structure of neurons, synaptic transmission

• motor neuron

  A) soma

  B) myelin sheath

  C) muscle fibres

  D) axon

  E) dendrites

  
• sensory neuron

  A) soma

  B) nucleus

  C) terminals

  D) myelin sheath

  E) axon

  F) dendrites

  
• relay neuron

  A) dendrites

  B) soma

  C) axon

  D) terminals

  
• sensory neuron

  connect external environment to internal nervous systems

  process info from all five senses

  take info from senses to brain

  attached to receptor cells
• relay neuron

  receive messages from sensory neurons and pass them onto other relays

  found only in brain or spinal cord

  middle man

  short axon but multipolar
• motor neuron

  receive messages from relay neurons and puts them onto organs and muscles

  CNS to PNS

  takes info from brain out to muscles

  makes movement happen

  attached to muscle fibres
• neuron activity

  sensory -> relay -> motor

  PNS -> CNS -> PNS

  senses -> brain and spinal cord -> muscles and organs
• how neurons work together

  1. sensory receptors detect heat
  2. sensory neurons transmit info to cns
  3. sensory neurons send message via relay neurons in the spine
  4. brain evaluates threat and determines action
  5. relay neurons transmit message about decision
  6. motor neurons send message to muscle fibres to move
• terminal button/pre-syn

  the end of the sending neuron from where neurotransmitter is released
• neurotransmitters

  chemical substance released by one neuron moving across a synapse to stimulate another
• post synpatic/dendrites

  the end of the receiving neuron, the area the neurotransmitter stimulates
• vesicles

  sac containing neurotransmitters and fuses with the end of the terminal button to release the neurotransmitter into the synapse
• synaptic cleft/gap

  microscopic gap that exists between 2 neurons. neurotransmitters travel across to continue the nerve impulse
• receptor site

  area on the surface of the post synpatic neuron that receives neurotransmitters
• synaptic transmission

  1. electrical signal travels down pre-syn
  2. electrical impulses causes NT to form in vesicles
  3. the electrical current causes vesicles to move and merge with pre-syn cell membrane
  4. NT released into synaptic fluid
  5. adjacent neuron takes up NT quickly, converted into electrical current with travels down post-syn
  6. post syn neuron reabsorbed by pre syn neuron or broken down into protein
• action potential

  a change in the electrical potential in an axon. associated with the passage of an impulse along the neuron
• excitatory

  depolarisation

  increases likelihood of post-syn firing

  causes action in post-syn

  message continues on to more neurons
• excitatory example

  noradrenaline. ‘on switch’, causes physiological changes by increasing post-syn action
• inhibitory

  hyperpolarisation

  decreases likelihood of post-syn firing

  causes inaction in post-syn firing

  message doesn’t continue on to other neurons

  calming
• inhibitory example

  GABA. ‘off switch’ for the NS, decreases neurons firing and makes receptor sites hard to stimulate
• summation

  the influences (excitatory/inhibitory) on the post-syn neuron are summed and net effect causes neuron to either fire or not