Term
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Definition
| awareness of where body limbs are in 3D space. This sensation is based on joint angles and muscle stretching. |
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Term
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Definition
II. large, myelinated (A-ß and A-λ) fastest
III. Smaller and lightly myelinated (A-δ)
IV. small, unmyelinated (C) slowest
Touch can be type II, III and IV fibers.
Kinesthesia is type II fibers.
Temperature is type III and possible type IV.
Pain can be type III or IV. |
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Term
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Definition
| Large diameter fibers (type II) conduct touch, kinesthesia, and fine discriminitive touch. The information ascends ipsillaterally and crosses in the brain stem. |
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Term
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Definition
| Small diameter (III and IV) fibers synapse on an intermediate cell that crosses over the spinal cord into the anterolateral quadrant. So, information travels up the spinal cord contralaterally. The anterolateral system is responsible for temperature and pain sensation. |
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Term
| Central connections for the somatosensory system |
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Definition
| Dorsal Column: Information from the lower extremities (below T7) goes to the nucleus gracilis and information from the upper extremities (above T6) goes to the more laterally located nucleus cuneatus. |
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Term
| Rapidly adapting mechanoreceptors |
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Definition
Meissner's corpuscle: found in non-hairy skin between the epidermis and dermis, small receptor field sensitive to poking and low frequency vibrations
Hair-follice receptor: free nerve ending is wrapped around root which detects hair movement
Pacinian corpuscle is a very rapidly adapting mechanoreceptor |
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Term
| Slowly adapting mechanoreceptors |
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Definition
Ruffini's Corpuscle: present in hairy skin, large receptive field responds to tugging or stretching of skin
Tactile: present in hairy skin, sensitive to touch
Merkel's Receptors: present in non-hairy skin, small receptor field, responds continuously to adequate stimuli |
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Term
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Definition
| If you apply a stimulus to a sharp point the receptor directly under that point will fire, but because the skin is displaced the neighboring receptors will also fire. The neighboring receptors will fire with less intensity. As the stimulus moves up the nervous system, it comes across inhibitory neurons. Since the neighboring receptors are less intense they will not reach the brain. Lateral inhibition allows us to sharpen a stimulus. |
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Term
| Function of kinesthesia receptors |
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Definition
Continuously monitor the change in a joint angle/stretching of muscles as well as the velocity of which it is moving.
System is made up of many cells that detect full range of motion as well as precise movements (which require sensitivity in a small range). |
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Term
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Definition
| The ability to sense a 3D object in your hand with your eyes closed and be able to identify it. The ability to sense joint angles and tactile information make this possible. |
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Term
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Definition
| If someone writes a letter in your hand, you are able to tell what that letter is. This is possible because of the small receptor fields that allow you to discriminate fine differences. With out the dorsal column system you would not be able to do that. |
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Term
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Definition
Temperature receptors work best when the temperature is changing. Warm receptors respond to increasing temperature and cool receptors respond to decreasing temperature.
Extremely hot and extremely cold temperatures (able to cause tissue damage) require nocioceptive receptors and result in pain. These do not respond to changes in temperature. |
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Term
| Define eppicritic pain, protopathic pain, and reffered pain |
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Definition
Eppicritic pain: fast pain that is localized, such as a razor cut or prick, caused by Aγ fibers
Protopathic pain: slow, agonizing pain that can not be localized, such as a toothe ache, mediated by C fibers
Reffered pain: pain sensation in a region of the body in the absence of a nocioceptor. follows the dermatone rule |
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Term
| Discuss the gate theory of pain |
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Definition
Pain is conducted through the nocioceptive transmission cell (t-cell), but an interneuron (in the substantia gelatinosa) controls the "gate" that allows access to the t-cell.
Group IV fibers: excite the t-cell which causes pain and inhibits the interneuron which opens the gate and allows more pain to reach the t-cell
Group II fibers: excite the interneurons which closes the gate and therefore reduces pain, this is why rubbing reduces pain
Group III fibers: results in fast pain because it excites the t-cell and the interneuron. So, it causes pain when it excites the t-cell, but then it excites the interneuron causing it to close the gate and prevent further pain. |
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