Nursing 1080A/B Lecture Notes - Lecture 4: Substantia Gelatinosa Of Rolando, Nociceptor, Peripheral Nervous System
6 Jun 2016
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Week 4
Pain Assessment (page 125- 148)
• Nurses assess the pain and the patient’s response to it providing pain relief
strategies and assessing the patient’s response and monitoring for adverse
effects
• Also includes being an advocate for the patient when pain-relieving
strategies need changing and teaching the patient and family how to manage
pain following discharge
• Nonpharmaceutical modalities such as therapeutic touch, acupuncture,
reflexology, transcutaneous electrical neural stimulation, Tai chi and Qi going
also relieve pain
• Pain does not relate to gender or age or genetic background
• Pain can affect quality of life, interactions with family and friends, sense of
wellbeing and self-esteem and financial resources
• Pain can be from surgery or injury but for others there may be no identifiable
cause
Pain has three components:
1. Sensory discriminative (severity and location of pain) which receives the
most attention within the health care professions
2. Affective motivational emotional aspects how the pain makes us feel
and what it makes us do
3. Cognitive evaluative (meaning attributed to the pain)
Peripheral Nervous System:
• Several different types of nerve fibres that transmit pain are located in the
peripheral nervous system. There are 2 main types:
1. A delta Fibre: large nerve fibres covered with myelin, they conduct pain
impulses rapidly.
Conducts a sharp or stabbing pain and is well localized. These fibres
stimulate motor responses such as withdrawal or flinching
2. C fibres: smaller unmyelinated nerve fibres; they conduct pain impulses
more diffusely and slowly. Patients describe pain as achy and ongoing
even after pain stimulus is removed (Purves). They are not well localized
and fibres stimulate a protective response such as guarding. C fibres
release a pain facilitating substance from nerve endings called substance
P. The function of substance P is to speed the transmission of the pain
stimulus up the pain pathway. Bradykinin another pain facilitating
substance is released at the site of the injury. It is a cellular chemical
released from the damaged tissue. The function of bradykinin is to cause
continues irritation to the injury site. These specialized peripheral A- and
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2
C- nerve fibres are referred to as nociceptors. They carry the pain signal
to the central nervous system.
Central Nervous System:
• Once the pain stimulus is transferred into the central nervous system
through the dorsal root ganglion, it synapses in the substantia gelatinosa in
the dorsal horn of the spinal cord and enters the central nervous system.
• Opening and closing the gate to nociception is controlled by the combined
effect of both the sum of the pain facilitating impulse and the facilitating
substances and the sum of the pain-blocking impulses and substances as they
are received in the substantia gelatinosa. If facilitator impulses predominate,
the pain stimulus is passed on; if blocking impulses predominate, the pain
stops.
• If the pain is allowed to continue, the pain stimulus passes through the
spinal cord into the lateral spinothalamic tracts, which lead directly to the
thalamus and hen into the limbic system. In the limbic system the emotions
that control pain are controlled and the stimulus is then passed to the
cerebral cortex when the sensation is recognized as pain. This process takes
milliseconds
• Pain transmission: some nerves use substance P to fire at synaptic junctions.
Glutamate is the neurotransmitter responsible for the communication of the
peripheral nervous system with the central nervous system. Also an
additional function of glutamate is thought to be activation of N-methyl D-
aspartate receptors, which can help intensify and prolong persistent pain.
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Gate Control:
• This theory is mostly accepted, that the body responds to a painful stimulus
by either opening a neural gate to allow pain to be produced or creating a
blocking effect at the synaptic
junction to stop the pain.
• Steps in the theory:
1. Continued pain stimulus on a peripheral neuron causes the gate to open
through depolarization of the nerve fibre. This is accomplished by ion
influx and outflow
2. The pain stimulus then passes from the peripheral nervous system at a
synaptic junction to the central nervous system up the afferent nerve
pathways
3. The 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:
• Means the perception of pain by sensory receptors located throughout the
body and called nociceptors. They can produce pain resulting from heat,
pressure or noxious chemicals such as those found in the inflammatory
process
• There are four steps:
1. Transduction: noxious stimuli create enough of an energy potential to
cause a nerve impulse perceived by nociceptors (free charge endings)
2. Transmission: the neuronal signal moves from the periphery to the spinal
cord
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Document Summary
Peripheral nervous system: several different types of nerve fibres that transmit pain are located in the peripheral nervous system. There are 2 main types: a delta fibre: large nerve fibres covered with myelin, they conduct pain impulses rapidly. Conducts a sharp or stabbing pain and is well localized. These fibres stimulate motor responses such as withdrawal or flinching: c fibres: smaller unmyelinated nerve fibres; they conduct pain impulses more diffusely and slowly. Patients describe pain as achy and ongoing even after pain stimulus is removed (purves). They are not well localized and fibres stimulate a protective response such as guarding. C fibres release a pain facilitating substance from nerve endings called substance: the function of substance p is to speed the transmission of the pain stimulus up the pain pathway. Bradykinin another pain facilitating substance is released at the site of the injury. It is a cellular chemical released from the damaged tissue.
