NROC64H3 Chapter Notes - Chapter 12: Lipid Bilayer, Meninges, Aspirin

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9 Jul 2011
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Somatic sensory system
somatic sensation-allows our body to feel, ache, chill and know what its parts are doing
-is sensitive to many kinds of stimuli; pressure, position, distension of bladder, temperature of brain and
limbs etc
when stimuli become strong, somatic sensation also responsible for offensive but imp feeling: pain
Somatic sensory systems is diff from other sensory system in 2 diff ways;
1)its receptors are distributed throughout the body vs being concentrated in small, specialized locations
2) it responds to many diff kinds of stimuli, i.e a group of 4 senses rather one single sense- --touch> temp.
>pain and body position
somatic sensory is a collective category for all sensations that are not seeing, hearing, smelling, tasting
etc.
a single receptor can encode stimulus features such as intensity, duration, position and sometimes
direction but a single stimulus activates many receptors---> the CNS interprets the activity of vast receptor
array and generates perceptions
1)Touch
sensation of touch begins at the skin
2 major types of skin; hairy and glabrous(=hairless)
skin's outer layer: epidermis
skin's inner layer; dermis
functions of skin:
--protective function
---prevents evaporation of body fluids into the environment
--provides direct contact withthe world
skin - largest sensory organ we have
-----is very sensitive
Mechanoreceptors
most of the sensory recpetors in skin are mechanoreceptors
are sensitive to physical distortion such as streching and bending:)
present thorugh out the body
they monitor contact with skin and pressure in the heart and blood vessels, stretching of the digestive
organ and urinary bladder and force against teeth
contain unmyelianted axon branches, these axons have mechanosensitive ion channels:>gating depends
on stretching or changes in tension of surrounding membrane
Pacinian corpuscle :
lies deep in the dermis
largest receptor
can be seen with naked eye
Ruffini's endings: smaller than pacinian corpuscle
found in both hairy and glabrous skin
Meissner's corpuscle-are located on the ridges of glabrous skin i.e on the tip of fingertips
1/10 SIZE OF pacinian corpuscles
Merkel's disks-located with in the epidermis
consist of a nerve terminal and a flattened non neural epithelial cell
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