Special Senses Flashcards
- Situated in the orbital cavity and supplied by the optic nerve (2nd cranial nerve).
- Almost spherical in shape and about 2.5 cm in diameter.
- Space between the eye and the orbital cavity is occupied by adipose tissue.
- The bony walls of the orbit and the fat protect the eye from injur
EYES and SIGHT
-(white of the eye) forms the outermost layer of the eyeball
-Consists of a firm fibrous membrane that maintains the shape of the eye
-Gives attachment to the extrinsic muscles of the eye
Sclera
Sclera continues as a clear transparent epithelial membrane, ____________
cornea
Light rays pass through the cornea to reach the _____________
retina
- Lines the posterior five-sixths of the inner surface of the sclera.
- Very rich in blood vessels
- Deep chocolate brown in color.
Choroid
Light enters the eye through the _______________
pupil
stimulates the sensory receptors in the ____________
retina
- The anterior continuation of the choroid consisting of ciliary muscle (smooth muscle fibers) and secretory epithelial cells
- Acts like a sphincter
- Supplied by parasympathetic branches of the oculomotor nerve (3rd cranial nerve).
Ciliary Body
- Visible colored ring at the front of the eye lying behind the cornea and in front of the lens.
- Composed of pigment cells and two layers of smooth muscle fibers - one circular and the other radiating
Iris
In the center is an aperture called the ________________
pupil
- Highly elastic circular biconvex body, immediately behind the pupil.
*Thickness is controlled by the ciliary muscle through the suspensory ligament.
Lens
*Innermost lining of the eye
*Extremely delicate structure and well adapted for stimulation by light rays
*Composed of several layers of nerve cell bodies and their axons - sensory receptor cells, rods and cone
Retina
▪Skin, muscle, and connective tissue
Eyelids
✓Prevents surface from drying out
✓Keeps foreign material out of eye
Blinking
▪Eye sockets
▪Form a protective shell around the eyes
Eye orbits
✓Lateral edge of eyeballs
✓Produce tears
Lacrimal glands
✓Medial aspect of eyeballs
✓Drain tears into nose
Nasolacrimal ducts
impairment of distance vision
Myopia
impairment of near vision
Hyperopia
▪ Distinguish shades of gray
▪ Testing
* Pelli-Robson contrast sensitivity chart
* Vistech Consultants vision contrast system
▪ Detect cataracts or retinal problems before sharpness is impaired
Contrast sensitivity
▪ Color-blindness
* May be inherited
* More common in males
▪ Tests
* Ishihara color system
* Richmond pseudoisochromatic color test
▪ Difficulties may indicate retinal or optic nerve disease
Color vision
Many animals secrete odorous chemicals called __________ play an important part in chemical communication in, for example, territorial behavior, mating and the bonding of mothers and their newborn.
pheromones
▪the sensory nerves of smell
Olfactory receptors
respond to changes in chemical concentrations
Chemoreceptors
concentrates volatile molecules in the roof of the nose- increases the number of olfactory receptors stimulated and thus perception of the smell
Sniffing
*Chemical can stimulate receptors for limited time
*Receptors fatigue and stop responding to chemical
* No longer smell odor
Sensory Adaptation
Taste buds contain chemoreceptors
found in the papillae of the tongue
where taste is perceived
Parietal lobe of the cerebral cortex
3 Different types of papillae
-vallate papillae
-fungiform papillae
-foliate papillae
form a row at the back of the tongue
vallate papillae
mushroom-shaped and are scattered over the entire surface of the tongue
fungiform papillae
located in small trenches on the lateral margins of the tongue, but most of their taste buds degenerate in early childhood
foliate papillae
3 CRANIAL NERVES IN TONGUE
-facial (VII) nerve
-glossopharyngeal (IX) nerve
-vagus (X) nerve
serves taste buds in the anterior 2/3 of the tongue
facial (VII) nerve
serves taste buds in the posterior 1/3 of the tongue
glossopharyngeal (IX) nerve
serves taste buds in the throat and epiglottis
vagus (X) nerve
the process of hearing
audition
3 PRINCIPLE REGIONS OF EARS
- external ear
- middle ear
- internal ear
uses air to collect and channel sound waves
external ear
uses a bony system to amplify sound vibrations
middle ear
generates action potentials to transmit sound and balance information to the brain
internal ear
Collects sound waves
auricle
Guides sound wave to tympanic membrane
External auditory canal
- Separates external canal and middle ear
- Vibrates when sound hits it
Tympanic membrane
