Graham Lindsley3/20/15Period 7Chapter 8 Objectives1. A few outcomes of muscular actions are walking, talking, breathing, sneezing, muscle tone, the propelling of body fluids and food, the generation of the heartbeat and, the distribution of heat.2. Each muscle fiber within a fascicle lies within a layer of connective tissue in the form of a thin covering called endomysium. Layers of connective tissue, therefore,enclose and separate all parts of a skeletal muscle3. There are many major parts of a skeletal muscle fiber, the parts include, myofibrils, myosin, actin, sarcomeres, sarcoplasmic reticulum, and transverse tubules. myofibrils play a fundamental role in muscle contraction. Myofibrils contain two kinds of protein filaments thick ones containing myosin and thin ones containing actin. The segment of a myofibril that extends from one line to the next in the line is called a sarcomere. The sarcoplasmic reticulum responds to the endoplasmic reticulum of other cells. Both the sarcoplasmic reticulum and transverse tubules activate the muscle contraction mechanism when the fiber is stimulated.4. First, acetylcholine stimulates the skeletal muscle fiber. Acetylcholine diffuses rapidly across the synaptic cleft and binds to a certain protein molecules in the muscle fiber membrane, stimulating a muscle impulse. This impulse passes in all directions over the surface of the muscle fiber membrane and travels through the transverse tubules deep into the fiber until it reaches the sarcoplasmic reticulum. plasmic reticulum contains a high concentration of calcium ions. A muscle impulse causes these ions to diffuse into the sarcoplasm of a muscle fiber. When there is a high concentration of calcium ions in the sarcoplasm troponin and tropomyosin interact in a way that exposes binding sites on actin. As a result, linkages form between actin and myosin filaments and the muscle fibers contract.5. To regenerate ATP, muscle fibers use creatine phosphate. Creatine Phosphate contains high energy phosphate bonds and stores excess energy released from the mitochondria. When ATP supply is sufficient an enzyme in the mitochondria catalyzes the synthesis of creatine phosphate which stores excess energy in its phosphate bonds. As ATP decomposes the energy from creatine phosphate can be transferred to ADP molecules converting them back into ATP.6. During strenuous exercise available oxygen is used primarily to synthesize ATP the muscle fiber requires to contract, rather than to make ATP for synthesizing glucose from lactic acid. Consequently as lactic acid accumulates a person develops an oxygen debt that must be repaid.7. If a muscle fiber is exposed to a single stimulus of sufficient strength to reach threshold, the muscle fiber contract and then relax this action-- a single contraction that lasts only a fraction of a second-- is called a twitch. A sustained contraction is produced from summation and recruitment acting together as one.8. The recruitment of motor units work in an all or none pattern, all the muscle fibers in a motor unit are stimulated at the same time. Summation occurs when a muscle fiber is exposed to a series of stimuli of increasing frequency and reaches a point when it is unable to completely relax before the next stimulus in a series arrives. Even when a muscle appears to be at rest its fibers undergo some sustained contraction. This is called muscle tone, a response to nerve impulses that originated repeatedly from the spinal cord and stimulate a few muscle fibers. Muscle tone is particularly important in maintaining posture.9. In multiunit smooth muscle the muscle fibers are separate rather than organized into sheets. Typically, multiunit smooth muscle tissue contracts only in response to stimulation by motor nerve impulses or certain hormones. Visceral smooth muscle is composed of sheets of spindle shaped cells in close contact with one another. free spyware scan stimulate each other when one fibers stimulated impulse moving over its surface may excite adjacent fibers which in turn stimulate still others. This occurs in rhythmicity.10. Both mechanisms include reactions of actin and myosin, both are triggered by membrane impulses and increase in intracellular calcium ions, and both use energy from ATP. However, smooth muscle is slower to contract and relax than skeletal muscle, on the other hand, smooth muscle can maintain a forceful contraction longer with a given amount of ATP. Also, unlike skeletal muscle, smooth muscle fibers can change length without changing tautness.11. Cardiac muscle and skeletal muscle are very similar. Each cell contains many filaments of actin and myosin, a cardiac muscle cell has a sarcoplasmic reticulum, many mitochondria, and a system of transverse tubules. However the cisternae of cardiac muscle fibers are less well developed and store less calcium than those of skeletal muscle. On the other hand the transverse tubules of cardiac muscle are larger, and they release many calcium ions into the sarcoplasm in response to muscle impulses. 12. When you make body movements you have a prime mover which is also referred to as an agonist. The prime mover,which is a muscle, provides most of the movement. Prime movers are also helped by synergist which assists the prime mover by contracting. There are also muscles that act as antagonists which resists the prime movers action.13. Your pectoralis major is of large size and is located in the pectoral region. The deltoid is shaped like a delta or triangle and is in the chest region. The extensor digitorum extends the digits. Your biceps brachii has two heads or points of origin and is located in the arm. The sternocleidomastoid is attached to the sternum, clavicle, and mastoid process. Your external oblique is located near the outside with fibers that run in a slanted direction(obliquely).