1. Locomotion. 2. Repositioning. 3. Internal movement

Transcription

1 MUSCLE and MOVEMENT Chapters 20, 8, Locomotion A. Movement B. 2. Repositioning A. 3. Internal movement A. 1 Muscle Cells 1. Contractile 2. Myocytes 3. Striated A. Skeletal B. Cardiac 4. Smooth 5. Striated is voluntary 6. Smooth is involuntary 2 The Musculoskeletal system 1. Provides the basic form and shape of the organism 2. Support 3. Protection 4. Body movement 5. Heat production 3 1

2 1. Bundles of muscle fibers 2. Attaches via connective tissue to bone 3. Antagonistic muscle groups Skeletal Muscle triceps biceps 4 Figure 20.1 The organization of skeletal muscles 5 Figure 20.1 The organization of skeletal muscles Muscle fiber MYOFYBRIL 6 2

3 MYOFYBRIL 7 8 Figure 20.2 Thick (myosin) and thin (actin) myofilaments are arranged in parallel in a sarcomere 9 3

4 Figure 20.3 Muscle contraction produced by sliding filaments 1. Myosin heads pull on thin filaments 2. Sarcomere unit shortens 10 Figure Fig 20.5 Molecular interactions that underlie muscle contraction 2 Breaking the Cross-bridge 1.Rigor Conformation 12 4

5 3. Hydrolyzing the ATP causes the angle of the head to change 4 And bind to the actin 13 6 The myosin unbinds ADP and remains bound to the actin 5. power stroke 14 Thin Filament 1. ACTIN A. binding site for myosin 2. Two regulatory proteins A. TROPOMYOSIN B. TROPONIN 15 5

6 Figure 20.6 The regulation of contraction 16 MUSCLE, HOW IT WORKS 1. Sequence of events in stimulation and contraction of muscle A. Stimulation B. Contraction C. Relaxation D. Rigor mortis happens when ATP is gone and myosin heads bind permanently to actin filaments Sarcolemma. 2. T (transverse) tubule 3. Sarcoplasmic reticulum: Sarcolemma (Sarcolemma) 18 6

7 Microscopic structure of skeletal muscle cell T-tubules with sarcomere unit 19 Figure 20.7 Excitation contraction coupling

8 Figure 20.7 Excitation contraction coupling 22 Figure 20.7 Excitation contraction coupling

9 Fig Myogram: graph of a muscle contraction. 1. In isometric contraction muscle does not shorten 2. In isotonic contraction, the muscle shortens as it moves a constant load 25 Fig Summation and Tetanus 1. Twitch 2. Summation 3. Tetanus

10 Box 20.1 The electric eel Electrophorus electricus possesses both strong and weak electric organs 1.Electric organs modified skeletal muscle 2.Electrocytes stacked in columns A.Respond to signals from motor neurons B.All electrocytes in column depolarize spontaneously C.Up to 600 V discharge 28 Muscle, How It Works: Contraction 1. Energy Sources A. glucose., glycogen, fat 2. Anaerobic respiration (glycolysis) A. 2 ATP/glucose B. Lactic acid C. Rapid 3. Aerobic respiration (Fig ) A. 36 ATP/glucose B. only enough ATP for 2-4 seconds of work a. creatine phosphate, which converts into ATP b. glycogen and fat are also kept in cell for longer work c. even longer work gets energy from metabolism of food and fat stores in the liver Oxygen debt (Fig. 8.6) A. if not enough oxygen, glycogen is metabolized anerobically and lactic acid builds up until muscle can t work 2. Muscle Fatigue (Fig. 8.8) 3. Muscle cramps 30 10

11 Classification of Skeletal Muscle Fibers 1. Tonic Fibers do not generate action potentials A. Relatively rare B. Mainly in postural muscles of lower vertebrates C. Slow cross-bridge cycling produces long sustained 2. Twitch Fibers generate action potentials 31 Twitch Muscles: Fig Fast glycolytic fibers (FG) A. Contract quickly, generate lots of power. Mainly fueled by glycolysis; high levels of glycolytic enzymes & low mitochondrial volume. 2. Slow oxidative fibers (SO): A. Contract relatively slowly. primarily fueled by oxidative metabolism, high levels of aerobic enzymes and lots of mitochondria and myoglobin. B. High levels of myoglobin and mitochondria make SO fibers more resistant to fatigue 32 Figure Whole muscles typically consist of mixtures of different types of fibers 33 11

12 The Motor Unit (Fig 20.15) 1. one somatic motor neuron & all the skeletal muscle cells (fibers) it stimulates A. One nerve cell supplies on average 150 muscle cells that all contract in unison. 2. muscle fiber in contact with only one motor neuron 3. When a motor neuron fires, all muscle fibers in the motor unit contract. 34 Figure Total strength of a contraction depends on how many motor units are activated & how large the motor units are Graded Contraction A. Contractions of muscle fibers are all or none B. Vary the frequency of action potentials C. Rate of stimulation that is very fast results in tetanus D. The neuron can cause many muscle fibers to contract at the same time 2. Muscle Force A. proportional to cross-sectional diameter and sarcomere length 36 12

13 1. Graded Contraction A. Contractions of muscle fibers are all or none B. Vary the frequency of action potentials C. Rate of stimulation that is very fast results in tetanus D. The neuron can cause many muscle fibers to contract at the same time 2. Muscle Force A. proportional to cross-sectional diameter and sarcomere length 37 Skeletal muscle 1. attaches to bone, skin or fascia 2. striated with light & dark bands visible with scope 3. voluntary control of contraction & relaxation 38 Cardiac Muscle 1. Striated 2. Short, branched fibers joined end-to-end A. gap junctions pass the electrical signal for contraction 3. Contraction in one part sends wave of contraction throughout 39 13

14 Cardiac Muscle 1. Contracts rhythmically 2. Sustained contraction is not possible 3. more mitochondria, works non-stop 4. Vertebrates are Myogenic 5. in some invertebrates it is controlled by the brain (neurogenic) 40 Smooth Muscle 1. Small, involuntary muscle cells A. autonomic nervous system, hormones, local chemicals 2. Tapering at ends 3. Single, oval, centrally located nucleus 4. found in organs and blood vessels 5. Slow, regular contractions 6. Prolonged contractions 41 Smooth Muscle 1. actin and myosin structure 2. fibers are not in register with each other 3. Sliding of thick & thin filaments transferred to intermediate filaments & dense bodies attached to sarcolemma 4. Muscle fiber contracts and twists into a helix as it shortens 5. relaxes by untwisting 42 14