Nerve & Sensory Anatomy – Quick Reference
Nerve Structure – Key Concepts
- Cell Body (Soma) with nucleus
- Dendrite
- Nissl body
- Axon hillock
- Axon
- Myelin
- Schwann cells
- Node of Ranvier
- Axolemma
- Axon collateral
- Axon terminal (synaptic knob)
- Vesicles
Nervous System Organization
- Central Nervous System (CNS)
- Peripheral Nervous System (PNS)
- Nuclei, Ganglia
- Tract, Nerve
- White matter, Gray matter
- Sensory (afferent) vs Motor (efferent)
- Oligodendrocytes (CNS), Schwann cells (PNS)
Microscopic Anatomy of a Nerve
- Axon
- Endoneurium
- Fascicle
- Perineurium
- Epineurium
- Vasa nervorum
Myelination & Connective Tissue (Essential Concept)
- Myelinated nerve fibers are associated with connective tissue sheaths (endoneurium, perineurium, epineurium)
Spinal Roots & Foramina
- Dorsal root
- Ventral root
- Intervertebral foramina
Cranial Nerves – Overview
- I Olfactory — smell
- II Optic — vision
- III Oculomotor — extrinsic eye muscles (and pupil/lens control)
- IV Trochlear — superior oblique
- V Trigeminal — ophthalmic, maxillary, mandibular (facial sensation; mastication)
- VI Abducens — lateral rectus
- VII Facial — facial expression; taste anterior 2/3
- VIII Vestibulocochlear — hearing and balance
- IX Glossopharyngeal — taste posterior 1/3; parotid
- X Vagus — thoracic/abdominal/visceral parasympathetic
- XI Accessory — trapezius, sternocleidomastoid
- XII Hypoglossal — tongue muscles
Sensory Receptors
- Free nerve endings — nociceptors (pain) and thermoreceptors (temperature)
- Merkel discs — light pressure
- Meissner's corpuscles — light touch (hairless skin; lips, fingertips)
- Pacinian corpuscles — deep pressure and vibration (subcutaneous tissue, tendons, ligaments)
- Golgi tendon organs — tendon stretch
- Muscle spindles — muscle stretch in skeletal muscles
Eye – Anatomy & Function
Extrinsic Eye Muscles
- Superior rectus — elevates eye; CN III
- Lateral rectus — moves eye laterally; CN VI
- Superior oblique — depresses and rotates eye; CN IV
- Medial rectus — moves eye medially; CN III
Internal Eye Structures
- Sclera — white outer layer
- Cornea — transparent front part
- Iris — regulates light via pupil
- Pupil — opening in iris
- Optic nerve — transmits visual information
- Choroid — vascular layer between sclera and retina
- Ciliary body — produces aqueous humor; controls lens shape
- Retina — photoreceptors; site of light detection
- Macula lutea / Fovea centralis — sharpest vision
- Rods and cones — photoreceptors
- Vitreous humor — jelly-like posterior segment
- Lacrimal gland — produces tears
Retinal Layers & Cells
- Photoreceptor layer — rods and cones
- Bipolar cells — transmit to ganglion cells
- Ganglion cells — form the optic nerve
Clinical & Functional
- Accommodation — lens shape change for near/far focus
- Presbyopia — age-related loss of elasticity
- Glaucoma — increased intraocular pressure
- Cones — color vision
- Rods — low-light vision
Eye – Quick Reference Concepts
- Accommodation
- Presbyopia
- Glaucoma
- Cones
- Rods
Ear – Anatomy & Function
Structures of the External & Middle Ear
- Pinna (auricle)
- External auditory canal
- Tympanic membrane
- Malleus, Incus, Stapes
- Oval window; Round window
- Pharyngotympanic (auditory) tube
- Tensor tympani; Stapedius
- Cochlea
- Utricle; Saccule
- Semicircular canals
- Vestibulocochlear nerve (CN VIII)
Inner Ear Fluids & Structures
- Perilymph — in bony labyrinth
- Endolymph — in membranous labyrinth
- Cochlear duct (scala media) — endolymph
- Tectorial membrane
- Basilar membrane
- Organ of Corti
- Hair cells
Microscopic Structures
- Vestibular membrane
- Organ of Corti
- Hair cells
- Ion channels (K⁺, Ca²⁺) activated by stereocilia bending
Vestibular Sense
- Maculae — linear acceleration and head position
- Cristae ampullares — angular (rotational) acceleration in semicircular canals
Hearing Organ Location
- Organ of Corti located in the cochlear duct (scala media)
- Round window at end of the scala tympani