A Slides 1 to 110 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Overview of Muscular System Types of Muscle Tissue Under voluntary control Skeletal muscles Attach to the skeleton The muscular system Under involuntary control Cardiac muscle Heart wall Smooth muscle Visceral organs Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Overview of Muscular System Skeletal muscles Perform four functions Produce movement of skeleton (“dynamic”) Maintain posture, balance & body position (“static”) Guard “entrances” (mouth) and “exits” (anus) oral sphincter & anal sphincter Maintain body temperature (ex: shivering) Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Anatomy of Skeletal Muscles Gross (can see with “naked eye”) Anatomy Connective tissue organization Epimysium Fibrous covering of whole muscle Perimysium Fibrous covering of fascicle Endomysium Fibrous covering of a single cell (a muscle fiber) Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Anatomy of Skeletal Muscles The Organization of a Skeletal Muscle Quiz on all of these! Figure 7-1

Skeletal muscles attach to bones… directly by way of tendons (thick dense regular connective tissue “ropes” indirectly by way of aponeuroses (thin connective tissue (sheets”)

Stop Here! Your first quiz will cover only the material on the first 5 slides that precede this one.

Anatomy of Skeletal Muscles Microanatomy of a Muscle Fiber Sarcolemma Muscle cell membrane Sarcoplasm Muscle cell cytoplasm Sarcoplasmic reticulum (SR) Like smooth ER Transverse tubules (T tubules) Myofibrils (contraction organelle) Sarcomeres Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Anatomy of Skeletal Muscles Sarcomere—Repeating structural unit of the myofibril Components of a sarcomere Myofilaments Thin filaments (mostly actin) Thick filaments (mostly myosin) Z lines at each end Anchor for thin filaments Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Anatomy of Skeletal Muscles The Organization of a Single Muscle Fiber Figure 7-2(a)

Anatomy of Skeletal Muscles The Organization of a Single Muscle Fiber Figure 7-2(b)

Anatomy of Skeletal Muscles The Organization of a Single Muscle Fiber PLAY Anatomy of Skeletal Muscles Figure 7-2(cde)

Anatomy of Skeletal Muscles Changes in the Appearance of a Sarcomere During Contraction of a Skeletal Muscle Fiber Figure 7-3 (1 of 2)

Anatomy of Skeletal Muscles Changes in the Appearance of a Sarcomere During Contraction of a Skeletal Muscle Fiber Figure 7-3 (2 of 2)

Control of Muscle Contraction Steps in Neuromuscular Transmission Motor neuron action potential Acetylcholine release and binding Action potential in sarcolemma T tubule action potential Calcium release from SR Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Control of Muscle Contraction The Neuromuscular Junction Synaptic terminal Acetylcholine release Synaptic cleft Motor end plate Acetylcholine receptors Acetylcholine binding Acetylcholinesterase Acetylcholine removal Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Control of Muscle Contraction The Structure and Function of the Neuromuscular Junction Figure 7-4(a)

Figure 7-4(b-c) 1 of 5 Action potential Axon Synaptic terminal Arrival of an action potential at the synaptic terminal Axon Arriving action potential Synaptic terminal Sarcolemma Vesicles ACh Synaptic cleft AChE molecules ACh receptor site Muscle fiber Sarcolemma of motor end plate ACh binding at the motor and plate Appearance of an action potential in the sarcolemma Release of acetylcholine Vesicles in the synaptic terminal fuse with the neuronal membrane and dump their contents into the synaptic cleft. The binding of ACh to the receptors increases the membrane permeability to sodium ions. Sodium ions then rush into the cell. An action potential spreads across the surface of the sarcolemma. While this occurs, AChE removes the ACh. Action potential Na+ Na+ Na+ Figure 7-4(b-c) 1 of 5 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Anatomy of Skeletal Muscles The Contraction Process Actin active sites and myosin cross-bridges interact Thin filaments slide past thick filaments Cross-bridges undergo a cycle of movement Attach, pivot, detach, return Troponin-tropomyosin control interaction Prevent interaction at rest Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Cross-bridge formation Resting sarcomere Active-site exposure Cross-bridge formation ADP Myosin head ADP + Sarcoplasm P + P Troponin ADP + P Ca2+ Ca2+ Ca2+ ADP Active site Ca2+ Tropomyosin Actin + ADP ADP P P + P + Myosin reactivation Cross bridge detachment Pivoting of myosin head ADP ATP ADP + P + P Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ ADP P + ATP ADP + P Figure 7-5 1 of 7 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Control of Muscle Contraction Summary of Contraction Process Table 7-1

Control of Muscle Contraction Key Note Skeletal muscle fibers shorten as thin filaments interact with thick filaments and sliding occurs. The trigger for contraction is the calcium ions released by the SR when the muscle fiber is stimulated by its motor neuron. Contraction is an active process; relaxation and the return to resting length is entirely passive. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings