Foundations of the Nervous System – Core Vocabulary

Vocabulary flashcards covering anatomical terminology, organisation and histology of the nervous system, neuron physiology, and key cell types.

Anatomical Position

Standard body orientation: standing erect, facing observer, eyes forward, feet parallel and flat, arms at sides with palms forward.

Sagittal Plane

Imaginary plane dividing the body into left and right portions; midsagittal if exactly at the midline.

Frontal (Coronal) Plane

Plane that separates the body into anterior (front) and posterior (back) sections.

Transverse (Horizontal) Plane

Plane that divides the body into superior (upper) and inferior (lower) portions.

Oblique Plane

Any plane that cuts the body or organ at an angle other than 90°.

Central Nervous System (CNS)

Comprises the brain and spinal cord; processes sensory input and coordinates motor output.

Peripheral Nervous System (PNS)

All nervous tissue outside the CNS, including cranial nerves, spinal nerves, and ganglia.

Somatic Nervous System (SNS)

PNS subdivision providing voluntary motor control of skeletal muscle and conscious sensory input.

Autonomic Nervous System (ANS)

Involuntary PNS subdivision controlling smooth muscle, cardiac muscle, and glands; includes sympathetic and parasympathetic divisions.

Enteric Nervous System (ENS)

"Brain of the gut"; network within the GI tract that regulates digestion and can operate independently.

Afferent Component

Sensory pathways that carry information toward the CNS.

Efferent Component

Motor pathways that transmit commands from the CNS to effectors.

Sympathetic Division

ANS branch that supports exercise and emergency responses; "fight-or-flight" functions.

Parasympathetic Division

ANS branch that promotes "rest-and-digest" activities and conserves energy.

Neuron

Electrically excitable cell that transmits information via action potentials and neurotransmitters.

Cell Body (Soma)

Central part of a neuron containing the nucleus and most organelles.

Dendrite

Branching neuronal process that receives synaptic input.

Axon

Long neuronal projection that conducts action potentials away from the soma.

Myelin Sheath

Lipid-rich insulation around axons formed by oligodendrocytes (CNS) or Schwann cells (PNS).

Node of Ranvier

Gap between myelin segments where action potentials are regenerated during saltatory conduction.

Neuroglial Cell

Supportive cell of nervous tissue; outnumbers neurons and maintains homeostasis.

Astrocyte

Most abundant CNS glial cell; provides structural support, regulates ion balance, and modulates synapses.

Oligodendrocyte

CNS glial cell that produces myelin sheaths for multiple axons.

Microglia

Immune cells of the CNS responsible for phagocytosis and neuroinflammation.

Ependymal Cell

Glial cell lining brain ventricles and central canal; produces and circulates cerebrospinal fluid.

Schwann Cell

PNS glial cell that myelinates a single axon segment and aids nerve regeneration.

Satellite Cell

Glial cell that surrounds neuron cell bodies in PNS ganglia, regulating their microenvironment.

White Matter

Regions dominated by myelinated axons, giving a pale appearance.

Grey Matter

Regions containing neuron cell bodies, dendrites, unmyelinated axons, and glia.

Nucleus (CNS)

Cluster of neuron cell bodies located within the central nervous system.

Ganglion (PNS)

Collection of neuron cell bodies located outside the CNS.

Nerve

Bundle of axons in the PNS surrounded by connective tissue layers.

Tract

Bundle of axons within the CNS connecting specific regions.

Epineurium

Outermost connective tissue sheath surrounding an entire nerve.

Perineurium

Connective tissue that encloses a fascicle within a nerve.

Endoneurium

Delicate connective tissue surrounding individual axons.

Resting Membrane Potential

Electrical charge difference across a neuron’s membrane at rest (≈ −70 mV).

Graded Potential

Localized change in membrane potential whose magnitude varies with stimulus strength.

Action Potential

All-or-none rapid depolarization and repolarization that propagates along an axon.

Depolarization

Phase of an action potential when membrane potential becomes less negative due to Na⁺ influx.

Repolarization

Return of membrane potential toward resting level, largely via K⁺ efflux.

Hyperpolarization

Membrane potential becomes more negative than resting level, producing an undershoot.

Continuous Conduction

Slower propagation of action potentials along unmyelinated axons.

Saltatory Conduction

Rapid impulse transmission in myelinated axons where action potentials jump from node to node.

Synapse

Specialized junction where a neuron communicates with another cell via neurotransmitter or direct electrical coupling.

Neurotransmitter

Chemical messenger released from presynaptic neurons to influence postsynaptic cells.

Synaptic Plasticity

Ability of synapses to strengthen or weaken over time, crucial for learning and recovery.

Multipolar Neuron

Neuron with one axon and multiple dendrites; most common in CNS (e.g., pyramidal cells).

Bipolar Neuron

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

Unipolar (Pseudounipolar) Neuron

Sensory neuron with a single process that splits into peripheral and central branches; common in dorsal root ganglia.

Sensory (Afferent) Neuron

Neuron that conveys information from receptors to the CNS.

Motor (Efferent) Neuron

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

Interneuron

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

Pyramidal Cell

Large multipolar neuron of cerebral cortex and hippocampus involved in cognition and plasticity.