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Somatosensory System Flashcards

Card 1
Somatosensory Transduction & Mechanical Channels

• What is transduction? The process where sensory receptors convert mechanical stimuli (like touch) into electrical signals.

• How does it happen? Pressure physically distorts the receptor, opening ion channels that allow positive ions to flow in, triggering an electrical signal.

• Connection: Similar channels are involved in detecting pain through A-delta and C fibers.

Card 2
Receptive Fields & Sensory Detail

• Center-Surround Fields:

  • Touch in Center → Excitation

  • Touch in Surround → Inhibition

• Why is this important? This contrast sharpens your sense of touch by enhancing the boundary between where you are and aren’t being touched.

• Connection: Similar contrast-enhancing patterns appear in vision (lateral inhibition).

Card 3
Homunculus & Sensory Priorities

• Homunculus: A brain map in the primary somatosensory cortex where areas with more sensory receptors (e.g., fingers, lips) occupy more space.

• Connection to Motor Cortex: The motor homunculus is organized similarly, reflecting areas where fine motor control is most important.

Card 4
Pain Fibers & Pain Types

• A-Delta Fibers: Myelinated for fast, sharp pain (e.g., stepping on glass).

• C Fibers: Unmyelinated for slow, dull pain (e.g., lingering ache).

• Capsaicin Response: C fibers are activated by capsaicin, explaining the burning sensation from spicy food.

• Connection to Pain Management: Treatments like TENS units activate non-pain touch fibers to reduce C fiber pain signals.

Card 5
Touch vs. Pain Pathways

• Dorsal Column (Touch): Carries touch and proprioception signals; crosses at the medulla.

• Lateral Pathway (Pain): Carries pain and temperature signals; crosses immediately in the spinal cord.

• Why Separate Pathways? This explains why injuries like spinal cord damage may affect one sense but not the other.

Card 6
Pain Perception & Emotional Response

• Somatosensory System: Detects the physical sensation of pain.

• Motivational System: Adds an emotional layer to pain (e.g., anxiety, frustration).

• Key Brain Areas: The anterior cingulate cortex and insula contribute to the emotional impact of pain.

Card 7
Pain Relief Mechanisms

• Gate Control Theory: Non-pain touch signals “close the gate,” blocking some pain signals.

• TENS Units: Use electrical stimulation to trigger this system.

• Placebos: Can reduce pain by activating the brain’s endorphin system.

• Connection to Opioids: Drugs like morphine mimic endorphins to reduce pain perception.

Card 8
Primary Somatosensory Cortex (S1)

• Location: Postcentral gyrus in the parietal lobe.

• Organization: Organized in a homunculus map by body part.

• Contralateral Information Flow: The left side of the brain processes touch from the right side of the body and vice versa.