Nerve-Muscle Relationship

nerve

skeletal muscle MUST be stimulated by _____

somatic motor neurons

nerve cell bodies (soma) in brainstem and spinal cord, axons extend from brainstem/spinal cord to muscle fibers

neuromuscular junction

point of contact between nerve axon and muscle fiber

motor unit

one nerve fiber (axon) + all muscle fibers (cells) innervated by it

small

_____ motor units have a fine degree of control, about 3-6 muscle fibers per neuron, e.g., eye and hand muscles

large

_____ motor units have more strength than dexterity, 100s of muscle fibers per neuron, e.g., gastrocnemius of calf

junctional folds

increase surface area in sarcolemma for more (ACh) receptor proteins

Na⁺

these ions move through ACh channels once ACh binds to them in order to trigger action potential

botox

neurotoxin produced by bacterium, blocks release of ACh at NMJ, leading to muscle paralysis, originally developed to help with spasticity (uncontrolled contractions)

-90 mV

muscle fiber RMP

-65 mV

muscle fiber threshold