Neurons

• Motor neuron function (1)

  Sends a message from the CNS to the PNS
• specialised features of a motor neuron

  short dendrites, long axon, large cell body
• motor neuron function(2)

  carry action potentials away from the CNS, towards an effector
• sensory neuron function (1)

  sends messages about the environment from the PNS to the CNS
• sensory neuro function (2)

  carry action potentials away from a sense organ or receptor in the PNS to the CNS
• Relay neuron function (1)

  send messages quickly between sensory and motor neurons, involved in reflexes
• Relay neuron function (2)

  carry action potentials between neurons in the CNS
• sensory neurons special features

  long dendrites, short axon, small cell body
• relay neuron special features

  situated in the spinal chord and brain, many axons/dendrites
• how many neurons are in the brain and spinal chord

  •100 billion in the brain

  •1 million in the spinal chord
• what is an action potentials use?

  a way of sending electrical signals from one cell to the next
• What happens when a neuron is at rest?

  the inside of the neuron is more negatively charged compared to the outside
• what happens when a neuron is activated?

  the inside of the cell becomes positively charged for a short time
• what is an action potential?

  the electrical impulse that travels through the axon to the end of the neuron
• what is a reflex arc?

  the nerve pathway which makes a fast, automatic response possible