Sensory System II

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Questions and Answers

What causes non-painful stimuli to become painful due to hypersensitivity?

Damage to the dorsal root ganglion

Inflammation in the dermatomal segment

Facilitation of pain transmission (correct)

Injury to the spinal cord

What is a significant effect of syringomyelia on sensory perception?

Increased sensitivity to all types of stimuli

Dissociation of cutaneous sensations (correct)

Impairment of vibration and proprioceptive sensation

Complete loss of all sensory modalities

Which virus is associated with severe pain in the dermatomal segment supplied by the infected ganglion?

Cytomegalovirus

Herpes simplex virus

Epstein-Barr virus

Herpes zoster virus (correct)

In Brown Sequard syndrome, what type of paralysis occurs below the level of the lesion?

Spastic paralysis on the same side Signup and view all the answers

Which of the following is true regarding Tabes dorsalis?

It affects dorsal columns and posterior roots of the spinal cord Signup and view all the answers

Which symptom is commonly associated with Brown-Sequard Syndrome?

Positive Babinski's sign on the affected side Signup and view all the answers

What characterizes the thalamic pain experienced after thalamic syndrome?

It may manifest after a few months of no sensation Signup and view all the answers

Which of the following is NOT a characteristic of a cortical lesion?

Loss of crude sensation Signup and view all the answers

What type of sensations are lost due to a brain stem lesion?

All sensations on the opposite side of the body Signup and view all the answers

What is a common assessment finding in individuals with Brown-Sequard Syndrome on the affected side?

Hyperactive deep reflexes Signup and view all the answers

Which of the following mechanisms is responsible for the symptoms of increased tone in spinal cord lesions?

Loss of inhibitory signals from the cortex Signup and view all the answers

What results from a complete destruction of posterior horn cells in Brown-Sequard Syndrome?

Loss of tactile sensations on the same side Signup and view all the answers

Which type of sensory loss is typically not present in the early stages of thalamic syndrome?

Loss of pain sensation Signup and view all the answers

What type of pain is characterized by fast pricking sensation and is associated with flexor withdrawal reflex?

Cutaneous pain Signup and view all the answers

Which type of pain receptors is stimulated primarily by strong mechanical stimuli?

Mechanosensitive pain receptors Signup and view all the answers

What chemical is primarily associated with the neurotransmission of slow pain?

Substance P Signup and view all the answers

Where are pain receptors most abundant in the body?

Skin Signup and view all the answers

What is the characteristic sensation of deep pain?

Dull aching and poorly localized Signup and view all the answers

Which type of pain is often associated with ischemia of skeletal muscle?

Deep pain Signup and view all the answers

What type of nerve fibers transmit fast pain?

A delta fibers Signup and view all the answers

Visceral pain is primarily described as which of the following?

Slow and deep Signup and view all the answers

Study Notes

Pain Sensation: Pain is an unpleasant sensation for body protection, occurring with tissue damage.
Damaged tissue releases chemicals (bradykinin, prostaglandins, substance P, K+, and H+) initiating inflammation.
Pain Receptors (Nociceptors): Free nerve endings, categorized as mechanosensitive (strong mechanical stimuli), thermosensitive (extreme thermal stimuli), and chemosensitive (histamine and strong acids).
Pain Receptor Distribution: More receptors in skin, periosteum, arteries, joint surfaces, falx & tentorium cerebelli, and cranial sinuses. Fewer in deep tissue (e.g. liver, lung alveoli, brain, which are pain insensitive).
Pain Receptor Nerve Fibers: A delta and C fibers.
Pain Receptor Adaptation: Slow or non-adaptive receptors

Types of Pain

Somatic Pain: Originates from skin and deep tissues.
Cutaneous Pain: Surface pain (e.g., prickling, fast pain, burning, slow pain). Fast pain is characterized by a quick, sharp sensation, while slow pain is a lingering, aching sensation affecting skin. Includes quick prickling sensations and slower burning sensations.
Deep Pain: Deep tissue pain from muscles, tendons, ligaments, and periosteum. Characterized by dull aching and poor localization, often associated with nausea and vomiting. It can be referred to the skin. (e.g. musculoskeletal pain)
Visceral Pain: Originates from internal organs. Poorly localized (few receptors) and often described as dull, aching, burning, or colicky.
- Referred Pain: Pain originating in a visceral structure that is perceived as being from an area of skin innervated by the same segmental level as the visceral afferent. Examples: Anginal pain (referred to the left shoulder and arm), gastric pain (referred to the epigastrium above the umbilicus), gall bladder pain (referred to the right shoulder), renal pain (referred to the inguinal region and testis), appendicular pain (referred to the umbilicus), and tooth pain (referred to the head). Visceral pain can trigger autonomic or emotional responses (e.g. nausea, vomiting, bradycardia).

Pain Receptors

Occur in various locations (skin, arteries, meninges), different types of nociceptors react to various stimuli.
These receptors exist in different parts of the body, allowing for the perception of various sensations and pain.
Mechanisms
The mechanisms of transmission and localization of pain signals play a key role in the experience of pain in different parts of the body.

Pain Control

This involves extensive modification of sensory signals along sensory pathways before reaching the central nervous system.
Gate Control Theory: In the Posterior Horn of the Spinal Cord, pain signals are reduced or interrupted by gate mechanisms. This occurs via two key mechanisms:
- Lateral Inhibition: Collaterals originating from ascending sensory neurons produce a reduction of signal strength through collateral modulation.
- Analgesia System: Descending pathways from higher brain centers suppress pain signals.

Pain-Analgesia System

The brain's built-in pain control system (analgesia).
Mechanisms for suppressing pain transmission:
- Opioid receptors (endorphins, enkephalins, dynorphins)
Components of the opioid analgesic system:
Periaqueductal gray matter and periventricular area, raphe magnus nucleus in the lower pons and upper medulla, pain inhibitory complex in the dorsal horn of the spinal cord

Lesions of Sensory System

Peripheral Nerves: Lesions on one or multiple peripheral nerves cause loss of sensation in the affected areas.
- Loss of sensation, diffuse lesion (e.g., peripheral neuritis leading to glove and stocking neuropathy), lesion of dorsal root, loss of sensation from dermatomes, hyperalgesia (increased pain sensitivity in inflamed areas).
Spinal Cord: Different lesions within the spinal cord result in varying sensory deficits.
- Herpes zoster affecting the dorsal root ganglion, inflammation leading to widening of the central canal (syringomyelia), tabes dorsalis (posterior column degeneration), Brown-Séquard syndrome (hemisection of the spinal cord)
Thalamus: Damage to specific thalamic structures can result in specific syndromes (e.g., thalamic syndrome).
Brain stem: Lesions can cause loss of all sensations on opposite side of the lesion.
Cortical lesions: Damage can affect fine localization, perception of pressure, stereognosis, and body part orientation.

Headaches

Intracranial headaches:
- Meningeal irritation (e.g. meningitis, brain tumor).
- Migraine headaches (vascular phenomenon, vasospasm followed by vasodilation).
- Hypertension (cerebral vessel expansion).
- Constipation (toxin absorption leading to meningeal irritation).
Extracranial headaches:
- Muscle spasm.
- Irritation of nasal sinuses
- Issues from refraction, Otitis media, toothache, systemic disorders (e.g., anemia).

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Description

This quiz explores the complexities of pain sensation and the sensory system. It covers pain receptors, types of pain, and the physiological responses involved. Test your understanding of how pain is perceived and processed in the body.

Sensory System II - Pain Mechanisms

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