Lecture 6: General Sensory Mechanisms III Flashcards
Two-point discrimination touch
Ability to distinguish 2 separate points as close to 2 mm apart
Lateral inhibition
Blocks lateral spread of excitatory signals, increasing degree of contrast in cerebral cortex
Fast pain
Felt within 0.1 s after stimulus, not felt in deeper tissue, elicited by mechanical/thermal stimuli; carried by A fibers terminating in lamina I
Slow pain
Begins 1 s after stimulus is applied and gradually increases, described as aching/throbbing, elicited by mechanical/thermal/chemical stimuli; carried by C fibers which terminate in layers II and III
Which pain fibers make up the neospinothalamic tracts?
Fast pain
Which pain fibers make up the paleospinothalamic pathway?
Slow pain
Which neurotransmitter is used by A fibers of fast pain path?
Glutamate
What do the slow pain C fibers release during their pathway?
Glutamate and substance P
Brown-Sequard Syndrome
Occurs when there is a hemisection of spinal cord; all motor, kinesthetic function, 2-point touch lost on side of transection and below, spinothalamic sensations lost on opposite side of body and in dermatomes 2-6 segments below
What are the 3 components of the Analgesia system?
Periaquaductal gray and periventricular regions of brainstem and third ventricle, Raphe magnus nucleus and retircular nuclei in medulla, Pain inhibitory complex in dorsal horns
What are the 3 types of receptors that discriminate thermal gradations?
Cold, Warmth, Pain
Referred pain
Occurs when visceral pain fibers are stimulated and stimulate some of the pain fibers that conduct pain signals from the skin
What kind of stimuli excites visceral pain nerve endings?
Ischemia of visceral tissue, chemical damage to surface, smooth muscle spasm, etc.
Name 2 visceral areas that are insensitive to pain of any type
Parenchyma of liver, alveoli of lungs
Headaches
Result of pain referred to surface of head from deep head structures; may result from meningitis, low CSF pressure, alcohol, muscle spasm, etc.
Where do secondary fibers of the paleospinothalamic pathway terminate?
A. VPL of thalamus
B. Ventrobasal nuclei of thalamus
C. Throughout the brainstem
D. Somatosensory cortex
C. throughout the brainstem
Which of the following is not a result of Brown-Sequard syndrome?
A. All motor functions blocked on the side of the transection below level of transection
B. All vibration and two-point touch lost on the side of transection below level of transection
C. All sensations of pain, heat, cold are lost on the side of transection 2-6 dermatomes below transection
D. All sensations of pain, heat cold are lost on the opposite side of transection 2-6 dermatomes below transection
C. All sensations of pain, heat cold are lost on the side of transection 2-6 dermatomes below transection
Which of the following is not a component of the analgesia system?
A. Pain inhibitory complex
B. Olivary nuclei
C. Periaquaductal grey
D. Raphe magnus nucleus
B. Olivary nuclei
What type of fibers transmit visceral pain from thoracic and abdominal cavities?
A. A fibers
B.Group IIA fibers
C. C fibers
D. Group IIIB fibers
C. C fibers
