neurons n dat

• label the myelinated motor neuron

  label

  A) dentrite

  B) cell body

  C) axon

  D) myelin sheath

  E) node of ranvier

  F) axon terminal

  G) schwann cells

  
• what is the cell body of a neuron?


  contains all the organelles of an animal cell, proteins and neurotransmitters are also made there
• what do dentrites do?


  carry action potential to surrounding cells
• what is an axon?


  conductive, long fibre that carries the nervous impulse along the motor neurone
• what are schwann cells?


  wrap around the axon to form the myelin sheath which is a lipid and doesnt let ions pass through it
• what are the nodes of ranvier?


  gaps between the myelin sheath
• how do we maintain resting potential?

  1. there are more positive ions in the outside of the cell compared to the inside so the inside is more negative
  2. resting potential is maintained by the sodium-potassium pump involving active transport and ATP
  3. K+ ions move in and Na+ ions move out
  4. this created an electrochemical gradient and results in k+ diffusing out an Na+ diffusing in
  5. the membrane is more permeable to K+
• what is action potential?


  when neurons voltage increases beyond a set point from the resting potential which generates a nervous impulse
• when is the neurons more permeable to Na+


  when theres an increase in voltage or depolarisation
• what is the process of depolarisation , repolarisation and hyperpolarisation?

  DEPOLARISATION:

  • the voltage dependant sodium gates open and Na+ moves in
  • K+ ions move out

  REPOLARISATION:

  • k+ channel opens and its now more positive outside than inside

  HYPERPOLARISATION

  • below -70 mv
• What does a bigger stimuli do to the frequency of action potential ?

  increases the frequency so organisms only respond to large enough stimuli
• what are three reasons a refractory period is important?

  1. ensures discrete impulses
  2. ensures action potential travels in one direction
  3. limits the number of impulse transmission to prevent over reaction
• what are three factors affecting the speed of an action potential?

  1. myelanated and saltatory conduction
  2. axon diameter
  3. temperature
• how does saltatory conduction allow fast transmission?

  because of the nodes of ranvier, the action potential has to jump from node to node so action potential wont have to be generated the entire length and only at the nodes
• how does axon diameter help with the speed of transmission?


  if its wider , then there is less leakage of ions so action potential travels faster
• how does temperature increase speed of transmission?


  1. ions diffuse faster
  2. enzymes involved in respiration work faster so more ATP for active transport in the sodium-potassium pump