Alpha motor neuron every striated muscle has encapsulated Gamma moto muscle fibers neuron scattered throughout the muscle called muscle spindles Extrafusal muscle fibers Extrafusal and muscle fibers intrafusal fibers
•Every striated muscle has encapsulated muscle fibers scattered throughout the muscle called muscle spindles. •Extrafusal and intrafusal fibers
Alpha motor neuron The extrafusal muscle fibers are innervated by alpha motor Gamma motor neuron neuron The intrafusal muscle fibers are innervated by gamma motor Extrafusal neurons muscle fibers Intrafusal muscle fibers
The extrafusal muscle fibers are innervated by Alpha motor neuron The intrafusal muscle fibers are innervated by Gamma motor neurons
Motor units A single motor neuron(a motor) and all (extrafusal) muscle fibers it innervates The physiological functional unit in muscle (not the cell All cells in motor unit contract synchronously
Motor units ⚫ A single motor neuron (a motor) and all (extrafusal) muscle fibers it innervates ⚫ The physiological functional unit in muscle (not the cell) ◼All cells in motor unit contract synchronously
Motor units and innervation ratio (A) (B) Motor neuron in spinal cord Innervation ratio Fibers per motor neuron Extraocular muscle 3: 1 Gastrocnemius 2000: 1 Muscle fibers innervated by a single motor neuron PUe织g164 o 2001 Sinauer Associates, Inc
Motor units and innervation ratio Purves Fig. 16.4 Innervation ratio Fibers per motor neuron Extraocular muscle 3:1 Gastrocnemius 2000:1
(B) Motor neuron in spinal cord · The muscle cells of a motor unit are not grouped but are interspersed among cells from other motor units Muscle fibers innervated by · The coordinated a single motor movement needs neuron the activation of several motors
•The muscle cells of a motor unit are not grouped, but are interspersed among cells from other motor units •The coordinated movement needs the activation of several motors