Essentials of Human Anatomy & Physiology PDF

Essentials of Human Anatomy & Physiology Twelfth Edition Chapter 6 The Muscular System Lecture Presentation by...

Essentials of Human Anatomy & Physiology Twelfth Edition Chapter 6 The Muscular System Lecture Presentation by Patty Bostwick-Taylor Florence-Darlington Technical College Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved The Muscular System Muscles are responsible for all types of body movement Three basic muscle types are found in the body 1. _________ muscle 2. _________ muscle 3. _________ muscle Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Muscle Types (1 of 6) Skeletal and smooth muscle cells are elongated (muscle cell = muscle fiber) Contraction and _________ of muscles are due to the movement of microfilaments All muscles share some terminology – Prefixes _____ and mys- refer to “muscle” – Prefix _______ refers to “flesh” Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Muscle Types (2 of 6) Skeletal muscle – Most skeletal muscle fibers are attached by ______ to bones – Skeletal muscle cells are _______, cigar-shaped, and multinucleate – Also known as ________ muscle because of its obvious stripes – Also known as ________ muscle because it is the only muscle tissue subject to conscious control Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Muscle Types (3 of 6) Skeletal muscle cells are surrounded and bundled by connective tissue – ___________—encloses a single muscle fiber – __________—wraps around a fascicle (bundle) of muscle fibers – ____________—covers the entire skeletal muscle – ___________—on the outside of the epimysium Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Muscle Types (4 of 6) The epimysium of skeletal muscle blends into a connective tissue attachment – __________—cordlike structures ▪ Mostly collagen fibers ▪ Often cross a ______ because of their toughness and small size – Aponeuroses—sheetlike structures ▪ Attach muscles _________ to bones, cartilages, or connective tissue coverings Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Muscle Types (5 of 6) Smooth muscle – No striations – _____________—no conscious control – Found mainly in the walls of hollow ____________ (such as stomach, urinary bladder, respiratory passages) – Spindle-shaped fibers that are __________ – Contractions are _______ and sustained Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Muscle Types (6 of 6) Cardiac muscle – Striations – ___________ – Found only in the walls of the _________ – Uninucleate – Branching cells joined by _______________called intercalated discs – Contracts at a _________ rate set by pacemaker Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Muscle Functions Whereas all muscle types produce ___________, skeletal muscle has three other important roles: – Maintain _________ and body position – _______ joints – Generate _______ Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Microscopic Anatomy of Skeletal Muscle (1 of 6) ______________—specialized plasma membrane ___________—long organelles inside muscle cell – Light (I) bands and dark (A) bands give the muscle its striated (banded) appearance Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Microscopic Anatomy of Skeletal Muscle (2 of 6) Banding pattern of myofibrils – I band = light band ▪ Contains only thin filaments ▪ Z disc is a midline interruption – A band = dark band ▪ Contains the entire length of the thick filaments ▪ H zone is a lighter central area ▪ M line is in center of H zone Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Figure 6.3b Anatomy of a Skeletal Muscle Fiber (Cell) Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Microscopic Anatomy of Skeletal Muscle (3 of 6) Sarcomere—contractile unit of a muscle fiber – Structural and functional unit of skeletal muscle Organization of the sarcomere – Myofilaments produce banding (striped) pattern ▪ Thick filaments = myosin filaments ▪ Thin filaments = actin filaments Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Microscopic Anatomy of Skeletal Muscle (4 of 6) Thick filaments = myosin filaments – Composed of the protein myosin – Contain ATPase enzymes to split ATP to release energy for muscle contractions – Possess projections known as myosin heads – Myosin heads are known as cross bridges when they link thick and thin filaments during contraction Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Microscopic Anatomy of Skeletal Muscle (5 of 6) Thin filaments = actin filaments – Composed of the contractile protein actin – Actin is anchored to the Z disc At rest, within the A band there is a zone that lacks actin filaments called the H zone During contraction, H zones disappear as actin and myosin filaments overlap Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Figure 6.3c Anatomy of a Skeletal Muscle Fiber (Cell) Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Microscopic Anatomy of Skeletal Muscle (6 of 6) Sarcoplasmic reticulum (SR) – Specialized smooth endoplasmic reticulum – Surrounds the myofibril – Stores and releases calcium Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Stimulation and Contraction of Single Skeletal Muscle Cells Special functional properties of skeletal muscles – ____________ (also called responsiveness)—ability to receive and respond to a stimulus – _________—ability to forcibly shorten when an adequate stimulus is received – __________—ability of muscle cells to be stretched – __________—ability to recoil and resume resting length after stretching Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved The Nerve Stimulus and Action Potential (1 of 7) Skeletal muscles must be stimulated by a _________ neuron (nerve cell) to contract ____________—one motor neuron and all the skeletal muscle cells stimulated by that neuron Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved The Nerve Stimulus and Action Potential (2 of 7) ________________ junction – Association site of axon terminal of the motor neuron and sarcolemma of a muscle ________________ – Chemical released by nerve upon arrival of nerve impulse in the axon terminal – ___________ (ACh) is the neurotransmitter that stimulates skeletal muscle Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved The Nerve Stimulus and Action Potential (3 of 7) ___________ cleft – ______ between nerve and muscle filled with interstitial fluid – Although very close, the nerve and muscle do not _______________ Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved The Nerve Stimulus and Action Potential (4 of 7) When a nerve impulse reaches the axon terminal of the motor neuron, – Step 1: Calcium ________ open, and calcium _____ enter the axon terminal – Step 2: Calcium ion entry causes some synaptic vesicles to release _____________ (ACh) – Step 3: ACh diffuses across the synaptic cleft and attaches to __________ on the sarcolemma of the muscle cell Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved The Nerve Stimulus and Action Potential (5 of 7) – Step 4: If enough ACh is released, the sarcolemma becomes temporarily more __________ to sodium ions (Na+) ▪ Potassium ions (K+) ______________________ ▪ More sodium ions enter than potassium ions leave ▪ Establishes an _________ in which interior has more positive ions (depolarization), thereby opening more Na+ channels Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved The Nerve Stimulus and Action Potential (6 of 7) – Step 5: _______________ opens more sodium channels that allow sodium ions to enter the cell ▪ An _________________is created ▪ Once begun, the action potential is ____________ ▪ Conducts the electrical ________ from one end of the cell to the other – Step 6: _________________ (AChE) breaks down acetylcholine into acetic acid and choline ▪ AChE ______ muscle contraction ▪ A single nerve impulse produces only ______ contraction Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved The Nerve Stimulus and Action Potential (7 of 7) Cell returns to its resting state when: 1. Potassium ions (K+) ___________of the cell 2. Sodium-potassium pump moves sodium and potassium ions back to their _________________ Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Mechanism of Muscle Contraction: The Sliding Filament Theory What causes filaments to slide? – Calcium ions (Ca2+) bind regulatory proteins on thin filaments and expose myosin-binding sites, allowing the myosin heads on the thick filaments to attach – Each cross bridge pivots, causing the thin filaments to slide toward the center of the sarcomere – Contraction occurs, and the cell shortens – During a contraction, a cross bridge attaches and detaches several times – ATP provides the energy for the sliding process, which continues as long as calcium ions are present Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Contraction of a Skeletal Muscle as a Whole (1 of 7) Graded responses – Muscle fiber contraction is “_________,” meaning it will contract to its fullest when stimulated adequately – Within a whole skeletal muscle, not all fibers may be stimulated during the same interval – Different ___________ of muscle fiber contractions may give differing _________ – Graded responses—different degrees of skeletal muscle ________ Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Contraction of a Skeletal Muscle as a Whole (2 of 7) Graded responses can be produced in two ways – By changing the __________ of muscle stimulation – By changing the _______ of muscle cells being stimulated at one time Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Contraction of a Skeletal Muscle as a Whole (3 of 7) Muscle response to increasingly rapid stimulation – Muscle ________ ▪ Single, brief, _______ contraction ▪ Not a _______ muscle function Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Contraction of a Skeletal Muscle as a Whole (4 of 7) Muscle response to increasingly _______ stimulation – In most types of muscle activity, nerve impulses are delivered at a _______ rate – As a result, contractions are “summed” (_________) together, and one contraction is immediately followed by another Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Contraction of a Skeletal Muscle as a Whole (5 of 7) Muscle response to increasingly rapid stimulation – When stimulations become more ______, muscle contractions get _______ and smoother – The muscle now exhibits unfused (________) tetanus Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Contraction of a Skeletal Muscle as a Whole (6 of 7) Muscle response to increasingly rapid stimulation – Fused (complete) tetanus is achieved when the muscle is stimulated so rapidly that no evidence of relaxation is seen – Contractions are smooth and sustained Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Contraction of a Skeletal Muscle as a Whole (7 of 7) Muscle response to stronger stimuli – Muscle force depends upon the number of fibers stimulated – Contraction of more fibers results in greater muscle tension – When all motor units are active and stimulated, the muscle contraction is as strong as it can get Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Providing Energy for Muscle Contraction (1 of 5) ATP – Only energy source that can be used to directly power muscle contraction – Stored in muscle fibers in small amounts that are quickly used up – After this initial time, other pathways must be utilized to produce ATP Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Providing Energy for Muscle Contraction (2 of 5) Three pathways to regenerate ATP 1. Direct phosphorylation of ADP by creatine phosphate 2. Aerobic pathway 3. Anaerobic glycolysis and lactic acid formation Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Providing Energy for Muscle Contraction (3 of 5) Direct phosphorylation of ADP by creatine phosphate (CP)—fastest – Muscle cells store CP, a high-energy molecule – After ATP is depleted, ADP remains – CP transfers a phosphate group to ADP to regenerate ATP – CP supplies are exhausted in less than 15 seconds – 1 ATP is produced per CP molecule Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Providing Energy for Muscle Contraction (4 of 5) Aerobic respiration – Supplies ATP at rest and during light/moderate exercise – A series of metabolic pathways, called oxidative phosphorylation, use oxygen and occur in the mitochondria – Glucose is broken down to carbon dioxide and water, releasing energy (about 32 ATP) – This is a slower reaction that requires continuous delivery of oxygen and nutrients Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Providing Energy for Muscle Contraction (5 of 5) Anaerobic glycolysis and lactic acid formation – Reaction that breaks down glucose without oxygen – Glucose is broken down to pyruvic acid to produce about 2 ATP – Pyruvic acid is converted to lactic acid, which causes muscle soreness – This reaction is not as efficient, but it is fast – Huge amounts of glucose are needed Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Muscle Fatigue and Oxygen Deficit If muscle activity is strenuous and prolonged, muscle fatigue occurs Suspected factors that contribute to muscle fatigue include: – Ion imbalances (Ca2+, K+) – Oxygen deficit and lactic acid accumulation – Decrease in energy (ATP) supply After exercise, the oxygen deficit is repaid by rapid, deep breathing Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Types of Muscle Contractions Isotonic contractions – Myofilaments are able to slide past each other during contractions – The muscle shortens, and movement occurs – Example: bending the knee; lifting weights, smiling Isometric contractions – Muscle filaments are trying to slide, but the muscle is pitted against an immovable object – Tension increases, but muscles do not shorten – Example: pushing your palms together in front of you Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Muscle Tone Muscle tone – State of continuous partial contractions – Result of different motor units being stimulated in a systematic way – Muscle remains firm, healthy, and constantly ready for action Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved Effect of Exercise on Muscles Exercise increases muscle size, strength, and endurance – Aerobic (endurance) exercise (biking, jogging) results in stronger, more flexible muscles with greater resistance to fatigue ▪ Makes body metabolism more efficient ▪ Improves digestion, coordination – Resistance (isometric) exercise (weight lifting) increases muscle size and strength ▪ Individual muscle fibers enlarge Copyright © 2018, 2015, 2012 Pearson Education, Inc. All Rights Reserved