pain and temperature

Question 1

Impulses from nociceptors (pain) are transmitted via two types of fibers/ axons.

Answer 1

1. A delta fibers (Aδ): conduct at rates of 12 -30m/s. they are bigger to c fibers.
2. C fibers: conduct at low rates of 0.5 -2m/s

Question 2

types of thermoreceptors fibers/axons

Answer 2

1. myelinated A delta (Aδ) fibers/axons

2. unmyelinated C fibers/axons

Question 3

1. cold receptors are attached to which axons/ fibers?

2. warmth(heat) receptors are attached to which axons/fibers?

Answer 3

1. both A delta and c fibers

2. only on C fibers

Question 4

types of nociceptors/ pain receptors

Answer 4

1. Thermal nociceptors: are activated by noxious heat or cold at various temperatures.
2. Mechanical nociceptors: respond to excess pressure or mechanical deformation.
3. Chemical nociceptors: have TRP channels that respond to a wide variety of spices.
4. silent/sleeping: These are typically referred to as silent or sleeping nociceptors since their response comes only at the onset of inflammation to the surrounding tissue. respond to injury only, if no injury then no response.
5. Polymodal: Polymodal
   Many neurons perform only a single function; therefore, neurons that perform these functions in combination are given the classification “polymodal.

Question 5

Thermal nociceptors are activated by skin temperature above………………….

Answer 5

45° C

Question 6

The threshold for activation of warmth receptors is …….., and they increase their firing rate up to …………

Answer 6

30° C, and 46° C

Question 7

Cold receptors are inactive at temperatures of ……………………, but then steadily increase their firing rate as skin temperature falls to about …………………………..
As skin temperature further decreases, the firing rate of cold receptors decreases until the temperature reaches…………………………….. Below that temperature, they are inactive and the cold becomes an effective local anesthetic.

Answer 7

40° C but 24° C

reaches 10° C

Question 8

Two types of vanilloid receptors

Answer 8

VR1 and VRL-1

Question 9

which vanilloid receptors respond not only to capsaicin but also to protons, and to potentially harmful temperatures above 43®C?

Answer 9

The VR1 receptors

Question 10

which vanilloid responds to temperatures above 50®C but not to capsaicin, has been isolated from C fibers?

Answer 10

VRL-1

Question 11

Chemically sensitive nociceptors respond to various agents like ……., …….., ……., …….., and ………

Answer 11

Bradykinin, histamine, high acidy, and environment irritants.

Question 12

u

Answer 12

u

Question 12

Three types of stimuli excite pain receptors

Answer 12

Mechanical, thermal and chemical

Question 13

………………………., and ………………………..enhance the sensitivity of pain endings but do not directly excite them.

Answer 13

prostaglandins, and substance P

Question 14

Fast pain is due to activity in the fibers/axon……………………….

Answer 14

Aδ pain fibers

Question 15

slow pain is due to activity in the fibers/axon……………………

Answer 15

C fibers.

Question 16

Pain is frequently classified ……………….. and…………….

Answer 16

1. physiologic or acute pain: typically has a sudden onset, and recedes during the healing process. Acute pain can be considered as good pain, as it serves an important protective mechanism.
2. pathologic or chronic pain: can be considered as bad pain because it persists long after recovery from an injury and is often refractory to common analgesic agents, including nonsteroidal anti-inflammatory drugs (NSAIDs) and opiates.

Question 17

…………………..is a medical condition that causes an increased sensitivity to pain. Individuals with ……………. experience pain when exposed to normal stimuli. They also experience worse pain, when exposed to painful stimuli, than someone who does not have the condition

Answer 17

hyperalgesia

Question 18

innocuous/not harmful or offensive stimuli cause ……………… pain

Answer 18

allodynia.

Question 19

Injured cells release chemicals such as……………….that depolarize nerve terminals, making nociceptors more responsive.

Answer 19

K+

Question 20

Injured cells also release ……….. and …………… which can further sensitize nociceptive terminals.

Answer 20

bradykinin and substance P

Question 21

………….is released from mast cells, ………….. from platelets, and …………. from cell membranes, all are contributing to the inflammatory process and they activate or sensitize the nociceptors.

Answer 21

Histamine, serotonin (5HT) and prostaglandins

Question 22

………………..pain is felt on the surface of the body, resulting from the damage to an internal organ; it may be the only painful sensation whereas no pain is felt in the viscera itself; therefore it is important for clinical diagnosis.

Answer 22

referred pain

Question 23

Types of intracranial headache

Answer 23

1. Headache of meningitis: meningitis causes inflammation of all meninges.
2. Headache caused by low cerebrospinal fluid pressure. The weight of the brain stretches and distorts the various dural surfaces and thereby elicits the pain that causes the headache.
3. Migraine headache: the cause of migraine headache may be prolonged emotion or tension which causes reflex vasospasm of some arteries of the head including arteries that supply the brain.
4. Alcoholic headache: alcohol is toxic to tissues, directly irritates the meninges, and causes intracranial pain.
5. Headache caused by constipation, may result from absorbed toxic products or from changes in the circulatory system resulting from loss of fluid into the gut.

Question 24

Extracranial types of headache

Answer 24

1. Headache resulting from muscle spasm.
2. Headache is caused by irritation of nasal and accessory nasal structures.
3. Headache caused by eye disorders.