Fundamentals of the Nervous System & Nervous Tissue

A set of vocabulary flashcards covering basic terminology of the nervous system, including structural components, neuron classification, and physiological concepts.

Central Nervous System

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

Peripheral Nervous System

The division of the nervous system consisting of nerves and ganglia outside the brain and spinal cord.

Somatic

Relating to the body walls and limbs, particularly skeletal muscles and the external environment.

Visceral

Relating to the internal organs and involuntary functions of the body.

Neuron

The functional unit of the nervous system specialized for receiving, processing, and transmitting information via electrical and chemical signals.

Neuroglia

Non-neuronal cells in the nervous system that provide support, nourishment, and protection for neurons.

Dendrite

Branching extensions of the neuron that receive incoming signals from other neurons and conduct them toward the cell body.

Soma/Cell Body

The biosynthetic center of the neuron containing the nucleus and common organelles.

Axon Hillock

The cone-shaped area of the cell body where the axon originates and where action potentials are typically initiated.

Myelin

A fatty, insulating layer surrounding the axons of many neurons that increases the speed of impulse conduction.

Axon/Axon Proper

The long, singular extension of a neuron that conducts nerve impulses away from the cell body toward other cells.

Nissl Body

Large granular structures in the neuron cell body consisting of rough endoplasmic reticulum and free ribosomes for protein synthesis.

Axon Terminal

The distal end of an axon that branches out and forms junctions with other cells.

Node of Ranvier

Periodic gaps in the myelin sheath along an axon where the axonal membrane is exposed to the extracellular space.

Synaptic End Bulb

The expanded tip of an axon terminal that contains synaptic vesicles filled with neurotransmitters.

Afferent Neuron

A sensory neuron that carries electrical impulses from sensory receptors toward the central nervous system.

Efferent Neuron

A motor neuron that carries electrical impulses away from the central nervous system to effectors like muscles or glands.

Interneuron

Neurons located entirely within the central nervous system that integrate and process information between sensory and motor pathways.

Unipolar Neuron

A neuron with a single process extending from the cell body that branches into a central and peripheral axon.

Bipolar Neuron

A neuron with two processes extending from the cell body: one axon and one dendrite.

Multipolar Neuron

A neuron with many dendrites and a single axon extending from the cell body; the most common neuron type in the CNS.

Resting Membrane Potential

The electrical potential difference across the plasma membrane of a resting neuron, typically measured at approximately $-70\,mV$.

Threshold

The critical level of depolarization required to trigger an action potential, often around $-55\,mV$.

Depolarization

A change in membrane potential where the interior of the cell becomes less negative (more positive) relative to the outside.

Repolarization

The return of the membrane potential to its resting negative state following depolarization.

All-or-None Phenomenon

The principle that if a stimulus is strong enough to reach threshold, an action potential will occur at full strength; if not, no action potential occurs.

Absolute Refractory Period

The period after an action potential begins during which the neuron cannot generate a second action potential, regardless of stimulus strength.

Relative Refractory Period

The period following the absolute refractory period during which a second action potential can be triggered only by a stimulus stronger than normal.

Wave Propagation

The movement of an action potential along the length of an axon.

Saltatory Conduction

The rapid mode of impulse conduction in myelinated axons where the action potential "jumps" from one Node of Ranvier to the next.

Synapse

The specialized junction where a neuron communicates with another neuron or an effector cell.

Neurotransmitter

Chemical messengers released by neurons at a synapse to transmit signals to other cells.

Astrocyte

A star-shaped neuroglial cell in the CNS that supports neurons and helps form the blood-brain barrier.

Microglia

Small, phagocytic neuroglial cells in the CNS that act as the primary immune defense by removing debris and pathogens.

Ependymal Cell

Line the ventricles of the brain and the central canal of the spinal cord, assisting in the production and circulation of cerebrospinal fluid.

Oligodendrocyte

A type of neuroglial cell in the CNS that produces the myelin sheath for multiple axons.

Schwann Cell

A neuroglial cell in the PNS that forms the myelin sheath around a single segment of an axon.

Satellite Cell

Small neuroglial cells that surround and support neuron cell bodies within ganglia in the PNS.