Nervous System Anatomy and Physiology

Vocabulary practice flashcards covering peripheral and central nervous system structures, meninges, cerebrospinal fluid, cranial nerves, spinal nerves, motor and sensory pathways, and reflex arcs.

Nerve

A bundle of axons in the PNS.

Tract

A bundle of axons in the CNS.

Endoneurium

Connective tissue layer that surrounds an individual nerve fiber.

Perineurium

Connective tissue layer that surrounds a fascicle, or bundle of nerve fibers.

Epineurium

Connective tissue layer that surrounds the entire nerve.

Decussation

Crossing to the opposite side.

Contralateral

Opposite side.

Ipsilateral

Same side.

Meninges

Three protective membranes around the brain and spinal cord, ordered from outer to inner as dura mater, arachnoid mater, and pia mater.

Dura mater

Tough outer protective layer of the meninges.

Arachnoid mater

The middle, web-like meningeal layer.

Pia mater

The delicate inner meningeal layer attached to the CNS surface.

Subarachnoid space

The space located between the arachnoid and pia mater where CSF is found around the CNS.

Choroid plexuses

Structures located in the brain ventricles that produce most CSF.

Cerebrospinal fluid (CSF)

Fluid that cushions and protects the CNS and helps transport nutrients and waste.

Meningitis

Inflammation of the meninges.

Hydrocephalus

Excess CSF buildup in the brain's ventricles.

CN I (Olfactory)

A sensory cranial nerve responsible for smell.

CN II (Optic)

A sensory cranial nerve responsible for vision.

CN III (Oculomotor)

A motor cranial nerve responsible for most eye movements, eyelid elevation, and pupil constriction.

CN IV (Trochlear)

A motor cranial nerve that controls the superior oblique eye muscle.

CN V (Trigeminal)

A mixed cranial nerve responsible for facial sensation and chewing.

CN VI (Abducens)

A motor cranial nerve that moves the eye laterally.

CN VII (Facial)

A mixed cranial nerve responsible for facial expression, taste from the anterior two-thirds of the tongue, tears, and saliva.

CN VIII (Vestibulocochlear)

A sensory cranial nerve responsible for hearing and balance.

CN IX (Glossopharyngeal)

A mixed cranial nerve responsible for taste from the posterior one-third of the tongue, swallowing, and salivation.

CN X (Vagus)

A mixed cranial nerve responsible for swallowing, voice, and parasympathetic control of thoracic and abdominal organs.

CN XI (Accessory)

A motor cranial nerve responsible for head turning and shoulder shrugging.

CN XII (Hypoglossal)

A motor cranial nerve responsible for tongue movement.

Sensory-only cranial nerves

CN I, II, and VIII.

Motor-only cranial nerves

CN III, IV, VI, XI, and XII.

Mixed cranial nerves

CN V, VII, IX, and X.

Dorsal root

Carries sensory information into the spinal cord.

Dorsal root ganglion

Contains sensory neuron cell bodies.

Ventral root

Carries motor information out of the spinal cord.

Ventral horn

Contains somatic motor neuron cell bodies.

Spinal nerve

A mixed nerve containing sensory and motor axons, existing in 31 pairs: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal.

Dorsal ramus

Branch of a spinal nerve that supplies the skin and muscles of the back.

Ventral ramus

Branch of a spinal nerve that supplies limbs and the front and sides of the trunk, and carries fibers involved in autonomic pathways.

Cervical plexus

Supplies the neck and related regions, giving rise to the phrenic nerve which supplies the diaphragm.

Phrenic nerve

Mainly arises from C3–C5 and stimulates the diaphragm for breathing.

Brachial plexus

Nerve plexus that supplies the upper limb.

Lumbar plexus

Nerve plexus that mainly supplies pelvic regions and anterior thigh/leg pathways.

Sacral plexus

Nerve plexus that mainly supplies the buttock and posterior/distal lower-limb pathways.

First-order sensory neuron

Carries information from a sensory receptor into the CNS.

Second-order sensory neuron

Relays sensory information toward the thalamus, with many pathways crossing sides.

Third-order sensory neuron

Carries information from the thalamus to the primary somatosensory cortex.

Upper motor neuron

A neuron carrying a motor command from the brain toward the brainstem or spinal cord.

Lower motor neuron

A neuron carrying a motor command from the CNS to skeletal muscle.

Preganglionic neuron

An autonomic neuron carrying a signal from the CNS to a ganglion.

Postganglionic neuron

An autonomic neuron carrying a signal from a ganglion to a target organ.

Five steps of a reflex

Receptor, sensory neuron, integration center, motor neuron, and effector.

Somatic reflex

A reflex that changes skeletal muscle activity.

Visceral reflex

An autonomic reflex that regulates organs, glands, cardiac muscle, or smooth muscle.

Withdrawal reflex

A reflex where painful heat activates sensory input to the spinal cord, initiating motor output to pull the body part away.

Baroreflex

An autonomic reflex that adjusts heart and blood vessel activity to help regulate blood pressure.

Afferent

Traveling toward the CNS; sensory.

Efferent

Traveling away from the CNS; motor.