nervous system

• the nervous system detects ... and reacts to ...

  change, stimuli
• nervous system


  the network of nerve cells and fibres that transmits nerve impulses between parts of the body which allows humans to react to their surroundings.
• why do organisms need to respond to stimuli?

  in order to survive
• central nervous system (CNS)

  in vertebrates, this consists of the brain and spinal cord only. in mammals, the CNS is connected to the body by sensory and motor neurones
• the CNS coordinates the...

  response
• how does the CNS coordinate a response?

  it receives information from the receptors and then coordinates a response (decides what to do about it), which is carried out by effectors
• automatic control system


  stimulus > receptor > CNS > effector > response
• peripheral nervous system (PNS)

  the sensory and motor neurons that connect the CNS to the rest of the body
• nerve


  a bundle of neurones
• neurones


  individual cells in the nervous system that receive, integrate, and transmit information through electrical impulses.
• what are the three types of neurones? (in order)

  sensory > relay > motor
• sensory neurones


  the neurones that carry information as electrical impulses from the receptors to the CNS
• sensory neurone diagram

  
• relay neurones


  neurones that carry information from a sensory nerve cell to a motor nerve cell
• relay neurone diagram

  
• motor neurones


  the neurones that carry information as electrical impulses from the CNS to effectors
• motor neurone diagram

  
• dendrites


  branchlike parts of a neuron that are specialized to receive information
• axon


  a threadlike extension of a neuron that carries nerve impulses away from the cell body
• myelin sheath


  a layer of fatty tissue that covers the axon of some neurons and helps speed up neural impulses
• ... connect neurones


  synapse
• synapse


  a junction where information is transmitted from one neuron to the next
• synaptic cleft


  a gap into which neurotransmitters are released from the axon terminal
• presynaptic neurone


  neurone that conducts electrical impulses into the synaptic cleft
• neurotransmitters


  chemical messengers that cross the synaptic gaps between neurones
• postsynaptic neurone


  neurone which has receptor sites that the neurotransmitter binds to after diffusing across the synaptic cleft
• synapse diagram

  
• stimulus


  a change in an organism's surroundings that causes the organism to react
• receptors are cells that...

  detect stimuli
• receptors


  special structures that allow living organisms to sense the conditions of their internal or external environment
• what type of receptors are there?

  sight, hearing, smell, taste, touch
• where are sight receptors located?

  in the retina of the eyes
• what stimulates sight receptors?

  light
• where are the hearing receptors located?

  in the cochlea of the inner ear
• what stimulates hearing receptors?

  vibrations in sound waves
• where are smell receptors located?

  the naval cavity in the internal part of the nose
• what stimulates smell receptors?

  substances that give off chemical molecules (scent) that enter the nose
• where are taste receptors located?

  taste buds on the tongue
• what stimulates taste receptors?

  chemicals in food (or other substances) interacting with saliva
• where are touch receptors located?

  in the dermis and epidermis of the skin