Muscles & Movement II: Muscle Structure & Contraction

Muscles & Movement II: Muscle Structure & Contraction

Muscles II: Microscopic Anatomy and Contraction October 31 Nov 3 2014 Muscle Structure Muscle Fascicle (bundle of fibers) Muscle Fiber (single cell) Myofibril Sarcomere

(unit of contraction) Microscopic Anatomy of Skeletal Muscle Large, cylindrical, multinucleate cells Contain many mitochondria; nearly filled with myofibrils Some organelles have unique vocabulary: Sarcolemma: cell membrane Sarcoplasm: cytoplasm Sarcoplasmic

reticulum: modified ER, surrounds each myofibril; store Ca2+ Microscopic Anatomy of Skeletal Muscle Each myofibril can be divided into contractile units called sarcomeres.

Sarcomeres consist of overlapping protein filaments of actin and myosin. Regular arrangement of dark and light bands. Dark Microscopic Anatomy of Skeletal Muscle The M line is where the myosin

attaches Z discs (a membrane) mark the edge of each sarcomere; serve as attachment site for actin Microscopic Anatomy of Skeletal Muscle Use the picture to come up with a definition of the following: I band

A band H zone Microscopic Anatomy of Skeletal Muscle Use the picture to come up with a definition of the following: I band area without myosin fibers; aka light band

A band area with myosin fibers; aka dark band H zone area without actin fibers Turn & Talk First match the words actin cell myofibril group of cells

sarcomere fascicle cell membrane protein muscle fiber organelle sarcolemma contractile unit

Then, write a paragraph that uses all the words in both columns above and explains that structure of the muscle. Contraction Overview Globular heads of myosin filaments attach to actin filaments. Myosin pulls actin filaments : Sliding filament theory

Causes sarcomere to shorten, particularly the light bands Contraction Overview Globular heads of myosin filaments attach to actin filaments. Myosin pulls actin filaments : Sliding filament theory

Causes sarcomere to shorten, particularly the light bands light dark light dark

light light Contraction Overview Which shows contracted muscle fibers? How can you tell? Contraction Overview Relaxed muscle (large light bands)

Contracted muscle (small light bands) Contraction Overview What are these? Mitochondria See animation! Contraction Details 1. A motor neuron stimulates the muscle cell by releasing the neurotransmitter acetylcholine ACh into the synaptic cleft between the neuron and muscle cell.

Note: A motor unit is a single motor neuron and all the muscle fibers it activates Contraction Details 1. 2. A motor neuron stimulates the muscle cell by releasing the neurotransmitter acetylcholine ACh into the synaptic cleft between the neuron and muscle cell. ACh causes an electric current called an action potential to move through the muscle cell.

Contraction Details 1. 2. 3. A motor neuron stimulates the muscle cell by releasing the neurotransmitter acetylcholine ACh into the synaptic cleft between the neuron and muscle cell. ACh causes an electric current called an action potential to move through the muscle cell. The action potential causes the release of Ca 2+ from the sarcoplasmic reticulum.

Contraction Details 4. Ca2+ exposes myosin-binding sites on actin filaments. 5. Myosin heads (& ADP) attach to actin binding sites, forming cross-bridges. actin ADP + P myosin head myosin

Muscle relaxed. No Ca2+ present. Ca2+ present. Cross-bridge formed. Contraction Details 6. Myosin heads release ADP, move the actin filament in power stroke actin myosin

Power stroke, ADP + P released Contraction Details 6. Myosin heads release ADP, move the actin filament in power stroke 7. ATP binds to myosin head. The crosslink between actin and myosin breaks. 8.

ATP becomes ADP + P, readying the myosin head to reattach to actin. actin myosin Power stroke, ADP + P released ATP binds, cross-links break Contraction Details

If Ca2+ is still present, cycle will repeat, with myosin heads reattaching and contracting the muscle even more. Once the action potential is over, the Ca2+ is reabsorbed into the sarcoplasmic reticulum. Without Ca2+, myosin cannot attach to actin. Watch me!

Contraction Details NOTE: ATP is required to break cross-links, not to form them. Explains rigor mortis Why then do muscles need ATP? To reset head so it can contract further -contraction is a series of sliding motions. Turn & Talk Describe the role of each of the following in muscle

contraction Scholar with more siblings. ACh Ca2+ Scholar with less siblings ATP Action potential Exit Ticket 1. In comparing electron micrographs of a relaxed skeletal muscle fiber and a fully contracted muscle fiber, which would be seen only in the relaxed fiber? a) b)

c) d) e) Z discs Triads I bands A bands H zones Exit Ticket 2. Which word describes the unit of contraction of a muscle? a) b)

c) d) Myofibril Sarcomere A band H band Exit Ticket 3. Which of the following correctly lists the order of structure of the muscle from largest to smallest? a) b) c)

d) fascicle, myofibril, sarcomere, muscle fiber myofibril, fascicle, sarcomere, muscle fiber fascicle, muscle fiber, myofibril, sarcomere muscle fiber, fascicle, myofibril, sarcomere Exit Ticket 4. Which of these stores calcium ion? a) b) c) d) Sarcoplasmic reticulum

Sarcomere Sarcolemma mitochondria Exit Ticket 5. Which of these best describe the process of muscle contraction? a) b) c) d) The The The

The actin filaments shorten myosin filaments shorten light bands shorten dark bands shorten Exit Ticket 6. Which of these best describe the process of muscle contraction? a) Myosin heads attach to actin filaments that are exposed by the presence of ATP b) Myosin heads attach to actin filaments that are exposed by the presence of Ca2+

c) Actin heads attach to myosin filaments that are exposed by the presence of ATP d) Actin heads attach to myosin filaments that are exposed by the presence of Ca2+

Recently Viewed Presentations

  • Marketing Channels - Jackson

    Marketing Channels - Jackson

    Just Have a Look Why Channel Producer Consumer Advertisements, commissions, Bonuses, Channel Discounts etc. account for distribution channel costs, which is passed on to consumers. Channel Development Role of Marketing Channels Producers Lack Financial Resources and Expertise to deal with...
  • Chapter 3 Expressions - McMaster University

    Chapter 3 Expressions - McMaster University

    Title: Chapter 3 Expressions Author: qiao Last modified by: qiao Created Date: 6/4/2008 11:24:48 AM Document presentation format: On-screen Show Other titles
  • Modern Control Systems (MCS) - Dr. Imtiaz Hussain

    Modern Control Systems (MCS) - Dr. Imtiaz Hussain

    Modern Control Systems (MCS) Dr. Imtiaz Hussain. Assistant Professor. ... -transform of the output the response of the system due to the initial conditions with the input zero is of the form. ... (BIBO) stable if its response to any...
  • Za vsako bolezen raste roica. Po 7 letih

    Za vsako bolezen raste roica. Po 7 letih

    Za vsako bolezen raste rožica. CAMELIA SINENSIS Po 7 letih doseže čajevec ustrezno kakovost za obiranje Liste v času vegetacije trgajo vsakih 5-14 dni Več 9000 milijonov čajnih grmov Med S in J vzporednikom 45° zemljepisne širine Na nadmorski višini...
  • Introduction to Scripture

    Introduction to Scripture

    The flood, then, is a "type" signifying sacramental Baptism [1 Pt 3:21]. Typology depends upon the unity of all Sacred Scripture and upon the salvific intent of God from all eternity. The prophets are typological in their interpretation of historical...
  • Presentación de PowerPoint

    Presentación de PowerPoint

    CARP. Contrast: Two or more page elements display differently in color, size, shape, texture, orientation, position or movement to group or separate elements on the page Repetition: Repeated elements can include colors, shapes, textures, fonts, typography, graphics, spatial relationships and...
  • Real-world Models of Integrated Behavioral Health Care Within

    Real-world Models of Integrated Behavioral Health Care Within

    Mental health and other healthcare professionals share the. same sites, vision, and systems. ... MAP, Pharmacotherapy, APC services. Same day appointments . ... Under scarcity, our perception of reality tunnels, living out important information and negatively affecting our interactions and...
  • Chapter 1

    Chapter 1

    BUILDING RESOURCE CAPABILITIES AND ORGANIZING THE WORK EFFORT Screen graphics created by: Jana F. Kuzmicki, PhD, Mississippi University for Women