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Essential Question: What is the significance of muscle contraction?

Student Learning Objective: SWBAT describe the three types of muscle in humans and explain how muscles contract. Essential Question: What is the significance of muscle contraction?. Brain POP: Where is the smallest and largest muscle located.

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Essential Question: What is the significance of muscle contraction?

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  1. Student Learning Objective: SWBAT describe the three types of muscle in humans and explain how muscles contract. Essential Question: What is the significance of muscle contraction? Brain POP: Where is the smallest and largest muscle located. stapedius, 5.08 millimeters located in the middle ear

  2. muscular system • muscle fiber • skeletal muscle • tendon • smooth muscle • cardiac muscle • myofibril • sarcomere • actin • myosin • synaptic cleft • acetylcholine Vocabulary Terms: • motor unit • motor neuron • neuromuscular junction • acetylcholine • action potential • all-or-none law • axon • axon terminals • cross bridges • fast-twitch • slow-twitch • sarcolemma

  3. Humans have three types of muscle. • The muscular system moves substances throughout the body. • Motion • bones of the skeletal system • food through digestive system • blood through circulatory system • fluids through excretory system • Maintenance of posture • Heat production

  4. SMOOTH MUSCLE CARDIAC MUSCLE SKELETAL MUSCLE • skeletal muscle • There are three types of muscle tissue. • smooth muscle • cardiac muscle

  5. SMOOTH MUSCLE Smooth muscle around this artery allows the artery to regulate blood flow by shrinking and expanding. • Smooth muscle is involuntary. • muscle of the viscera (internal organs) eg. Lining/walls of blood vessels, intestine, other 'hollow' structures/organs in the body) • move food through digestive organs • empty liquid from the bladder • control width of blood vessels

  6. CARDIAC MUSCLE • Cardiac muscle is found only in the heart. • pumps blood throughout body • controlled by pacemaker • contains more mitochondria than skeletal muscle cells

  7. SKELETAL MUSCLE • Tendons connect muscle to bone. • Skeletal muscles are mostly voluntary • Striated muscle (repeating sarcomeres) • Contraction of a muscle fiber is an all-or-nothing event • Skeletal muscle attaches to the skeleton by tendons.

  8. myofibril Structure: Epimysium-connective tissue ensheaths entire muscle Perimysium- sheath of connective tissue that groups muscle fibers into bundles or fascicles Endomysium- connective tissue that ensheaths each individual muscle fiber

  9. muscle fiber muscle myofibril sarcomere Muscles contract when the nervous systems causes muscle filaments to move. • Muscle fibers are CELLS of the muscular system. • Each myofibril is divided into sarcomeres. • Myofibrils are long strands of protein in the muscle fiber • Sarcomeres contain filaments that cause contraction.

  10. Sarcomeres contain filaments that cause contraction. • Each myofibril is divided into sarcomeres. • Actin filaments are pulled during contraction. • Myosin filaments pull actin during contraction. Cell membrane organelle where Ca+ is stored

  11. Neuron Structure • How does contraction in skeletal muscles occur?

  12. neuromuscular junction neuron MUSCLE • How does contraction in skeletal muscles occur? • Motor neuron stimulates muscle at the neuromuscular junction. • Motor unit-single motor neuron and all the muscles that it stimulates (the functional unit) • One motor neuron may stimulate up to 2000 skeletal muscle fibers

  13. How does contraction in skeletal muscles occur? • Begins at the neuromuscular junction=axon terminal and muscle fiber meet • Synaptic cleft=gap between axon terminal and muscle fiber

  14. Resting Potential- when a neuron is at rest • Contains potential energy needed to transmit an impulse • Occurs because there are unequal concentrations of ions inside and • outside the neuron. • More channels for K+ than for Na+ , so positive charges leave the cell much faster than they enter : unequal diffusion of ions along a gradient • Sodium-potassium pump, uses energy to actively transport Na+ ions out of the cell and bring K+ ions into the cell. The neuron has a net negative charge compared with its surroundings because there are fewer positive ions inside the neuron.

  15. Action Potential Because more sodium enters than potassium exits, the net effect inside is a positive charge (Depolarization)

  16. Action Potential

  17. The Neuromuscular Junction When impulse reaches the axone terminal a neurotransmitter is released=acetylcholine makes sarcolemma temporarily permeable (chemical signal)

  18. The Neuromuscular Junction NA+ channels open and a net positive charge is created because Na+ Rushes in at a faster rate then K+ exits

  19. actin myosin Z line • Impulse travels along the Sarcoplasmic Reticulum (SR), the calcium gates in the membrane of the SR open. As a result, CALCIUM diffuses out of the SR and among the myofilaments • Calcium exposes binding sites. • Myosin binds to actin and pulls it. Calcium ions move into the sarcomere from storage sites by facilitated diffusion (spontaneous passage of molecules/ions across a biological membrane passing through a specific channel) due to its concentration gradients Ca+ • As the sarcomere shortens, the muscle contracts. Cross-bridges: head of myosin attach to actin

  20. Homework Read/Outline 29.1 and 29.2 FAQ’s pg 819 FAQ’s pg 823

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