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Neuron Cell Structure
NEURON CELL STRUCTURE
Summary
Functional Categories
- Sensory Neurons
- Receive sensory information
- Interneurons
- Interpret and relay information
- Motor Neurons
- Command motor cells
Structural Categories (Based on number of processes extending from cell body)
- Multipolar – 3 or more processes
- Bipolar – 2 processes
- Pseudo-unipolar – 1 process that branches like a "T"
- Unipolar – 1 process
Cell body
- Command center of neuronal signaling
- Houses common eukaryotic organelles
Dendrites
- Receive signals
Axon
- Transmits signals
- Sometimes covered in myelin sheath (increases action potential conduction speed)
- Schwann cells in PNS and Oligodendrocytes in CNS
- Each piece is around 0.5 to 1.0mm in length
- Gaps between each piece are called Nodes of Ranvier
- Multiple sclerosis occurs due to immunologic attack on myelin, destroying it
Synapses
- Axodendritic – axon to dendrite
- Axosomatic – axon to cell body
Signaling Steps:
1) Signal travels to end of presynaptic axon
2) Fusion of vesicle containing neurotransmitters
3) Neurotransmitters diffuse across the synaptic cleft
4) Neurotransmitters bind to receptors on postsynaptic cell and induce a response
Resting Ionic Concentrations
- Sodium – 150mM outside the cell and 15mM inside
- Chloride – 120mM outside the cell and 10mM inside
- Potassium – 5mM outside the cell and 150mM inside
- Organic anions – 100mM inside the cell