Basics of Muscles Flashcards
4 principles of muscles
1) contractility (muscle action creates force)
2) excitability by nervous stimulation
3) extensibility (returns after shortening)
4) elasticity (returns when stretched)
Muscle/tendon arrangements
2 heads/biceps 3 heads/triceps 4 heads/quadriceps 2 bellies/digastric many bellies/multigastric spincters/radial
Tendon arrangements
cord- quadriceps tendon
fleshy- looks like the muscle attaches directly to the tendon
aponeurotic- IT band
Muscle fiber orientation
- longitudinal (parallel to tendon- used for maximizing shortening of muscle)
- unipennate (pack more fibers in at an angle, so used for force)
- bipennate
- multipennate
What covers the bundle of myofibrils comprising the muscle fiber, then the fasicle, and then the muscle?
- endomysium
- perimyseium
- epimysium
What is the function of muscle CT coverings?
1) provides strength
2) allow fibers and fasicles to slide passed each other
3) attaches muscle to tendon b/c CT coverings are continuous w/ tendon
4) walls off tissue damage/injury/infection in muscle cells, so it doesn’t affect other muscle cells
What covers the collagen fiber fasicles and then the tendon?
- peritendineum (continuous with the perimysium)
- epitendineum (continuous with the epimysium)
What is the myotendinous junction? What is the osteotendinous junction? And describe the components/purposes of both junctions.
- myotendinous: where the muscle joins the tendon
- -convoluted end of muscle fiber (greater SA) attaches to collagen fibers of tendon
- osteotendinous: where the tendon joins the bone
- -collagen fibers (Sharpey’s fibers) of tendon to nonmineralized fibrocartilage zone to mineralized fibrocartilage zone to mineralized bone
- -collagen fibers of tendon are associated with elastic fibers that create wavy pattern in tendon when muscle isn’t active
- -give a gradual transition from low to high stiffness to reduce risk of injury or separation of tissues
Explain the purpose of the tendon sheaths and components of tendon sheath.
- attaches tendon to bony surface to help create smooth movements and prevent “bowstringing”
- 2 components: fibrous covering (made of collagen and resists tensile forces) and synovial tendon sheath (bilayer w/ synovial fluid in between- protect tendon from friction and heat of fibrous covering)
Describe the 2 ways our body can reduce compressional stresses from a tendon wrapped around a bone.
- incorporating fibrocartilage to resist the compressional stress
- bursae: fibrous sacs lined w/ synovial membrane and contains synovial fluid; reduces frictional stress w/ lubrication and increasing contact area
How is a lever system defined?
by the relationship b/w the fulcrum/axis of rotation, muscular force/effort, load/external force
What is a moment/torque? How do you find it?
- tendency of a force to create a rotation
- Force x moment arm (perpendicular distance from the axis of rotation to the line of applied force)
What is an agonist? Antagonist? Co-Contraction (and benefits)?
- the muscle or muscle group controlling the movement or position
- the muscle or muscle group on the opposite side of the joint of the agonist, that when activated will control the opposite movement
- both agonist and antagonist are activated (increase compressional forces across the joint and energetically wasteful)- see in stabilization, stiffening joint and when learning a new joint
What are the rules for determining a shortening/concentric action (internal moment greater than external moment)?
- movement is in a direction opposite to that of the external force
- movement is against inertia; performed parallel to the ground or across gravity
- movement is in the direction of the external force but is faster than a movement produced solely by the external force
What are the rules for determining a lengthening/eccentric action (internal moment is less than external moment)?
-the movement is in the same direction as the external force but is slower than the force would produce alone
