Nervous System: Neurons, Glial Cells, and Nervous Tissue Organization

Comprehensive vocabulary flashcards covering neuron structure and classification, glial cell types and functions, myelination, and the tissue organization of the nervous system.

Neurons

Nerve cells that receive stimuli, conduct action potentials, and transmit signals to other neurons or effector organs.

Neuron cell body

The region of a neuron containing a single nucleus as the source of information for gene expression, surrounded by extensive rough endoplasmic reticulum, a Golgi apparatus, mitochondria, neurofilaments, and microtubules.

Dendrites

Short, highly branching cytoplasmic extensions tapered from their bases at the neuron cell body to their tips that receive information from other neurons or sensory receptors and transmit it toward the cell body.

Axon

A single long cell process extending from the neuron cell body with uniform diameter that conducts action potentials.

Axon hillock

The specialized area of the neuron cell body from which the axon leaves.

Collateral axons

Branches that emerge along the length of an axon.

Sensory neuron

A functional class of neuron that conducts action potentials toward the CNS from a specific receptor in the body.

Motor neuron

A functional class of neuron that conducts action potentials away from the CNS to an effector organ in the body.

Multipolar neurons

Neurons characterized structurally by having many dendrites and a single axon; they comprise most neurons within the CNS and nearly all motor neurons.

Bipolar neurons

Neurons with two processes—one dendrite and one axon—located in sensory organs such as the retina of the eye and the nasal cavity.

Pseudo-unipolar neurons

Neurons having a single process extending from the cell body that divides into two extensions functioning as a single axon; they transmit peripheral sensory information toward the CNS and constitute most sensory neurons.

Glial cells (Neuroglia)

The supportive cells of the CNS and PNS that do not conduct action potentials, enhance neuron function, maintain normal nervous tissue conditions, and retain the ability to divide.

Astrocytes

Major supporting glial cells of the CNS that regulate nearby neuron signaling, form scar tissue that can block damaged axon regeneration, and participate in forming the blood-brain barrier.

Blood-brain barrier

A permeability barrier formed between the blood and the CNS by astrocytes participating with blood vessel endothelium.

Ependymal cells

Glial cells lining the fluid-filled cavities (ventricles and canals) of the CNS; some produce cerebrospinal fluid, and ciliated types help circulate it.

Microglia

Glial cells that act as immune cells within the CNS, protecting the brain by removing bacteria and cellular debris.

Oligodendrocytes

Glial cells that provide the insulating myelin sheath surrounding axons in the central nervous system.

Schwann cells

Glial cells that form the insulating myelin sheath around axons located in the peripheral nervous system.

Satellite cells

PNS glial cells that cluster around neuron cell bodies to provide support, nutrition, and protection from heavy-metal poisons such as lead and mercury.

Myelin sheaths

Specialized layers of tightly wrapped cell membranes formed by oligodendrocytes or Schwann cells that wrap around axons and act as electrical insulators.

Nodes of Ranvier

Gaps in the myelin sheath occurring about every millimeter along an axon where ion movement across the cell membrane can take place.

Unmyelinated axons

Axons that lack myelin sheaths and instead rest in indentations of oligodendrocytes in the CNS or Schwann cells in the PNS.

Gray matter

Nervous tissue consisting of groups of neuron cell bodies and their dendrites with very little myelin.

Cortex

Gray matter located on the surface of the brain in the central nervous system.

Nuclei

Clusters of gray matter located deeper within the brain in the central nervous system.

Ganglion

A cluster of neuron cell bodies located in the peripheral nervous system (PNS).

White matter

Nervous tissue consisting of bundles of parallel axons with whitish myelin sheaths.

Nerve tracts

Conduction pathways formed by white matter in the CNS that propagate action potentials from one area of the CNS to another.

Nerves

Structures of the PNS consisting of bundles of axons and associated connective tissue forming white matter.