1.3 The Neuron and Neural Firing

Neuron

nerve cell; the basic building block of the nervous system

Send messages all over your body to allow you to do everything from breathing to talking, eating, walking, and thinking

Glial cells

support, nourish, and protect neurons; they may also play a role in learning, thinking, and memory

Soma

Keeps neuron alive - responsible for maintaining the life of the cell

Dendrites

primarily the surfaces of the dendrites that receive chemical messages from other neurons

Axon

transmit an electro-chemical signal to other neurons

Myelin Sheath

series of fatty cells which have wrapped around an axon many times - makes the message go

faster

Multiple Sclerosis

immune system attacks the myelin sheath - loss of myelin sheath forms scar tissue called sclerosis. These areas are also called plaques or lesions. When the nerves are damaged in this way, they can’t conduct electrical impulses normally to and from the brain.

Axon Terminal/Terminal Button/Axon Ending/Axon Foot/Synaptic Knob

at the very end of the axon, it is there that the electro-chemical signal that has travelled the length of the axon is converted into a chemical message that travels to the next neuron - releases the neurotransmitters that relay signals across a synapse

Synapse

 space where the chemical messengers (neurotransmitters) travel from one neuron to another

Myasthenia gravis (MG)

antibodies destroy the communication between nerves and muscle, resulting in weakness of the skeletal muscles

The Electrochemical Process

movement of the action potential down the length of the axon is an electrical event, and the movement of the neurotransmitter across the synaptic space represents the chemical portion of the process

Resting Membrane Potential

neuron at rest is more negative inside the cell membrane relative to outside the membrane

Threshold

minimum amount of stimulus required for an action potential

Depolarization

rapid rise in potential moving the energy levels up closer to 0

All-or-nothing Principle

nerve cells either fire at full strength or do not

Action Potential

The brief change in potential. This neural impulse travels down the length of the axon to the axon terminals. (burst of energy)

All or None response

neuron’s reaction of either firing with full strength or not firing. (Like shooting a gun) The more intense a stimulus, the more frequent a neuron fires.

Repolarization

falling of energy with the loss of positive potassium ions

Refractory Period

follows the polarization changes during which the neuron is resistant to a retriggering of an action potential