Ch.10 PAIN Flashcards
What is Pain?
▪️unpleasant sensation
▪️body defence mechanism
▪️complex mechanisms
▪️subjective scales
Level of stimulation to elicit a pain response
➰ usually does not vary between individual
Pain threshold
The ability to cope with pain. Culturally related. Varies between individuals
Pain tolerance
A receptor is a specialized region of a sensory (afferent) neutron that detects a specific stimulus
Sensory Receptors
Sensory Receptor Types:
▪️mechanoreceptor
▪️photoreceptor
▪️chemoreceptor
▪️nociceptor
Sensory receptor for tactile skin sensation, deep tissue sensation, hearing and proprioception
Mechanoreceptor
Sensory receptor for vision?
Photoreceptor
Sensory receptor for taste and smell?
Chemoreceptor
Sensory receptor for pain?
Nociceptor
Example for tactile skin sensation?
Merkel cells
Examples of deep-tissue sensation
🔘Ruffini endings 🔘Meissen corpuscles 🔘Pacinian corpuscle 🔘Hair follicle end organ 🔘Free nerve endings
Example for this function is Cochlear sound receptor
Hearing
Example for this function are rods & cons
Vision
Example for this function is taste bud receptor
Taste
Example for this function is olfactory epithelium receptors
Smell
Example for this function is free nerve endings
Pain
What are the causes of pain?
▫️inflammation ▫️thermal (above 45°C and below 5°C) ▫️infection ▫️ischemia and tissue necrosis ▫️stretching of tissue (distention) ▫️stretching of tendons, ligaments, joint capsule ▫️chemicals ▫️burns ▫️muscle spasm
Examples of pain-genesis?
▫️atherosclerosis
▫️distension or contraction of hollow organs
▫️surgical incisions
▫️muscle and tendon tears leading to inflammation
▫️compression/entrapment of nerves (neuropathic pain and radicular pain)
“Sensing of pain” - activation of nociceptors and the subsequent feeling of pain.
Nociception
Pain consists of several events:
- Signal transduction (activation of nociceptos)
- Signal transmission (along 1st, 2nd and 3rd order neutrons)
- Perception of pain - occurs in cerebrum
- Signal modulation (enhance or depress pain signal)
responsible for detection of injured (inflamed) tissue
▫️they are found primarily in the skin and mucous membranes
Nociceptors
Nociceptive vs. Neuropathic pain
Nociceptive pain: the sensation that is felt from activation of nociceptors
Neuropathic pain: sensation felt from direct neural damage (nerve compression or partial severance)
Types of Sensory Fibers:
▫️A-fibers
▫️A-alpha fibers
▫️A-Beta fibers
▫️A-delta fibers
▫️B-fibers
▫️C-fibersis large, myelinated fibers - mostly cutaneous
A-fibers
an A-fibers transmit motor impulses and proprioceptive information
A-alpha fibers
an A-fibers that transmit touch and pressure sensation
A-beta fibers
An A-fibers that transmit thermal and pressure sensations (hot, cold, pressure, stretch)
A-delta fibers
“Fast pain fibers” ➡️ pain conducted along these fibers is usually described as “sharp, stabbing and localized”
A-delta fibers
A smaller myelinated fibers found mainly in the pre-ganglionic fibers of the autonomic nervous system.
This fiver transmit motor impulses only.
B-fibers
Small un-myelinated fibers located mostly in the viscera and are stimulated by chemical irritants (plus some stretching /distension)
“Slow pain fibers”
Pain along these fibers are described as “diffuse, dull, and aching”
C-fibers
The pain information travelling to the CNS from the nociceptor is involved with two functions:
- Reflex motor response
2. Alerting the brain
First-order neurons synapse with motor neurone (w/ or w/o an intervening interneuron) to cause a rapid muscle contraction to remove injured body part away from harmful substance
Reflex motor response
The spinothalmic tract consists of two separate pathways:
▫️Neospinothalmic tract for FAST PAIN
▫️Paleospinothalmic tract for SLOW PAIN
signal transmission that has longer pathway
Alerting the brain
Pain signals from the neospinothalamic and paleospinothalamic tract terminate in the ______ where pain is perceived (but through different paths).
____________ neurons complete this task by carrying pain impulses to the ______________ of the cerebral cortex where precise pain is determined.
Thalamus
Third-order neurons ➡️ primary somatosensory area
What are the process of nociception?
- Transduction of noxious stimuli into nerve impulse and depolarization of the nerve stimulate the conduction of the sensory impulse
- Transmission of the nerve impulse from tissues to the CNS
- Modulation of the pain occurs during transmission of the impulse
- Perception of the pain response
Pain management of acute pain focuses less on the cause of pain and moe on the ________________.
Patient’s response to it
The control or treatment of pain can be exercised in one of three areas:
- Altering the pain message at periphery
- Altering the message at the spinal cord
- Altering the message in the brain
This theory postulates that there is a “gate” to modulate input to the second-order neutrons
“Gate control theory”
When interneurons in the spinal cord are activated by large type A beta fibers carrying touch impulses, pain impulse transmission by ____________ is blocked (I.e. Gate is closed)
small C fibers
Altering the pain message at the periphery is:
Altering the message of first order neurons
▫️ex: apply heat or cold
▫️ex: local anesthetics at nerve endings or nerve plexus
Altering the message at the spinal cord is by:
Altering the message of second order neurons
▫️ex. Epidural, massage, TENS
🔘TENS and massage work by neural manipulation
Altering the message in the brain:
These will be covered in Pharmacology 👻
__________ pain : perception of pain different from source. Original source may be difficult to determine.
▫️characteristic of visceral damage in the abdominal organs
▫️heart attack or ischemia in the heart
Referred Pain
_______ pain: perception of pain or other sensation (itching, tingling) after amputation.
▫️does not usually respond to usual pain therapies
Phantom pain
