NURS 1660 Lecture 4: Pain
10 Jun 2018
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Week Four (October 2- 6, 2017)
Health Assessment I
Unit One
Chapter SEVEN: Pain Assessment (Pgs. 125 - 147)
Pain has three components:
- Sensory Discriminative: Severity and location.
- Affective Motivational: Emotional Aspects; how it makes us feel and what it makes us do.
- Cognitive Evaluative: Meaning attributed to the pain.
Anatomy and Physiology Overview
There are several types of nerve fibers that transmit pain; they are located in the peripheral
nervous system. Two main types of nerve fibers are as follows:
1. A delta fibers:
a. Large nerve fibers covered with myelin;
b. Conduct pain impulses rapidly.
c. Produces sharp, stabbing, centralized pain.
d. Simulates withdrawal or flinching.
2. C fibers:
a. Smaller unmyelinated nerve fibers.
b. Conduct pain impulses more diffusely and slowly.
c. Produces non-well localized achy, and ongoing pain; even after stimulus is
removed.
d. Stimulate protective response (ie. guarding).
→ C fibers release a pain-facilitating substance from nerve endings called substance P:
which speeds the transmission of the pain stimulus up the pain pathway.
→ Bradykinin, another pain-facilitating substance, is released at the site of injury;
released from damaged tissue and its function is to cause continued irritation at the
injury site.
These specialized A- and C-nerve fibers are referred to as pain receptors; they carry pain to the
CNS.
Peripheral Nervous System
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Week Four (October 2- 6, 2017)
1. Pain begins as a message received by nerve endings (nociceptors).
2. Release of substance P, bradykinin, and prostaglandins sensitizes
the nerve endings; helping transmit pain from site of injury toward
the brain.
3. The pain signal travels as an electrochemical impulse along nerve to
dorsal horn on spinal cord.
4. Spinal cord then sends the message to thalamus and the to the
cortex.
5. Pain relief starts with signals from the brain that descend by way of
spinal cord.
6. Chemicals (endorphins) are then released in dorsal horn to diminish
pain message.
Gate Control Theory
- Developed by Ron Melzak (a Canadian psychologist) and Patrick Wall.
- The Gate Control Theory posits that the body responds to a painful stimulus by
either opening a neutral gate to allow pain to be produced or creating a blocking
effect at the synaptic junction to stop/block the pain. The steps for pain
transmission in the gate control theory are as follows:
1. Continued painful stimuli on peripheral neuron causes “gate” to
open through depolarization of nerve fibre.
2. The pain stimulus then passes from PNS at a synaptic junction to
the CNS up the afferent nerve pathways.
3. Pain stimulus passes up through and across the dorsal horn of the
spine to the structures of the limbic system and the cerebral
cortex.
4. In the cerebral cortex, the stimulus is identified as pain and a
response is created. The response, once generated, passes down
the efferent pathways where reaction to the pain is created.
Nociception
- The most common clinical interpretation of pain
transmission is a concept called nociception; the perception of pain by sensory
receptor located throughout the body called nociceptors.
- Nociceptors can produce pain resulting from heat, pressure or noxious chemicals
- There are four steps in nociception:
- Transduction: Noxious stimuli create enough of an energy potential to
cause a nerve impulse perceived by nociceptors (free nerve endings).
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Week Four (October 2- 6, 2017)
- Transmission: The neuronal
signal moves from the
periphery to the spinal cord and
up to the brain.
- Perception: The impulse being
transmitted to the higher areas
of the brain are identified as
pain.
- Modulation: Inhibitory and
facilitating input from the brain
modulates/influences the
sensory transmission at the
level of the spinal cord.
Persistent or chronic pain can exist without any
identifiable causes and result in the body to adapt or
change how it transmits or perceives pain signals. This is known as neuroplasticity.
Pain-Facilitating Substances: Pain-Blocking Substances:
- Substance P
- Bradykinin
- Glutamate
- Serotonin
- Opioids (both natural and synthetic)
- GABA: gabapentin (Neurontin) and
pregabalin (Lyrica)
Pain Classification
Pain can be classified based on duration (acute, chronic), frequency (intermittent, continuous),
form (nociceptive, neuropathic), cause (etiology), location and association with cancer and its
treatments.
Duration: Acute Pain
- Pain of short duration that has an identifiable cause such as trauma, surgery or
injury.
Duration: Chronic/Persistent Pain
- Pain that lasts beyond the expected healing period of 3-6 months.
- May be non identifiable cause.
- Ex. Low back pain and sickle cell pain.
Frequency: Continuous or Intermittent/Episodic Pain
- Pain can be continuous, episodic or intermittent.
- Ex. Arthritis, migraines.
Form: Nociceptive Pain
- Nociceptive pain has various locations:
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Document Summary
Affective motivational: emotional aspects; how it makes us feel and what it makes us do. Cognitive evaluative: meaning attributed to the pain. There are several types of nerve fibers that transmit pain; they are located in the peripheral nervous system. C fibers release a pain-facilitating substance from nerve endings called substance p: which speeds the transmission of the pain stimulus up the pain pathway. Bradykinin, another pain-facilitating substance, is released at the site of injury; released from damaged tissue and its function is to cause continued irritation at the injury site. These specialized a- and c-nerve fibers are referred to as pain receptors; they carry pain to the. Developed by ron melzak (a canadian psychologist) and patrick wall. The gate control theory posits that the body responds to a painful stimulus by either opening a neutral gate to allow pain to be produced or creating a blocking effect at the synaptic junction to stop/block the pain.
