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1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Human Biology Sylvia S. Mader Michael Windelspecht Chapter.

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Presentation on theme: "1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Human Biology Sylvia S. Mader Michael Windelspecht Chapter."— Presentation transcript:

1 1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Human Biology Sylvia S. Mader Michael Windelspecht Chapter 12 Muscular System Lecture Outline

2 2 Muscles of the human body Orbicularis oculi: blinking, winking, responsible for crow’s feet Orbicularisor is: “kissing” muscle Pectoralis major: brings arm forward and across chest Serratus anterior: pulls the scapula (shoulder blade) forward, as in pushing or punching External oblique: compresses abdomen; rotation of trunk Quadriceps femoris: straightens leg at knee; raises thigh Tibialis anterior: turns foot upward, as when walking on heels Extensor digitorum longus: raises toes; raises foot Limbs Arm: above the elbow Forearm: below the elbow Thigh: above the knee Leg: below the knee Achilles tendon Gastrocnemius: turns foot downward, as when standing on toes; bends leg at knee Biceps femoris: bends leg at knee; extends thigh back Gluteus maximus: extends thigh back Extensor digitorum: straightens fingers and wrist Extensor carpi group: straightens wrist and hand Triceps brachii: straightens forearm at elbow Latissimus dorsi: brings arm down and backward behind the body Trapezius: Raises scapula, as When shrugging shoulders; pulls head backward Masseter: a chewing muscle; clenches teeth Deltoid: brings arm away from the side of body; moves arm up and down in front Biceps brachii: bends forearm at elbow Rectus abdominis: Bends vertebral column; compresses abdomen Flexor carpi group: bends wrist and hand Adductor longus: moves thigh toward midline; raises Sartorius: raises and laterally rotates thigh; raises and rotates leg close to body; these combined actions occur when “crossing legs” or kicking across, as in soccer b.a. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 12.5 The major skeletal muscles of the human body Overview of the Muscular System

3 3 Muscle fibers/cells Terminology for cell structure –The plasma membrane is called the ___________. –The cytoplasm is called the _____________. –The SER of a muscle cell is called the ______________________ and stores calcium Skeletal Muscle Fiber Contraction

4 4 Terminology for structure within a whole muscle –Muscle fibers are arranged in ___________ called fascicles. –Myofibrils are bundles of myofilaments that run the length of a fiber. –_______________ are proteins (actin and myosin) that are arranged in repeating units. –______________ are the repeating units of actin and myosin found along a myofibril Skeletal Muscle Fiber Contraction Muscle fibers/cells

5 5 Visualizing muscle structure myofilament one myofibril sarcolemma mitochondrion sarcoplasm A myofibril has many sarcomeres. 6,000× A muscle contains bundles of muscle fibers, and a muscle fiber has many myofibrils. bundle of muscle cells (fibers) myofibril skeletal muscle cell (fiber) T tubule sarcoplasmic reticulum nucleus Z lineone sarcomereZ line (myofi bril): © Biology Media/Photo Researchers, Inc. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 12.6 The structure of a skeletal muscle fiber Skeletal Muscle Fiber Contraction

6 6 The sarcomere Made of 2 protein myofilaments –A thick filament is composed of several hundred molecules of the protein myosin. Each myosin molecule is shaped like a ____ ____ –Primarily, a thin filament consists of 2 intertwining strands of the protein actin. –These filaments _____ over one another during muscle contraction Skeletal Muscle Fiber Contraction

7 7 The sarcomere Figure 12.6 The structure of a skeletal muscle fiber Skeletal Muscle Fiber Contraction Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. I bandA bandZ line myosin cross- bridge Sarcomeres are relaxed. Sarcomeres are contracted. H band actin

8 8 The beginning of muscle contraction: The sliding filament model 1.Nerve impulses travel down a motor neuron to a _____________________. 2._______________ (ACh) is released from the neuron and binds to the muscle fiber. 3.This binding stimulates the fiber causing ____________ to be released from the sarcoplasmic reticulum Skeletal Muscle Fiber Contraction

9 9 The beginning of muscle contraction Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. skeletal muscle fiber axon branch axon terminal a. One motor axon goes to Several muscle fibers. axon terminal synaptic vesicle synaptic cleft sarcolemma b. Asynaptic cleft exists between an axon terminal and a muscle fiber. c.Neurotransmitter (ACh) diffuses across synaptic cleft and binds to receptors in sarcolemma. Ach receptor folded sarcolemma acetylcholine (ACh) synaptic cleft synaptic vesicle (photo):© Victor B. Eichler Figure 12.7 Motor neurons and skeletal muscle fibers join neuromuscular junctions Skeletal Muscle Fiber Contraction

10 10 Muscle contraction continued… 4.Released calcium combines with ___________, a molecule associated with actin. 5.This causes the ______________ threads around actin to shift and expose myosin binding sites. 6._______ heads bind to these sites forming cross- bridges. 7.______ binds to the myosin heads and is used for energy to pull the actin filaments towards the center of the sarcomere – contraction now occurs Skeletal Muscle Fiber Contraction

11 11 Visualizing the roles of calcium and myosin in muscle contraction myosin head 4.Binding of fresh ATP causes myosin Head to return to resting position. myosin heads actin b. Function of myosin myosin filament actin filament cross-bridge 3.Upon ADP + P releases, power stroke occurs: head bends and pulls actin. ADP ATP P 1.ATP is split when myosin head is unattached. 2. ADP+ P are bound to myosin asmyos in head attaches to actin. actin filament troponin myosin-binding sites tropomyosin Function of Ca 2+ Troponin—Ca+ complex pulls tropomyosin away, exposing myosin-binding sites. Ca 2+ Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 12.8 The role of calcium ions and ATP during muscular contraction Skeletal Muscle Fiber Contraction


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