are fibrous, dense tissues, whose primary function is to allow the body to move by repeated contraction and relaxation. Besides movement, the muscle is also responsible for maintaining
posture, stabilizing the joints, and producing body heat through muscle function.
muscle is also known as the skeletal muscle, because it is attached mainly to the bones and skin, and is responsible for the
mobility of the body and limbs.
of striated muscle is controlled voluntarily, unlike the smooth muscle of the internal organs and the cardiac muscle of the
heart, which are involuntary.
muscles are composed of muscle fibers, long fused cells containing multiple nuclei. The muscle fibers are packed together
in bundles by connective tissue and are packed with myofibrils.
are cylindrical arrangements of myofilaments, made up of proteins called actin and myosin, and which cause the light and dark
banded appearance of muscle fiber. These myosin and actin filaments slide across each other, causing the muscle to contract.
of the myofilaments is caused by neural impulses. The axon terminuses of motor neurons located directly above the muscle fibers
create a neuromuscular junction, in which synapses are formed between the muscle and the nerve.
nerve impulse travels down the axon, it causes the release of the neurotransmitter acetylcholine into the synapse. Acetylcholine
diffuses across the synapse and attaches to the membrane of the muscle fiber, the sarcolemma.
causes sodium ion gates in the sarcolemma to open, and the rushing in of sodium ions causes an action potential across the
membrane of the muscle cell, causing the entire muscle fiber to contract. The contraction of skeletal muscles pulls on the
bones they are attached to, causing the entire appendage to move.