Chapter 18 – Nervous System Cells

Vocabulary flashcards summarizing key terms, structures, cell types, functions, reflex pathways, tissue organization, and disorders related to nervous system cells in Chapter 18.

Nervous System

The organ system that detects internal and external stimuli, processes information, and coordinates body responses.

Central Nervous System (CNS)

Composed of the brain and spinal cord; the functional center that integrates and correlates information.

Peripheral Nervous System (PNS)

All cranial and spinal nerves; relays information between the CNS and the rest of the body.

Somatic Nervous System (SNS)

Voluntary motor division of the PNS that controls skeletal muscles.

Somatic Sensory Division

Afferent fibers that carry sensory information to the CNS from skin, muscles, and joints.

Somatic Motor Division

Efferent fibers that carry commands from the CNS to skeletal muscles.

Autonomic Nervous System (ANS)

Involuntary motor division that regulates visceral effectors like cardiac muscle, smooth muscle, and glands.

Sympathetic Nervous System

ANS subdivision that mediates 'fight-or-flight' responses.

Parasympathetic Nervous System

ANS subdivision that supports 'rest-and-repair' (normal resting) activities.

Sensory (afferent) Function

Detection of stimuli and transmission of that information to the brain and spinal cord.

Integrative Function

Processing and decision-making function of the nervous system that analyzes sensory input.

Motor (efferent) Function

Transmission of commands from the CNS to muscles or glands to elicit a response.

Neuroglia (glial cells)

Supportive cells of nervous tissue that nourish, protect, and insulate neurons; do not conduct impulses.

Astrocytes

Star-shaped CNS glia that transfer nutrients, form the blood-brain barrier, and support neurons.

Blood-Brain Barrier (BBB)

Selective barrier created by astrocytes that restricts movement of substances from blood to brain tissue.

Microglia

Small CNS glia acting as resident macrophages that perform phagocytosis of debris and pathogens.

Ependymal Cells

Ciliated epithelial glia lining CNS cavities that produce and circulate cerebrospinal fluid.

Cerebrospinal Fluid (CSF)

Fluid produced by ependymal cells that cushions, nourishes, and removes waste from the CNS.

Oligodendrocytes

CNS glia that form the myelin sheath around multiple axons, speeding impulse conduction.

Multiple Sclerosis

Autoimmune CNS disease characterized by demyelination by which plaques replace myelin, impairing conduction.

Schwann Cells

PNS glia that form the myelin sheath around a single axon and aid in regeneration.

Neuron

Excitable cell that generates and conducts nerve impulses.

Soma (cell body)

Central part of a neuron containing the nucleus, organelles, and metabolic machinery.

Dendrite

Branching process that conducts impulses toward the neuron's cell body.

Axon

Single long process that conducts impulses away from the neuron's cell body.

Nodes of Ranvier

Gaps between adjacent Schwann cells (or myelin segments) where the axonal membrane is exposed.

Synaptic End Bulb

Expanded axon terminal that stores and releases neurotransmitters into the synaptic cleft.

Synaptic Cleft

Microscopic space between communicating neurons or between a neuron and effector.

Multipolar Neuron

Neuron with one axon and several dendrites; common motor neuron/interneuron type.

Bipolar Neuron

Neuron with one axon and one dendrite; found in retina, inner ear, and olfactory pathway.

Unipolar Neuron

Neuron with a single process that splits into central and peripheral branches; typical sensory neuron.

Sensory (afferent) Neuron

Neuron that conveys impulses toward the CNS from receptors.

Motor (efferent) Neuron

Neuron that carries impulses away from the CNS to effectors.

Interneuron

Neuron located within the CNS that integrates sensory and motor information.

Reflex

Fast, involuntary, unplanned response to a specific stimulus.

Reflex Arc

Neural pathway that mediates a reflex, typically consisting of five components.

Sensory Receptor

Structure that detects a stimulus and initiates a nerve impulse in a reflex arc.

Effector

Muscle or gland that responds to motor neuron signals in a reflex arc.

White Matter

Regions of the CNS composed primarily of myelinated axons.

Gray Matter

CNS tissue composed of neuronal cell bodies, dendrites, unmyelinated axons, and neuroglia.

Endoneurium

Delicate connective tissue layer surrounding each individual nerve fiber.

Perineurium

Connective tissue sheath that bundles groups of nerve fibers into fascicles.

Epineurium

Outermost fibrous connective tissue covering an entire peripheral nerve.

Neuroma

General term for a tumor arising from nerve tissue.

Glioma

Tumor derived from neuroglia; includes several specific types.

Astrocytoma

Tumor originating from astrocytes; severity varies with grade.

Glioblastoma Multiforme

Highly malignant, rapidly spreading astrocytic tumor invading white matter.

Ependymoma

Glial tumor arising from ependymal cells lining CNS ventricles.

Acoustic Neuroma

Benign Schwann-cell tumor on cranial nerve VIII affecting hearing and balance.

Neurofibromatosis

Genetic disorder characterized by multiple nerve sheath tumors and skin spots.

Three-Neuron Arc

Most common reflex arc containing sensory neuron, interneuron, and motor neuron.

Two-Neuron Arc

Simplest reflex arc containing only a sensory and a motor neuron.

Resting Membrane Potential

Electrical charge difference across the plasma membrane of a resting neuron maintained by ion gradients.