Nervous System Overview – Lecture Vocabulary

A comprehensive set of vocabulary flashcards covering divisions, cells, structures, and electrophysiology of the nervous system for exam preparation.

Central Nervous System (CNS)

Brain and spinal cord; integrates sensory information and coordinates motor output.

Peripheral Nervous System (PNS)

All neural tissue outside the CNS; links CNS to the rest of the body.

Receptor

Structure that detects stimuli and sends afferent (sensory) signals to the CNS.

Effector

Muscle, gland, or adipose tissue that receives efferent (motor) commands from the CNS.

Afferent Division

PNS pathway carrying sensory information from receptors to the CNS.

Efferent Division

PNS pathway carrying motor commands from the CNS to effectors.

Somatic Nervous System (SNS)

Efferent subdivision controlling skeletal muscles; includes voluntary movement and reflexes.

Autonomic Nervous System (ANS)

Efferent subdivision regulating smooth muscle, cardiac muscle, and glands.

Sympathetic Division

ANS branch mediating fight-or-flight responses; associated with adrenaline (epinephrine).

Parasympathetic Division

ANS branch mediating rest-and-digest functions; primarily uses acetylcholine and some norepinephrine.

Enteric Nervous System (ENS)

Neural network within the digestive tract capable of independent function but modulated by ANS.

Neuron

Basic functional unit of the nervous system that conducts electrical (action potentials) and chemical (neurotransmitters) signals.

Neuroglia (Glial Cells)

Supporting cells that protect, nourish, and insulate neurons.

Choroid Plexus

Specialized brain region where cerebrospinal fluid (CSF) is produced.

Cerebrospinal Fluid (CSF)

Fluid cushioning the brain and spinal cord; produced by ependymal cells in the choroid plexus.

Dendrite

Branched neuron process that receives chemical signals and converts them to electrical impulses.

Axon

Long neuron process that propagates action potentials away from the soma toward axon terminals.

Axon Hillock

Cone-shaped region of the soma where the all-or-none action potential is initiated.

Initial Segment

First axonal segment where threshold depolarization triggers an action potential.

Telodendria

Fine distal branches of an axon ending in axon terminals.

Axon Terminal

Synaptic ending that releases neurotransmitters into a synapse.

Myelin Sheath

Insulating membrane around axons that speeds action-potential conduction; destroyed in multiple sclerosis.

Multiple Sclerosis (MS)

Autoimmune disorder that degrades myelin in the CNS, impairing neural transmission.

Multipolar Neuron

Neuron type with many dendrites and one axon; common for motor control of skeletal muscle.

Anaxonic Neuron

Neuron with indistinguishable axon; found in brain and special sense organs (e.g., retina, olfactory bulb).

Bipolar Neuron

Neuron with one dendrite and one axon; typical in sensory organs like the eye and ear.

Unipolar Neuron

Neuron with a single process that splits into peripheral and central branches; major sensory neuron of the PNS.

Nociceptor

Pain receptor detecting tissue damage.

Exteroceptor

Receptor on body surface sensing touch, temperature, and pain.

Interoceptor

Receptor monitoring internal organs, blood pressure, pH, and oxygen levels.

Proprioceptor

Receptor in muscles and joints that monitors body position and movement.

Motor Neuron

Neuron that carries commands from the CNS to muscles and glands.

Autonomic Ganglion

Cluster of neuron cell bodies acting as relay station between pre- and postganglionic fibers.

Preganglionic Fiber

ANS axon extending from CNS to an autonomic ganglion; releases acetylcholine.

Postganglionic Fiber

ANS axon extending from ganglion to effector; releases ACh or norepinephrine depending on division.

Ependymal Cell

CNS glial cell that lines ventricles and produces CSF.

Astrocyte

Star-shaped CNS glial cell that maintains blood-brain barrier and provides structural support.

Microglia

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

Oligodendrocyte

CNS glial cell that forms myelin sheaths around multiple axons.

Satellite Cell

PNS glial cell that surrounds neuron cell bodies in ganglia, regulating environment.

Schwann Cell

PNS glial cell that myelinates a single axon segment.

Membrane Potential

Electrical voltage difference across a cell membrane due to ion distribution.

Resting Membrane Potential

Stable −70 mV potential in neurons maintained by the Na⁺/K⁺ pump (3 Na⁺ out, 2 K⁺ in).

Action Potential

All-or-none electrical impulse that propagates along an axon when threshold is reached.

All-or-None Principle

Once threshold is reached at the axon hillock, an action potential of fixed amplitude is generated.

Chemically Gated Ion Channel

Membrane channel that opens when a specific ligand (neurotransmitter) binds; common in synapses.

Voltage-Gated Ion Channel

Channel that opens or closes in response to changes in membrane potential; essential for action potentials.

Mechanically Gated Ion Channel

Channel that opens in response to physical deformation (stretch, pressure, vibration), e.g., inner ear receptors.

Depolarization

Upward shift in membrane potential toward zero during an action potential.

Repolarization

Return of membrane potential to resting level after depolarization.

Hyperpolarization

Membrane potential becomes more negative than resting level, often following an action potential.

Na⁺/K⁺ Pump

Active transporter maintaining ion gradients by moving 3 Na⁺ out and 2 K⁺ into the neuron using ATP.