1 / 41

The Muscular System

This chapter explores the characteristics and functions of skeletal muscles, including their origin, microscopic anatomy, and contractions. Learn about the major muscles in the human body and the four functional groups of muscles. Understand how muscles produce movement, maintain posture, stabilize joints, and generate heat. Discover the interactions and roles of agonists, antagonists, synergists, and fixators in muscle activity. Dive into the detailed structure of skeletal muscles, including connective wrappings and microscopic anatomy. This comprehensive guide provides valuable insights into the intricate workings of the muscular system.

fouche
Download Presentation

The Muscular System

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. The Muscular System Textbook Reference: chapter 6

  2. Unit ___ Goals Describe the characteristics and function of skeletal muscle Differentiate between a muscle’s origin and its insertion Identify the microscopic anatomy of skeletal muscle Differentiate between different muscular contractions Define the 4 functional groups of muscles Describe how a muscle is stimulated to contract and the mechanism of muscle shortening Identify the major muscles of the human body

  3. Muscles: the machines of the body • Skeletal Muscle Characteristics • Voluntary: move due to a conscious decision • Striated: striped in appearance • Multinucleate: Cells long; more nuclei • More mitochondria for energy production • 500+ muscles, 40-50% body weight

  4. Skeletal Muscle Extras • Soft and fragile yet TOUGH • Exerts TREMENDOUS power • Power provided by bundles of muscle fibers wrapped in connective tissue • Connective tissue coverings allows for transmission of blood and nerves to muscles & provides support

  5. Functional Characteristics of Skeletal Muscle • Produces movement: for locomotion, manipulation and responding to the external environment; also for expressing emotions • Maintaining posture: works continuously to fight downward pressure of gravity

  6. Functional Characteristics of Skeletal Muscle • Stabilizing joints: muscle tendons stabilize and reinforce joints that have poor articulating surfaces • Generating heat: heat is a by-product of muscular activity; maintains normal body temperature

  7. Skeletal Muscle Interactions • Muscles are arranged in the body to either work together or work in opposition of each other • Number 1 Rule of Muscle Activity: • MUSCLES ONLY PULL*** THEY NEVER PUSH! • In other words, muscle contractions are caused by SHORTENING of fibers

  8. Insertion: the movable attachment of a muscle Examples: biceps tendon attachment to radial tuberosity Origin: the fixed, immovable point of attachment Examples: biceps tendon attachment to greater tubercle Skeletal Muscle Interactions A muscle contraction involves a muscle’s insertion moving toward its origin

  9. Origins and Insertions

  10. 4 Functional Groups of Skeletal Muscles • 1.) Agonists (prime movers): a muscle that provides the major force for providing a specific movement • Example: biceps brachii- prime mover of elbow flexion

  11. 4 Functional Groups of Skeletal Muscles • 2.) Antagonists: muscles that oppose/reverse a movement; relaxed when the agonist is active; helps regulate action of agonist by providing resistance • Can also be agonists • Example: the triceps brachii is the antagonist to the biceps during elbow flexion

  12. 4 Functional Groups of Skeletal Muscles • 3.) Synergists: “work together”; aids agonist by promoting the same movement or reducing unnecessary movements that might occur as the agonist contracts • Example: biceps brachii and brachioradialis in elbow flexion

  13. 4 Functional Groups of Skeletal Muscles • 4.) Fixators: a synergist that immobilizes a bone or a muscle’s origin • Example: erector spinae (muscles for posture) • All types of muscles work together to provide smooth, coordinated and precise movements. • Any one muscle can be in any functional group, dependant on its action

  14. Detailed Skeletal Muscle • Deep fascia: sheet/band of dense connective tissue covering muscles • Epimysium: connective tissue covering many fascicles, all bound together

  15. Connective Wrappings of Skeletal Muscle

  16. Fascicle: a bundle of fibers wrapped in perimysium Perimysium: connective tissue surrounding a bundle of muscle fibers Endomysium: connective tissue surrounding each muscle fiber Aponeuroses: sheetlike epimysia that connects muscle to each other and to cartilage/bone Detailed Skeletal Muscle

  17. Detailed Skeletal Muscle • Tendon: cordlike band of epimysia connecting muscles to bones • Durable and able to cross bony projections • Small in diameter to fit in crowded joint spaces

  18. Microscopic Anatomy of Skeletal Muscle • Muscle cell = muscle fiber • Sarcoplasm: cytoplasm of muscle fiber • Sarcolema: plasma membrane of muscle fiber • Sarcoplasmic reticulum: site of calcium storage used for contraction

  19. Microscopic Anatomy

  20. Microscopic Anatomy of Skeletal Muscle • Sarcomere: contractile units of myofibrils, aligned end-to-end • Myofibril: contractile proteins of muscle cells; lie parallel along length of fiber • Thin myofilaments: actin, tropomyosin and troponin • Thick myofilaments: myosin

  21. Microscopic Anatomy of Skeletal Muscle • Z line: separates sarcomeres; where actin filaments attach • I band:light bands; where the actin filaments are aligned; extends to tips of myosin filaments • A band: where the myosin filaments are aligned • H Zone: less dense portion of A band where thin filaments don’t overlap thick filaments

  22. Sarcomere

  23. Nervous Stimulation of a Muscle Cell • Skeletal muscle cells possess unique abilities: • Excitability: can receive & respond to a stimulus • Contractility: they can shorten • Extensibility: lengthen or stretch • Elasticity: cells return to resting form after contracted or stretched • When a skeletal muscle contracts, it is told to do so by the nervous system

  24. Nervous Stimulation of a Muscle Cell • Motor Neuron: nerve extending from spinal cord to muscle fiber • Motor Unit: one motor neuron and all the skeletal muscle cells it stimulates • Neuromuscular Junction: where the end of the nerve and the beginning of the muscle fiber meets • Synaptic cleft: space between nerve and muscle fiber • Motor end plate: highly folded sarcolema; lines synaptic cleft

  25. Motor Unit

  26. Nervous Stimulation of a Muscle Cell • Neurotransmitter: a chemical that carries a signal from the nerve to the muscle; continues the nervous stimulation • Synaptic Vesicles: sacs at motor end plate that holds ACh • Acetylcholine (ACh): the neurotransmitter specific to muscles • Action Potential: an electrical current that can cause a muscular contraction

  27. Nervous Stimulation of a Muscle Cell • The nervous system sends a neural signal to the motor unit. This causes a release of ACh into the neuromuscular junction, where it binds to receptors on the muscle cell. This causes an action potential to run throughout the muscle cell, initiating a muscle contraction.

  28. Synaptic Cleft

  29. Graded Responses of Skeletal Muscle Contraction • A graded response: the degree of muscle shortening dependant on • 1. The speed of muscle stimulation • 2. The number of muscle cells stimulated

  30. Speed of Stimulation • Muscle Twitch: a single, brief contraction caused by a mistake of the nervous system • Summing of Contractions: when nervous impulses are delivered to a muscle at a rapid rate so it can’t relax between impulses; the contractions are summed(added) to create a smooth, strong contraction • Tetanus: no relaxation between contractions; smooth and sustained

  31. Number of Cells Stimulated • Small, weak contractions: few cells initiated • Large, strong contractions: all motor units are active and all muscle cells stimulated

  32. Types of Skeletal Muscle Contractions • Isotonic: same tone or tension • Myofilaments slide, muscle shortens & movement occurs

  33. Types of Skeletal Muscle Contractions • Isometric: same length • Muscles DO NOT shorten • Myosin myofilaments do not move, tension in the fibers build • Muscle tries to move but cannot

  34. Energy for Muscle Contractions • There are 3 different energy systems in the body that provide for muscle contractions • Definitions: • Creatine Phosphate (CP): high energy molecule only in muscles which help replenish energy stores • Adenosine Triphoshate (ATP): energy source in the body • Glucose: blood sugar • Glycogen: storage form of blood sugar

  35. Energy for Muscle Contractions • Lactic Acid: a byproduct of an anaerobic pathway; causes muscle burning • Aerobic: using oxygen during activity • Anaerobic: not using oxygen during activity

  36. Energy Systems • There are 3 ways energy is utilized for muscular activity: • 1. ATP-PC/Rapid Recovery • Anaerobic, lasting no more than 20 seconds • ATP production rate is rapid • ATP stores broken down rapidly and resupplied by creatine phosphate (transfers a phosphate to ADP) • More creatine stored in muscles than ATP

  37. Energy Systems • 2. Lactic Acid/Anaerobic • Breaks down glucose for energy without using oxygen • Muscles are working too fast for oxygen & glucose to be delivered by aerobic respiration • Results in build up of lactic acid in muscles: promotes muscle fatigue and soreness

  38. Lactic Acid/Anaerobic Continued • Muscle fatigue: when a muscle is unable to contract even though it is still being stimulated. • Oxygen Debt: occurs during prolonged muscle activity; can’t get oxygen fast enough for the muscle’s needs; lactic acid builds up leading to fatigue; repaid by breathing deeply until the muscles receive enough oxygen to get rid of lactic acid and make more ATP and creatine phosphate

  39. Energy Systems • 3. Aerobic Respiration • During light exercise, ATP stores are regenerated by using oxygen • Can last for hours if glucose supplies are present • Used in endurance activities

  40. Types of Skeletal Muscle Fibers • There are 2 different kinds: • 1. Slow twitch • For endurance • Speed of contraction is slow • Uses aerobic respiration • Low glycogen stores-more fats used • Slow rate of fatigue

  41. Types of skeletal muscle fibers • 2. Fast twitch • Explosive movements for short distances • Speed of contraction very fast • Some aerobic, some anaerobic fibers • High glycogen stores but fatigues quickly The distribution of muscle fibers is not complete until the teenage years. It varies between muscles, within muscles and between people.

More Related