Special senses

What is a stimulus?

Any change in the environment that triggers a sensory response.

What is a receptive field?

The size of the area monitored by a single sensory neuron.

What is sensory adaptation?

Decreased sensitivity to a constant stimulus over time.

What are tonic receptors?

Receptors that do NOT adapt and continue responding (ex: pain).

What are phasic receptors?

Receptors that adapt and stop responding after time (ex: smell, touch).

What are general sense receptors?

Receptors found throughout the body (somatic and visceral).

What are special sense receptors?

Receptors located in organs of the head (vision, hearing, smell, taste, equilibrium).

What are exteroceptors?

Receptors that detect stimuli from outside the body.

What are interoceptors?

Receptors that detect internal body stimuli.

What are proprioceptors?

Receptors that detect body position and movement.

What are chemoreceptors?

Receptors that detect chemicals (taste and smell).

What are thermoreceptors?

Receptors that detect temperature.

What are photoreceptors?

Receptors that detect light (rods and cones).

What are mechanoreceptors?

Receptors that detect pressure, vibration, and movement.

What are nociceptors?

Pain receptors that detect tissue damage.

What do free nerve endings detect?

Pain, temperature, and itching.

What do root hair plexuses detect?

Hair movement.

What do tactile discs (Merkel cells) detect?

Light touch and texture.

What do tactile corpuscles detect?

Light touch.

What do lamellated corpuscles detect?

Deep pressure and vibration.

What do end bulbs detect?

Light pressure.

What do bulbous corpuscles detect?

Skin stretch.

What do muscle spindles detect?

Muscle stretch.

What do tendon organs detect?

Tendon tension.

What do joint kinesthetic receptors detect?

Joint position.

What is referred pain?

Pain felt in an area different from its source.

What are odorants?

Airborne chemical molecules that stimulate smell receptors.

Where is the olfactory epithelium located?

In the superior portion of the nasal cavity.

What are olfactory receptor cells?

Cells that detect odor molecules.

What do supporting cells do in the olfactory epithelium?

Provide support and nourishment.

What are basal cells in the olfactory epithelium?

Stem cells that replace receptor cells.

What does the lamina propria contain?

Olfactory glands that produce mucus.

What are olfactory hairs?

Cilia that detect odor molecules.

What carries smell signals to the brain?

Olfactory nerves.

What is the step-by-step pathway of smell?

Odorant enters nose → dissolves in mucus → binds olfactory hairs → receptor activated → signal sent to brain.

What are papillae?

Structures on the tongue that contain taste buds.

What cells detect taste?

Gustatory cells.

What do supporting cells do in taste buds?

Provide support.

What are basal cells in taste buds?

Stem cells that replace gustatory cells.

What is a taste pore?

Opening where dissolved chemicals enter taste buds.

What are the 5 basic tastes?

Sweet, sour, salty, bitter, umami.

Which cranial nerves are involved in taste?

CN VII, CN IX, CN X.

What is the step-by-step pathway of taste?

Food dissolves → enters taste pore → binds gustatory cells → signal sent to brain

Accessory structures that protect the eye

Eyebrows, eyelashes, eyelids, lacrimal ducts, conjunctiva, eye muscles

Eyebrows function

Divert sweat away from the eyes

Eyelashes function

Protect eyes from debris

Lacrimal ducts function

Produce and drain tears

Conjunctiva

Thin membrane lining eyelids and covering front of eye

Pupil

Opening that allows light into the eye

Iris

Colored part of eye that controls pupil size

Sphincter pupillae function

Constricts the pupil

Dilator pupillae function

Dilates the pupil

Pupillary reflex

Automatic change in pupil size in response to light

Anterior cavity

Space between cornea and lens filled with aqueous humor

Posterior cavity

Space behind lens filled with vitreous humor

Cornea

Transparent front part of the eye that bends light

Corneal epithelium

Outer protective layer of cornea

Corneal endothelium

Inner corneal layer that regulates fluid

Aqueous humor

Fluid that nourishes cornea and lens

Lens

Structure that focuses light onto retina

Ciliary body

Controls lens shape

Ciliary muscles

Adjust lens shape for focusing

Suspensory ligaments

Hold lens in place

Retina

Layer that contains photoreceptors

Neural layer of retina

Contains photoreceptor, bipolar, and ganglion cells

Photoreceptor cells

Detect light

Bipolar cells

Relay signals between photoreceptors and ganglion cells

Ganglion cells

Send signals to optic nerve

Choroid

Pigmented layer that absorbs excess light

Sclera

White outer layer of eye

Vitreous humor

Gel that fills posterior cavity

Optic disc

Blind spot where optic nerve exits

Fovea centralis

Area of sharpest vision

Rods

Photoreceptors for dim light and black/white vision

Cones

Photoreceptors for color and detail

Stereoscopic vision

Depth perception using both eyes

Step-by-step path of light through eye

Cornea → aqueous humor → pupil → lens → vitreous humor → retina

Chalazion

Blocked oil gland causing lump on eyelid

Stye

Infected eyelash gland

Conjunctivitis

Infection of conjunctiva (pink eye)

Myopia

Nearsightedness (image forms in front of retina)

Hyperopia

Farsightedness (image forms behind retina)

Cataracts

Clouding of the lens

Detached retina

Retina separates from eye wall

Vestibulocochlear nerve number

Cranial nerve VIII

Function of vestibulocochlear nerve

Carries hearing and balance signal

Auricle

External ear that collects sound

External acoustic meatus

Ear canal that directs sound inward

Tympanic membrane

Eardrum that vibrates with sound

CeTympanic cavity

Air-filled space in middle ear

Auditory tube function

Equalizes air pressure

Ossicles

Three small bones that amplify sound

Malleus

Bone attached to tympanic membrane

Incus

Middle ossicle bone

Stapes

Bone that touches oval window

Tensor tympani function

Reduces vibration of tympanic membrane

Stapedius function

Reduces vibration of stapes

rumen

Earwax that protects ear canal

Bony labyrinth

Structure containing cochlea, vestibule, semicircular canals

Cochlea

Hearing structure