1. Ch.10 Muscle Tissue Skeletal Muscle Tissue and the Muscular System

2. 3 Types of muscle tissue Skeletal Skeletal Cardiac Cardiac Smooth Smooth Skeletal muscles attach to bones directly or indirectly. Skeletal muscles attach to bones directly or indirectly. Functions: Produce skeletal movement, maintain posture, support soft tissues, guard entrances/exits, and maintain body temperature. Functions: Produce skeletal movement, maintain posture, support soft tissues, guard entrances/exits, and maintain body temperature.

3. Organization of Connective Tissues Each muscle cell or fiber is surrounded by an endomysium. Each muscle cell or fiber is surrounded by an endomysium. Bundles of muscle fibers are sheathed by a perimysium. Bundles of muscle fibers are sheathed by a perimysium. The entire muscle is covered by an epimysium. The entire muscle is covered by an epimysium. At the ends of the muscle are tendons or aponeuroses that attach muscle to bones. At the ends of the muscle are tendons or aponeuroses that attach muscle to bones.

4. Skeletal Muscle Fibers A skeletal muscle fiber has a sarcolemma, or cell membrane; sarcoplasm (cytoplasm); and sarcoplasmic reticulum similar to smooth ER of other cells. A skeletal muscle fiber has a sarcolemma, or cell membrane; sarcoplasm (cytoplasm); and sarcoplasmic reticulum similar to smooth ER of other cells. Transverse tubules and myofibrils aid in contraction. Transverse tubules and myofibrils aid in contraction. Filaments in a myofibril are organized into repeating functional untis called sarcomeres. Filaments in a myofibril are organized into repeating functional untis called sarcomeres. Myofilaments called thin filaments and thick filaments form myofibrils. Myofilaments called thin filaments and thick filaments form myofibrils.

5. Contraction of Skeletal Muscle When muscle cells contract, they contract tension and pull on the attached tendons (fig 10-9 in text) When muscle cells contract, they contract tension and pull on the attached tendons (fig 10-9 in text) The activity of a muscle fiber is controlled by a neuron at a neuromuscular junction The activity of a muscle fiber is controlled by a neuron at a neuromuscular junction

6. Tension Production The amount of tension produced by a muscle fiber depends on the number of cross bridges formed. The amount of tension produced by a muscle fiber depends on the number of cross bridges formed. Skeletal muscle fibers can contract most forcefully when stimulated over a narrow range of resting lengths Skeletal muscle fibers can contract most forcefully when stimulated over a narrow range of resting lengths A twitch is a cycle of contraction and relaxation produced by a single stimulus. A twitch is a cycle of contraction and relaxation produced by a single stimulus.

7. Repeated stimulation at slow rate produces treppe, a progressive increase in twitch tension. Repeated stimulation at slow rate produces treppe, a progressive increase in twitch tension. The number and size of a muscle’s motor units determine how precisely controlled its movements are. (fig. 10-17 text) The number and size of a muscle’s motor units determine how precisely controlled its movements are. (fig. 10-17 text)

8. Normal activites generally include both isotonic contractions 9in which the tension in a muscle rises and the length of the muscle changes) and isometric contractions (in which tension rises, but the length of muscle remains constant) fig. 10-18 text). Normal activites generally include both isotonic contractions 9in which the tension in a muscle rises and the length of the muscle changes) and isometric contractions (in which tension rises, but the length of muscle remains constant) fig. 10-18 text). Resistance (load) and speed of contraction are inversely related. Fig 10-19 text Resistance (load) and speed of contraction are inversely related. Fig 10-19 text The return to resting length after a contraction may involve elastic forces, the contraction of opposing muscle groups, and gravity. The return to resting length after a contraction may involve elastic forces, the contraction of opposing muscle groups, and gravity.

9. Energy Use and Muscular Activity Muscle contractions require large amounts of energy. Muscle contractions require large amounts of energy. Creatine phosphate can release stored energy to convert ADP to ATP. Creatine phosphate can release stored energy to convert ADP to ATP. At rest or at moderate levels of activity, aerobic metabolism can provide most of the ATP needed to suport muscle contractions. At rest or at moderate levels of activity, aerobic metabolism can provide most of the ATP needed to suport muscle contractions. At peak levels of activity, the cell relies heavily on the anaerobic process of glycolysis to generate ATP, because the mitochondria can’t obtain enough oxygen to meet the existing ATP demands. At peak levels of activity, the cell relies heavily on the anaerobic process of glycolysis to generate ATP, because the mitochondria can’t obtain enough oxygen to meet the existing ATP demands.

10. As muscular activity changes, the pattern of energy production and use changes. As muscular activity changes, the pattern of energy production and use changes. A fatigued muscle can no longer contract, because of changes in pH due to the buildup of lactic acid, and the exhaustion of energy resources. A fatigued muscle can no longer contract, because of changes in pH due to the buildup of lactic acid, and the exhaustion of energy resources. The recovery period begins immediately after a period of muscle activity and continues until conditions inside the muscle have returned to preexertion levels. Oxygen debt created during exercise is the amount of oxygen required during the recovery period to restore the muscle to its normal condition. The recovery period begins immediately after a period of muscle activity and continues until conditions inside the muscle have returned to preexertion levels. Oxygen debt created during exercise is the amount of oxygen required during the recovery period to restore the muscle to its normal condition.

11. Types of Skeletal Muscle Fibers 3 types: fast fibers, slow fibers, and intermediate fibers. 3 types: fast fibers, slow fibers, and intermediate fibers. Fast fibers- large in diameter containing densely packed myofibrils with large glycogen reserves and few mitochondria. Produce rapid and powerful contractions of brief duration. Fast fibers- large in diameter containing densely packed myofibrils with large glycogen reserves and few mitochondria. Produce rapid and powerful contractions of brief duration.

12. Slow fibers About half the diameter of fast fibers and take three times as long to contract after stimulation. About half the diameter of fast fibers and take three times as long to contract after stimulation. Abundant in mitochondria Abundant in mitochondria High concentrations of myoglobin enable slow fibers to continue contracting for extended periods. High concentrations of myoglobin enable slow fibers to continue contracting for extended periods.

13. Intermediate Fibers Very similar to fast fibers Very similar to fast fibers Have a greater resistance to fatigue Have a greater resistance to fatigue

14. Muscle Performance Muscles dominated by fast fibers appear pale and are called white muscles. Muscles dominated by fast fibers appear pale and are called white muscles. Muscles dominated by slow fibers are rich in myoglobin and appear as red muscles. Muscles dominated by slow fibers are rich in myoglobin and appear as red muscles. Training to develop anaerobic endurance can lead to hyprtrophy (enlargement) of the stimulated muscles. Training to develop anaerobic endurance can lead to hyprtrophy (enlargement) of the stimulated muscles.

15. Physical Conditioning Anaerobic endurance- the time over which musclular contrations can be sustained by glycolysis and reserves of ATP and Creatine. Anaerobic endurance- the time over which musclular contrations can be sustained by glycolysis and reserves of ATP and Creatine. Aerobic endurance- the time over which a muscle can continue to contract while supported by mitochondrial activities. Aerobic endurance- the time over which a muscle can continue to contract while supported by mitochondrial activities.

16. Cardiac Muscle Tissue Is located only in the heart. Is located only in the heart. Cells are small and have one nucleus. Cells are small and have one nucleus. Contract without neural stimulation Contract without neural stimulation Contrations last longer than skeletal muscle. Contrations last longer than skeletal muscle.

17. Smooth Muscle Tissue Nonstriated, involuntary muscle tissue Nonstriated, involuntary muscle tissue Lack sarcomeres Lack sarcomeres Thin filaments are anchored to dense bodies. (fig 10-23 text) Thin filaments are anchored to dense bodies. (fig 10-23 text) Contracts when calcium ions interact with calmodulin. Contracts when calcium ions interact with calmodulin. Functions over a wide range of lengths Functions over a wide range of lengths