Nervous Tissue & Nervous System Overview

Vocabulary flashcards covering major structures, cell types, functions, and terminology of nervous tissue and the nervous system, designed to aid exam preparation.

Nervous tissue

Specialized tissue composed of neurons and neuroglia that forms the organs of the nervous system.

Homeostasis

Stable internal balance maintained by body systems, chiefly the nervous and endocrine systems.

Nervous system

Fast-acting control system that uses nerve impulses to regulate body functions, perception, behavior, memory, and voluntary movement.

Endocrine system

Slower control system that uses hormones in the bloodstream to influence target cells and maintain homeostasis.

Neurology

Branch of medical science that studies the nervous system and its disorders.

Neurologist

Physician who diagnoses and treats diseases of the nervous system.

Central Nervous System (CNS)

Brain and spinal cord; processes sensory input, emotions, thoughts, memories, and initiates most motor signals.

Peripheral Nervous System (PNS)

All nervous tissue outside the CNS, including nerves, ganglia, sensory receptors, and enteric plexuses.

Brain

Organ within the skull containing ~85 billion neurons; major processing center for the CNS.

Spinal cord

Cylindrical CNS structure in the vertebral canal with ~100 million neurons; connects brain to body via spinal nerves.

Nerve

Bundle of hundreds to thousands of axons plus connective tissue and blood vessels in the PNS.

Sensory receptor

Specialized structure that detects internal or external stimuli (e.g., touch, light, odor).

Cranial nerves

Twelve pairs of nerves that emerge from the brain to serve head and neck regions (and some viscera).

Spinal nerves

Thirty-one pairs of nerves that emerge from the spinal cord to innervate specific body regions.

Sensory (Afferent) Division

PNS subdivision that conveys input from sensory receptors to the CNS.

Somatic senses

General sensations such as touch, temperature, pain, and proprioception.

Special senses

Smell, taste, vision, hearing, and balance.

Motor (Efferent) Division

PNS subdivision that carries output from the CNS to effectors (muscles or glands).

Somatic Nervous System (SNS)

Motor pathway that sends voluntary signals from the CNS to skeletal muscles.

Autonomic Nervous System (ANS)

Motor pathway that sends involuntary signals from the CNS to smooth muscle, cardiac muscle, and glands.

Sympathetic Nervous System

ANS branch producing “fight-or-flight” responses such as increased heart rate.

Parasympathetic Nervous System

ANS branch producing “rest-and-digest” responses such as slowed heart rate.

Enteric Nervous System (ENS)

Network of neurons in the GI tract that autonomously regulates gut muscle and gland activity.

Sensory function

Detection of internal or external stimuli and transmission to the CNS.

Integrative function

CNS analysis and decision-making regarding sensory information.

Motor function

CNS-initiated signals to effectors causing muscle contraction or gland secretion.

Neuron

Electrically excitable cell that generates and conducts nerve impulses.

Neuroglia (glial cells)

Supporting cells that nourish, protect, and maintain the environment of neurons; can divide.

Electrical excitability

Ability of neurons (and muscle cells) to respond to a stimulus by generating an action potential.

Stimulus

Any environmental change strong enough to initiate an action potential.

Action potential (nerve impulse)

Electrical signal that propagates along the membrane of a neuron or muscle fiber.

Cell body (soma)

Neuron region containing the nucleus and organelles; site of most metabolic activities.

Dendrite

Short, branched neuron process that receives signals and conveys them toward the cell body.

Axon

Single long neuron process that conducts impulses away from the cell body to other cells.

Axon hillock

Cone-shaped region where the axon joins the soma; typical site where impulses begin.

Axon terminal

Fine distal branches of an axon that form synapses with target cells.

Synapse

Functional junction where a neuron communicates with another neuron, muscle cell, or gland cell.

Synaptic vesicle

Membranous sac in synaptic end bulbs containing neurotransmitter molecules.

Neurotransmitter

Chemical messenger released at a synapse to transmit signals to a neighboring cell.

Ganglion (ganglia)

Cluster of neuron cell bodies located in the PNS.

Multipolar neuron

Neuron with many dendrites and one axon; most common type in CNS.

Bipolar neuron

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

Unipolar neuron

Neuron whose single process splits into two branches functioning as dendrite and axon; mainly sensory.

Sensory (afferent) neuron

Neuron that carries impulses toward the CNS; usually unipolar.

Motor (efferent) neuron

Neuron that carries impulses away from the CNS to effectors; typically multipolar.

Interneuron (association neuron)

Neuron located within the CNS that connects sensory and motor neurons; mostly multipolar.

Astrocyte

Star-shaped CNS glial cell that supports neurons and helps maintain chemical environment.

Oligodendrocyte

CNS glial cell that forms myelin sheaths around multiple axons.

Microglial cell

Small CNS glial cell that acts as a macrophage, removing debris and pathogens.

Ependymal cell

CNS glial cell lining ventricles and central canal; helps produce and circulate cerebrospinal fluid.

Schwann cell

PNS glial cell that forms a myelin sheath around a single axon segment.

Satellite cell

PNS glial cell that surrounds neuron cell bodies in ganglia, providing support and regulation.

Myelin sheath

Lipid-rich insulating layer around axons that increases the speed of nerve conduction.

Node of Ranvier

Gap between myelin sheaths where axonal membrane is exposed; facilitates rapid impulse conduction.

Multiple Sclerosis

Autoimmune disease that damages CNS myelin, slowing or blocking nerve impulses.

Tay-Sachs disease

Genetic disorder leading to accumulation of lipids in neurons and myelin destruction.

Nucleus (neural)

Cluster of neuron cell bodies located within the CNS.

Tract

Bundle of axons running within the CNS, connecting different regions.

Gray matter

CNS tissue containing neuron cell bodies, dendrites, unmyelinated axons, terminals, and glia; site of processing.

White matter

CNS tissue composed mainly of myelinated axons; specialized for rapid communication over distances.