POWERPOINT LECTURE SLIDE PRESENTATION by LYNN CIALDELLA MBA
POWERPOINT® LECTURE SLIDE PRESENTATION by LYNN CIALDELLA, MBA, The University of Texas at Austin Additional Material by J. Padilla exclusively for Physiology 31 at ECC UNIT 2 12 PART A Muscles HUMAN PHYSIOLOGY AN INTEGRATED APPROACH DEE UNGLAUB SILVERTHORN Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings FOURTH EDITION
The Three Types of Muscle Cylindrical shaped, multinuclei, straited, voluntary, fibers of different speeds Branched, uni/binuclei, involuntary, striated, rhythmic contractions Spindled shaped, one nucleus, involuntary, non-straited, internal organs Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 12 -1 a
Muscles: Summary Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings
Skeletal Muscle § Usually attached to bones by tendons- sometimes attached directly to bone (pectoralis major) § Origin: closest to the trunk- usually does not move a joint when contracts. § Insertion: more distal- moves joint when contracts § Flexor: brings bones together- decreases angle at joint § Extensor: bones move away- increases angle at joint § Antagonistic muscle groups: flexor-extensor pairsantagonistic muscles are usually in opposite sides. Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings
Anatomy Summary: Skeletal Muscle Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 12 -3 a (1 of 2)
Anatomy Review: Muscle Fiber Structure Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings
Ultrastructure of Muscle Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 12 -3 b
Anatomy Summary: Skeletal Muscle Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 12 -3 a (2 of 2)
Ultrastructure of Muscle Myosin are motor proteins. 250 myosins join to form the thick filaments. The thin filament is made up of a string of actin with tropomyosin and tropnin attached. Titin and nebulin anchor and stabilize. Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 12 -3 e
Ultrastructure of Muscle Actin and myosin form crossbridges A band (c) Z disk Sarcomere Z disk Myofibril M line I band (d) H zone Titin Z disk Thick filaments M line Thin filaments (f) (e) Myosin tail Myosin heads Hinge region Titin Tropomyosin Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Myosin molecule Z disk M line Troponin Nebulin G-actin molecule Actin chain Figure 12 -3 c–f
Summary of Muscle Contraction Muscle tension: force created by muscle Load: weight that opposes contraction Contraction: creation of tension in muscle Relaxation: release of tension Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 12 -7
Neuromuscular Junction: Overview § Terminal boutons- insulate the site of the neuromuscular juction and secrete supportive growth factors § Synaptic cleft- space between the axon terminal and the sarcolemma § Acetylcholine- neurotransmitter released involves calcium and binds to nicotinic receptors § Motor end plate- folds on the sarcolemma of the muscle § On muscle cell surface § Nicotinic receptors Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings
Anatomy of the Neuromuscular Junction Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 11 -12 (1 of 3)
Anatomy of the Neuromuscular Junction Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 11 -12 (2 of 3)
Anatomy of the Neuromuscular Junction Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 11 -12 (3 of 3)
Mechanism of Signal Conduction § Axon terminal (of presynaptic cell) § Action potential signals acetylcholine release § Motor end plate – series of folds in the plasma membrane of the postsynaptic cell § Two acetylcholine bind § Opens cation channel § Na+ influx – K+ efflux § Membrane depolarized § Stimulates fiber contraction as a result in increased intracellular calcium concentration Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings
Events at the Neuromuscular Junction Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 11 -13 a
T-tubules and the Sarcoplasmic Reticulum Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 12 -4
Excitation-Contraction Coupling 1 Somatic motor neuron releases ACh at neuromuscular junction. (a) 1 Axon terminal of somatic motor neuron ACh Muscle fiber Motor end plate Sarcoplasmic reticulum T-tubule Ca 2+ DHP receptor Tropomyosin Z disk Troponin Actin M line Myosin head Myosin thick filament Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 12 -11 a, step 1
Excitation-Contraction Coupling 1 Somatic motor neuron releases ACh at neuromuscular junction. 2 (a) Net entry of Na+ through ACh receptor-channel initiates a muscle action potential. 1 Axon terminal of somatic motor neuron ACh Muscle fiber n tio 2 potential K+ Ac Action potential Na+ Motor end plate Sarcoplasmic reticulum T-tubule Ca 2+ DHP receptor Tropomyosin Z disk Troponin Actin M line Myosin head Myosin thick filament Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 12 -11 a, steps 1– 2
Excitation-Contraction Coupling 3 Action potential in t-tubule alters conformation of DHP receptor. 4 DHP receptor opens Ca 2+ release channels in sarcoplasmic reticulum and Ca 2+ enters cytoplasm. 5 Ca 2+ binds to troponin, allowing strong actinmyosin binding. (b) 4 3 Ca 2+ released 5 7 6 Myosin thick filament M line 6 Myosin heads execute power stroke. Distance actin moves 7 Actin filament slides toward center of sarcomere. PLAY Animation: Muscular System: The Neuromuscular Junction Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 12 -11 b
Changes in Sarcomere Length during Contraction PLAY Animation: Muscular System: Sliding Filament Theory Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 12 -8
Regulatory Role of Tropomyosin and Troponin In the relaxed state the myosin head is at 90 o but it is unbound to actin because the binding sites on actin are blocked. Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 12 -10 a
Regulatory Role of Tropomyosin and Troponin** (b) Initiation of contraction 1 Ca 2+ levels increase in cytosol. 2 Ca 2+ binds to troponin. 3 Troponin-Ca 2+ complex pulls tropomyosin away from G-actin binding site. 4 Power stroke 3 Tropomyosin shifts, exposing binding site on G-actin Pi ADP TN 4 Myosin binds to actin and completes power stroke. 5 2 5 Actin filament moves. G-actin moves 1 Cytosolic Ca 2+ Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 12 -10 b
The Molecular Basis of Contraction Tight binding in the rigor 1 state. The crossbridge is at a 45° angle relative to the filaments. 2 45 ° ATP binding site Myosin binding sites 1 2 3 ATP binds to its binding site on the myosin. Myosin then dissociates from actin. Myosin filament 4 ATP 1 2 3 4 G-actin molecule Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 12 -9, steps 1– 2
The Molecular Basis of Contraction The ATPase activity of myosin 3 hydrolyzes the ATP. ADP and Pi remain bound to myosin. The myosin head swings over 4 and binds weakly to a new actin molecule. The crossbridge is now at 90º relative to the filaments. ADP 90° Pi Pi 1 2 3 4 Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings 1 2 3 4 Figure 12 -9, steps 3– 4
The Molecular Basis of Contraction Release of Pi initiates the power 5 stroke. The myosin head rotates on its hinge, pushing the actin filament past it. At the end of the power stroke, 6 the myosin head releases ADP and resumes the tightly bound rigor state. ADP Pi 1 2 3 4 5 Actin filament moves toward M line. Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 12 -9, steps 5– 6
The Molecular Basis of Contraction Myosin filament 1 Tight binding in the rigor state. The crossbridge is at a 45° angle relative to the filaments. Myosin binding sites 1 2 6 3 4 1 5 At the end of the power stroke, the myosin head releases ADP and resumes the tightly bound rigor state. 2 3 4 ATP binds to its binding site on the myosin. Myosin then dissociates from actin. ATP 3 5 Release of Pi initiates the power stroke. The myosin head rotates on its hinge, pushing the actin filament past it. 90° 1 3 4 The ATPase activity of myosin hydrolyzes the ATP. ADP and Pi remain bound to myosin. ADP Pi Sliding filament 5 Actin filament moves toward M line. 2 Contractionrelaxation Pi 1 2 G-actin molecule ADP 1 45° ATP binding site 2 3 4 1 2 3 4 Pi 2 3 4 Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings 4 The myosin head swings over and binds weakly to a new actin molecule. The crossbridge is now at 90º relative to the filaments. Figure 12 -9
Muscle Fatigue: Multiple Causes § Extended submaximal exercise § Depletion of glycogen stores § Short-duration maximal exertion § Increased levels of inorganic phosphate § May slow Pi release from myosin § Decrease calcium release § Potassium is another factor in fatigue Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings
Length-Tension Relationships in Contracting Muscle The strength of the contraction is related to the length before the muscle contracts. Very short fibers do not produce much tension because there is a lot of overlap not allowing for much sliding and not many new crossbridges. At optimum lenght there is an optimum number of cross-bridges to there is optimum tension. At a longer length there is less overlap and less ability to produce optimal force Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 12 -16
Electrical and Mechanical Events in Muscle Contraction A twitch is a single contraction-relaxation cycle Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 12 -12
Summation of Contractions Stimuli is too far apart and allows the muscle to relax and lose tension If action potentials come in at a closer time they recruit more fibers and the additive effect results in increased muscle tension Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 12 -17 a
Summation of Contractions The more stimulus the more fibers recruited until there is a maximum tension but is there is alot of time between the stimulus the muscle relaxes resulting in an unfused tetanus Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 12 -17 c
Summation of Contractions Complete tetanus results when action potentials arrive close enough to not allow the muscle to relax. Maximum tension can only be sustained for a limited time because fatigue Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 12 -17 d
Motor Units: Fine motor movements have more innervations Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings
Mechanics of Body Movement § Isotonic contractions create force and move loadcreates force and moves a load. § Concentric action is a shortening action- contraction that flexes the joint while working against a load § Eccentric action is a lengthening action- contraction that extends the joint while resisting a load § Isometric contractions create force without moving a load- the muscle produces tension and contracts but does not move the joint. Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings
Isotonic and Isometric Contractions Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 12 -19
Muscle Contraction Duration of muscle contraction of the three types of muscle- in smooth muscle contraction and relaxation happen slower and can be sustained for a longer time. Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 12 -24
Smooth Muscle: Properties § Uses less energy- can maintain maximum tension while using only a small percentage of the total maximum cross bridge § Maintain force for long periods- allows organs to be tonically contracted and maintain tension for a long time (sphincter muscles) § Low oxygen consumption- allows for to maintain tension for a long time without fatiguing (bladder). Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings
Smooth Muscle § Smooth muscle is not studied as much as skeletal muscle because § It has more variety- impossible to come up with a single muscle function model- special types for vascular, gastrointestinal, urinary, respiratory, reproductive, and ocular § Anatomy makes functional studies difficult- fibers within cells and muscle layers within organs run indifferent directions. § It is controlled by hormones, paracrines, and neurotransmitters § It has variable electrical properties- contraction is not triggered only action potential § Multiple pathways influence contraction and relaxation- acts as an integrating center to interpret mutiple excitatory and inhibitory signals that may arrive at the same time Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings
Smooth Muscle Locations § IV. Smooth Muscle- A tissue formed by uninucleated spindle shaped cells found in six areas of the body: blood vessel walls, respiratory tract, digestive tubes, urinary organs, reproductive organs, and the eye. Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings
Smooth Muscle layer orientations Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings
Cellular details of smooth muscle Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings
Muscle Disorders § Muscle cramp: sustained painful contraction – hyperexcitability of the motor unit, countered with stretching § Overuse – excessive use that causes tearing in the muscle structures (fibers, sheaths, tendon connection) § Disuse- loss of muscle activity causes muscle atrophy because of loss of blood flow, can recover is disuse is less than a year § Acquired disorders – infectious diseases and toxin poisoning that lead to muscle weakness or paralysis § Inherited disorders § Duchenne’s muscular dystrophy – muscle degenrates from pelvis up, happens most often in women, people live to be 20 -30, die of respiratory failure § Dystrophin –links actin to proteins in cell membrane § Mc. Ardle’s disease – limited exercise tolerance § Glycogen to glucose-6 -phosphate – enzyme missing thus muscles do not have asthe energy source available. Copyright © 2007 Pearson Education, Inc. , publishing Benjamin Cummings
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