Pain

Question 1

What is the function of pain?

Answer 1

To protect the body and maintain homeostasis by detecting, localizing and identifying potential or actual tissue-damaging processes.

Question 2

Pain is both ______ and _______

Answer 2

a physical sensation and an emotion

Question 3

Descriptors of pain

Answer 3

• Described in terms of penetrating or tissue destructive processes (stabbing, burning, twisting, tearing, squeezing)
• Bodily / emotional reaction (nauseating, terrifying, sickening)

Question 4

Pain’s affected on vitals / body signs (5)

Answer 4

• Increased blood pressure
• Increased heart rate
• Increased pupil diameter
• Increased plasma cortisol levels
• Local muscle contraction

Question 5

Nocioceptor

Answer 5

• Neuronal cell
• Senses painful stimulation
• Afferent

Question 6

What are primary afferent nocioceptors?

Answer 6

Nerves that convey pain

Question 7

Where are nocioceptors located?

Answer 7

Start as spinal nerves before they branch out

Question 8

Nocioceptors consist of what?

Answer 8

Consist of axons. Both primary sensory afferents and motor neurons.

Question 9

Nicioceptors are classified by (3)

Answer 9

• Diameter
• Degree of myelination
• Conduction velocity

Question 10

Alpha-beta nerves

• Size
• Type
• Respond to what?
• Location
• Role in pain

Answer 10

• Largest diameter afferent fibers
• Somato-sensory fibers
• Respond maximally to light touch and/or moving stimuli
• Are present primarily in nerves that innervate the skin
• The activity of these fibers does not produce pain

Question 11

Myelinated A-Delta

- Function

Answer 11

Respond to painful stimuli: Convey low-intensity painful stimulation

Question 12

Unmyelinated C-Fiber Axons

Answer 12

Respond to painful stimuli: Convey high-intensity painful stimulation

Question 13

Two fibers of unmyelinated C-fiber axons

Answer 13

• One projects into dorsal root ganglion: Alongside alpha-delta (SOMATOSENSORY - skin pain)
• Other projects into sympathetic preganglionic region into the spinal cord (location of autonomic nervs (VISCERAL - organ pain)

Question 14

Examples of noxious stimuli (4)

Answer 14

• Intense temperatures
• Intense mechanical stimuli (eg pinch)
• Changes in pH (esp acidity)
• Chemical irritants (exogenous and endogenous)

Question 15

Examples of endogenous irritants

Answer 15

• Inflammatory mediators

- Some components of intracellular fluid (eg potassium)

Question 16

Sensitization: What happens? (2)

Answer 16

• Threshold for activating primary afferent nocioceptors is lowered
• the frequency of firing is higher for all

Question 17

Sensitization: What causes it?

Answer 17

Intense, repeated or prolonged stimuli are applied to damaged or inflammed tissues.

Question 18

Primary activation of sensitivity:

• Where does it happen?
• What are the players?

Answer 18

• Happens at site of injury
• Cell damage and death causes acidity. Cell lyses, acid and K+ are released into extracellular fluid.
• Prostaglandings and Bradykinin are released.

Question 19

Secondary activation of sensitivity:

When is Substance P released?

Answer 19

When the pain signal is conveyed to surrounding branches innervating the area.

Question 20

Action of Substance P (2)

Answer 20

TRIGGERS MORE INFLAMMATORY MEDIATORS:

1) Triggers mast cells, stimulates platelets
2) Triggers bradykinin in the bloodstream

Question 21

Referred pain is often the result of what?

Answer 21

ORAGAN pain

Question 22

Liver and gallbladder pain is predictably referred to: (2)

Answer 22

• Right shoulder

- RUQ of abdomen

Question 23

Heart pain is predictably referred to (4):

Answer 23

• Left chest
• Arm
• Shoulder
• Jaw

Question 24

Colon pain is predictably referred to (1):

Answer 24

Middle of abdomen

Question 25

What is the mechanism for referred pain?

Answer 25

Convergence of C-fibers at spinal nerve, merges with afferent nocioceptors of the corresponding dermatome

Question 26

Ascending pathways for pain: 2

Answer 26

- Somatosensory cortex | - Cerebral cortex (Anterior cingulate area, Frontal insular area)

Question 27

Somatosensory Cortex - functions

Answer 27

Responsible for the purely sensory aspects of pain (Location, intensity, quality)

Question 28

Cerebral cortex - Function - 2 areas

Answer 28

- Affective / unpleasant emotional aspects of pain, suffering - Areas: (1) Anterior Cingulate Area (2) Frontal Insular Area

Question 29

The descending pathways are responsible for _____ ______.

Answer 29

Pain modulation

Question 30

In descending pathways for pain, wehre do inputs originate (2)?

Answer 30

- Frontal cortex | - Hypothalamus

Question 31

In descending pathways, inputs from the frontal cortex and hypothalamus activate cells in the (1, 2) that ultimately control (3)

Answer 31

1) Midbrain 2) Medulla 3) Spinal-pain transmission cells

Question 32

What is physiologically responsible for the highly subjective nature of the experience of pain?

Answer 32

The descending Pain-Modulation Network

Question 33

Why does distraction provide pain relief?

Answer 33

Psychological variables can modulate the pain experience through the descending pain modulation network

Question 34

Opioid drugs work through what circuit?

Answer 34

Descending pain modulation network

Question 35

Each of the components of the descending pain pathway contain _____ receptors

Answer 35

OPIOID

Question 36

What two peptides are present in the descending pain pathway? What does this suggest?

Answer 36

- Enkephalins - Beta Endorphins **Suggests an endogenous opioid analgesic pathway