Dr Gawad Physiology Course Online Exams – Pain

The correct answer is "dermatomal rule can explain referred pain." The dermatomal rule states that pain originating from a specific area of the body is referred to the corresponding dermatome. This means that pain felt in a certain area of the body can be traced back to a specific nerve root. Referred pain occurs when pain is felt in a different area of the body than the actual source of the pain. The dermatomal rule helps to explain this phenomenon by showing how the nerves from different areas of the body converge and share pathways in the spinal cord.

The area of flare refers to the redness and swelling that occurs around an injured area. This is caused by the release of histamine, a chemical mediator, from the injured area. Histamine causes vasodilation and increased permeability of blood vessels, leading to the characteristic redness and swelling. This response is part of the inflammatory process and contributes to the sensitization of pain receptors in the area, leading to hyperalgesia. Therefore, the statement that the area of flare is due to the release of histamine from the injured area is true.

Severe cutaneous pain is associated with hypotension. When an individual experiences intense pain, it can trigger a physiological response known as the "fight or flight" response. This response includes the release of stress hormones, such as adrenaline, which can cause a decrease in blood pressure. This drop in blood pressure is what leads to the association between severe cutaneous pain and hypotension.

The correct answer is that the muscle is relaxed to avoid more pain. This is because when a muscle is in pain, it tends to tense up rather than relax. This is a natural protective mechanism of the body to prevent further injury or damage to the muscle. So, it is not true that the muscle would relax to avoid more pain.

Cardiac pain is conducted through afferent sympathetic nerve fibers because the heart is innervated by sympathetic nerve fibers that transmit pain signals to the brain. This type of pain is often described as a deep, crushing or squeezing sensation in the chest, and it can radiate to other areas of the body such as the left arm or jaw. The sympathetic nervous system is responsible for the body's "fight or flight" response, and it plays a role in regulating heart rate and blood pressure. Therefore, it makes sense that cardiac pain would be conducted through these nerve fibers.

Presynaptic inhibition by the local neuron is a mechanism by which the release of neurotransmitters from the presynaptic knob is inhibited. This occurs through the inhibition of exocytosis, which is the process by which neurotransmitters are released into the synaptic cleft. By inhibiting exocytosis, the local neuron reduces the amount of neurotransmitter available for binding to postsynaptic receptors, thereby decreasing synaptic transmission and inhibiting the propagation of signals. This mechanism plays a role in modulating synaptic activity and regulating the strength of neuronal communication in the brain's opiate analgesic system.

According to the spinal cord gate theory of pain, the correct statement is that stimulation of the sensory C fiber afferent of the lateral spinothalamic tract will inhibit the tonically active inhibitory interneuron. This theory suggests that the transmission of pain signals can be modulated by inhibitory interneurons in the spinal cord. When the C fiber afferents are stimulated, they can activate inhibitory interneurons, which in turn inhibit the transmission of pain signals. This mechanism helps to regulate and control the perception of pain.