3 - Muscle Function

3 - Muscle Function - Foundations of Occupation Foundations...

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Unformatted text preview: Foundations of Occupation: Foundations of Occupation: Kinesiology Muscle Function and Structure Muscle Function and Structure Lecture 3 – Summer 2010 Announcements Announcements Our wonderful classroom assistants and I love to help and want to answer all of your questions and concerns…please write them down and ask during breaks, labs, or office hours if we cannot get to your question in lecture (we know it moves very fast!) Wear your USC clothing and gear tomorrow for our PARTY!!! FIGHT ON!!! Friday’s Review Session (AKA Party): FIGHT ON! FIGHT ON! Test 1: Locations for Testing Test 1: Locations for Testing Test #1 on Monday, June 21 from 8:30 to 10:30 am Lecture will start at 10:45 am (no labs) April (139 kitchen) & Pierre’s (139 classroom) lab sections will be testing in the auditorium, Elyse & Jen’s labs will be in their regular classrooms. April’s section will be at the front of the auditorium and Pierre’s section will be in the back Did Someone Say Torque? Did Someone Say Torque? In order to lift the box, you need to overcome the TORQUE OF GRAVITY The perpendicular distance (moment arm) is the distance from the line of gravitational pull on the box and the upper extremity to the hip axis Demonstration by classroom assistants Overview Muscle Attachments and Names Brief Review of Muscle Structure & Function: The Contractile Unit Factors Influencing Muscle Function Types of Muscle Contractions Coordination of Muscle Actions Proximal attachment Distal attachment Muscle Attachments and Muscle Attachments and Names Muscle names ­ can give you information about location, shape, action, number of heads, attachments, direction of fibers, size of muscle Examples of Muscle Names Examples of Muscle Names Tibialis anterior Trapezius Biceps femoris External and internal obliques Example of Muscle Names (continued) Example of Muscle Names (continued) Parallel – Strap (muscle fibers arranged in parallel sheets: abductor muscles, sartorius – fusiform (muscle with fleshy belly tapering at either extremity, spindle­shaped: biceps brachii Penniform – Unipennate: posterior tibialis (central tendon fans out) – Bipennate: quads (fan both sides of central tendon) – Multipennate : deltoid (forms three sides) – Fan­shaped: pecs (common tendon) BRIEF REVIEW OF MUSCLE BRIEF REVIEW OF MUSCLE STRUCTURE AND FUNCTION Brief Review… Brief Review… The Contractile Unit of Muscle: Sarcomere Sliding Filament Theory of Muscle Contraction Sliding Filament Theory… Sliding Filament Theory… Watch it happen... Part II... FACTORS INFLUENCING FACTORS INFLUENCING MUSCLE FUNCTION Actual mechanical structure of joint Location of muscles Location of attachments of muscles Number of joints crossed Mechanical and Biomechanical Factors Influencing Muscle Function Active Tension and Passive Tension of Muscles Active tension ­ developed in contractile elements of muscles Passive tension ­ developed in noncontractile components of muscles Length­Tension Relationship Length­Tension Relationship Related to active and passive tension. Excursion = the distance from maximum elongation to maximum shortening. – For most muscles = 2:1 There is an optimal range in which a muscle contracts effectively…generally 1.2 times resting length – Maintaining an optimum length­tension relationship throughout range allows greatest contractile force. Active& Passive Insufficiency Active & Passive Insufficiency Active Insufficiency ­ a muscle reaches the point where it cannot shorten any further. Occurs to the agonist. Passive Insufficiency ­ a muscle cannot be elongated any farther without damage to the fibers. Occurs to the antagonist. Insufficiency Example… Insufficiency Example… Tenodesis Grasp Tenodesis Grasp Functional use of passive insufficiency TYPES OF MUSCLE TYPES OF MUSCLE CONTRACTIONS Types of Muscle Contractions Types of Muscle Contractions Isometric ­ production of force without change in length of muscle Isotonic ­ muscle contracts causing change in length of the muscle with joint angle change – concentric – eccentric Isotonic Contractions Isotonic Contractions Concentric – attachments move closer – occurs against gravity (raising motion) – used with acceleration – If movement with gravity,the muscle is overcoming a force greater than pull of gravity Eccentric – attachments move further apart – occurs with gravity (lowering motion – used with deceleration – contraction produces greater forces Co­Contraction Agonists & antagonists contract simultaneously Co­contractions are always isometric STABILITY More internal; holding a position Example of isometric co­ contraction: Evan holding his arm in abduction & elbow in extension while in prone on the plinth Co­Contraction vs. Isometric Co­Contraction vs. Isometric Contraction Isometric Contraction Can have an isometric contraction which does not co­contract Joint angle and muscle length do not change during contraction Example of isometric: Lab question­assume a hand­ shaking position and try to turn your forearm inward/outward Concentric contractions… Concentric contractions… Concentric Concentric contractions… Concentric contractions… Concentric contractions… Concentric contractions… Concentric contractions… Eccentric contraction… Eccentric contraction… Coordination of Muscle Actions Coordination of Muscle Actions Agonist (Mover) Antagonists Synergists: Any combination of… – Prime movers and assists – Prime movers and fixators/stabililzers – Prime movers and neutralizers – Prime movers and support muscle Agonists, Antagonists, & Assists (Oh My!) Agonists, Antagonists, & Assists (Oh My!) Different roles for different muscles depending on the action occurring Agonist: causes motion, prime mover Assist: assists motion of the prime mover Antagonist performs the opposite motion of the agonist Antagonist has the potential to oppose agonist but is usually relaxed when the agonist is working When the agonist is contracting at the same time as the antagonist, a ____________________is occurring. Examples of Antagonists Examples of Antagonists Muscles which oppose the agonist Example: trap 3 and serratus anterior during aBduction and aDduction of the scapula. For aBduction to happen, the serratus anterior must contract and trap 3 (antagonist to aBduction), must relax…so it does not oppose the movement. If trap 3 DID contract…while the serratus anterior was contracting (with equal force)…we’d have a co­contraction Synergists: Prime Mover & Fixator/Stabilizer Synergists: Prime Mover & Fixator/Stabilizer: stop unwanted action that occurs at fixed attachment of muscle that is working (contracts isometrically) Example: performing a bicep curl – posterior deltoid will serve as a fixator/stablizer of the arm by creating a force of extension on the arm at the shoulder joint that stops the biceps brachii from flexing the arm at the shoulder. The arm is “fixed/stabilized.” Synergists: Prime Mover & Fixator/Stabilizer Synergists: Prime Mover & Fixator/Stabilizer: stop unwanted action that occurs at fixed attachment of muscle that is working (contracts isometrically) Another Example: Levator scapulae contracts & creates a pulling force which moves both the scapula & the neck closer together. The lower trapezius will act as a fixator/stabilizer when it forces the scapula into depression; preventing the levator scapulae from elevating the scapula. Synergists: Prime Mover & Fixator/Stabilizer Synergists: Prime Mover & Fixator/Stabilizer: stop unwanted action that occurs at fixed attachment of muscle that is working (contracts isometrically) Another example in the shoulder girdle: when humerus is abducted; rhomboids & trap 3 can stabilize the scapula (hold it into aDduction) so that other muscles can rotate the scapula upward. Trap 3 & rhomboids are stabilizing synergies for the shoulder aBductors (deltoids mainly) Synergists: Prime Mover & Neutralizer Synergists: Prime Mover & Neutralizers: stop unwanted action at the mobile attachment – in another plane Example: same girl doing the bicep curl. Since the biceps brachii is the prime mover for elbow flexion & supination, the pronator teres will act as a neutralizer of the forearm to prevent the arm from supinating during the action. Synergists: Prime Mover & Neutralizer Synergists: Prime Mover & Neutralizers: stop unwanted action at the mobile attachment – in another plane In the shoulder girdle, can provide a pure motion (ie, scapular rotation), by cancelling out other actions. Example: trapezius & rhomboids working together create pure scapular adduction Another example: trap 2, 4 & serratus anterior (force couple) create scapular upward rotation Synergists: Prime Movers & Support Muscles Synergists: Prime Movers & Support muscles: hold a part of the body in position, while action is occurring, but do not work directly at the site of the action. Usually work against gravity, isometrically. Example: girl doing a bicep curl with a weight. With the weight in her right arm, it creates a force that would pull her trunk to the right into lateral flexion. The left lateral flexors (erector spinae) of the trunk would act as support muscles so that her trunk does not fall into right lateral flexion ...
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