Chapter 7 Lecture Slides PDF

Chapter 7 Lecture Slides Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.  Chapter 7-Muscular System Functions 1. Movement 2. Maintain posture 3. Respiration 4. Production of body heat 5. Communication 6. Heart beat 7. Contraction of...

Chapter 7 Lecture Slides Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.  Chapter 7-Muscular System Functions 1. Movement 2. Maintain posture 3. Respiration 4. Production of body heat 5. Communication 6. Heart beat 7. Contraction of organs and vessels Types of Muscles 1. Skeletal 2. Cardiac 3. Smooth 3 Abilities of Skeletal Muscles Contractility: ability to shorten Excitability: respond to stimulus Extensibility: can stretch Elasticity: recoil 4  Skeletal Muscle Characteristics Makes up 40% of body weight Named because attached to bones (skeleton) Many nuclei per cell (near periphery) Striated Longest of muscle types 5 6  Skeletal Muscle Structures- Connective Tissue Coverings Epimysium: connective tissue that surrounds entire skeletal muscle (outside) Muscle fasciculus: bundle of muscle fibers Perimysium: connective tissue around each muscle fasciculus 7  Muscle fiber: - skeletal muscle cells - many nuclei Endomysium: connective tissue that surrounds each muscle fiber 8 Figure 7.2a  Skeletal Muscle Structures- Muscle Fiber Structure Myofibril: thread-like proteins that make up muscle fibers Myofilament: - proteins that make up myofibrils - Ex. actin and myosin Sarcoplasm: cytoplasm of muscle fiber (cell) 10  Sarcolemma: - cell membrane - contains T-tubules T-tubules (transverse): - wrap around sarcomeres at A band - associated with sarcoplasmic reticulum Sarcoplasmic reticulum: - type of SER - surrounds myosin - stores and releases Ca2+ 12  Skeletal Muscle Structures- Actin and Myosin Myofilaments Actin: - thin myofilament - resemble 2 strands of pearls Myosin: - thick myofilament - resemble golf clubs Troponin: attachment site on actin for Ca2+ Tropomyosin: - filament on grooves of actin - attachment site on actin for myosin Figure 7.2c 15 16  Skeletal Muscle Structures- Sarcomeres Sarcomere: - contractile unit - contains actin and myosin Z disk: protein fibers that form attachment site for actin H zone: - center of sarcomere - contains only myosin  I band: contains only actin A band: where actin and myosin overlap M line: where myosin are anchored 19  Resting Membrane Potential Outside cell Inside cell Na+ K+ + charge – charge Na+ channels closed Some K+ channels open Why is the inside of cell negative if K+ is positive? K+ is able to diffuse out of cell freely but other larger negative molecules cannot. 20 21  Action Potential - “electricity” - stimulus that causes rapid depolarization and repolarization - causes muscle to contract 22  Depolarization - change in charges - inside becomes more + and outside more – - Na+ channels open 23  Repolarization - Na+ channels close - change back to resting potential 24  Sodium-Potassium Pump What is it? - pumps Na+ out of cell and transports K+ into cell - restores balance 25 26  Nerve Supply Motor neuron: nerve cells that carry action potentials to muscle fibers Neuromuscular junction (synapse): where nerve cell and muscle fiber meet Presynaptic terminal: end of nerve cell (axon) 27  Postsynaptic membrane: muscle fiber membrane Synpatic cleft: space between presynpatic terminal and postsynaptic membrane Synaptic vesicle: - in presynaptic terminal - store and release neurotransmitters 28  Neurotransmitter: - chemicals that stimulate or inhibit a muscle fiber - Ex. Acetylcholine Motor unit: group of muscle fibers that motor neuron stimulates 29 31  Steps in a Muscle Contraction (Sliding Filament Theory) 1. An action potential travels down motor neuron to presynaptic terminal causing Ca2+ channels to open. 2. Ca2+ causes synaptic vesicles to release acetylcholine into synaptic cleft. 3. Acetylcholine binds to receptor sites on Na + channels, Na+ channels open, and Na+ rushes into postsynaptic terminal (depolarization). 32 4. Na+ causes sarcolemma and t-tubules to increase the permeability of sarcoplasmic reticulum which releases stored calcium. 5. Ca2+ binds to troponin which is attached to actin. 6. Ca2+ binding to troponin causes tropomyosin to move exposing attachment sites for myosin. 7. Myosin heads bind to actin. 33 8. ATP is released from myosin heads and heads bend toward center of sarcomere. 9. Bending forces actin to slide over myosin. 10. Acetylcholinesterase (enzyme breaks down acetylcholine) is released, Na+ channels close, and muscle contraction stops. 34  Action Presynaptic potential terminal 1. Action potential travels down the motor neuron to presynaptic terminal causing Ca2+ channels to open. 35  Presynaptic terminal ACh 2. Ca2+ causes synaptic vesicles release acetylcholine into synaptic cleft. 36  Synaptic cleft Na+ ACh Receptor molecule Na+ 3. Acetylcholine binds to receptor molecules on Na+ channels, Na+ channels open, and Na+ rushes into the postsynpatic terminal (depolarization). 37  Ca2+ Sarcoplasmic reticulum T tubule Sarcomere in myofibril 4. Na+ causes sarcolemma and T-tubules to increase permeability of sarcoplasmic reticulum and stored Ca2+ is released. 38  Action potential Ca2+ Sarcolemma Sarcoplasmic reticulum T tubule Actin Ca2+ myofilament Sarcomere Myosin in myofibril myofilament Ca2+ Ca2+ binds to troponin Troponin Actin Tropomyosin myofilament Myosin myofilament 5. Ca2+ binds to troponin which is attached to actin. 39  Action potential Ca2+ Sarcolemma Sarcoplasmic reticulum T tubule Actin Ca2+ myofilament Sarcomere Myosin in myofibril myofilament Ca2+ Ca2+ binds to troponin Troponin Actin Tropomyosin myofilament Myosin myofilament 6. Ca2+ binding to troponin causes tropomyosin to move exposing attachment sites for myosin. 40  Ca2+ Active site Cross-bridge Active sites exposed 7. Myosin heads bind to actin. 41  ATP ATP ATP 8. ATP is released from myosin heads and the heads bend toward the center of the sarcomere. 42 9. The bending forces actin to slide over myosin. 43  ACh Choline Acetic acid ACh receptor site Acetylcholinesterase 10. Acetylcholinesterase is released and Na+ channels close and contraction stops. 44  ATP and Muscle Contractions Energy for muscle contractions supplied by ATP Energy is released as ATP → ADP + P ATP is stored in myosin heads ATP help form cross-bridge formation between myosin and actin New ATP must bind to myosin before cross- bridge is released Rigor mortis: person dies and no ATP is available to release cross-bridges  Other Information ATP is made in mitochondria from aerobic or anaerobic respiration. During a muscle contraction, H zone and I band shorten but A band stays the same. Striations of skeletal and cardiac muscle are due to sarcomeres (actin and myosin). 48  Terms Threshold: weakest stimulus needed to produce a response All or None Law: muscle contracts or doesn’t (no in between) Twitch: rapid contraction and relaxation of a muscle Tetanus: muscle remains contracted 50  Isometric: amount of tension increases (weight) Isotonic: amount of repetitions increases Tone: constant tension over a long period of time 51 Slow and Fast Twitch Fibers Slow Twitch Fibers Contract slowly Fatigue slowly Long distance runners Use aerobic respiration Energy from fat Dark meat Red or dark because of myoglobin Myoglobin: helps O2 bind in muscle 52  Fast Twitch Fibers Contract quickly Fatigue quickly Sprinters Use anaerobic respiration Energy from glycogen White meat 53  Other Facts about Twitch Fibers Humans have both types of fibers Distribution of fibers is genetically determined Neither type can be converted but capacity can be increased through intense exercise 54 Skeletal Muscle Anatomy Origin: nonmovable end Insertion: movable end Belly: middle Synergists: muscles that work together Antagonist: muscles that oppose each other 55  Nomenclature Muscles are named according to Location: Ex. tibialis anterior Origin/insertion: Ex. sternocleidomastoid 57  Size: Ex. gluteus maximus Shape: Ex. deltoid (triangular) Function: Ex. masseter Muscles of Head and Neck Occipitofrontalis: raises eyebrows (forehead) Orbicularis oculi: allows blinking (eyes) Orbicularis oris: kissing muscle (mouth) 59  Zygomaticus: smiling muscle (cheek) Masseter: chewing (mastication) muscle Muscles of Facial Expression 61  Thoracic Muscles External intercostals: elevate ribs for inspiration Internal intercostals: depress ribs during forced expiration Diaphragm: moves during quiet breathing Abdominal Wall Muscles Rectus abdominis: - center of abdomen - compresses abdomen External abdominal oblique: - sides of abdomen - compresses abdomen  Internal abdominal oblique: compresses abdomen Transverse abdominis: compresses abdomen  Upper Limb Muscles Trapezius: - shoulders and upper back - extends neck and head Pectoralis major: - chest - elevates ribs  Serratus anterior: - between ribs - elevates ribs Deltoid: - shoulder - abductor or upper limbs  Triceps brachii: - 3 heads - extends elbow Biceps brachii: - “flexing muscle” - flexes elbow and shoulder  Brachialis: flexes elbow Latissimus dorsi: - lower back - extends shoulder Muscles of Hips and Thighs Iliopsoas: flexes hip Gluteus maximus: - buttocks - extends hip and abducts thigh Gluteus medius: - hip - abducts and rotates thigh Muscles of Upper Leg Quadriceps femoris 4 thigh muscles Rectus femoris: - front of thigh - extends knee and flexes hip Vastus lateralis: extends knee Vastus medialis: extends knee Vastus intermedius: extends knee  Gracilis: adducts thigh and flexes knee Biceps femoris, semimembranosus, semitendinosus: - hamstring - back of thigh - flexes knee, rotates leg, extends hip Muscles of Lower Leg Tibialis anterior: - front of lower leg - inverts foot Gastrocnemius: - calf - flexes foot and leg Soleus: - attaches to ankle - flexes foot Figure 7.13b Cardiac Muscle Characteristics Heart 1 centrally located nucleus/cell Striated Rich in mitochondria Intercalated disks: special cell junctions that allow cells to act as a unit 80 Smooth Muscle Characteristics Found on organs 1 centrally located nucleus/cell Not striated Less actin and myosin Under involuntary control 81