IB Muscle Basics Post-Lecture Notes PDF

© Muscle Basics Dr. Sean McWatt, PhD [email protected] Learning Outcomes By the end of this lesson, you will be able to… Identify the different types of muscles in the body and describe the basic properties of muscle tissue Name the components of skeletal muscle and describe th...

© Muscle Basics Dr. Sean McWatt, PhD [email protected] Learning Outcomes By the end of this lesson, you will be able to… Identify the different types of muscles in the body and describe the basic properties of muscle tissue Name the components of skeletal muscle and describe the basic function of the sarcomere Explain the general mechanism for how muscles receive signals from the brain and describe the characteristics of a motor unit Explain how agonist, synergist, and antagonist muscles work with and against each other to produce different types of contractions and movements Discuss the clinical implications of exercise, aging, and injury on skeletal muscles Basic Muscle Structure Musculoskeletal System Muscular System Skeletal System Muscles Bones Tendons/aponeuroses Cartilage Motor unit Ligaments Functions Functions Skeletal movement Support Maintaining posture and position Protection Opening and closing of orifices Force translation Maintaining homeostasis Blood cell production Mineral storage Anterior views http://tiny.cc/ukmzaz https://www.pinterest.ca/pin/231231762096235747/ Types of Muscle This course will primarily focus Myocytes Specialized based on type on skeletal muscle, with some cardiac muscle in Unit 5 Skeletal muscle Cardiac muscle Smooth muscle Striated muscles with Found in the heart Found in viscera, blood myosin and actin Striated muscle vessels, skin Under voluntary control Involuntary control Not striated Under involuntary control Basic Muscle Properties Electrical excitability Motor units Electrical signals (e.g., heart) innervating Chemical signals (e.g., neuromuscular cleft) skeletal muscle Contractility Contraction (shortening) produces force Skeletal Skeletal muscles attached to bone via tendons, so contraction muscle (shortening) produces movement Extensibility Can stretch/lengthen (to an extent) without damage Elasticity Returns to its original length after contraction (shortening) or extension (lengthening) Greatest elasticity in smooth muscle Smooth While they have many common basic properties, muscle of the different types of muscles are specialized digestive tract based on their role in bodily function Drake, Gray’s Anatomy for Students, 2nd Ed., Copyright © 2009 by Churchill Livingstone Skeletal Muscle Tendon Anchors muscle The blood vessels that to bone supply a muscle and the Myofibril Repeating units nerves that innervate it Fascicle of sarcomeres Bundle of are found in the fascia muscle fibers Endomysium (connective tissue) that Endo- means ‘within’ surrounds it Epimysium Epi- means ‘upon’ Recent research has shown Perimysium Peri- means ‘around’ that fascia also helps with force production by limiting the expansion of the muscle it Actin Myosin Muscle fiber Thin filament Thick filament surrounds during contraction, Muscle cell Bundle of myofibrils thereby increasing the force Sarcomere transferred into the bones Sarcomeres Concentric Shortening Actin Thin filament Myosin Thick filament Eccentric Lengthening When we want to create force, we are actively trying to bring our actin and myosin together. If we are successful, the muscle shortens in a concentric contraction. If the muscle instead lengthens due to other forces, we get an eccentric contraction, wherein the actin and myosin move apart Basic Muscle Function Motor Neurons Innervating Neuron #1 = Motor unit #1 different fibers Contralateral control Neuron #2 of same muscle = Motor unit #2 Left side of brain controls right side of body and vice versa Upper motor neuron Motor unit A motor neuron and the muscle fibers it innervates Lower motor A single motor unit is one neuron and all of neuron the muscle fibers it innervates; however, several motor units are required to innervate an entire muscle Agur and Dalley, Grant’s Atlas of Anatomy, 13th Ed. Copyright © 2013 by Lippincott Williams and Wilkins Skeletal Muscle Muscles can only PULL, Origin(s): they can’t push! Immobile attachment (usually proximal) Insertion(s): Mobile attachment (usually distal) “Attachments” Muscles and joints are levers! A muscle can only cause motion at the joint(s) that it crosses! Biceps brachii m. The farther away from a joint that a muscle attaches, the greater its mechanical advantage and the more force it can produce at that joint! Anterior view (right) e.g., having a door handle near the hinge vs. far away from the hinge Gilroy, Anatomy: An Essential Textbook, Copyright © 2013 by Thieme Skeletal Muscle Contraction Muscles can produce force while shortening, lengthening, or Phasic contractions not moving at all; however, they are always trying to shorten Isometric contraction Isotonic contractions Muscle contracts but does not shorten Concentric contraction Eccentric contraction No movement Muscle shortens during contraction Muscle lengthens during contraction Actin Myosin Thin filament Thick filament Moore, Agur, and Dalley, Essential Clinical Anatomy, 5th Ed. Copyright © 2015 by Lippincott Williams and Wilkins Agonists vs. Antagonists Muscles do not work in perfect isolation! Agonist Primary driver of movement (concentric) Triceps brachii m. Biceps brachii m. Antagonist Antagonist (eccentric) Synergist (concentric) Controls, slows, or resists the antagonist (eccentric) Synergist Brachialis m. Additional muscles that assist the agonist (concentric) Agonist (concentric) The relationship flips during extension – the triceps brachii m. becomes the agonist by performing a concentric Flexion contraction and creating movement, while the biceps brachii and brachialis mm. act as antagonists by performing eccentric contractions to control, slow, or resist the motion Sagittal view (right) Agur and Dalley, Grant’s Atlas of Anatomy, 13th Ed. Copyright © 2013 by Lippincott Williams and Wilkins Aging, Exercise, and Injury Aging Muscle Atrophy Age 23 Age 70 Progressive muscle loss from approximately age 30 onward Muscle mass replaced by fibrous connective tissue and adipose (fat) Caused by loss of motor neurons, slower conduction speeds, and loss of muscle fibers What other Overall, less power lifestyle and and strength contextual factors can contribute to muscle atrophy (in aging or otherwise)?  Exercise In addition to Benefits at every age! cardiovascular, Increases pulmonary, and neural muscle mass benefits, exercise can also Hypertrophy make the musculoskeletal system more effective and resilient to injury It’s whole-body medicine! Increases Increases neuron firing rate bone density Agur and Dalley, Grant’s Atlas of Anatomy, 13th Ed. Copyright © 2013 by Lippincott Williams and Wilkins https://www.muscletesting.com/blog/ Muscle Strains Muscles and tendons strain, Doesn’t always whereas ligaments sprain require surgery! Strains Grade 1: Stretching or slight tearing Grade 2: Incomplete tear Grade 3: Complete tear Protection Rest Ice Compression Grade 1 Grade 2 Grade 3 Elevation Modern research has shown that aggressive physiotherapy can have equal (and sometimes better) outcomes to surgery for high-grade muscle strains Other Muscle Information Tips and tricks of muscle naming… Learn Greek and Latin… Points of attachment: Sternocleidomastoid m. Action: Levator scapulae m. Use muscle fiber direction(s) Shape: Biceps brachii m. Rhomboid major m. Size: Rhomboid minor m. Look for patterns and try to use logic to understand the body – once you figure out the language, naming structures becomes easy work! Sagittal view (right) Agur and Dalley, Grant’s Atlas of Anatomy, 13th Ed. Posterior view Copyright © 2013 by Lippincott Williams and Wilkins Learning Outcomes By now, you should better understand how to… Identify the different types of muscles in the body and describe the basic properties of muscle tissue Name the components of skeletal muscle and describe the basic function of the sarcomere Explain the general mechanism for how muscles receive signals from the brain and describe the characteristics of a motor unit Explain how agonist, synergist, and antagonist muscles work with and against each other to produce different types of contractions and movements Discuss the clinical implications of exercise, aging, and injury on skeletal muscles  © [email protected]