Anatomy and Physiology BIO 243 Chapter 17

Vision - Eye structures - Cornea

refracts light; outer transparent layer

Vision - Eye structures - Lens

focuses light onto retina

Vision - Eye structures - Retina

contains photoreceptors (rods for low-light, cones for color and sharp vision)

Vision - Eye structures - Macula lutea / fovea

area of highest visual acuity

Vision - Eye structures - Optic nerve (CN II)

transmits visual info to brain

Vision - Photoreceptor function - Rods

detect light/dark, peripheral vision

Vision - Photoreceptor function - Cones

detect color (red, green, blue), sharp vision

Vision - Accessory structures

eyelids, eyelashes, lacrimal glands for protection and lubrication

Vision - Diseases/conditions - Colorblindness

absence of one type of cone

Vision - Diseases/conditions - Presbyopia

lens loses flexibility with age

Vision - Diseases/conditions - Glaucoma

increased intraocular pressure damages optic nerve

Hearing & Balance - Outer ear

collects sound waves (auricle/pinna, external acoustic meatus)

Hearing & Balance - Middle ear

amplifies vibrations (tympanic membrane, ossicles: malleus, incus, stapes)

Hearing & Balance - Inner ear

converts vibrations into neural signals

Hearing & Balance - Inner ear - Cochlea

contains organ of Corti; hair cells detect sound

Hearing & Balance - Inner ear - Vestibular apparatus

utricle, saccule, semicircular canals detect balance and motion

Hearing & Balance - Cranial nerve

Vestibulocochlear (CN VIII) carries auditory and equilibrium info

Hearing & Balance - Diseases/conditions - Vertigo

vestibular dysfunction, can cause nystagmus

Hearing & Balance - Diseases/conditions - Hearing loss

damage to cochlear nerve or hair cells

Taste (Gustation) - Taste buds

located on tongue papillae (fungiform, circumvallate, foliate, filiform)

Taste (Gustation) - Six taste sensations

sweet, sour, salty, bitter, umami, fatty

Taste (Gustation) - Cranial nerves involved

CN VII (facial) – anterior 2/3 of tongue.

CN IX (glossopharyngeal) – posterior 1/3.

CN X (vagus) – epiglottis and pharynx.

Taste (Gustation) - Mechanism

tastants bind to gustatory cells → depolarization → neurotransmitter release → CNS perception

Smell (Olfaction) - Olfactory receptors

located in olfactory epithelium (nasal cavity)

Smell (Olfaction) - Olfactory nerve (CN I)

transmits smell info to CNS

Smell (Olfaction) - Connections

olfactory bulb → limbic system (emotions, memory)

Smell (Olfaction) - Diseases/conditions

anosmia (loss of smell), often linked with viral infections or injury

Reflexes & Sensory Integration - Pain/temperature

spinothalamic pathways

Reflexes & Sensory Integration - Fine touch, vibration

dorsal column pathways

Reflexes & Sensory Integration - Proprioception

spinocerebellar pathways

Reflexes & Sensory Integration - Reflex examples

Withdrawal reflex (hand from hot stove).

Light reflex (pupillary constriction).

Balance reflexes (adjusting posture when stepping on a tack).