Human Physiology, 14th edition (2016)

362 Chapter 12

Figure 12.2 The appearance of skeletal muscle fibers through the light microscope. The striations are produced by
alternating dark A bands and light I bands. (Note the peripheral location of the nuclei.)

Nuclei

Muscle fiber

Somatic motor neuron axon

Muscle fiber nucleus

Nerve fiber branches

Mitochondria

Folded sarcolemma

Synaptic vesicles

Neuromuscular cleft

Motor end plate

Motor end plate

Myofibril

(a)

Neuromuscular junction

Somatic motor axons

Motor end plate of muscle fiber

Muscle fibers

(b)

Figure 12.3 Motor end plates

at the neuromuscular junction. The

neuromuscular junction is the synapse

between the nerve fiber and muscle fiber.

The motor end plate is the specialized

portion of the sarcolemma of a muscle fiber

surrounding the terminal end of the axon.

( a ) An illustration of the neuromuscular

junction. Notice the slight gap between the

membrane of the axon and that of the muscle

fiber. ( b ) A photomicrograph of muscle fibers

and neuromuscular junctions.