PHS 305 Pain Physiology Flashcards
What is pain?
A complex unpleasant sensation with motion experience which arises as a result of potential actual tissue damage or described in terms of such
Pain may be a sign of dysfunction or warning so a dysfunction does not take place
Classification of pain can be based on
Based on:
1. Interpretation
2. Duration: acute - < than 6 months chronic - > 6 months
3. Origin: psychogenic and somatic
Difference between acute and chronic pain
Acute pain is a sharp pain of short duration with an easily identified cause.
Often it is localized in a small area before spreading to neighboring areas. Usually, it is treated with medications.
Chronic pain is intermittent or constant pain with different intensities. It lasts for longer periods. It is somewhat difficult to treat chronic pain and it needs professional expert care
What is Psycogenic and somatogenic pain
Psycogenic: of psycological origin
Somatogenic: related to tissue damage
Types of somatogenic:
nociceptive: body tissue damage
neuropathic: neuron damage
Symptoms that coexists with pain:
- emotional changes
- high bp
- high heart rate
- high respiratory rate
- flushing
- diaphoresis
- high blood sugar
- low gastric motility
- nausea and sometimes vomiting
Receptors of pain
Receptors of pain sensation are the free nerve endings, which are distributed throughout the body, nociceptors.
What are First Order Neurons
First-order neurons are the cells in the posterior nerve root ganglia, which receive the impulses of pain sensation from pain receptors through their dendrites. These impulses are transmitted to the spinal cord through the axons of these neurons.
(1st Order) Fast pain fibers
Fast pain sensation is carried by Aδ type (large and myelinated) afferent fibers which synapse with neurons of the marginal nucleus in the posterior gray horn
(1st Order) Slow pain fibers
Slow pain sensation is carried by C-type (small myelinated) afferent fibers, which synapse with neurons of substantia gelatinosa of Rolando in the posterior gray horn
Second Order Neurons
Neurons of the marginal nucleus and substantia gelatinosa of Rolando form the second-order neurons. Fibers from these neurons ascend in the form of the lateral spinothalamic tract
(2nd Order) Fast pain fibers
Fast pain fibers
Fibers of fast pain arise from neurons of the marginal nucleus. Immediately after taking origin, the fibers cross the midline via the anterior gray commissure, reach the lateral white column of the opposite side, and ascend.
These fibers form the neospinothalamic fibers in the lateral spinothalamic tract. These nerve fibers terminate in the ventral posterolateral nucleus of the thalamus. Some of the fibers terminate in the ascending reticular activating system of the brainstem
(2nd Order) Slow pain fibers
Slow pain fibers
Fibers of slow pain, which arise from substantia gelatinosa neurons, cross the midline and run along the fibers of fast pain as paleospinothalamic fibers in the lateral spinothalamic tract. One-fifth of these fibers terminate in the ventral posterolateral nucleus of the thalamus. The remaining fibers terminate in any of the following areas:
i. Nuclei of reticular formation in the brainstem
ii. Tectum of midbrain
iii. Gray matter surrounding the aqueduct of Sylvius.
Third Order Neurons
Third Order Neurons
third order pathway are the neurons in:
i. Thalamic nucleus
ii. Reticular formation
iii. Tectum
iv. Gray matter around the aqueduct of Sylvius.
Axons from these neurons reach the sensory area of the cerebral cortex. Some fibers from reticular formation reach the hypothalamus
Where is the center for Pain Sensation?
Center for pain sensation is in postcentral gyrus of parietal cortex. Fibers reaching hypothalamus are concerned with arousal mechanism due to pain stimulus.
Monro-Kellie doctrine
According to the Monro-Kellie doctrine or principle, though the cerebral arteries are compressed by increased intracranial pressure or cerebrospinal fluid pressure, the volume of brain tissue is not affected. This is because
the brain tissue is not compressible.
Simply put: the volume of the cranium is constant
