Physiology of Pain

Question 1

_____ are pain receptors, which detect
physical or chemical damage occurring in
the tissues.

Answer 1

Nociceptors

Question 2

Information from these sensory receptors is
transduced from a ____ or ____
stimuli into an electrical impulse in the
neuron, which is then carried to the CNS

Answer 2

physical or chemical

Question 3

There are several different types of sensory
receptors in the tissues:

Answer 3

○ Mechanoreceptors
○ Thermoreceptors
○ Nociceptors
○ Electromagnetic receptors
○ Chemoreceptors

Question 4

Incoming sensory information is processed
in the _____ of the brain.

Answer 4

somatosensory cortex

Question 5

Receptors that are specific for pain are ____
Nerve Endings in the skin and other tissues.

Answer 5

Free

Question 6

There are three main types of stimuli that can excite pain receptors when tissue damage is occurring

Answer 6

○ Mechanical: Pressure or crushing
○ Thermal: Burning or freezing
○ Chemical: Bradykinin, serotonin, histamine,
potassium ions, prostaglandins, etc

Question 7

Free Nerve Endings use two separate fibers for transmitting pain signals to the CNS

Answer 7

● Fast, sharp pain is transmitted from the peripheral tissue to the spinal cord via small type A delta fibers.
● Slower, aching pain is transmitted to
the spinal cord via type C fibers.

Question 8

____ stimulated pain is generally transmitted via the slower type C Fibers

Answer 8

Chemical

Question 9

After synapsing and decussating via
the anterior white commissure, the
signal is carried up the ____ of the spinal cord.

Answer 9

Spinothalamic Tract

Question 10

Along the way to the brain, some fibers synapse on cells in the _____ of the brainstem

Answer 10

Reticular Formation

Question 11

Most fibers make it to the Thalamus, where
the information is then relayed to the
_____ .

Answer 11

Somatosensory cortex

Question 12

The Somatosensory Cortex likely plays an especially important role of interpreting the pain ____

Answer 12

quality

Question 13

Three very important neurotransmitters (which are endogenous opiates) play a role in suppressing incoming pain signals:

Answer 13

○ Endorphin
○ Enkephalin
○ Dynorphin

Question 14

Studies have revealed that when incoming painful stimuli reaches the brain, efferent fibers may fire releasing these three neurotransmitters, which stimulates a chain of events result in pain relief. This natural pain relief chain of events is what we refer to as the CNS _____

Answer 14

Analgesia System

Question 15

The analgesia system consists of three major components

Answer 15

○ Periaqueductal Gray
○ Raphe Magnus Nucleus
○ Substantia Gelatinosa

Question 16

When ______ is released in the Substantia Gelatinosa, the endogenous opiate binds to opiate receptors, of which there are three types (μ, κ, and δ).

Answer 16

enkephalin

Question 17

Pain felt in more distant sites that have similar innervation. (well localized)

Answer 17

Referred pain

Question 18

Explain viseral pain

Answer 18

○ When hollow organs contract forcefully or are distended.
○ When solid organs like the liver distend and stretch their capsule.
○ Difficult to localize.
○ Can be gnawing, burning, cramping, or aching.