Pain

Question 1

Definition of Pain

Answer 1

Unpleasant sensory or emotional experience associated with actual or potential tissue damage.

Question 2

Protective roles of pain: List four.

Answer 2

1. Warns of a problem or threat.\n2. Prevents further damage by reflex guarding.\n3. Promotes rest for healing.\n4. Encourages seeking treatment.

Question 3

Pain transduction by nociceptors: Mechanism

Answer 3

1. Stimulation of pain receptors opens specific transduction channels.\n2. Na+ and Ca2+ inflow occurs, leading to depolarization (DP).\n3. Damaged tissues release proteolytic enzymes, K+, histamine, serotonin, ATP, bradykinin, and prostaglandins (PGs), which sensitize pain receptors.

Question 4

Mechanical pain receptors: Ion channel

Answer 4

Mechanical stimuli open degenerin channels in pain receptors.

Question 5

Thermal pain receptors: Channels

Answer 5

1. Extreme heat opens TRPV channels.\n2. Extreme cold opens Anktm channels.

Question 6

Chemical pain receptors: Example and mechanism

Answer 6

Example: HCL in peptic ulcers opens Acid-Sensing Ion Channels (ASIC).

Question 7

Polymodal pain receptors

Answer 7

These receptors respond to all types of stimuli (mechanical, thermal, chemical).

Question 8

Adaptation of pain receptors

Answer 8

Pain receptors are either slowly adapting or non-adapting.

Question 9

Distribution of pain receptors: More sites

Answer 9

Pain receptors are more abundant in skin, periosteum, arterial walls, and joints.

Question 10

Distribution of pain receptors: Less sites

Answer 10

Pain receptors are less abundant in deep tissues and internal viscera.

Question 11

Sites without pain receptors

Answer 11

Pain receptors are absent in liver parenchyma, lung alveoli, brain, and bones.

Question 12

Types of pain by site

Answer 12

1. Cutaneous pain (superficial).\n2. Deep pain (musculoskeletal).\n3. Visceral pain (organs).\n4. Neuropathic pain (nerves).

Question 13

Types of pain by quality

Answer 13

1. Fast (acute) pain.\n2. Slow (chronic) pain.

Question 14

Fast pain pathway

Answer 14

Neospinothalamic pathway.

Question 15

Slow pain pathway

Answer 15

Paleospinothalamic pathway.

Question 16

Neurotransmitter for fast pain

Answer 16

Glutamate.

Question 17

Neurotransmitter for slow pain

Answer 17

Substance-P.

Question 18

Characteristics of fast pain

Answer 18

1. Sharp, pricking, and well-localized.\n2. Travels via Aδ fibers (myelinated).\n3. Perceived quickly in sensory cortex and thalamus.

Question 19

Characteristics of slow pain

Answer 19

1. Dull, burning, poorly localized.\n2. Travels via C-fibers (unmyelinated).\n3. Perceived in the thalamus and limbic system (emotional aspect).

Question 20

Perception of fast pain

Answer 20

Occurs in the lateral part of the thalamus and somatic sensory area I. Provides information about location and intensity.

Question 21

Perception of slow pain

Answer 21

Occurs in the medial part of the thalamus and the limbic cortex (especially the cingulate gyrus). Responsible for emotional reactions to pain.

Question 22

Reactions to fast pain

Answer 22

1. Motor: Withdrawal reflex to remove the injured part.\n2. Autonomic: ↑HR and ↑BP.\n3. Emotional: Screaming and anxiety.

Question 23

Reactions to slow pain

Answer 23

1. Motor: Guarding rigidity (e.g., inflamed appendix).\n2. Autonomic: ↓HR and ↓BP, nausea, vomiting, sweating.\n3. Emotional: Depression.

Question 24

Why is cutaneous pain accurately localized?

Answer 24

1. High density of pain receptors in skin.\n2. Fast fibers reach the sensory cortex.\n3. Touch and vision assist in localization.

Question 25

Deep pain: Definition

Answer 25

Musculoskeletal pain originating from muscles, tendons, ligaments, joints, and periosteum of bones.

Question 26

Deep pain: Causes

Answer 26

1. Inflammation.\n2. Mechanical trauma.\n3. Ischemia.

Question 27

Ischemic pain: Cause and mechanism

Answer 27

Cause: Narrowing or compression of an artery → ischemia.\nMechanism: Accumulation of metabolites and release of proteolytic enzymes.

Question 28

Visceral pain: Key features

Answer 28

1. Diffuse (poorly localized) because of sparse pain receptors in viscera.\n2. Carried by C-fibers (slow dull pain).

Question 29

Visceral pain: Causes

Answer 29

1. Ischemia → ↑ H+, K+, bradykinin, PGs.\n2. Inflammation.\n3. Irritation (e.g., HCL in peptic ulcers).\n4. Overdistension of hollow viscera (e.g., bladder).\n5. Spasm of hollow viscera (e.g., gut, ureters).

Question 30

Referred pain: Definition

Answer 30

Pain felt at a site other than the injured one, usually on the skin surface.

Question 31

Dermatomal rule for referred pain

Answer 31

Pain is referred to a structure that developed from the same dermatome as the pain-producing organ.

Question 32

Mechanism of referred pain: Convergence-projection theory

Answer 32

1. Afferent pain fibers from the organ and skin converge on the same spinal cord neuron.\n2. Brain misinterprets the pain as coming from the skin due to better cortical representation of the skin.

Question 33

Mechanism of referred pain: Facilitation theory

Answer 33

1. Viscus afferents give collaterals to spinal cord cells.\n2. These cells receive pain signals from the skin, leading to facilitation and misinterpretation.

Question 34

Examples of referred pain: Cardiac pain

Answer 34

Referred to the left shoulder, left arm, root of the neck, lower jaw, and epigastrium.

Question 35

Examples of referred pain: Gall bladder pain

Answer 35

Referred to the right shoulder, tip of the right scapula, and epigastrium.

Question 36

Examples of referred pain: Gastric pain

Answer 36

Referred to the area between the xiphoid process and umbilicus.

Question 37

Examples of referred pain: Pancreatic pain

Answer 37

Referred to the back.

Question 38

Examples of referred pain: Renal pain

Answer 38

Referred to the flank, inguinal region (groin), and testicles (in males).

Question 39

Examples of referred pain: Appendicular pain

Answer 39

Referred to the area around the umbilicus.

Question 40

Examples of referred pain: Ovarian pain

Answer 40

Referred to the umbilicus.

Question 41

Examples of referred pain: Testicular pain

Answer 41

Referred to the pelvis and abdomen.

Question 42

Examples of referred pain: Diaphragmatic pain

Answer 42

Referred to the shoulder.

Question 43

Headache: Types and causes

Answer 43

Headache can originate from tension, vascular problems (e.g., migraines), or referred pain from deeper structures.

Question 44

Pain testing method: Procedure

Answer 44

1. Use an object with sharp and dull ends (e.g., safety pin).\n2. Apply stimuli randomly and perpendicularly to the skin.\n3. Ask the patient to indicate sharp/dull.\n4. Avoid rapid application to prevent impulse summation.

Question 45

Pain testing: Areas of the body

Answer 45

All areas of the body should be tested systematically.

Question 46

Sterilization of instruments after pain testing

Answer 46

The testing instrument must be sterilized or disposed of after use.