Structure of a Typical Neuron

^ Cell body (soma, perikaryon)

♦ Large, spherical, usually centrally located in the soma

♦ Highly euchromatic with a large, prominent nucleolus

♦ Well-developed cytoskeleton

■ Intermediate filaments (neurofilaments). 8-10nm in diameter

■ Microtubules. 18-20nm in diameter

♦ Abundant rough endoplasmic reticulum and polysomes (Nissl substance)

♦ Well-developed Golgi apparatus

♦ Numerous mitochondria ^ Dendrite(s)

• Usually multiple and highly branched at acute angles

• May possess spines to increase surface area for synaptic contact

• Collectively, form the majority of the receptive field of a neuron; conduct impulses toward the cell body

• Organelles

♦ Microtubules and neurofilaments

♦ Rough endoplasmic reticulum and polysomes

♦ Smooth endoplasmic reticulum

• Usually only one per neuron

• Generally of smaller caliber and longer than dendrites

• Branches at right angles, fewer branches than dendrites

• Organelles

♦ Microtubules and neurofilaments

♦ Lacks rough endoplasmic reticulum and polysomes

♦ Smooth endoplasmic reticulum

♦ Mitochondria

• Axon hillock. Region of the cell body where axon originates

♦ Devoid of rough endoplasmic reticulum

♦ Continuous with initial segment of the axon that is a highly electrically excitable zone for initiation of nervous impulse

• Usually ensheathed by supporting cells

• Transmits impulses away from the cell body to

♦ Effector structures. Muscle and glands

• Terminates in a swelling, the terminal bouton, which is the presy-naptic element of a synapse

Dendrites

Dendrites

Structure Multipolar Neuron

Multipolar neuron Pseudounipolar Bipolar neuron neuron figure 8.1. Types of neurons based on shape.

Multipolar neuron Pseudounipolar Bipolar neuron neuron figure 8.1. Types of neurons based on shape.

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