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Cells in the nervous system
There are two categories of cells: nerve cells (neurons) and glial cells.
Neurons are excitable and carry out signaling in the nervous system.
Glial cells provide support for neurons
Oligodendrocytes myelinate neurons in CNS.
Schwann cells myelinate neurons in the PNS.
Astrocytes nourish and maintain the chemical environment for neurons.
Very closely associated with capillaries
They help form the blood-brain barrier
Microglia are involved in immune response and are mobilized after injury,
infection, or disease. They often provide a phagocytic function.
Insulation of Neurons
Schwann cells insulate neurons by wrapping themselves around neurons in the PNS.
Oligodendrocytes wrap processes around neurons in the CNS.
Cell member is a phospholipid bilayer
Mostly hydrophobic, keeps away extracellular fluids
Production of myelin protein is encoded by genes.
Defects in genes can reduce myelination of neurons.
Reduced myelination results in substantial functional consequences for the animal.
Shiverer mouse – scant myelination
Multiple sclerosis – immune system attacks myelin
A nerve cell (a neuron)
Dendrites receive vast numbers of excitatory or inhibitory inputs from other neurons via
These inputs are summed at the axon hillock, where action potentials are initiated. An action potential travels down the axon extremely rapidly via salutatory conduction.
Myelin serves to insulate the neuron from surrounding tissue and increase the
conduction velocity of the action potential.
Arrival of the action potential at the end of the axon results in a release of chemicals
(neurotransmitters) at a tiny gap between cells called a synapse.
Neurotransmitters interact with the membrane of the post-synaptic cell and result in
excitation or inhibition.
The dendritic tree receives inputs
The dendritic tree of a neuron is very complex.