Introduction to the Nervous System: Anatomy, Glial Cells, and Neurons

Vocabulary practice flashcards covering anatomical divisions, functional pathways, neuroglia, neuron structures, classifications, and the sodium-potassium pump.

Central Nervous System (CNS)

The anatomical division of the nervous system consisting exclusively of the brain and the spinal cord.

Peripheral Nervous System (PNS)

The anatomical division of the nervous system composed of nerves that have exited or entered the brain and spinal cord, specifically cranial nerves and spinal nerves.

Afferent Pathway

A sensory pathway that carries sensory information from the peripheral nervous system into the central nervous system.

Efferent Pathway

A motor pathway that transmits motor commands and information exiting the central nervous system toward peripheral effectors.

Somatic

Pertaining to non-internal structures of the body, such as the skin, joints, and skeletal muscles.

Visceral

Pertaining to internal organs, such as the heart, lungs, stomach, intestines, and pancreas.

Somatic Nervous System

The somatic efferent pathway that sends motor commands from the central nervous system to control skeletal muscle.

Autonomic Nervous System

The visceral efferent pathway that carries motor commands from the central nervous system to regulate cardiac muscle, smooth muscle, and glands.

Schwann Cells

Glial support cells located exclusively in the peripheral nervous system that produce myelin to insulate axons and form cords to assist in repairing damaged neurons.

Oligodendrocytes

Support cells in the central nervous system responsible for myelinating axons to increase the conduction speed of electrical impulses; their destruction is associated with multiple sclerosis (MS).

Microglia

Small, phagocytic support cells within the central nervous system that migrate to clean up cellular debris, waste, and toxins following injury or stroke.

Ependymal Cells

Glial cells in the central nervous system that work alongside capillaries to assist in producing cerebrospinal fluid (CSF) to fill the hollow ventricles of the brain.

Astrocytes

Star-shaped support cells that maintain the blood-brain barrier and regulate the chemical composition of the fluid surrounding central nervous system neurons.

Blood-Brain Barrier

A protective barrier maintained by astrocytes wrapping around capillaries and neurons that prevents many substances, including certain cancer chemotherapy drugs, from entering the brain.

Dendrites

Branching extensions of a neuron that act as signal-receiving structures, accounting for roughly $90\%$ of all received signals.

Perikaryon

The cell body of a neuron, defined as the cytoplasmic region surrounding the nucleus.

Axon Hillock

The funnel-shaped junction connecting the cell body to the axon, functionally critical as the site where electrical impulses and action potentials originate.

Telodendria

The fine branching extensions located at the distal end of an axon that allow a single neuron to form multiple terminals and communicate with multiple target cells.

Nodes

The gaps between myelin-producing Schwann cells along an axon where there is no myelin and where action potentials occur.

Internodes

The myelinated segments of an axon located between adjacent nodes that allow electrical impulses to leap across them rapidly.

Synapse

The functional site of communication between a presynaptic cell sending a signal and a postsynaptic cell receiving the signal.

Unipolar Neurons

Structural neurons having a single process emerging from the cell body that divides into a fused dendrite and axon; these are large cells that carry sensory information from the PNS to the CNS.

Bipolar Neurons

Small sensory neurons possessing two distinct processes extending from the cell body (one dendrite and one axon), found exclusively in special sensory organs for vision, smell, and hearing.

Multipolar Neurons

Neurons having two or more dendrites and a single axon; this is the structural class characteristic of motor neurons controlling skeletal muscle.

Interneurons (Association Neurons)

The approximately $20\,\text{billion}$ processing neurons located mostly within the brain and spinal cord that integrate sensory information and coordinate motor responses between sensory and motor neurons.

Sodium-Potassium Pump

A membrane transport mechanism that hydrolyzes ATP to move $3$ sodium ($Na^+$) ions out of the cell and $2$ potassium ($K^+$) ions into the cell, thereby maintaining high intracellular potassium and high extracellular sodium gradients.