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Anatomy and Physiology Ch 11


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Protects a person by detecting changes in the environment
Sensory system
An environment change becomes what when it initiates a nerve impulse?
A stimulus becomes what only when a specialized area of the cerebral cortex interprets the nerve impulse it generates?
The part of the nervous system that detects a stimulus
Sensory receptor
Sensory receptor structures
Free dendrite (pain receptors)
End-organ on the dendrite of an afferent neuron (touch and temp)
Specialized cell associated with an afferent neuron (rods and cones)
Receptor classifications
Receptor, such as those for taste and smell, that detects chemicals in solution
Receptor located in the retina of the eye that responds to light
Receptor that detects changes in temperature
Receptors that respond to movement, such as stretch, pressure, or vibration
Sense that is localized in a special sense organ
Special sense
Stimulus that a receptor must recieve in order to respond and generate a nerve impulse
Threshhold stimulus
Sense that is widely distributed throughout the body
General sense
Special senses
Vision (eye)
Hearing (internal ear)
Equilibrium (internal ear)
Taste (tongue)
Smell (nasal cavities)
General senses
muscle attached to the upper eyelid
Levator palpebrae
Condition in which the muscle becomes weaker causing the eyelid to droop and interfere with vision
Thin membrane that lines the inner surfce of the euelids and covers the coible protion of the white of the eye(scelra)
Gland that produces tears
Lacrimal gland
Ducts near the nasal corner of the eye
Nasolacrimal ducts
Coats, or tunics, of the eyeball
The outermost tunic, made of tough connective tissue; white of the eye; contains no blood vessels
The second (middle) tunic composed of a delicate network of connective tissue interlaced with many blood vessels
The innermost tunic is the actual receptor layer of the eye; contains rods and cones
Generate nerve impulses associated with vision
Rods and Cones
The bending of light rays as they pass from one substance to another substance of different density
An anterior continuation of the sclera; transparent and colorless
The eye's transparent refracting parts (exterior to interior)
Aqueous humor
Vitreous body
Watery fluid that fills much of the eyeball anterior to the lens, helps maintain the slight forward curve of the cornea
Aqueous humor
A clear, circular structure made of a firm, elastic material; has two bulging surfaces and is described as biconvex
Lens (crystalline lens)
A soft jellylike substance that fills the entire space posterior to the lens; important in maintaining the shape of the eyeball as well as in aiding in refraction
Vitreous body
Cylindrical shape
About 120 million in each retina
Distributed toward the periphery (anterior) of the retina
Stimulated by dim light
Low visual acuity (sharpness)
Rhodopsin (visual purple)
No color perception
Flask shaped
About 6 million in each retina
Distribution concentrated at the center of the retina
Stimulated by bright light
High visual acuity (sharpness)
Pigments sensitive to red, green, or blue
Responds to color
Tiny depressed area near the optic nerve
Fovea Centralis
Difficulty seeing in dim light because there is too little light to activate the rods
Night blindness
Voluntary muscles attached to the eyeball's outer surface
Extrinsic muscles
Involuntary muscles located within the eyeball
Intrinsic muslces
The colored or pigmented part of the eye; composed of two sets of muscle fibers that govern the size of the central opening
The iris's central opening
Muscle shaped somewhat like a flattened ring with a central hole that size of the outer edge of the iris
Ciliary muscle
Filaments that the ciliary muscle hold the lens in place with
Suspensory ligaments
Carries visual impulses from the retinal rods and cones to the brain
Optic nerve
Carries impulses of pain, touch, and temperature from the eye and surrounding parts to the brain
Opthalmic branch of the trigeminal nerve
Blind spot; there are no cones or rods in the area of the optic nerve so no image can form on the retina at this point
Optic disk
largest nerve; supplies the voluntary and involuntaru motor impulses to all but two eye muscles
Oculomotor nerve
supplies the superior oblique extrinsic eye muscle
Trochlear nerve
supplies the lateral rectus extrinsic eye muscle
Abducens nerve
Steps in Vision
Light refracts
The muscles of the iris adjust the pupil
The ciliary muscle adjusts the lens
The extrinsic eye muscles produce convergence
Light stimulates retinal receptor cells (rods and cones)
The optic nerve transmits impulses to the brain
The occipital lobe cortex interprets the impulses
Results from an abnormally short eyeball; light rays can not bend sharply enough to focus on the retina
Results from the eyeball being too long or the cornea bends the light rays too sharply
Visual defect caused by irregularity in the curvature of the cornea or the lens
A deviation of the eye that results from lack of coordination of the eyeball muscles
Type of strabismus in which the eye deviates toward the nasal side, or medially
Convergent strabismus
Type of strabismus in which the affected eye deviates laterally; gives the cross-eyed appearance
Divergent strabismus
Loss of vision in a healthy eye because it can not work properly with the other eye
Inflammation of the conjunctiva which may be acute or chronic and may be caused by a variety of irritants and pathogens
A highly contagious acute conjuntivitis that is usually caused by cocci or bacilli
Pink eye
An acute eye infection caused by chlamydia trachomatis
Inclusion conjuntivitis
chronic form of inclusion conjunctivitis
An acute infection of the eye of the newborn, caused by organisms acquired during passage through the birth canal
Opthalmia neonatorm
The most common eye injury
Laceration or scratch of the cornea caused by a foreign body
An operation to remove the eyeball
Opacity of the lens or the outer covering of the lens
A condition characterized by excess pressure of the aqueous humor
Disorder in which the retina is damagedby blood vessel hemorrhages and growth of new vessels
Diabetic retinopathy
Disorder in which the retina separates from the underlying layer of the eye as a result of trauma or an accumulation of fluid or tissue between the layers
Retinal detachment
The yellow area of the retina that contains the fovea centralis
Macula lutea
Three main sections of the ear
Outer ear
Middle ear
Inner ear
Section of the ear that includes an outer projection and a canal ending at a membrane
Outer ear
The section of the ear that is an air space containing three small bones
Middle ear
The section of the ear that is the most complex and contains the sensory receptors for hearing and equalibrium
Inner ear
Visible projecting portion of the outer ear
Pinna (auricle)
Portion of the outer ear that conects to the pinna and leads into the deeper parts of the ear
External auditory canal (meatus)
Wax producing glands contained in the meatus
Ceruminous glands
Boundry between the meatus and the middle ear; vobrates freely as sound waves enter the ear
tympanic membrane (eardrum)
Three small bones (ossicles) contained within the middle ear
The first ossicle (bone) shaped like a hammer and attached to the tympanic membrane
The second ossicle (bone) shaped like an anvil and connected to both the Malleus and the Stapes
The third ossicle (bone) shaped like the stirrup of a saddle and in contact with the inner ear
Connects the middle ear cavity with the throat (pharynx)
Eustachian tube
Allows pressure to equalize on both sides of the tympanic membrane
Eustachian tube
Described as a labyrinth because it has a complex mazelike construction
Inner ear
Skeleton of the inner ear
Bony labyrinth
Three divisions of the bony labyrinth
Semicircular canals
Consists of two bony chambers that contain som of the receptors for equalibrium
Three projecting bony tubes located toward the posterior; bases also contain receptors for equalibrium
Semicircular canals
Coiled like a snail shell and is located toward the anterior; contains receptors for hearing
Fluid contained in the bony labyrinth
Exact replica of bony shell contained within the bony labyrinth
Membraneous labyrinth
Fluid contained in the membraneuos labyrinth
Organ of hearing; consists of ciliated receptor cells located inside the membraneous cochlea
Organ of Carti
The steps in hearing
Sound waves enter the external auditory canal
The tympanic membrane vibrates
The ossicles transmit vibrations across the middle ear cavity
The stapes transmits the vibrations to the inner ear fluid
Vibrations move cilia on hair cells of the organ of Corti in the cochlear duct
Movement against the tectorial membrane generates nerve impulses
Impulses travel to the brain in the cochlear nerve
The temporal lobe cortex interprets the impulses
Small crystals of calcium carbonate contained in the fluid above the ciliated cells which add drag to the fluid around the receptor cells and increase the effect of gravity's pull
Equalibrium that resuslts from movement of the body in a straight line.
Static equalibrium
Equalibrium that results from the body spinning or moving in different directions
Dynamic equalibrium
Receptors for static equalibrium; located in the two small chambers of the vestibule
Receptors for dynamic equalibrium; located at the base of the semicircular canals
Formed from nerve fibers from the vestibule and the semicircular canals
Vestibular nerve
Infection and inflammation of the middle ear; fairly common; caused by a variety of bacteria and viruses
Otitis media
Procedure that cuts the tympanic membrane to releave pressure
Inflammation of the external auditory canal; caused by fungus or bacterium
Otitis externa (swimmer's ear)
Hearing disorder resulting from interference with the passage of sound waves from the outside to the inner ear
Conductive hearing loss
Hereditary bone disorder that prevents normal vibration of the stapes
Hearing disorder involving the cochlea,the vestibulocochlear nerve, or the brain areas concerned with hearing; may result from prolonged exposure to loud noises
Sensorineural hearing loss
Slowly progressive hearing loss that often accompanies aging
Sense of taste
Taste receptors ocated along the edges of small, depressed areas
Taste buds
tastes that are most acutely experienced at the tip of the tongue
tastes that are experienced most acutely at the anterior sides of the tongue
Tastes that are experienced most acutely by taste buds located laterally on the tongue
Tastes that are experienced most acutely at the posterior part of the tongue
sense of smell
The touch receptors found mostly in the dermis of the skin and around hair folicles
tactile corpuscles
Temperature receptors
free nerve endings

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