Nervous System, Special Senses, and Eye Anatomy

Vocabulary practice flashcards covering nervous system anatomy, cranial and peripheral nerves, plexuses, dermatomes, eye tunics, extrinsic eye muscles, retinal histology, and the vestibular apparatus.

Cranial Nerve VII (Facial Nerve)

The cranial nerve responsible for transmitting taste sensations from the anterior two-thirds of the tongue.

Cranial Nerve IX (Glossopharyngeal Nerve)

The cranial nerve that innervates and conveys taste sensation from the posterior one-third of the tongue.

Precentral Gyrus

The primary motor brain structure whose damage on the right side prevents a stroke patient from moving their left arm.

Schwann Cells

Glial cells responsible for myelinating the axons of neurons in the peripheral nervous system (PNS).

Medulla

The region of the brainstem associated with the control of hiccups.

Axillary Nerve

A peripheral nerve of the brachial plexus that originates from the $C5$ and $C6$ spinal nerve roots.

Ulnar Nerve

A peripheral nerve of the brachial plexus arising from the $C8$ and $T1$ spinal nerve roots.

Ape Hand

A characteristic hand deformity, also known as the hand of benediction, resulting from injury to the median nerve.

Flexor Digitorum Profundus

A forearm muscle that receives dual motor innervation from both the median nerve and the ulnar nerve.

Median Nerve

An upper extremity nerve formed by the confluence of the lateral cord and medial cord, encompassing spinal levels $C5$ through $T1$.

Femoral Nerve

A major lumbar plexus nerve ($L2-L4$) that innervates the hip flexors and quadriceps, and carries sensation from the anteromedial thigh and medial leg.

Pectineus

A lower extremity muscle that receives dual innervation from both the femoral nerve and the obturator nerve.

Adductor Magnus

A massive medial thigh muscle with dual motor innervation supplied by the obturator nerve and the tibial nerve.

Sciatic Nerve

A large nerve of the sacral plexus that travels inferior to the piriformis and bifurcates at the popliteal fossa into the tibial and common fibular nerves.

Tibial Nerve

The medial division of the sciatic nerve that innervates posterior compartment leg muscles (including the gastrocnemius, soleus, and flexor digitorum longus) and conveys sensation from the calf and sole of the foot.

Common Fibular Nerve

The lateral branch of the sciatic nerve that innervates anterior and lateral leg muscles and transmits cutaneous sensation from the anterolateral leg and the dorsum of the foot.

Nociceptors

Sensory receptors that detect painful stimuli, such as the pain produced when stepping on a Lego.

Dermatome

A specific cutaneous area of skin innervated by the sensory fibers of a single spinal nerve root.

Shingles

A painful condition caused by the reactivation of the herpes zoster virus (chickenpox) that manifests as tingling, burning, and skin lesions distributed along a dermatomal pattern.

Migraine

A vascular headache associated with vessel dilation compressing sensory neurons, typically originating around the eyes and presenting with photophobia and visual auras.

Peripheral Neuropathy

A condition characterized by damage to specific peripheral nerves or nerve endings, producing sensory disturbances such as numbness, tingling, or burning sensations.

Carpal Tunnel Syndrome

A repetitive-motion peripheral neuropathy caused by compression or damage to the median nerve, leading to tingling and numbness in the hand.

Diabetic Neuropathy

A systemic peripheral neuropathy wherein chronically elevated blood glucose levels destroy nerve endings, typically causing loss of protective sensation in the feet first.

Conjunctiva

The thin epithelial membrane lining the surface of the eye.

Lacrimal Gland

An accessory structure located on the superolateral surface of the eye that produces salty tears to flush debris, reduce friction, and provide nutrients.

Conjunctivitis

A highly contagious bacterial or viral infection of the conjunctival epithelium, commonly known as pink eye.

Sty

An infected eyelash oil gland presenting as a small, tender bump that is managed with warm compresses and must not be popped.

Trochlear Nerve (Cranial Nerve IV)

The cranial nerve responsible for providing motor innervation to the superior oblique extrinsic eye muscle.

Abducens Nerve (Cranial Nerve VI)

The cranial nerve responsible for providing motor innervation to the lateral rectus extrinsic eye muscle.

Superior Oblique Muscle

An extrinsic eye muscle running deep to the superior rectus in an angled, seven-like trajectory that directs the eyeball inferolaterally.

Inferior Oblique Muscle

An extrinsic eye muscle with a scoop-like structure that pulls the eyeball superolaterally.

Aqueous Humor

A thin, watery fluid located in the anterior segment of the eye that is continually produced and replenished.

Vitreous Humor

A thick, gelatinous fluid located in the posterior segment of the eye that is permanent and not continuously synthesized.

Sclera

The tough, opaque fibrous coat that forms the white of the eye and constitutes the majority of the fibrous tunic.

Cornea

The transparent anterior portion of the fibrous tunic that is the first structure light hits, bending light into the pupil.

Scleral Venous Sinus

An ocular vascular structure that drains, recycles, and replenishes aqueous humor.

Choroid

The deeply pigmented, black posterior layer of the vascular tunic that absorbs light to prevent it from scattering.

Suspensory Ligaments

Fibrous bands connecting the ciliary body to the lens that allow changes in lens shape for focusing on near or distant objects.

Sphincter Pupillae

A smooth muscle of the iris innervated by parasympathetic fibers from cranial nerve III (oculomotor nerve) that constricts the pupil.

Dilator Pupillae

A smooth muscle of the iris controlled by sympathetic input that dilates the pupil in response to low light or stress.

Pupillary Light Reflex

The autonomic reflex in which pupils constrict in response to light, tested clinically to determine the presence of a brain injury.

Ganglion Cells

Neurons in the neural tunic of the retina whose axons converge and exit the posterior eyeball to form the optic nerve.

Rods

Retinal photoreceptors specialized for night vision and the perception of black, white, and shades of gray.

Cones

Retinal photoreceptors responsible for color vision that specifically detect red, blue, and green light.

Ora Serrata

The scalloped anterior border of the retina that marks the separation between the retina and the ciliary body.

Fovea Centralis

A specialized central depression within the macula lutea containing exclusively cones, providing maximum visual acuity and clarity.

Optic Disc

The ocular blind spot where the optic nerve exits the eyeball, completely lacking photoreceptors.

Anterior Semicircular Canal

A vestibular structure that detects rotational acceleration and deceleration during sagittal plane motions, such as somersaults.

Posterior Semicircular Canal

A semicircular canal that detects rotational acceleration during coronal plane motions, such as cartwheels.

Lateral Semicircular Canal

A semicircular canal specialized for detecting rotational movements around a vertical axis.