Neurons

1
Neurons

• Ted Miles

2
Neuron structure

• Composed of
• Dendrites- receive information via
  neurotransmitters, then produce graded
  potentials.
• Soma
• Axon Hillock- responsible for making the decision
  to fire an action potential.
• Axon-transmit action potentials to deliver
  information via neurotransmitters from the axon
  terminals.

3
Neuron conduction of Action Potential

• An action potential occurs when there is a
  reversal of the normal resting potential (goes
  from negative to positive). Also called
  depolarization.
• Depolarization occurs due to the opening of
  voltage gated Na channel allowing the influx of
  Na. Repolarization of the cell is due to
  Potassium efflux.
• If membrane potential is excited to the threshold
  level an action potential is propagated

4
Myelination of Neurons

• Produced by 2 types of cells
• Acts as an insulator between ECF and INF
• Schwann cells
• PNS
• Each axon is wrapped with many schwann cells
  leaving small gaps called nodes of Ranvier
• Oligodendricytes
• CNS
• One cell produces extension to many different
  axons

5
Myelination of Neurons

• Body has both myelinated and nonmyelinated fibers
• Myelination increases conduction velocity of
  fiber due to saltatory conduction of the action
  potential
• Action potential jumps from node of ranvier to
  the next without having to travel the entire
  length of the neuron

6
Terminal

• Once the Cell reaches threshold and action
  potential is sent down the axon
• Action potential reaches axon
• Calcium is released into the cell
• Synaptic vesicles release neurotransmitter into
  the synaptic cleft which diffuses to the
  receptors on the post-synaptic cell.

7
Terminal
8
Bibliography

• Widmaier, E.P., Raff, H., and Strang, K.T. 2006.
  Vanders Human Physiology, 10th edition. McGraw
  Hill.