Download Senses Notes

Sensation- a feeling resulting from a sensory impulse
2 Major Categories
1) Special Senses - smell, taste, sight, hearing and balance
2) General Senses - touch, pressure, pain, temp, vibration,
itch and proprioception (sense of movement and
position of the body and limbs)
Sensory adaptation - when receptors adapt and fail to send
signals.
Receptor - sensory nerve ending in the skin and other
tissues capable of responding to stimuli by
developing action potentials
Types of Receptors
1. Mechanoreceptors - respond to mechanical stimuli
(bending or stretching)
2. Chemoreceptors - respond to chemicals
3. Photoreceptors - respond to light
4. Thermoreceptors - respond to temp changes
5. Nociceptors - respond to pain sensations
1. Sensory Nerve Fibers - free nerve endings found
in epithelial tissue and are associated with touch
and pressure.
2. Meissner’s Corpuscles - loose fibers surrounded by
flattened connective tissue related to the sensation
of light touch. Numerous in hairless portions of skin
(lips, soles, fingertips, palm, genitals, etc)p451 Fig15-1
3. Pacinian Corpuscles - bigger and found deep in tissues
(tendons, muscles, ligaments in joints etc)Associated
with heavy or deep pressure
Meissner
Sensory
pacinian
Heat receptors (free nerve endings)
Cold receptors
(free nerve endings)
1) acute pain fibers - sharp, well-localized, pricking,
or cutting pain resulting from rapidly conducting
action potentials
2) chronic pain fibers - diffuse, burning, or dull aching
pain resulting from slow conducting action
potentials (visceral pain stimuli are normally
perceived as diffuse pain)
Referred pain - a painful sensation perceived to originate
in a region of the body that is not the source
of the pain stimulus p450 Box 15-1
exp: heart …….. Referred to the left shoulder or left arm
-smell and taste, hearing and balance, vision and light
I. Olfaction - sense of smell
Undergo sensory adaptation
P454 Fig 15-2
*The olfactory receptor cells (bipolar neurons) are
equipped with olfactory hairs, long cilia that protrudes
out from the nasal epithelium and are layered by mucus.
When stimulated by chemicals dissolved in the mucus,
they transmit impulses along the olfactory nerve.
*closely tied to the limbic system “emotional brain” thus smells are
long lasting and very much a part of our memories and emotions
II. Taste
Taste bud - specific receptors for the sense of taste
papillae - small peg-like projections that cover the
dorsal tongue surface p455 Fig 15-4
II. Taste
Taste cell - modified epithelial cells that function as
receptors
*taste pore on the surface and projecting out of the
pore are taste hairs
4 Basic Types
1. Sour
2. Salty
3. Sweet
4. Bitter
5. Umani (MSG)
Humans have almost 10,000 taste buds, some of them
are on the roof of your mouth.
Girls usually have more taste buds than boys
The older you get the fewer taste buds you have
Insects are better at tasting than animals
III. Hearing
External Ear
P457 Fig 15-5
1. Auricle - funnel like structure that
helps collect sound waves and
direct them to the external auditory
meatus
2. External Auditory Meatus - s-shaped
tube that leads to the temporal
bone.
P457 15-5
III. Hearing
1. Tympanic membrane (eardrum): coneMiddle Ear
shaped semitransparent membrane
covered by a thin layer of skin.
2. Auditory Ossicles - 3 bones that connect
the eardrum to the inner ear and
function in transmitting vibrations
The 3 bones (based on shape)
1. Malleus or hammer
2. Incus or anvil
3. Stapes or stirrup
III. Hearing
P457 15-5
Oval window - an opening that leads to the inner
ear. Transmits vibrations from the stapes to the
fluid within the inner ear, which is responsible for
stimulating hearing receptors.
Auditory Tube (eustachian tube) - connects middle ear to
throat. It helps maintain equal air pressure on each
side of the eardrum
III. Hearing
*Inflamation of the middle ear otitis media - result
of sore throat in children whose auditory tubes are
more horizontal.
III. Hearing
p457 Fig 15-5, p458 Fig 15-6
Inner Ear - a maze of bony chambers called osseous or
bony labyrinth
3 Divisions of the Bony Labyrinth
1. 3 semicircular canals - involved in kinetic
equilibrium/balance
2. Cochlea - (resembles a small snail) contains
receptors for hearing
3. Vestibule - between semicircular canals and
cochlea, sense of movement and static eq
III. Hearing
P458 Fig 15-6
* The bony labyrinth is filled with plasma like fluid
called perilymph. The system of membranes that follow
the shape of the bony labyrinth is the membraneous
labyrinth. The thicker fluid inside the membraneous
labyrinth is called endolymph.
III. Hearing
p462 Fig 15-8
Static Equilibrium - sense the position of the head with
respect to the pull of gravity when
the body is not moving found in the
vestibule.
Maculae - a patch of receptor cells with their “hairs”
embedded in a gel-like material containing
otoliths (tiny stones made up of calcium salts).
As the head moves otoliths respond to the pull of gravity
and creates a pull on the gel and bends the hairs.
III. Hearing
p463 Fig 15-8
Dynamic Equilibrium - responds to angular or rotary
movements of the head, the receptors
are found in the semicircular canals.
Crista ampullaris - a receptor site within each semicircular canal that contains a tuft of hair
covered with a gelatinous cap or cupula
When head moves in a circular motion the endolymph pushes the
cupula in the opposite direction of the body’s motion. When the
motion stops the endolymph flows in the opposite direction
causing that reversed motion feeling you get when you suddenly stop.
III. Hearing
P458 Fig 15-6
Mechanisms of Hearing
Organ of Corti - contains hearing receptors with
hair cells and when stimulated the hairs
transmit impulses along the cochlear nerve
to the temporal lobe where the sound is
interpreted.
http://www.sumanasinc.com/webcontent/animation
s/content/soundtransduction.html
http://www.youtube.com/watch?v=qgdqp-oPb1Q&safe=active
*Hearing is the last sense to leave our awareness
when we fall asleep and die and the first to return
when we awaken
External and Accessory Structures
*6 extrinsic or external eye muscles attached to outer
surface of eye and make it possible for eyes to follow
moving objects.
External and Accessory Structures
Eyelids - thin skin that covers the outer surface of the eye
and fuses with the margin of the lid
Composed of 4 layers
1) skin
2) muscle
3) connective tissue
4) conjunctiva - lines the eyelids and secretes mucus to
lubricate and keep eyeball moist
External and Accessory Structures
p468 Fig 15-18
Lacrimal Apparatus *lacrimal glands - secrete tears and the tears then
flush across the eyeball into the lacrimal canals then
into the lacrimal sac and finally into the nasolacrimal
duct which empties into the nasal cavity
*If you very gently pull down the inside corner of your eye. When you see a tiny little hole,
you've found the tear duct/lacrimal canal.
Internal Eye Structures
Eyeball - the eye, its wall is composed of 3 layers or
tunics and its interior is filled with fluids that help
maintain its shape.
Internal Eye Structures
The Tunics
p464 Fig 15-10
1. Outermost tunic - (fibrous tunic)
sclera - or fibrous tunic “white of eye” the thick,
white, connective tissue that supports
and protects the eye.
cornea - the transparent “window” where light
enters the eye. It helps focus light rays.
The cornea is the only tissue that can be transplanted
w/out the worry of rejection b/c it has no blood vessels
Internal Eye Structures
p464, p465
II. Middle Tunic – (vascular tunic)
Choroid - blood-rich nutritive tunic that
contains a dark pigment that prevents
light from scattering inside the eye
Ciliary body - thickest part of the middle tunic
to which the lens and iris attach,
muscular structure that manipulates
the lens.
Internal Eye Structures
p464, 465, and 467
Lens - the elastic, double convex structure in the
eye that focuses the light on the retina.
Iris - the pigmented, involuntary muscle that acts
as the diaphragm of the eye (colored portion).
Pupil - rounded opening through which light passes
bright light - circular fibers contract and pupils constrict
to decrease the amt of light entering eye
dim light - radial fibers contract and pupils dialate to
allow more light to enter the eye. Fig 10.21
Internal Eye Structures
III. Innermost Tunic
Retina - the innermost tunic which contains photoreceptors (rods and cones) that respond to
light.
Fovea centralis - the region of sharpest vision inside the
retina
Optic disk or blind spot - is where nerve fibers from
the retina leave the eye and become part
of the optic nerve.
P464, p466
*The lens divides the eye into two chambers the
aqueous chamber, anterior to the lens, contains a clear
watery fluid called aqueous humor. The vitreous chamber,
posterior to the the lens, is filled with a gel-like substance,
vitreous humor.
As light passes through the eye it passes through the cornea
then past the aqueous humor, the lens, and then the vitreous
humor and retina.
http://www.youtube.com/watch?v=gvozcv8pS3c&safe=active
Common correctable vision problems
Myopia
(near sighted)
light focuses in front of the retina
Hyperopia
(far-sighted)
light focuses behind the retina
Astigmatism
irregular curvature of the cornea,
causes light to focus on more than
one point = blurriness
Glaucoma
a result of excessive accumulation of
aqueous humor, increased pressure
in the eye
Cataract
Cloudy lens that obstructs the light
before it hits the retina
http://www.youtube.com/watch?v=6YxffFmi4Eo&safe=active