Sensory Organs

General sense organs (somatic senses) are touch, pressure, pain, and temperature

Special senses- are hearing, balance, taste, smell, and vision

Receptors allow awareness of stimuli caused by environmental changes

Activation of a receptor causes a change in the electrical potential of a cell (graded response)

Classification of receptors: Sense

Chemoreceptors chemicals (smell and taste)

Photoreceptors light (vision)

Thermoreceptors hot and cold

Nociceptors Tissue damage (pain)

Mechanoreceptors Deformation or change in position (proprioception, touch,

pressure, hearing, and balance

Somatic receptors can be classified by location: exteroceptors (exterior), visceroreceptors (internal organs), proprioceptros (muscles, joints)

Somatic senses

- nociceptors- free nerve endings (not present in brain). Discuss “referred pain”, fibers are acute or chronic

-mechanoreceptors- touch and pressure. Meissner’s corpuscles in skin devoid of hair, Ruffini’s corpuscles in dermis- slowly adapting, Pacinian corpuscles- dermis- fast adapting

-stretch receptors-muscle spindle senses muscle stretch and contracts muscle

-Golgi tendon organs (GTOs) sense excessive muscle contraction and lengthen muscle

Stretch receptors and GTOs work together to maintain posture

Special senses:

Smell- olfaction- chemoreceptors in olfactory cells have nerve endings for the olfactory nerve that pass through the cribriform plate at the top of the nasal passage and into the olfactory tract into the cerebral cortex

Taste- gustation-papillae or raised areas of the tongue contain taste buds with gustatory cells with gustatory hairs. Nerve endings carry information received by chemoreceptors into the brainstem. Major tastes sensed are sweet, salty, bitter, and sour

Vision: photoreceptors in the retina called rods and cones sense wavelengths of light and send the information through the optic nerve into the central nervous system

Anterior cavity (filled with aqueous humor) Posterior cavity (filled with vitreous humor)

Cornea (no blood vessels) sclera

Lens choroid

Pupil (space inside iris)

Iris muscle (color of eye) fovea centralis in macula lutea (blind spot)

Conjunctiva optic nerve

Rods cones

Black and white Pigment is rhodopsin) color (red, green and blue)

Peripheral location central location (fovea centralis)

Sense peripheral vision sense central vision

More fewer

Blurry image, motion sensed senses clearly

Hearing and balance: mechanoreceptor hair cells sense vibration and send nervous impulses from sensory organs (hearing- organ of Corti in the cochlea, balance the macula in the utricle and cristae ampullaris in the ampullae of the semicircular canals)

External ear Middle ear Inner ear (bony and membraneous labrynths)

Auricle or pinna Openings: Ampullae in semicircular canals

External auditory meatus 1) tympanic membrane utricle (otoliths) and saccule of vestibule

(into temporal bone) 2) oval window organ of Corti in cochlea

Ear (auditory) canal 3) round window fluids: endolymph (membr.)

4) Eustachian tube perilymph (between bone and

5) Spaces in mastoid bone membr. labrynths

Bones- Malleus, incus, stapes