Sensory lecture Flashcards
ANTERIOR LATERAL TRACT
primary afferents will travel and synapse on this same side After the first synapse, the ascending information decussates
Discriminative touch
Localization of touch and vibration
Ability to discriminate between two closely spaced points touching the skin
Conscious proprioception
Awareness of the movements and relative position of body parts
Stereognosis
Ability to use touch and proprioceptive information to identify an object
Dorsal column/Medial lemniscus system
Cross the midline
transmits discriminative touch, proprioception, vibration, 2 pt discrimination to consciousness into the CNS and up to the thalamus
Anterolateral column/Spinothalamic pathway
Crosses midline via anterior white commissure and ascend to thalamus as spinothalamic tract
transmits pain, temperature and poor localization into the CNS and up to the thalamus
Spinocerebellar projections
these relay information about muscle tension, limb position and spinal cord level of activity to the cerebellum for planning of movements
Brown-Sequard Syndrome
Loss of pain and temp.side opposite and below
Loss of light touch and 2-point ipsilateral and below the lesion
Upper motor lesion ipsilateral below the level of the lesion
Lower motor lesion at the level of the lesion due to the injury of cells directly and not axons
Speed of information processing is determined by the following
Diameter of the axons
Degree of axonal myelination
Number of synapses in the pathway
Tonic receptors
Do not adapt to the stimulus
Light on a photoreceptor, pressure, chemoreception
either on or off
Phasic receptors
Adapt to the stimulus
Some types of pain, noise, vibration
Mechanoreceptors
Respond to mechanical deformation of touch, pressure, stretch, or vibration.
Chemoreceptors
Respond to released substances by cells, including damaged cells after injury or infection.
Thermoreceptors
Respond to heat or cold.
Nociceptors
Stimulation results in the sensation of pain.
Example: Pressure mechanoreceptors are stimulated by stubbing a toe; the sensation experienced is pain rather than pressure.
Usually activated when cell damage/death might occur
What does distribution pattern tell you?
Spinal level of impairment
Brain involvement
Peripheral nerve damage
Ways to test for spinothalamic tract damage
sharp object and use of cold object
Ways to test for dorsal column tract damage
cotton swab and filament testing
Meissner corpuscles
a cutaneous nerve ending responsible for transmitting the sensations of fine, discriminative touch and vibration.
Pacinian corpuscles
sensory nerve that acts as a receptor for pressure and vibration.
Vibration: discriminative
30 Hz stimulates Meissner corpuscles
256 Hz stimulates Pacinian corpuscles
Two-point Discrimination
Accuracy of sensory fields Can 2 points be detected Differing sizes in different areas of the body Back are the largest Face and fingers are the smallest
Stereognosis: discriminative
Requires cortical processing and interpretation
Can objects be recognized by touch only
Difficult to test if patient has expressive aphasia or anomia
Diabetic neuropathy
Primarily loss of vibratory and position sense
Muscle denervation can occur
Paresthesia, numbness, coldness, other distortions of thermal sensations
Why have a NCS?
In addition to determining the location of peripheral nervous system lesions, a primary diagnostic value of NCS is to determine whether the neuropathic lesion is one of axonal loss or demyelination.
