Question

For this discussion, I would like you to think about a time when you experinced pain. Describe your pain experience including clinical manifestations. Include the pain pathway from the painful area to the brain back to the response, the pain receptor that may have been activated, which fiber may have been activated, and the transmission tract involved.

Answer 1

On March 5th 2018, I fell down from my scooter and fractured by forearm. I experienced a lot of pain.

Due to extreme pain, the symptoms I had

*) Shivering

*) Fever

*) Insomnia

*) Restlessness

*) Emotional status altered

*) Easily angered

Pain :

The International Association for the Study of Pain defines it as an "unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage"

Pain perception, or nociception (from the Latin word for "hurt"), is the process by which a painful stimulus is relayed from the site of stimulation to the central nervous system. There are several steps in the nociception process:

Contact with stimulus -- Stimuli can be mechanical (pressure, punctures and cuts) or chemical (burns).

Receptors - A nerve ending senses the stimulus.

Transmission -- A nerve sends the signal to the central nervous system. The relay of information usually involves several neurons within the central nervous system.

Pain center reception -- The brain receives the information for further processing and action.

Nociception uses different neural pathways than normal perception (like light touch, pressure and temperature). With nonpainful stimulation, the first group of neurons to fire are normal somatic receptors. When something causes pain, nociceptors go into action first.

Types of nociceptors :

A δ mechanosensitive receptors -- lightly myelinated, faster conducting neurons that respond to mechanical stimuli (pressure, touch)

A δ mechanothermal receptors -- lightly myelinated, faster conducting neurons that respond to mechanical stimuli (pressure, touch) and to heat

Polymodal nociceptors (C fibers) -- unmyelinated, slowly conducting neurons that respond to a variety of stimuli.

Ascending Pathway :

​The signals travel into the spinal cord through the dorsal roots. There, they make synapses on neurons within the dorsal horn.

They synapse on neurons within the spinal cord segment that they entered and also on neurons one to two segments above and below their segment of entry.

These multiple connections relate to a broad area of the body -- this explains why it's sometimes difficult to determine the exact location of pain, especially internal pain.

The secondary neurons send their signals upward through an area of the spinal cord's white matter called the spinothalamic tract.

This area is like a superhighway where traffic from all of the lower segments rides up the spinal cord.

The signals of the spinothalamic tract travel up the spinal cord through the medulla (brain stem) and synapse on neurons in the thalamus, the brain's relay center. Some neurons also synapse in the medulla's reticular formation, which controls physical behaviors.

Descending pathway :

Descending pathways originate in the somatosensory cortex (which relays to the thalamus) and the hypothalamus.

Thalamic neurons descend to the midbrain. There, they synapse on ascending pathways in the medulla and spinal cord and inhibit ascending nerve signals.

This produces pain relief (analgesia). Some of this relief comes from the stimulation of natural pain-relieving opiate neurotransmitters called endorphins, dynorphins and enkephalins.

Pain signals can set off autonomic nervous system pathways as they pass through the medulla, causing increased heart rate and blood pressure, rapid breathing and sweating.

The extent of these reactions depends upon the intensity of pain, and they can be depressed by brain centers in the cortex through various descending pathways.

As the ascending pain pathways travel through the spinal cord and medulla, they can also be set off by neuropathic pain -- damage to peripheral nerves, spinal cord or the brain itself.

However, the extent of the damage may limit the reaction of the brain's descending pathways.

The influences of the descending pathways might also be responsible for psychogenic pain (pain perception with no obvious physical cause).