Special Senses

I Olfactory nerve

Sensory for smell.

II Optic nerve

Sensory for vision.

III Oculomotor nerve

Motor fibers to eye muscles.

IV Trochlear nerve

Motor fibers to eye muscles.

V Trigeminal nerve

Sensory for the face; motor fibers to the face.

VI Abducens nerve

Motor fibers to eye muscles.

VII Facial nerve

Sensory for taste; motor fibers to the pharynx.

VIII Vestibulocochlear nerve

Sensory for balance and hearing.

IX Glossopharyngeal nerve

Sensory for taste; motor fibers to pharynx.

X Vagus nerve

Sensory and motor fibers for pharynx, larynx, and viscera (homeostasis).

XI Accessory nerve

Motor fibers to neck and upper back.

XII Hypoglossal nerve

Motor fibers to tongue.

Sensation

Conscious awareness of incoming sensory information.

Touch

A general sense located in the dermis and subcutaneous tissue.

Nociceptors

Respond to heat, mechanical stress, and chemicals associated with tissue damage.

Thermoreceptors

Respond to changes in temperature.

Mechanoreceptors

Respond to physical distortion of cell membrane.

Baroreceptors

Sensitive to internal pressures such as blood pressure.

Proprioceptors

Monitor muscle stretch.

Tactile receptors

Respond to touch, pressure, and vibration.

Merkel cells

Function as touch receptors in association with sensory nerve endings.

Meissner’s corpuscles

Nerve endings responsible for sensitivity to light touch.

Chemoreceptors

Respond to changes in concentration of specific chemicals.

Photoreception

Process by which the eye detects light energy.

Eyebrows

Hairs that shade the eyes and keep perspiration out.

Eyelids (palpebrae)

Protect the eye from physical danger and drying out.

Lacrimal glands

Secretes a saline solution that cleanses and protects the eye.

Ciliary and Meibomian Glands

Secrete sweat and oils for lubrication of the eyelids.

Conjunctiva

Mucous membrane that prevents the eyes from drying out.

Sclera

White connective tissue that anchors and protects the eye.

Cornea

Allows light to pass through and refracts light.

Iris

The colored part of the eye that controls pupil dilation.

Pupil

Central opening of the iris that regulates light entering the eye.

Aqueous humor

Fluid that supports, nourishes, and removes waste in the eye.

Lens

Biconcave structure that changes shape to focus light on the retina.

Vitreous humor

Gel-like substance that keeps the eye from collapsing.

Photoreceptors

Modified neurons that detect light energy.

Rods

Highly sensitive photoreceptors best suited for night vision.

Cones

Photoreceptors adapted for bright light and color vision.

Optic nerve

Transmits visual information from the retina to the brain.

Optic disc

Site where the optic nerve leaves the eye; lacks photoreceptors.

Binocular vision

Ability to see with two eyes.

Pinna (auricle)

Collects sound.

External auditory canal

Channels sound inward.

Tympanic membrane

Eardrum that covers the opening from the auditory canal.

Auditory tube

Equalizes pressure between the middle ear and throat.

Malleus (hammer)

First bone in the middle ear that transmits sound vibrations.

Incus (anvil)

Middle bone in the chain within the middle ear.

Stapes (stirrup)

Last bone in the chain that transfers sound to the inner ear.

Cochlea

Contains the organ of Corti that transmits sound impulses.

Static equilibrium

Sense of balance in the vestibule.

Dynamic equilibrium

Sense of balance in the semicircular canals.

Maculae

Sensory receptors for static equilibrium.

Olfactory epithelium

Receptors in the roof of the nasal cavity for the sense of smell.

Taste buds

Sensory receptor organs for taste located in the oral cavity.

Gustatory hair (papillae)

Hairs that contact chemicals to signal taste.