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

Muscles of the human body 12.1 Overview of the Muscular System Muscles of the human body Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Orbicularis oculi: blinking, winking, responsible for crow’s feet Masseter: a chewing muscle; clenches teeth Trapezius: Raises scapula, as When shrugging shoulders; pulls head backward Orbicularisor is: “kissing” muscle Deltoid: brings arm away from the side of body; moves arm up and down in front Latissimus dorsi: brings arm down and backward behind the body Pectoralis major: brings arm forward and across chest Serratus anterior: pulls the scapula (shoulder blade) forward, as in pushing or punching Biceps brachii: bends forearm at elbow Triceps brachii: straightens forearm at elbow Rectus abdominis: Bends vertebral column; compresses abdomen Extensor carpi group: straightens wrist and hand External oblique: compresses abdomen; rotation of trunk Flexor carpi group: bends wrist and hand Extensor digitorum: straightens fingers and wrist Adductor longus: moves thigh toward midline; raises Gluteus maximus: extends thigh back Quadriceps femoris: straightens leg at knee; raises thigh 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 Biceps femoris: bends leg at knee; extends thigh back Tibialis anterior: turns foot upward, as when walking on heels Gastrocnemius: turns foot downward, as when standing on toes; bends leg at knee 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 a. b. Figure 12.5 The major skeletal muscles of the human body.

Muscle fibers/cells Terminology for cell structure 12.2 Skeletal Muscle Fiber Contraction 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.

Muscle fibers/cells Terminology for structure within a whole muscle 12.2 Skeletal Muscle Fiber Contraction Muscle fibers/cells 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. 4

Visualizing muscle structure 12.2 Skeletal Muscle Fiber Contraction Visualizing muscle structure Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. A muscle contains bundles of muscle fibers, and a muscle fiber has many myofibrils. bundle of muscle cells (fibers) myofibril sarcolemma mitochondrion one myofibril sarcoplasm skeletal muscle cell (fiber) myofilament Z line one sarcomere Z line T tubule sarcoplasmic reticulum nucleus A myofibril has many sarcomeres. 6,000× (myofi bril): © Biology Media/Photo Researchers, Inc. Figure 12.6 The structure of a skeletal muscle fiber.

The sarcomere Made of 2 protein myofilaments 12.2 Skeletal Muscle Fiber Contraction 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.

Sarcomeres are relaxed. Sarcomeres are contracted. 12.2 Skeletal Muscle Fiber Contraction The sarcomere Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. cross- bridge myosin actin H band Sarcomeres are relaxed. Z line A band I band Sarcomeres are contracted. Figure 12.6 The structure of a skeletal muscle fiber. 7

The beginning of muscle contraction: The sliding filament model 12.2 Skeletal Muscle Fiber Contraction The beginning of muscle contraction: The sliding filament model Nerve impulses travel down a motor neuron to a _____________________. _______________ (ACh) is released from the neuron and binds to the muscle fiber. This binding stimulates the fiber causing ____________ to be released from the sarcoplasmic reticulum.

The beginning of muscle contraction 12.2 Skeletal Muscle Fiber Contraction The beginning of muscle contraction Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. skeletal muscle fiber axon branch axon terminal (photo):© Victor B. Eichler synaptic vesicle a. One motor axon goes to Several muscle fibers. synaptic cleft acetylcholine (ACh) axon terminal synaptic vesicle synaptic cleft folded sarcolemma sarcolemma Ach receptor 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. Figure 12.7 Motor neurons and skeletal muscle fibers join neuromuscular junctions.

Muscle contraction continued… 12.2 Skeletal Muscle Fiber Contraction Muscle contraction continued… Released calcium combines with ___________, a molecule associated with actin. This causes the ______________ threads around actin to shift and expose myosin binding sites. _______ heads bind to these sites forming cross-bridges. ______ binds to the myosin heads and is used for energy to pull the actin filaments towards the center of the sarcomere – contraction now occurs.

Visualizing the roles of calcium and myosin in muscle contraction 12.2 Skeletal Muscle Fiber Contraction Visualizing the roles of calcium and myosin in muscle contraction Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. actin filament troponin myosin-binding sites Ca2+ Ca2+ tropomyosin Troponin—Ca+ complex pulls tropomyosin away, exposing myosin-binding sites. Function of Ca2+ actin filament P ADP myosin filament cross-bridge myosin head 1.ATP is split when myosin head is unattached. ATP 2. ADP+ P are bound to myosin asmyos in head attaches to actin. 4.Binding of fresh ATP causes myosin Head to return to resting position. myosin heads actin 3.Upon ADP + P releases, power stroke occurs: head bends and pulls actin. b. Function of myosin Figure 12.8 The role of calcium ions and ATP during muscular contraction.