15: Pathophysiology of Pain Flashcards
What is pain in animals?
Aversive sensory and emotional experience which represents an awareness by the animal of damage or threat of damage to integrity of tissues.
What is nociception?
Physiologic neural processes for encoding pain –> transduction, conduction –> CNS processing;
Process that leads to the perception of pain
What is adaptive pain?
“Normal” pain, occurs when injury stimulus is applied to body/tissues;
Intensity/duration proportional to stimulus
What is maladaptive pain?
Pain uncoupled from noxious stimulus or healing tissues;
Dysfunctional, results from abnormal functioning of the nervous system;
Abnormal sensory processing;
Persistent or recurrent, pain as disease
What is acute pain?
Follows bodily injury, disappears with healing, self-limiting
What is chronic pain?
Outlasts original injury, expected healing time, or a specified time (3-6 months)
Why treat pain?
As veterinarians we have an ethical and moral responsibility to prevent and relieve animal suffering, and consider the patient’s well being
What are 7 negative physiologic sequela of pain and stress?
- Decreased pulm function
- CV = Increased HR, BP –> increased myocardial work
- Decreased immune function
- Increased stress hormones
- Coagulation = increased plt adhesion, decreased fibrinolysis
- GI & GU = increased sphincter tone, decreased muscle tone
- Immobility, inappetence, insomnia
What is somatic pain?
Originates from damage to bones, joints, muscles, or skin;
Described as localized, constant, sharp
What is visceral pain?
Arises from stretching, distention, or inflammation of viscera;
Described as deep, aching, without good localization
What is neuropathic pain?
Originates from injury or involvement of the PNS or CNS;
Described as burning or shooting
+/- neurological deficits
What are the steps to nociception/pain?
- Transduction
- Transmission
- Modulation
- Projection
- Perception
Where are transduction nociceptors present?
Skin, muscle, viscera
Most transduction nociceptors are _____, some are _____.
polymodal, silent
Transduction nociceptors transform mechanical, thermal, and chemical stimuli into _____.
action potentials
What is the MOA of transduction?
Injurious stimulus activates nociceptor cell membrane –> ion channels open –> influx of Na, Ca –> action potential
What is transmission?
Action potential is transmitted to cell body in DRG –> to dorsal horn of spinal cord
What does transmission utilize?
Aδ nociceptor axon fibers that are myelinated and C nociceptor axon fibers that are unmyelinated
What pain is transmitted by Aδ nociceptors?
Sharp, pricking “first pain”
What pain is transmitted by C nociceptors?
Slow onset, “second pain”; burning, aching
What is modulation?
Synapse with neurons in dorsal horn of spinal cord grey matter;
Impulses are amplified or suppressed;
Glutamate = excitatory, Substance P, Glycine, GABA = inhibitory
What is projection?
Nociceptive information conveyed to brain by nerve tracts (spinothalamic and spinocervicothalamic)
What is perception?
Integration, processing, and recognition of sensory info occurring in multiple areas of the brain
What system is part of perception?
Reticular Activating System;
Integration of sensory experience;
Mediates motor, autonomic, endocrine response
