PATHO EXAM 4
*Nociception - Sensation of pain resulting from transmission of neural impulses to the brain that is
caused by noxious stimuli
* Non-nociceptive Pain - Neuropathic Pain [peripheral and central]
Nociceptors - Free nerve endings located throughout the body in the afferent PNS that re...
*Nociception - Sensation of pain resulting from transmission of neural impulses to the brain that is
caused by noxious stimuli
* Non-nociceptive Pain - Neuropathic Pain [peripheral and central]
Nociceptors - Free nerve endings located throughout the body in the afferent PNS that respond to
chemical, mechanical and thermal stimuli.
1. Nociceptors are not evenly distributed throughout the body. Sensitivity to pain differs
according to their location
2. Fingertips have more nocicpetors than the skin of the back
* Nystagmus - Involuntary unilateral or bilateral rhythmic movements of the eyes. Happens at rest or
when the eye is following a moving object. (eyes shake back and forth)
*Jerk Nystagmus- One eye moves faster than the other.
* Strabismus - One eye deviates from the other when the person is looking at an object. This is caused
by a weak or hypertonic muscle in the eye. (primary symptom= diplopia)
* 4 processes of nociception
1. Transduction - Begins when tissue is damaged by exposure to chemical, mechanical, or
thermal noxious stimuli. This causes the activation of nociceptors.
2. Transmission - Is the conduction of pain impulses along the A-beta and C-fibers into the
dorsal horn of the spinal cord.
3. Perception - Is the conscious awareness of pain, which occurs primarily in the reticular and
limbic systems, and the cerebral cortex.
4. Modulation - Involves many different mechanisms that increase or decrease the
transmission of pain signals throughout the nervous system. Depending on the mechanism,
modulation can occur before, during, or after pain is perceived.
* The Gate Control Theory Of Pain.
Pain transmission is modulated by a balance of impulses conducted to the spinal cord, where cells in
the substantial gelatinosa function as a "gate" that regulates the nociceptive transmission to higher
centers in the CNS. Does not account for phantom pain.
Gate opens= Increased perception of pain (Large A fibers)
Gate closes= Decreased perception of pain (small C fibers)
* The Pattern Theory Of Pain
Describes the role of impulses, intensity, and the re-patterning of the CNS. Although this theory
evolved to provide an explanation for neuropathic pain, this theory does not account for all types of
pain experiences.
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The intensity of pain is directly related to the amount of associated tissue pain.
Only accounts for acute pain.
* Neuromatrix Theory of Pain
The brain produces patterns of nerve impulses drawn from various inputs, including genetic,
psychologic, and cognitive experiences. The qualities we normally feel from the body, including pain,
also can be felt in the absence of inputs from the body (phantom limb pain.) This theory added to our
knowledge of pain combined with the gate control theory.
* interpretive centers for pain located In the brainstem, midbrain, diencephalon and cerebral cortex
* Efferent pathways necessary for pain descend from the CNS back to the dorsal horn of the spinal
cord and modulate pain.
* Perception- Is the conscious awareness of pain.
1. Sensory-discriminating system
2. effective-motivational system
3. cognitive-evaluative system
* primary order neurons are nociceptors.
secondary order neurons are interneurons in the dorsal horn of the spinal column.
third order neurons are afferent neurons in the spinothalamic tract
* The cortex is the processing center for pain
* Myelinated A-delta fibers
1. Fast transmission
2. Conveys mechanical and thermal, sharp, and localized pain.
* Unmyelinated C polymodal fibers
1. Slower transmission.
2. Conveys diffuse burning and aching sensations
* interneurons are located on the dorsal horns of the spinal cord
* pain pathway responsible for the modulation or inhibition of afferent pain signals is the efferent
pathways from the periaqueductal gray matter in the midbrain
* The thalamus, cortex and postcentral gyrus is the pain pathway perceives, describes, and localizes
pain.
* The reticular formation and limbic system is the pain pathway that controls the emotional and
affective responses to pain.
This study source was downloaded by 100000812546443 from CourseHero.com on 01-27-2022 04:47:12 GMT -06:00
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