Pain Physiology and Receptors

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Which chemical transmitters are associated with pain responses from tissue injury?

Histamine (correct)

Serotonin

Acetylcholine

Epinephrine

What reaction is likely stimulated by severe pain?

Sympathetic changes like hypotension

Parasympathetic changes like hypotension (correct)

Sympathetic changes like bradycardia

Parasympathetic changes like tachycardia

Which type of pain is likely to be poorly localized and dull aching?

Visceral pain (correct)

Superficial somatic pain

Cutaneous pain

Deep pain (correct)

What type of fibers are associated with cutaneous pain?

A delta fibers Signup and view all the answers

Which symptom is associated with autonomic reactions to mild pain?

Increase in BP Signup and view all the answers

What is a common emotional response to pain?

Anxiety Signup and view all the answers

Which statement is true about visceral pain?

Dull aching and poorly localized Signup and view all the answers

What distinguishes superficial somatic pain from deep somatic pain?

Arises from skin and subcutaneous tissue Signup and view all the answers

What is the primary function of pain as described in the content?

To initiate the withdrawal reflex Signup and view all the answers

Which type of stimuli can lead to the activation of pain receptors?

Mechanical, thermal, or chemical stimuli Signup and view all the answers

Where are the cell bodies of pain receptors primarily located?

In the spinal ganglia and trigeminal nerve ganglia Signup and view all the answers

Which of the following substances is NOT typically a pain-producing substance?

Dopamine Signup and view all the answers

What term is used to describe receptors that do not adapt to sustained stimulus?

Non-adapting receptors Signup and view all the answers

What pathway does the pain signal take from the spinal cord to the brain?

Spinothalamic tract Signup and view all the answers

What is the role of sensitized nociceptors in response to tissue injury?

Facilitate pain processing Signup and view all the answers

Which of the following statements is correct regarding the transmission of pain signals?

Pain signals travel both to the brain and back to the site of injury. Signup and view all the answers

Which statement best describes referred pain?

It is experienced in a location different from the site of injury. Signup and view all the answers

What mechanism explains the perception of pain in both the skin and viscera?

Convergence projection theory. Signup and view all the answers

Which area is most likely to experience referred pain from the heart?

Inner aspect of the left arm. Signup and view all the answers

Which structure is NOT involved in the pain pathway to the brain?

Lateral geniculate nucleus. Signup and view all the answers

What role does the thalamus play in the perception of pain?

It relays pain signals to the sensory cortex. Signup and view all the answers

What is one result of the reflex contraction of overlying muscles in response to pain?

Ischaemia leading to more pain. Signup and view all the answers

Which type of nerves transmit the pain signals from the skin to the spinal cord?

Somatic nerves. Signup and view all the answers

In which dermatome is referred pain from the appendix most commonly felt?

Right lower quadrant. Signup and view all the answers

What characterizes pain that serves a protective function?

It is associated with both behavioral and emotional responses. Signup and view all the answers

What type of nerve fibers are pain receptors primarily composed of?

Unmyelinated C fibers and small diameter myelinated Aδ fibers. Signup and view all the answers

Where are pain receptors most abundantly located in the body?

In the superficial layer of the skin. Signup and view all the answers

What type of pain is characterized as unpleasant sensory and emotional experience?

Pain in general. Signup and view all the answers

Which statement is true regarding the distribution of pain receptors?

They are absent in the brain tissue. Signup and view all the answers

Which of the following best describes the free nerve endings that function as pain receptors?

They are unmyelinated and sensitive to tissue damage. Signup and view all the answers

What is the primary role of nociceptors?

To detect pain associated with potential tissue damage. Signup and view all the answers

What types of behaviors are typically associated with pain responses?

Social withdrawal and avoidance. Signup and view all the answers

Study Notes

Pain Physiology

Pain is an unpleasant sensation caused by noxious stimulation of sensory nerve endings due to actual or potential damage.
Pain has a protective function, initiating the withdrawal reflex.
Pain can be produced by mechanical, thermal, or chemical stimuli leading to tissue damage.

Pain Receptors

Pain receptors are free nerve endings with cell bodies in spinal ganglia (body) and trigeminal nerve ganglia (face).
They are widely distributed, particularly in the skin.
Nociceptors respond to various stimuli when their intensity reaches a noxious threshold.
They are non-adapting receptors, meaning they continue to respond as long as the stimulus persists.

Mechanism of Pain Receptor Stimulation

Pain receptors are stimulated chemically by substances released from damaged tissue.
Examples of pain-producing substances (PPS) include bradykinin, histamine, serotonin, acids, excess K+ ions, and prostaglandins.

Mechanisms of Pain Receptors

Nociceptive pain involves thermal, chemical, and mechanical stimuli.
The DRG (dorsal root ganglion) carries pain signals to the spinal cord.

Mechanism of Pain

Tissue injury releases substances like prostaglandins, bradykinin, and leukotrienes.
These substances sensitize nociceptors.
Sensitized nociceptors release neurotransmitters like aspartate, neurotensin, glutamate, and substance P.
These neurotransmitters transmit pain signals to the brain via the dorsal horn.

Reactions Associated with Pain

Autonomic reactions: Mild pain stimulates the posterior hypothalamus triggering sympathetic changes (tachycardia, increased blood pressure, pupillary dilation, increased respiration). Severe pain stimulates the anterior hypothalamus triggering parasympathetic changes (bradycardia, hypotension).
Motor reactions: Withdrawal reflex and reflex contraction of overlying muscles (deep somatic and visceral pain).
Emotional effects: Crying, anxiety, and depression.

Quality of Pain

Fast pricking pain is carried by A delta fibers and is immediate, short-lasting, and sharp.
Slow burning pain is carried by C fibers and follows fast pain, lasting longer, and is described as burning.

Pain Localization

Well-localized pain originates from the skin; it is transmitted through the sensory cortex.
Poorly localized pain originates from subcutaneous tissues and viscera; it is transmitted through the thalamus.
Glutamate is the chemical transmitter for well-localized pain, while substance P is for poorly localized pain.

Types of Pain

Cutaneous pain: Arise from the skin, transmitted by thin myelinated A delta fibers.
Deep somatic pain: Arise from muscles, ligaments, and joints; transmitted by non-myelinated C fibers; characterized as dull and aching, poorly localized.
Visceral pain: Arise from internal organs; transmitted by non-myelinated C fibers and autonomic fibers; also poorly localized and dull and aching.

Pain Pathway

Pain signals travel from nociceptors to the posterior somatosensory cortex, where quality and location are determined.
The pathway involves the spinal cord, thalamus, and other brain regions like the midbrain, pons, reticular formation, and medulla.

Referred Pain

Pain is referred to the dermatome supplied by the same dorsal nerve roots as the diseased structure.
Referred pain is explained by two theories:
- Convergence projection theory: Pain fibers from the skin area and diseased viscera converge on the same second-order neuron, leading the brain to perceive the pain as originating from the skin. Diagram of the convergence projection theory is included.
- Facilitation theory: Visceral pain fibers send collaterals to facilitate the second-order neuron of the pain pathway from the skin, leading to pain perception in the skin area. Diagram of the facilitation theory is included.
Examples of organs and their referred pain locations

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz covers the essential concepts of pain physiology and the role of pain receptors. It explores how pain is facilitated by nociceptors and the stimulation mechanisms involved. Test your understanding of the protective functions and responses of pain receptors.