Cells of Nervous System Neurons or nerve • cells –Receive stimuli and transmit action potentials –Organization ● •Cell body or soma ● •Dendrites: Input ● •Axons: Output
Structure and Function Typical Neuron has 4 Regions Cell Body • • Dendrites • Axon • PresynapticTerminals
Functional Classification of Neurons·Sensory (afferent) neurons·Carry impulses from the sensory receptors·Cutaneous sense organs·Proprioceptors – detect stretch or tension·Motor (efferent) neurons·Carry impulses from the central nervoussystem
Neuron AnatomyExtensions outsidethe cell bodyDendrites –conductimpulses towardthe cell bodyAxons –conductimpulses awayfrom the cell body (only 1!)
Dendrites of Motor Neurons•Short, tapering, anddiffusely branchedprocesses•They are thereceptive, or input,regions of theneuron•Electrical signals are conveyed as gradedpotentials (not action potentials)
Axons: Structure•Slender processes of uniform diameter arising from the hillock•Long axons are callednerve fibers•Usually there is only oneunbranched axon per neuron•Rare branches, if present, are called axoncollaterals•Axonal terminal – branched terminus of an axon
Myelin Sheath•Whitish, fatty (protein-lipid), segmented sheatharound most longaxons•It functions in:–Protection of the axon–Electrically insulating fibers from one another–Increasing the speed of nerve impulsetransmission
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