

  • both require stimulus
  • both initiate response differences
• Involuntary action is

  • not controlled by our will
  • may be quick or slow
  • does not require a stimulus
  • initiated at brain