Nervous System Cells

Central Nervous System (CNS)

Central Nervous System (CNS)

The brain and spinal cord.

Peripheral Nervous System (PNS)

The nerves in the outer regions, including spinal and cranial nerves.

Afferent Nerves

Sensory nerves that collect information from the periphery and send it to the CNS.

Efferent Nerves

Motor nerves that send information from the CNS to the periphery.

Somatic Nervous System

The part of the PNS that carries information to and from voluntary skeletal muscles.

Autonomic Nervous System

The part of the PNS that controls involuntary functions and sends responses to visceral effectors such as muscles and glands.

Sympathetic Nervous System

Prepares the body for threats and sends out appropriate responses, such as increasing breathing rate.

Parasympathetic Nervous System

The rest and repair system that keeps the body in balance.

Neurons

Excitable cells that initiate impulses in the nervous system.

Dendrites

Receive information from sensory receptors or other nerves and send it to the cell body.

Axon

Nerve fiber/process that takes information away from the cell body.

Synaptic Knob

The far end of a neuron that communicates with glands, muscles, or other nerves.

Nodes of Ranvier

Gaps in the myelin sheath where the axon is exposed, allowing for faster transmission of action potentials.

Axonal Transport

The process by which mitochondria and vesicles with neurotransmitters travel through the cell from the cell body to the end of the axon.

Input Zone

The part of the neuron that receives input, including dendrites and the cell body.

Summation Zone

The part of the neuron where inputs are combined, generating an impulse, including the axon hillock.

Conduction Zone

The part of the neuron where the impulse conducts along the axon away from the cell body.

Output Zone

The part of the neuron where neurotransmitters are released into a synapse to communicate, including telodendria and synaptic knobs of the axon.

Glia Cells

Support cells of the nervous system that promote the efficiency of neurons.

Microglia

Small, stationary glia cells that undergo phagocytosis to engulf and destroy microorganisms and cellular debris during inflammation.

Ependymal Cells

Thin sheets of epithelial cells that line fluid-filled cavities in the CNS and produce cerebrospinal fluid (CSF).

Oligodendrocytes

Glia cells specific to the CNS that hold nerve fibers together and produce myelin sheaths.

Astrocytes

The largest and most numerous glia cells that transport nutrients from blood to neurons, help restore ion gradients in extracellular fluid, and form the blood-brain barrier.

Schwann Cells

Glia cells specific to the PNS that wrap around nerves, forming a myelin sheath around peripheral nerve fibers.

Nodes of Ranvier

Gaps in the myelin sheath along the axon, allowing for faster conduction of impulses.

Nerves

Bundles of nerve fibers/axons in the PNS.

Tracts

Bundles of nerve fibers/axons in the CNS.

Gray Matter

Collections of cell bodies and unmyelinated fibers.

Motor Nerves

Nerves that contain motor neurons.

Sensory Nerves

Nerves that contain sensory neurons.

Mixed Nerves

Nerves that contain both sensory and motor neurons.

Endoneurium

The fibrous connective tissue inner covering that wraps each axon/nerve fiber.

Perineurium

The connective tissue middle covering that holds together a group of axons/nerve fibers forming a fascicle.

Epineurium

The outer covering that groups all of the fascicles together, made of fibrous connective tissue.

Repair of Nerve Fibers

The process of repairing damaged nerves, which can only occur if the cell body and neurilemma are intact and scarring has not occurred.