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senses
are the means by which the brain receives information about the environment and the body
are ability to perceive stimuli
sensation
is the process initiated by stimulating sensory receptors
perception
is the conscious awareness of those stimuli
sensory receptors
are sensory nerve endings or specialized cells capable of responding to stimuli by generating action potentials that are propagated to the spinal cord and brain.
general senses
special senses
we recognize many more senses and divide them into two basic groups:
general senses
receptors over large part of body that sense touch, pressure, pain, temperature, and itch
somatic senses
visceral senses
2 groups of general senses
somatic senses
provide sensory information about the body and the environment
visceral senses
provide information about various internal organs, primarily involving pain and pressure.
special senses
are more specialized in structure and are localized to specific parts of the body. (senses)
smell
taste
vision
hearing
balance
special senses are:
mechanoreceptors
chemoreceptors
photoreceptors
thermoreceptors
nociceptors
types of receptors
mechanoreceptors
respond to mechanical stimuli, such as the bending or stretching of receptors.
detect movement
ex. touch, pressure, vibration
chemoreceptors
respond to chemicals.
For example, odor molecules bind to —, allowing us to perceive smells.
photoreceptors
respond to light
thermoreceptors
respond to temperature changes.
nociceptors
respond to stimuli that result in the sensation of pain
proprioception
, which is the sense of movement and position of the body and limbs
free nerve endings
Structurally, the simplest and most common types of sensory receptors are —
These are relatively unspecialized neuronal branches similar to dendrites.
some — respond to painful stimuli, some to temperature, some to itch, and some to movement
touch receptors
are structurally more complex than free nerve endings.
Many—- are enclosed by capsules.
merkel disks
hair follicle receptors
meissner corpuscles
ruffini corpuscle
pacinian corpuscle
types of touch receptors
merkel disks
detect light touch and pressure
hair follicle receptors
associated with hairs, are also involved in detecting light touch.
Light touch receptors are very sensitive but not very discriminative, meaning that the point being touched cannot be precisely located.
meissner corpuscle
are receptors for fine, discriminative touch and are located just deep to the epidermis.
These receptors are very specific in localizing tactile sensation
ruffini corpuscle
are deeper tactile receptors and play an important role in detecting continuous pressure in the skin
pacinian corpuscle
are the deepest receptors and are associated with tendons and joints.
These receptors relay information concerning deep pressure, vibration, and body position (proprioception).
righting reflex
that enables us to maintain an upright position, even if our body is on “uneven ground.”
pain
is characterized by a group of unpleasant perceptual and emotional experiences
can be localized or diffuse
localized
type of pain sensation that is sharp, pricking, or cutting pain resulting from rapidly conducted action potentials
diffuse
type of pain sensation that is , burning, or aching pain resulting from action potentials that are propagated more slowly
local anesthesia
suppresses action potentials from pain receptors in local areas of the body through the injection of chemical near a sensory receptor or nerve.
general anesthesia
Pain sensations can also be suppressed if loss of consciousness is produced. T
a treatment where chemical anesthetics that affect the reticular activating system are administered.
referred pain
is perceived to originate in a region of the body that is not the source of the pain stimulus.
we sense — when deeper structures, such as internal organs, are damaged or inflamed
olfaction
sense of smell is called
odorants
olfaction occurs in response to airborne molecules called—
mucus
keeps the nasal epithelium moist, traps and dissolves airborne molecules, and facilitates the removal of molecules and particles from the nasal epithelium.
400
There are at least— functional olfactory receptors in humans.
10,000
These multiple combinations of odorants and receptors allow us to detect an estimated —- different smells.
taste buds
sensory structures that detect taste stimuli
are oval structures located on papillae on tongue, hard palate, throat
40 taste cells
Specialized epithelial cells form the exterior supporting capsule of each taste bud, and the interior consists of about —
taste hairs
Each taste cell contains hairlike processes, called —-, that extend into taste pores
sweet
sour
salty
bitter
umami
Taste sensations are divided into five basic types:
visual system
includes the eyes, the accessory structures, and sensory neurons.
We obtain much of our information about the world through the —
accessory structures
protect, lubricate, and move the eye
eyebrows
eyelids
conjunctiva
lacrimal apparatus
extrinsic eye muscles
accessory structures include:
eyebrows
protect the eyes by preventing perspiration from running down the forehead and into the eyes, causing irritation.
They also help shade the eyes from direct sunlight
eyelids
protect the eyes from foreign objects
If an object suddenly approaches the eye, the —- protect the eye by closing and then opening quite rapidly
Blinking also helps keep the eyes lubricated by spreading tears over the surface
conjunctiva
is a thin, transparent mucous membrane covering the inner surface of the eyelids and the anterior surface of the eye
secretions of the — help lubricate the surface of the eye.
lacrimal apparatus
produce tears
extrinsic eye muscles
are skeletal muscles and are responsible for the movement of each eyeball
eyeball
is a hollow, fluid-filled sphere
tunics
The wall of the eyeball is composed of three tissue layers, or —
fibrous tunic
vascular tunic
nervous tunic
3 tunics:
fibrous tunic
the outermost tunic which consists of the sclera and cornea
sclera
is the firm, white, outer connective tissue layer
helps maintain the shape of the eye, protects the internal structures, and provides attachment sites for the extrinsic eye muscles
cornea
is the transparent anterior sixth of the eye, which permits light to enter
As part of the focusing system of the eye, the — also bends, or refracts, the entering light.
vascular tunic
The middle tunic of the eye is called the — because it contains most of the blood vessels of the eye.
choroid
This very thin structure consists of a vascular network and many melanin-containing pigment cells, causing it to appear black
The black color absorbs light, so that it is not reflected inside the eye
delivers 02 and nutrients to retina
ciliary body
is continuous with the anterior margin of the choroid
helps hold lens in place
ciliary muscles
ciliary body contains smooth muscles called —
controls shape of lens
suspensory ligaments
ciliary muscles which attach to the perimeter of the lens by —
helps holds lens in place
lens
is a flexible, biconvex, transparent disc
focuses light onto retina
iris
is the colored part of the eye
surrounds and regulates pupil
pupil
which controls the amount of light entering the eye.
lots of light = constricted
little light = dilated
nervous tunic
is the innermost tunic and consists of the retina.
retina
covers the posterior five-sixths of the eye and is composed of two layers
pigmented retina
outer layer, with the choroid, keeps light from reflecting back into the eye
sensory retina
contains photoreceptor cells as well as numerous interneurons
rods and cones
photoreceptor cells which include —, respond to light
rods
are 20 times more common
can function in dim light because they are very sensitive, meaning they require lower levels of light to be stimulated.
do not provide color vision.
cones
require much more light
hey do provide color vision.
There are three types each sensitive to a different color: blue , green, or red
macula
fovea centralis
When the posterior region of the retina is examined with an ophthalmoscope, two major features can be observed:
macula
is a small spot near the center of the posterior retina
fovea centralis
center of macula
is the part of the retina where light is most focused when the eye is looking directly at an object.
contains only one cone cells, and is the region with the greatest ability to discriminate fine images, which explains why objects are best seen straight ahead
optic disk
white spot medial to macula
blood vessels enter eye and spread over retina
axons exit as optic nerve
• no photoreceptors
called blind spot
anterior chamber
posterior chamber
vitreous chamber
The interior of the eyeball is divided into three areas, or chambers:
anterior chamber
located between cornea and lens
filled with aqueous humor
aqueous humor
helps maintain pressure, refracts light, and provide nutrients to inner surface of eye
posterior chamber
located behind anterior chamber
contains aqueous humor
glaucoma
If aqueous humor flow from the eye through the venous ring is blocked, the pressure in the eye increases, resulting in a condition called
vitreous chamber
located in retina region
filled with vitreous humor: jelly-like substance
vitreous humor
jelly-like substance
r helps maintain pressure within the eye and holds the lens and the retina in place, refracts light
light refraction
bending of light
focal point
As the light rays converge, they finally reach a point at which they cross. The crossing point is called the —
occurs just anterior to the retina
the tiny image that is focused on the retina is inverted compared to the actual object.
accommodation
Changes in shape of the lens so image can be focused on retina
enables eye to focus on images closer than 20 feet
rhodopsin
photosensitive pigment in rod cells
opsin
colorless protein in rhodopsin
retinal
yellow pigment in rhodopsin
requires vitamin A
color blindness
is the absence of perception of one or more of perception of one or more color
loss may involve perception of all three colors or of one or two colors.
Most forms of — occur more frequently in males and are X-linked genetic traits
night blindness
A person with a vitamin A deficiency may have a condition called — characterized by difficulty seeing in dim light
retinal detachment
Night blindness can also result from —- which is the separation of the sensory retina from the pigmented retina.
optic nerve
leaves the eye and exists orbit through optic foramen to enter the cranial cavity
optic chiasm
where 2 optic nerves connect
optic tracts
route of ganglion axons
visual field
the image seen by each eye is the — of that eye
ears
The organs of hearing and balance are located in the —
external ear
middle ear
inner ear
Each ear is divided into three areas:
external ear
is the part extending from the outside of the head to the tympanic membrane, commonly called the eardrum
middle ear
air filled chamber with ossicles
inner ear
is a set of fluid-filled chambers medial to the middle ear