Lecture 12 (Cut off for Exam 3)

Question 1

Pain Physiological Steps (4)

Answer 1

1. Transduction
2. Transmission
3. Perception
4. Modulation

Question 2

Transduction

Answer 2

• Nociceptors - free nerve ending at surface of skin that convert physical stimuli into action potentials
• Physical Stimuli - pressure, tension, heat, and cold
• Chemical Stimuli - K+, lactate, histamine, bradykines, prostaglandins (alter membrane potentials to cause an action potential)

Question 3

Prostaglandin Inhibitors

Answer 3

• Aspirin, Ibuprofen, other NSAIDs, corticosteroids
• Prostaglandins are produced by COX-1 to protect gastric mucosa from damage by acids
• By blocking COX-1, you inhibit release of prostaglandins

Question 4

Transmission

Answer 4

• Signalling of peripheral nervous system to the central nervous system via the spinal cord
• Done with Ad fibers and C fibers

Question 5

Ad Fibers

Answer 5

• Large and myelinated
• 10% of fibers
• Fast
• Mechanical pain
• Sharp, stinging, cutting, pinching, localized pain

Question 6

C Fibers

Answer 6

• Unmyelinated
• Slower
• 90% of fibers
• Mechanical, chemical, and thermal pain
• Dull, throbbing, burning, aching, unlocalized pain

Question 7

Transmission to Spinal Cord

Answer 7

• Glutamate carries impulse from primary afferent fibers to secondary neurons
• NMDA receptor binding can induce memory from repeated or excessive action of C-fibers by glutamate sensitization (mild stimulation becomes painful)
• Other neurotransmitters - Substance P, GABA, endorphins, and serotonin

Question 8

Tract of Lissauer

Answer 8

• First step upon reaching spine in transmission
• Fibers branch and form collaterals that go up and down the spinal cord for a few segments
• Helps maintain posture during withdrawal reflex

Question 9

Lamina 1

Answer 9

• Second step of spine transmission
• Ad and C fibers carry impulse to this region which then send them across the spinal cord and activates neurons in anterolateral tract

Question 10

Substantic Gelantinosa

Answer 10

• Multiple synaptic area that contains afferent sensory, interneurons, and anterolateral neurons
• Strategic location to target for modulating of pain

Question 11

Lamina V

Answer 11

• Area where somatic and visceral (organ) fibers converge

- Leads to referred pain sensations

Question 12

Referred Pain

Answer 12

• Pain perceived in area other than the injury
• Can be far from actual site of injury
• Caused by nociceptors convergence in the dorsal horn
• Brain can’t differentiate between two sources of pain so it attributes visceral pain to the surface
• Certain patterns of reffered pain can be used to identify the region of concern or pathology occuring in the body

Question 13

Lamina VI-VIII

Answer 13

Sensory input from joints, muscles, and organs

Question 14

Transmission to Brain

Answer 14

• Ad fiber signals are transmitted through neospinothalmic division. Rapid transfer to thalmus/somatosensory cortex
• C fiber signals are transmitted through pateospinothalmic division. Slower bit more widespread travel throughout the brain

Question 15

Brain Areas Associated with Pain

Answer 15

Stimuli&raquo_space; Thalmus&raquo_space; Other areas of Brain

• Primary Sensory Cortex - perceive and localize pain
• Cortical Association Area - Integration of pain with other sensory inputs
• Limbic forebrian - adds emotion to pain response

Question 16

Pain Perception and Tolerance

Answer 16

• Perception of pain involves neural processing of pain (awareness, interpretations of area, severity, etc.)
• Influenced by other factors like attention, fear, anxiety, fatigue, expectations, etc.
• Combination of pain tolerance and threshold

Question 17

Pain Threshold

Answer 17

Level at which pain is perceived. Similar for different people.

Question 18

Pain Tolerance

Answer 18

Pain level when you seek relief from pain. Varies greatly between people and within one person depending on what factors are influencing them.

Question 19

Modulation of Pain - Spinal Cord

Answer 19

• Modulation in spinal cord is the most understood
• Pain perception initiates descending pain and inhibits signals to dorsal horn
• Norepinephrine and serotonin stimulate interneurons to release endogenous opioids that provide presynaptic inhibition of neurotransmitter release from Ad and C fibers

Question 20

Endorphins

Answer 20

• ENDOgenous moRPHINe

- Refers to enkephalins and (alpha, beta, gamma) endorphins which are the body’s endogenous pain killers

Question 21

Opioid Modulation

Answer 21

• Bind presynaptically to prevent transmission of signals and the release of Substance P to block pain
• Mechanoreceptor activation also triggers opioid release from dorsal horn interneurons (deep tissue massage or acupuncture)

Question 22

Pain Treatments - Inhibiting Transduction/Transmission

Answer 22

• NSAIDs and steroids

- Local anesthetics (lidocaine and novacaine) block sodium influx and action potentials

Question 23

Pain Treatments - Alter Spinal Cord Transmission/Modulation

Answer 23

• Cutaneous stimulation (opioid release) - massage and acupuncture
• Spinal analgesia (opioids)
• Dorsal Column stimulation - implant an electrode and stimulate dorsal horn interneurons to release opioids

Question 24

Pain Treatments - Perception/Integration Alterations

Answer 24

• Systemic Opioids - impacts brain perception and integration as well as spinal cord modulation. Affects many other receptors in the body so many side effects
• Distraction (imagery, hypnosis) - Force brain to attend to multiple stimuli and not just pain
• Relaxation and biofeedback - increase blood flow to that area, dilute pain-inducing chemicals, and increase endorphin release