Neurophysiology: Pain

Question 1

what is pain

Answer 1

Pain is defined as a response to noxious stimuli which is damaging or potentially damaging to the normal tissues. Pain can be decribed in a lot of ways including:
-pricking
-stabbing
-ache
-shooting
-burning
-throbbing

Question 2

what is the importance of pain sensation

Answer 2

1. Pain gives warning signal about the existence of
   a problem or threat. It also creates awareness of
   injury.
2. Pain prevents further damage by causing reflex
   withdrawal of the body from the source of injury
3. Pain forces the person to rest or to minimize the
   activities thus enabling rapid healing of injured part
4. Pain urges the person to take required treatment to
   prevent major damage.

Question 3

what are the various ways of classifying pain

Answer 3

-based on the duration
-pathophysiological classification
-anatomical classification
-depending on components

Question 4

what are the types of pain according to its components

Answer 4

Fast pain and Slow pain

Question 5

what is fast pain

Answer 5

Fast pain is the1st sensation of pain when a stimulus is applied. It is a bright sharp, localized pain. it is followed by slow pain.

Fast pain is carried by Aδ fibres

Question 6

what is slow pain

Answer 6

Slow pain is the pain that follows after fast pain. It is a dull, diffused, unpleasant pain.

It is carried by C fibers.

Question 7

what are the classifications of pain under its duration

Answer 7

-Acute pain
-Chronic pain

Question 8

dwhat is acute pain?

Answer 8

An acute pain is a sharp and intense (severe) pain that is localized and easily identified.
-It is usually localized before spreading to other areas
-It is caused by injury to muscle, bone, or other visceral organs
-The injury stimulates nociceptors
-The pain usually disappears after the source of the pain is treated, and the injury heals. It is usually treated with mediciations.

Question 9

what is chronic pain

Answer 9

Chronic pain lasts for a longer period of time
-It is not easily described
-It is usually associated with a long term disease like osteoarthritis
-It is resistant to treatment by medication

Question 10

what are the pathophysiological classifications of pain

Answer 10

-Nociceptive pain
-Neuropathic pain

Question 11

What is nociceptive pain

Answer 11

This kind of pain results from activation of nociceptors, on injury to the tissues.
It has 2 types
-somatic pain
-visceral pain

Question 12

wetin be somatic pain

Answer 12

This is pain resulting from stimulation of
-skin
-mucus membrane
-bone
-cartilage
-muscles
-ligament
-tendons
-joints
-connective tissue

Question 13

what is visceral pain

Answer 13

This is due to stimulation of receptors in the visceral organs.
It is unpleasant and poorly localised.
The pain receptor in the visceral organs are stimulated by:
->substances like bradykinin and proteolytic enzymes released during ischemic reactions
->chemical substances like gastric juice that leak from ruptured ulcers into the peritoneal cavity
->spastic contraction of hollow organs (GIT esp.)
->Over distension of hollow organs

Question 14

the pain receptors in visceral organs is stimulated by

Answer 14

The pain receptor in the visceral organs are stimulated by:
->substances like bradykinin and proteolytic enzymes released during ischemic reactions
->chemical substances like gastric juice that leak from ruptured ulcers into the peritoneal cavity
->spastic contraction of hollow organs (GIT esp.)
->Over distension of hollow organs

Question 15

what is neuropathic pain

Answer 15

Neuropathic pain is due to the dysfunction, damage, compression or disease of a nervous structure.
It is either peripheral neuropathic pain or central neuropathic pain

Question 16

what is peripheral neuropathic pain

Answer 16

This pain is caused by a damage or lesion of a peripheral nerve or dorsal root or dorsal root ganglion

Question 17

what is central neuropathic pain

Answer 17

this occurs due to a lesion or disease of the structures of the spinal cord or brain

Question 18

what is the anatomical classification of pain

Answer 18

the location on the body of affected tissue. Examples:
shoulder pain
neck pain
tooth ache
stomach ache
muscle cramps
neurological pain
myofascial pain

Question 19

what is referred pain?

Answer 19

Referred pain is a pain perceived adjacent to or at a site away from the site of origin.
Deep pain of the visceral organs is referred to other areas, BUT superficial pain is not referred.

Question 20

give examples of referred pain

Answer 20

1. Cardiac pain is felt at inner part of left arm and left
   shoulder
2. Pain in ovary is referred to umbilicus
3. Pain from testis is felt in abdomen
4. Pain in diaphragm is referred to shoulder
5. Pain in gallbladder is referred to epigastric region
6. Renal pain is referred to loin.

Question 21

where is cardiac pain referred

Answer 21

at the inner part of the left arm and left shoulder

Question 22

where testiscular pain felt

Answer 22

abdomen

Question 23

where is kidney pain felt

Answer 23

loin

Question 24

where is gallbladder pain felt

Answer 24

epigastric region

Question 25

where is ovary pain felt

Answer 25

umblical region

Question 26

what is the the mechanism of referred pain (dermatomal rule)

Answer 26

According to dermatomal rule, pain is referred to a structure, which is developed from the same dermatome from which the pain producing structure is developed. A dermatome includes all the structures or parts of the body, which are innervated by afferent nerve fibers of one dorsal root. -For example, the heart and inner aspect of left arm originate from the same dermatome. So, the pain in heart is referred to left arm.

Question 27

comment on the pathway of pain from the skin and deeper structures

Answer 27

A. FIRST ORDER NEURONS first order neurons are from the posterior nerve root ganglia which receive pain sensations from pain receptors via their dendrites and then transmit those impulses to the spinal cord via their axons. -fast pain fibers are carried by Aδ fibres that end in the marginal nucleus of the posterior grey horn -slow pain fibres are carried by C fibres and the end in the substantia gelatinosa of rolando in the posterior grey horn B. SECOND ORDER NEURONS Generally they ascend as the lateral spinothalamic tract (i.e from the marginal nucleus and substantia gelatinosa of rolando) -fast pain fibers originate from the marginal nucleus and cross the midline and ascend as the neospinothalamic fibres of the lateral spinothalamic tracts. These nerves terminate in the ventral posterolateral nucleus of the thalamus, and some in the ascending reticular activating system of the brainstem. -slow pain fibers originate from the substantia gelatinosa of rolando and also cross the midline and ascend as the paleospinothalamic fibers of the lateral spinothalamic fibers. They end in the: => 1/5th terminate in the ventral posterolateral nucleus with the fast fibres =>Nuclei of the reticular formation of the brainstem =>Tectum of the midbrain =>Grey matter surrounding the aqueduct of sylvius C. THIRD ORDER NEURONS The third order neurons are in: -thalamic nucleus -reticular formation -tectum -grey matter around the aqueduct of sylvius D. CENTER OF PAIN SENSATION -> the postcentral gyrus of the cerebral cortex ->Hypothalamus: for arousal associated with pain stimuli

Question 28

comment on t

Question 29

comment on the pain pathway from the face

Answer 29

It is carried by the trigeminal nerve

Question 30

comment on the pain pathway from the pelvic region

Answer 30

It is conveyed by the sacral parasympathetic nerves (S1-S4)

Question 31

Comment on the pain pathway from the viscera

Answer 31

=>The viscera are insensitive to: -Touching -Cutting -Pinching =>Sensitive to -Pain Visceral stimulants include, distention, excessive contraction, irritation by toxins and chemicals -Pain sensation from thoracic and abdominal viscera is transmitted by sympathetic (thoracolumbar) nerves. -Pain from esophagus, trachea and pharynx is carried by vagus and glossopharyngeal nerves. -By the way, sensations like satiety, hunger, thirst, nausea are transmitted by the vagus nerves.

Question 32

what are the NT's of pain sensation

Answer 32

Glutamate and substance P are the neurotransmitters secreted by pain nerve endings. =>Aδ afferent fibers,which transmit impulses of fast pain secrete glutamate. =>The C type fibers, which transmit impulses of slow pain secrete substance P.

Question 33

comment on the first order neurons of the pain pathway from skin and deeper regions

Answer 33

The first order neurons are in the posterior nerve root ganglia that receive impulses via their dendrites from receptors for pain, and then transmit those impulses to the spinal cord. -Fast pain sensations are transmitted via Aδ fibres which end in the marginal nucleus of the posterior grey horn. -slow pain sensation is transmitted via C fibres in the susbtantia gelatinosa of rolando of the posterior grey horn

Question 34

comment on the second order neurons of the pain pathway from the skin and deeper regions

Answer 34

-Slow pain from the substantia gelatinosa (of rolando) of the spinal cord cross over the midline and ascend as the paleospinothalamic part of the lateral spinothalamic tract. They end in: -1/5th end in the ventral spinothalamic nucleus of the thalamus -tegmentum of the midbrain -grey matter surrounding the aqueduct of sylvius -nuclei of reticular formation of the brainstem

Question 35

comment on the 3rd order neurons of the pain pathway of the skin and deeper regions

Answer 35

They are in: -thalamic nucleus -Tegmentum -grey matter surrounding aqueduct of sylvius -reticular formation

Question 36

what is the pain centre (last part of the pain pathway of the skin and deeper regions)

Answer 36

-The parietal cerebral cortex: postcentral gyrus -The hypothalamus: arousal associated with pain

Question 37

comment on the visceral sensory fibers

Answer 37

-Similar to those in the skin but are sparser and smaller in diameter -Free nerve endings in the gut wall are the receptors for pain -Nerve fibres are small myelinated and unmyelinated fibres -Nerve fibres traverse through the splanchnic nerve and sympathetic ganglia ( no synapsis) -Enter posterior roots by way of white rami communicantes -The cell bodies are in the posterior root ganglia and the central processes synapse in the posterior horn -The nerve fibres cross over and ascend close to the spinothalamic tract to reach the thalamus

Question 38

outline visceral organs an their sensory innervation

Answer 38

=>Heart – sensory fibres from the cardiac nerve connected centrally with T1- T5 =>Liver, stomach, duodenum, small intestines and kidneys – receive splanchnic nerve T6 – T12 =>Large intestines – receive sympathetic sensory supply via hypogastric plexus; impulses pass through T10 – L2 segments =>Pelvic organs – parasympathetic sensory nerve which pass through posterior roots of S1 –S4

Question 39

WHAT IS DEEP PAIN

Answer 39

-Pain initiated by stimulation of nociceptors in the ligaments, tendons, bones, blood vessels fasciae and muscles -Deep pain is dull, aching and poorly localised. Examples are seen in sprain and broken bone -Dull pain is persistent or chronic pain but usually does not stop one from daily activities

Question 40

outline the processes of pain sensation

Answer 40

Transduction Transmission Perception Modulation

Question 41

what are the types of noxious stimuli

Answer 41

Chemical Thermal Mechanical

Question 42

what is phantom pain

Answer 42

pain felt in a part of the body that has been removed eg amputation

Question 43

what is total pain

Answer 43

includes emotional, social and spiritual factors that affect a persons perception of pain lol

Question 44

what is psychogenic pain

Answer 44

It is affected by psychological factors, often times have physical origin (tissue or nerve damage) but the pain is increased in intensity or prolonged by fear, stress, anxiety or depression

Question 45

what are the structures of pain sensation in the forebrain

Answer 45

cerebral cortex, thalamus, hypothalamus

Question 46

what are the structures of pain sensation in the midbrain

Answer 46

periaqueductal grey matter, reticular formation, locus coeruleus

Question 47

what are the structures of pain sensation in the medulla

Answer 47

nucleus reticularis, gigantocellularis, nucleus raphe - Neospinothalamic (fast pain) - paleospinothalamic tract(slow pain)

Question 48

what are the structures of pain sensation in the spinal cord

Answer 48

-Dorsal root ganglion -Dorsal horn ( laminae I – vI) -Nerve fibres – C- fibres, delta- fibres

Question 49

what is pain threshold

Answer 49

This is the set point peculiar to each individual for the perception of a stimulus as pain

Question 50

what are the symptoms of pain

Answer 50

Negative:- this refers to sensation of numbness Positive :- this is sensation of abnormal experience

Question 51

what are the processes of pain modulation

Answer 51

They are adaptive changes for information reception-: =>Sensory end organs - cease to respond after variable period of stimulation =>Presympathetic inhibition of adjacent nerve cells by collaterals from active nerve cells =>Regulation of synaptic transmission in sensory nuclei by the motor cortex =>Pyramidal tract fibres send collaterals to the cuneate, gracile and trigeminal nuclei and the ventrobasal thalamus =>Alterations in the state of awareness at a cortical or subcortical level

Question 52

what is pain modulation

Answer 52

Pain modulation is the process by which the body alters pain signals along the transmission pathway of the pain. These alterations are adaptive changes for the reception of information. This explains why individuals respond to the same stimulus differently. Pain modulation is in form of a circuit with inputs arising from areas like the hypothalamus, the amygdala and rostral anterior cingulate cortex and outputs from the midbrain (periaqueductal gray region) to the medulla.