Anatomy lecture 16: sense organs

General senses

Have receptor cells within multiple body organs. Touch, pain, body movement

Special senses

Have receptor cells within specialized sensory organs. Taste, smell, hearing, balance, and vision

Chemoreceptors

Respond to chemicals to detect taste, smell, and blood pH

Photoreceptors

Respond to light

Mechanoreceptors

Respond to physical forces to detect hearing, motion, touch, etc.

Thermoreceptors

Detect changes in temperature

Nociceptors

Respond to tissue damage (pain)

Receptive field

Area of body supplied by a single sensory neuron. Precision determined by size of field.

First-order neuron

Carries signal from sensory receptor to CNS

Second-order neuron

Crosses over and carries signal to thalamus

Third-order neuron

Carries signal to primary somatosensory cortex

Lingual papillae

Bumps on the tongue surface to grip and position food

Taste buds

Contain gustatory receptor cells for detecting taste stimuli. Most found in lingual papillae

Olfactory neurons

Have receptors that bind chemicals in air

Olfactory nerves

Bundles of axons from olfactory neurons

Olfactory bulb

Structure where olfactory neurons synapse

Olfactory tracts

Bilateral bundles of nerve fibers that connect to brain

Auricle

Visible part of ear that collects sound waves. Determines sound direction

External acoustic meatus

Passage for sound through temporal bone

Tympanic membrane

Membrane that transmits sound to middle ear

Auditory ossicles

Three small bones that transmit sound to inner ear (MIS)

Malleus

Hammer-shaped ossicle attached to the tympanic membrane

Incus

Middle, anvil-shaped ossicle

Stapes

Stirrup-shaped ossicle attached to the oval window

Auditory tube

Passage that connects from middle ear to throat. Opens to equalize air pressure

Oval window

Membrane in vestibule where stapes attaches

Vestibule

Central chamber that is involved in equilibrium

Semicircular canals

Three tubes that detect rotation of head

Cochlea

Snail-shaped cavity involved in hearing

Round window

Membrane at end of cochlea

Vestibular duct

A perilymph-filled cavity behind oval window

Vestibular membrane

Separates the vestibular and cochlear duct

Cochlear duct

Endolymph-filled cavity that contains the spiral organ

Basilar membrane

Separates the cochlear and tympanic ducts

Tympanic duct

A perilymph-filled cavity behind round window

Spiral organ

The receptor organ for hearing in the cochlear duct

Hair cells

Convert fluid movements to nerve signals

Stereocilia

Extensions of hair cell that send signals when bent

Tectorial membrane

Lays over stereocilia of hair cells

CN VIII

Nerve signals transmitted

Sclera

The white, fibrous outer layer of the eye

Cornea

Clear covering that allows light to pass through anterior eye

Choroid

The highly vascular middle layer of the eye

Ciliary body

Smooth muscle that controls the shape of the lens

Iris

Pigmented diaphragm that regulates the amount of light reaching the retina

Pupil

Open hole at center of iris that light passes through into eye

Retina

Inner, light-sensitive layer that contains photoreceptors

Optic disc

Spot on the retina where axons leave and blood vessels enter. No photoreceptors present

Macula

Oval-shaped pigmented area for high-resolution, color vision

Aqueous humor

Clear, watery fluid that fills space anterior to lens

Lens

Transparent structure that focuses light on retina

Vitreous body

Clear gel that fills the space posterior to lens

Rod cells

Specialized for low-light vision. Use rhodopsin as photopigment

Cone cells

Specialized for color vision. Use photopsins as photopigments

Bipolar cells

Connect rod and cone cells to retinal ganglion cell

Retinal ganglion cells

Transmit image-forming and non-image information to the brain