B10 THE HUMAN NERVOUS SYSTEM

• internal environment

  is the conditions inside your body
• homeostasis

  the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function, in response to internal and external changes
• why is homeostasis important?

  to maintain optimal conditions for enzyme and all cell functions
• human body homeostasis includes...

  glucoregulation, thermoregulation, osmoregulation
• homeostasis involves...

  coordination and control, detecting changes and responding to them with automatic control systems
• the systems include...

  nervous responses (nervous system), chemical response (hormone system)
• all control systems include...

  receptors, coordination centres, effectors
• receptors are...


  cells that detect changes (stimuli) in your internal/external environment
• coordination centres...


  areas that receive and process information coming from the receptors
• examples of coordination centers

  brain, spinal cord, pancreas
• effectors are...


  muscles or glands that generate responses to the stimulus
• the human nervous is made up of the...

  CNS and PNS
• the CNS is...


  the central nervous system which consists of the brain and spinal cord
• the PNS is...


  the peripheral nervous system which consists of nerves that transmit electrical impulses
• what are neurones?


  special cells that electrical impulses pass along
• the sensory neurons...


  transmit impulses from receptors to the CNS
• the relay neurons...


  are connectors that transmit impulses from the sensory to motor neurons inside the CNS
• the motor neurons...


  transmit impulses from CNS to the effector
• nerve cell

  drawing

  A) dendrites

  B) axon

  C) myelin sheath

  
• types of neurons:

  1. sensory
  2. relay
  3. motor
• types of receptors:

  1. light receptors (eye)
  2. touch, pressure, pain, temperature
  3. stretch (muscle)
  4. sound receptors (ear)
• reflexes are...


  automatic and rapid actions and do not involve the conscious part of the brain
• what is the reflex arc?

  an electrical impulse passes from receptor {along a sensory neuron{to CNS{ relay neuron (usually spinal cord) { along a motor neurons { the impulse arrives at an effector
• the time between a stimulus and reflex action is...

  short because reflexes bypass conscious areas of the brain
• what are synapses?


  junctions which form physical gaps between neurons
• what chemicals are released when electrical impulses cross synapses?

  neurotransmitters
• how are new electrical impulses created?

  after an impulse arrives at a junction, neurotransmitters are released and move by diffusion across the synapse, binding to receptor sites on the next neuron