Ear and Eye, Neuroanatomy of the Brain: Structures, Functions, and Pathways, Muscles & Structures

Ciliary Body

Vascular tunic; contains ciliary muscles and processes; controls lens shape

Suspensory Ligament

Connects ciliary body to lens; holds lens in place

Iris

Part of vascular tunic; controls pupil diameter (light regulation)

Retina

Neural tunic; contains photoreceptors (rods & cones)

Sclera

Fibrous tunic; outer protective layer ("white" of eye)

Choroid Coat

Vascular tunic; supplies blood to retina

Cornea

Transparent front part; refracts light into eye

Lens

Focuses light on retina; changes shape for near/far vision

Optic Nerve (CN II)

Transmits visual info to brain

Vitreous Humor

Gel-like fluid filling posterior segment

Aqueous Humor

Fluid in anterior and posterior chambers

Pupil

Central opening of iris; allows light in

Optic Disc

"Blind spot" — where optic nerve exits, no receptors

Tapetum Lucidum

Reflective layer in animals (night vision)

Fovea Centralis

Sharpest vision point; high cone density

Conjunctiva

Mucous membrane lining eyelids & sclera

Ciliary Process

Secretes aqueous humor

Ciliary Muscle

Alters lens shape for focus (accommodation)

Eyelid

Protects eye; lined with palpebral conjunctiva

Lacrimal Gland

Produces tears

Lacrimal Duct

Drains tears to nasal cavity

Anterior Chamber

Space between cornea and iris (aqueous humor)

Posterior Chamber

Between iris and lens (aqueous humor)

Posterior Segment

Behind lens; filled with vitreous humor

Superior Oblique

CN IV; Moves eye down & out

Inferior Oblique

CN III; Moves eye up & out

Lateral Rectus

CN VI; Moves eye out (abduction)

Medial Rectus

CN III; Moves eye in (adduction)

Inferior Rectus

CN III; Moves eye down & in

Superior Rectus

CN III; Moves eye up & in

Auricle (Pinna)

Outer ear flap; collects sound

Lobule

Lower soft part of pinna

External Auditory Canal / Meatus

Directs sound to tympanic membrane

Tympanic Membrane

Eardrum; vibrates with sound waves

Malleus (Hammer)

Attached to eardrum

Incus (Anvil)

Middle bone

Stapes (Stirrup)

Transmits vibrations to oval window

Eustachian (Pharyngotympanic) Tube

Connects middle ear to nasopharynx; equalizes pressure

Cochlea

Hearing; spiral-shaped

Round Window

Releases pressure from cochlea

Oval Window

Where stapes attaches; transmits vibrations

Vestibule

Static balance (utricle & saccule)

Semicircular Canals

Dynamic equilibrium

Vestibulocochlear Nerve (CN VIII)

Hearing & balance

Scala Vestibuli (Vestibular Duct)

Upper chamber; perilymph

Scala Tympani (Tympanic Duct)

Lower chamber; perilymph

Scala Media (Cochlear Duct)

Middle chamber; endolymph

Vestibular Membrane

Roof of cochlear duct

Basilar Membrane

Floor of cochlear duct; supports hair cells

Tectorial Membrane

Contacts hair cells of Organ of Corti

Hair Cells

Sensory receptors for hearing

Organ of Corti

Hearing receptor organ within cochlear duct

Perilymph

Fluid in vestibuli & tympani

Endolymph

Fluid in cochlear duct

External Ear

Pinna

External Auditory Meatus

Canal leading to the eardrum

Malleus

Hammer-shaped bone in the middle ear

Incus

Anvil-shaped bone in the middle ear

Stapes

Stirrup-shaped bone in the middle ear

Cerebrum

Largest part of the brain; responsible for thinking, learning, emotion, sensory processing, and voluntary movement.

Cerebellum

Located under the cerebrum at the back of the brain; coordinates balance, posture, and fine motor control.

Spinal Cord

Connects brain to the rest of the body; transmits nerve signals between brain and body.

Medulla Oblongata

Lowest part of brainstem; controls vital functions like heart rate, breathing, and blood pressure.

Midbrain

Uppermost part of brainstem; controls eye movement and auditory/visual reflexes.

Cerebral Peduncles

Fiber tracts on anterior midbrain; carry motor signals between cerebrum and brainstem.

Corpora Quadrigemina

Four rounded bumps on posterior midbrain; involved in reflexes to visual (superior) and auditory (inferior) stimuli.

Superior Colliculi

Visual reflex centers; track moving objects.

Inferior Colliculi

Auditory reflex centers; respond to sound.

Pituitary Gland

Small endocrine gland under hypothalamus; secretes hormones controlling growth, metabolism, and reproduction.

Olfactory Bulb

Front underside of brain; receives smell input from nasal cavity.

Olfactory Tract

Carries smell signals from olfactory bulbs to cerebrum.

Optic Nerve

Transmits visual information from eyes to optic chiasma.

Optic Chiasma

X-shaped crossing where some optic nerve fibers switch sides.

Optic Tract

Carries visual information from chiasma to occipital lobe.

Cerebral Cortex

Outer gray layer of cerebrum; site of consciousness, reasoning, and sensory interpretation.

Arbor Vitae

White matter of cerebellum shaped like a tree; coordinates muscle movements.

Cerebellar Peduncles

Three fiber tracts connecting cerebellum to brainstem; carry sensory and motor information.

Corpus Callosum

Thick band of white matter connecting left and right hemispheres; allows communication between them.

Thalamus

Central relay station for sensory information going to the cerebral cortex.

Hypothalamus

Below thalamus; regulates hunger, thirst, temperature, hormones, and autonomic functions.

Pineal Gland

Small gland behind thalamus; produces melatonin for sleep regulation.

Lateral Ventricles

Paired chambers within cerebrum; contain CSF.

Third Ventricle

Narrow cavity between thalamic halves; filled with CSF.

Cerebral Aqueduct

Narrow channel through midbrain connecting 3rd and 4th ventricles.

Mammillary Body

Round structure beneath hypothalamus; involved in memory and smell reflexes.

Infundibulum

Stalk connecting hypothalamus to pituitary gland; transmits hormones.

Longitudinal Fissure

Deep groove separating left and right cerebral hemispheres.

Sulcus

Shallow grooves between folds (gyri) of the brain.

gyrus

Raised folds on the brain's surface that increase surface area for neural processing.

Dura Mater

Tough, outer protective layer of meninges.

Arachnoid Mater

Middle, web-like meningeal layer containing cerebrospinal fluid.

Pia Mater

Thin, inner layer that clings tightly to the surface of the brain and spinal cord.

Fourth Ventricle

Cavity between the pons and cerebellum; filled with cerebrospinal fluid.

Fornix

Fiber tract arching below corpus callosum; connects hippocampus and hypothalamus.

Pons

Bridge between medulla and midbrain; assists in regulating respiration.

Choroid Plexus

Network of capillaries in ventricles that produce cerebrospinal fluid.

Intermediate Mass of Thalamus

Small bridge joining the two thalamic halves.

Corpus Callosum (Body, Genu, Rostrum, Splenium)

Large fiber tract connecting left and right cerebral hemispheres; Genu (front), Body (middle), Splenium (back), Rostrum (below front).

Frontal Lobe

Responsible for cognition, reasoning, planning, and voluntary motor function.

Parietal Lobe

Processes sensory input and body awareness; involved in movement coordination.