Page 91 - Headlines Histology2024_Neat

Neuroglia of the PNS

Neurolemmocytes (Schwann cells)

• They are the supporting cells of the PNS.
• The primary function of these cells is the formation of myelin sheath around

the myelinated axons.
• In non-myelinated axons, each neurolemmocytes ensheathes a variable number

of axons.
• Each axon is located inside an invagination within the surface of these cells.
Satellite cells

• They are flattened neurolemmocytes that surround the neuronal cell bodies
within the ganglia.

PERIPHERAL NERVOUS SYSTEM (PNS)

• The PNS consists of cranial and spinal nerves, nerve endings, and ganglia.
• The term nerve fiber refers to a single myelinated axon with its surrounding

schwan cells or to a single nonmyelinated axon.
• The term refers to a collection of axons (thousands), each invested by

neurolemmocytes and all surrounded by connective tissue.
Types of nerve fibers

Afferent (sensory) fibers
• They transmit nerve impulses from receptors in the body tissues and organs
to CNS. Afferent neurons are pseudounipolar and are located in the
craniospinal ganglia.
? Afferent somatic: are distributed to skin, skeletal muscle and bone.
? Afferent visceral: are distributed to visceral organs and glands.

Efferent (motor) fibers
• They transmit nerve impulses from the CNS to various tissues and organs.
• Efferent somatic (voluntary) innervates skin, skeletal muscle and joints.

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