MA+Muscle+System

Muscular System (1) What are the three types of muscles in the human body? (Describe and include pictures)
 * 1) Cardiac Muscle: involuntary and occurs in the walls of the heart.[[image:cardiacmuscle.jpg]]
 * 2) Smooth Muscle: involuntary and occurs in walls of internal organs
 * 3) Skeletal muscle: voluntary, contains bundles of muscle fibers called fascicles and is usually attached by tendons to the skeleton[[image:skeletalmuscle.gif]]

(2) List and discuss the functions of muscles. (3) Give an example that illustrates how muscles work in antagonistic pairs. (pictures good) The biceps brachii and the triceps brachii: The biceps flex the forearm and the triceps extend the forearm. (4) Describe the microscopic anatomy of muscle fiber and explain the sliding filament model of muscle contraction. (long answer) (5) Describe the structure and function of the neuromuscular junction. Muscle fibers are stimulated to contract by motor neurons whose axons are in nerves. The axon of one motor neuron can stimulate from a few to several branches. Each branch of an axon ends in an axon terminal that lies in close proximity to the sarcolemma of a muscle fiber. A small gap, called a synaptic cleft, seperated the axon terminal from the sarcolemma. This entire region is called a neruomuscular junction. (6) Describe the events as myosin pulls actin toward the center of the sarcomere. Calcium binds to troponin, exposing myosin binding sites. Atp is hydrolyzed when myosin head is unattached. ADP+p are bound to myosin as myosin head attaches to actin. Upon ADp+P release power stroke occurs: head bends and pulls actin. Binding of fresh ATP causes myosin head to return to resting position. (7) Contrast a muscle twitch with summation and tetanus. A twitch relies on anareobic or aerobic means of acquiring atp. (8) What is muscle tone, and how is it maintained? Muscle tone is a continuous slight tension and is maintained by muscle motor units that take turns contracting.
 * Helps maintain posture
 * Provide movement and heat
 * protect underlying organs
 * Sarcolemma: plasma membrane of a muscle fiber that forms t tubules
 * sarcoplasm: cytoplasm of a muscle fiber that contains the organelles, including myofibrilis
 * glycogen: a polysaccharide that store energy for muscle contraction
 * myoglobin: a red pigment that stores oxygen for muscle contraction
 * t tubule: extension of the sarcolemma that extends into the muscle fiber and conveys impulses that cause Ca2+ to be released from that sarcoplasmic reticulum.
 * sarcoplasmic reticulum: the smooth er of a muscle fiber that stores ca2+
 * myofibril: a bundle of myofilaments that contracts
 * myofilament: actin filamentsor myosin filaments, whose structure and function account for muscle striation and contractions.