Hygiene Atlas

Atlas · Plate IV · Physiology · 06

Nerve and muscle

The sympathetic system drives fight or flight, raising heart rate and blood pressure, while the parasympathetic system handles rest and digest. Receptor types explain many drug effects: alpha-1 narrows vessels, beta-1 speeds and strengthens the heart, and beta-2 opens the airways. Local anesthetics block sodium channels, so small pain fibers go numb before touch, pressure and motor fibers.

High-yield facts · 6

  1. The sympathetic system is "fight or flight" (raises heart rate and BP); the parasympathetic is "rest and digest."S49
  2. Acetylcholine is the main parasympathetic neurotransmitter; norepinephrine is the main sympathetic one.S49
  3. Alpha-1 receptors constrict vessels; beta-1 receptors raise heart rate and force; beta-2 receptors dilate bronchi.S51
  4. Local anesthetics block voltage-gated sodium channels, stopping nerve impulse conduction.S14
  5. Small myelinated fibers are blocked before large ones: pain goes first, then temperature, touch, pressure, motor.S14
  6. Nodes of Ranvier speed conduction in myelinated nerves; about 8-10 mm of nerve (three nodes) must be bathed in anesthetic to block it.T1

Facts are written in our own words; each tag links to its source. Values marked "sources vary" differ between references, so check the one your program uses.