Modalities of cutaneous/skin sensation (refer to page 106 in manual
for which receptors detects
each sensation):
1. heat - Organ
of Ruffini
2. cold - Bulb
of Krause
3. light touch - Meissner's
Corpuscles
4. pain - Free
Nerve Endings
5. deep pressure- Pacinian
Corpuscles
Itch and tickle are usually excluded because of their mysterious origin.
In the face, tongue, and hands - Cutaneous
Receptors are more densely arranged than in the trunk, hips, and legs
....and accordingly (refer to Fig. 3.13 in the manual)
- Large areas of the brain are devoted
to touch perception and the motor activity of the face and hands; Small
areas of the brain are devoted to trunk, hips, and legs
Four basic taste stimuli:
All nuances of taste are due to different combinations of these, with the additional information derived from olfactory and touch receptors.
The Eye
1. Sclera and Cornea - The sclera is opaque and the cornea is transparent.
2. Choroid - The vascular layer that prevents incoming light ray from scattering and reflecting off the inner surface of the eye.
3. Retina
a. Rods
b. Cones
c. Macula
Lutea contains Fovea Centralis=area of best visual acuteness
The optic nerve arises from the retinal layer in the back of the eye.
Visual images are
transmitted from retina
to the occipital lobe of brain
The optic disc is the blind spot=area
where the optic nerve connects to the eye; there are no cones or rods on
the optic disk
Other parts of the eye:
1. Pupil
2. Vitreous body - soft, jelly-like substance maintaining the eyes shape.
3. Iris--has 2 muscles 1. Dilator Pupillae (open pupil) 2. Sphincter Pupillae (close pupil)
4. Lens--changes shape to focus
an image
Accomodation:
Near: Increased convexity
Distant: Decreased
convexity
Refraction: Bending of light
rays
B.
Myopia: Near-sightedness, caused
by elongated eyeball or misshapen cornea; image is in front of the retina
C.
Hyperopia: Far-sightedness,
caused by eyeball being too shallow, lens being too flat, or misshapen
cornea; Image is behind the retina
D.
Astigmatism: Abnormal curvature
of the cornea or lens or an irregularity in their surface; light rays are
incorrectly bent causing blurred vision and eyestrain
Click here to learn more about Ocular Diseases
Image formation on the retina:
The Ear
1. Sound waves enter the ear through the
External Ear=Pinna and
External Auditory Canal
2. Sound waves cause
Tympanic membrane to
vibrate
3. The vibrations from the tympanic membrane vibrate the three bones of the middle ear:
a. Malleus
b. Incus
c. Stapes
4. The bones vibrate against the membrane of the
Oval Window
5. Vibration of
the oval window causes
pressure waves in perilymph
6. Pressure waves pass through perilymph of scala vestibuli.
7. Waves strike vestibular membrane
and cause it to vibrate; this causes waves in endolymph
8. Waves in the endolymph strike the basilar membrane and cause it to vibrate. Movement of the basilar membrane causes the hairs associated with the basilar membrane to strike against the tectorial membrane. This contact bends the hairs and stimulates nerves at the base of those hairs. Nervous impulses then travel along these nerves to auditory areas of the cerebral cortex.
9. The waves, after stimulating the hairs, then are
absorbed by the round window
