touch 2

Monkey Experiment – Raised Letters

Monkeys felt letters. SA1 = sharp details, RA = texture sensing.

Spinal Cord Connections

Dorsal root ganglion → sends touch signals. Motor neurons → move muscles

Penfield’s Brain Mapping

Brain has a map of the body. More brain space = better touch sensitivity.

Phantom Limb Sensations

Brain still processes signals for lost limbs. Face touch can trigger phantom limb feeling.

Pain Pathway Differences

Dorsal Column = fast, Spinothalamic = slow. Cross-over location differs.

Neural Plasticity – Training & Sensitivity

Use a body part more → bigger brain representation → better touch sensitivity.

Evoked Potential – Measuring Touch in the Brain

Touch activates brain areas. More use = stronger response in somatosensory cortex.

Pain Promotes Healing

Prevents injury worsening (motor movements) & supports natural recovery.

Nociceptors – Pain Receptors

Free nerve endings respond to harmful stimuli (cuts, pressure, temperature).

Pain Signal Creation

Skin tension change → activates free nerve endings → pain perception.

L Nerve Fibers (Beta)

Fast, myelinated (light touch).

S Nerve Fibers (Omega & C)

Slow, unmyelinated (pain & temp).

Afferent Pain Pathways

Pain signals travel up spinal cord to brain

Descending Pain Pathways

Brain suppresses pain signals in spinal cord.

Periaqueductal Gray (PAG) & Pain Inhibition

blocks pain signals & inhibits pleasure processing in VTA.

Gate Control Theory – How Touch Reduces Pain

T-Cells send pain signals when is open. Touching activates L Fibers, sending inhibitory signals to close.

Pain Modulation – Mind Over Pain

Brain can suppress pain signals through shock, focus, or distraction.

Opioids – Pain Relief Mechanism

Block neurotransmitter release → stop pain signals in spinal cord & brain.

Binding Affinity & Drug Strength

Higher receptor binding = stronger pain relief (but more risk).

Opioid Overdose Risk

Suppresses breathing by blocking signals in medulla neurons.