Chapter 12: The Nervous System, Neurons, and Glial Cells

Comprehensive practice flashcards reviewing the anatomical and functional divisions of the nervous system, neuronal anatomy, and central and peripheral neuroglial cells from Chapter 12.

Central Nervous System (CNS)

The anatomical division of the nervous system consisting of the brain located within the cranial cavity and the spinal cord located within the vertebral canal.

Peripheral Nervous System (PNS)

The anatomical division encompassing all nervous tissue situated outside the brain and spinal cord, including cranial and spinal nerves.

Gray Matter

Regions within the central nervous system composed primarily of localized collections of neuron cell bodies and dendrites.

White Matter

Regions of nervous tissue dominated by myelinated axons, named for the whitish appearance of the lipid-rich myelin sheath.

Nucleus (Nervous System)

A discrete localized collection or cluster of neuron cell bodies located specifically within the central nervous system.

Tract

A bundle of axons or nerve fibers sharing a common origin and destination within the central nervous system, such as the optic tract.

Ganglion

A knotlike swelling or cluster of neuron cell bodies situated within the peripheral nervous system.

Nerve

A cordlike bundle of axons and associated connective tissues located in the peripheral nervous system, such as the optic nerve.

Sensation

The primary nervous system function of detecting internal or external environmental stimuli that register a change from homeostatic conditions.

Integration

The central processing function that combines incoming sensory stimuli with memories, learning, and emotional state to formulate an appropriate output.

Response (Motor Function)

The generation and delivery of motor commands to effector organs (such as skeletal, smooth, or cardiac muscle, or glands) following integration.

Somatic Nervous System (SNS)

The functional division of the nervous system responsible for conscious perception, voluntary motor commands targeting skeletal muscle, and somatic reflexes.

Autonomic Nervous System (ANS)

The functional division responsible for involuntary, subconscious regulation of cardiac muscle, smooth muscle, and glands to maintain homeostasis.

Sympathetic Division

A branch of the autonomic nervous system that prepares the body for physical exertion or emergency states, commonly termed the 'fight or flight' response.

Parasympathetic Division

A branch of the autonomic nervous system responsible for energy conservation and restorative functions, commonly termed the 'rest and digest' response.

Enteric Nervous System (ENS)

A specialized division of the peripheral nervous system embedded within the gastrointestinal tract that regulates digestive smooth muscle and secretions independently of the central nervous system.

Neuron

An excitable cell specialized to receive, generate, and propagate electrical impulses to communicate with target cells.

Soma (Cell Body)

The core metabolic center of a neuron that houses the nucleus and cytoplasmic organelles.

Dendrite

A highly branched cytoplasmic process of a neuron that receives incoming chemical or physical stimuli and carries signals toward the soma.

Axon

A single elongated process of a neuron that conducts outgoing nerve impulses away from the cell body toward target cells.

Axon Hillock

The cone-shaped transition zone connecting the soma to the axon where outgoing action potentials typically originate.

Axon Terminal

The branched distal ending of an axon terminating in synaptic end bulbs (knobs) that release neurotransmitters across synapses.

Synapse

The functional junction where an axon terminal communicates with a target cell through the release of chemical signaling molecules called neurotransmitters.

Neuroglia (Glial Cells)

Non-excitable supporting cells in the central and peripheral nervous systems that do not propagate impulses but physically and biochemically support neurons.

Astrocyte

A star-shaped neuroglial cell in the CNS that regulates extracellular ion and chemical balances, cleanses excess neurotransmitters, repairs damaged tissue, and forms the blood-brain barrier.

Blood-Brain Barrier (BBB)

A selective physiological barrier established by astrocyte foot processes and capillary endothelial tight junctions that limits the entry of bloodborne substances, drugs, and leukocytes into the CNS.

Oligodendrocyte

A central nervous system glial cell with multiple cellular extensions that simultaneously insulates multiple axon segments with myelin.

Microglia

Small, phagocytic neuroglial cells of the CNS derived from macrophage lineages that ingest cellular debris, necrotic tissue, and pathogens during injury or stroke.

Ependymal Cell

An epithelial-like glial cell of the CNS that lines the brain ventricles and central canal, possessing apical cilia to circulate cerebrospinal fluid and participating in fluid filtration at choroid plexuses.

Choroid Plexus

A specialized vascular structure located within brain ventricles where ependymal cells filter blood plasma to produce cerebrospinal fluid containing oxygen, glucose, vitamins, and ions.

Satellite Cell

A glial cell of the peripheral nervous system that surrounds and electrically insulates neuron cell bodies within ganglia and regulates localized nutrient-waste exchange.

Schwann Cell (Neurolemmocyte)

A peripheral nervous system glial cell that wraps around a single axon segment to produce a segment of the myelin sheath and neurilemma, speeding electrical propagation.

Myelin Sheath

A multilayered, lipid-rich insulating sheath composed of plasma membrane phospholipids that wraps around axons to accelerate action potential conduction.

Node of Ranvier

Unmyelinated gaps along an axon between adjacent Schwann cells or oligodendrocyte myelin segments that facilitate rapid nerve impulse transmission.

Neurilemma

The outer nucleated cytoplasmic layer of a Schwann cell wrapping the outermost layer of the myelin sheath along peripheral axons.