Somatosensory Function, Pain, & Headache Flashcards
(42 cards)
Describe the function of the somatic nervous system
The somatic nervous system provides awareness of the body, both conscious and autonomic
What aspects does the somatic nervous system cover?
- tactile
- thermal
- position
- pain
Describe tactile, thermal, position, & pain
1. Tactile Pressure/vibration Initial response, often total adaptation 2. Thermal (thermoception) Initial response, partial adaptation 3. Position (proprioception) Sense of limb/body movement without using vision 4. Pain (nociception)
What is pain?
“Unpleasant sensory & emotional sensation associated with actual & potential tissue damage”
- Warns of impending injury
- Motivates seeking help
- Motivates avoidance of future injury
What are the two main pathways of pain?
A & B – “fast pain”
- Large, myelinated
- Pressure/touch, cold, mechanical pain, heat pain
C – “slow pain”
- Small, non-myelinated fibers
- Mechanical/chemical/heat/cold pain
Three Levels of Neurons Involved inSomatic Sensation
First-order: detect the sensation
Second-order: in the spinal cord; transmit message to brain
Third-order:
in the brain
What is a dermatome?
Region of body wall supplied by single pair of dorsal root ganglia
Pain theories: Specificity theory
Pain is a separate modality caused by activity of a specific receptor (nociceptor)
Pain theories: Pattern theory
Pain receptors share pathways and/or nerve endings with other sensory modalities
Example: light touch may not cause pain, but heavy touch of same area may.
Pain theories: Gate control theory
- Neural gate mechanisms in spinal cord can block pain info from going to brain by, for example, involving fibers that sense touch
- Recent research suggests this is a simplistic approach
Pain theories: Neuromatrix theory
- Multifactoral
- Widely distributed neural network with genetic, cognitive and sensory influences
- Helps explain phantom & chronic pain
Describe pain threshold
- Point at which a nociceptive stimulus is perceived as painful
- Uniform from person to person
Describe pain tolerance
- Maximum intensity or duration of pain a person is willing to endure
Variable: - psychological, familial, cultural, environmental
Describe acute pain
Short duration; ceases when cause removed
Serves as a warning
1. Early wave
- Hyperexcitability of neurons
- Secondary wave
- Longer lasting
- Inflammatory reaction to tissue injury
Describe chronic pain
- When pain persists longer than normally expected
- Highly variable
- Often not “usual” pain characteristics
- Peripheral (m/s, organ, vascular)
- Peripheral-central (neuralgias, PLP)
- Central (CNS disease/injury)
Possible negative consequences of Chronic Pain
- Physiological
- Loss of appetite
- Sleep disorders - Psychological
- depression - Familial
- Economic
chronic pain serves no useful purpose
Cutaneous pain
- Arises from skin/subcutaneous tissue
- Sharp, burning, abrupt/slow
- Usually localized
Deep somatic pain
-From deep structures (muscles, tendons, joints, blood vessels)
-Diffuse, radiation
E.g. angina
Visceral pain
- From activation of nociceptors of thoracic, pelvic, abdominal viscera (organs)
- Highly sensitive to distension, ischemia, inflammation (i.e. diseases)
- Relatively insensitive to cutting/burning
- Diffuse, often referred
- Deep/squeezing/sickening
- Accompanied by nausea, vomiting, emotional changes
Referred pain
-Originating in viscera; experienced as pain more near body surface
-Alone or concurrent with localized pain from source
Why?
-Visceral and peripheral neurons converge
-Structures develop nearby as embryo
Describe pain terms
Analgesia: absensce of pain
Hyperalgesia: increased sensitivity to pain
Hypoalgesia: decreased sensitivity to pain
Hyperpathia: unpleasant, prolonged response to pain, explosive
Hyperesthesia: Abnormal increase in sensitivity to sensation
Hypoesthesia: Abnormal decrease in sensitivity to sensations
Paresthesia: Abnormal touch sensation without external stimuli; tingling, pins/needles
Allodynia: Pain produced by stimuli that do not normally cause pain
Causes of neuropathic pain & focal/global
Causes (pathology of nervous system)
Pressure on nerve
Physical/chemical injury to neuron
Infection/ischemia/inflammation of neuron
Focal: trauma/disease of neuron
Global: endocrine disease (DM), neurotoxic meds, chronic alcoholism
Neuropathic pain
Occurring without evidence of provocation
Widespread pain
Sensory deficits
Occurring with light touch (example of allodynia)
Burning/stabbing/etc.
Persistent/intermittent
Neuralgias
Severe, brief, repetitive attacks of lightening-like/throbbing pain along spinal or cranial nerve
Usually precipitated by stimulation of cutaneous region supplied by nerve
So not “neuropathic” as stimulus begins in non-neuronal tissue
Trigeminal neuralgia
Postherpetic neuralgia
