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KIN: Muscular Consid
| Question | Answer |
|---|---|
| Approximately how many muscles are in the adult human? | 660 |
| How much of one's body weight is from skeletal muscle | 45% |
| What percentage of skeletal muscle is water? | 75% |
| Skeletal muscle is surrounded by what? | Epimysium |
| Epimysium contains what? | Muscle fasicles |
| What are muscle fascicles surrounded by? | Perimysium |
| What does perimysium contain? | Muscle fibers |
| What are muscle fibers surrounded by? | Endomysium |
| What does endomysium contain? | Myofibrils |
| What are myofibrils composed of? | Sarcomeres |
| What do sarcomeres contain? | Dark, thick myosin and light, thin actin |
| During a contraction, overlapping myosin and actin filaments repeadtedly form cross-bridges to slide actin filaments towards the center of myosin which is called what? | M line |
| How is the physiologic cross-sectional area of a muscle measured? | Perpendicular to muscle fibers |
| What is the angle of pennation? | Angle at which individual fibers are oriented |
| What is the pennation angle of most human muscles? | 0-30 degrees |
| How do the fibers in a fusiform muscle run? | Parallel along the muscles length |
| What is the shape of fusiform muscles? | Wide in the middle and tapered at the end |
| How is the anatomic cross-sectional area of a muscle measured? | Longitudinal axis of the muscle |
| Characteristics of fusiform muscles | Straight, PCSA = ACSA, increased velocity, decreased max force |
| Characteristics of pennate muscles | Angled, PCSA > ACSA, decreased velocity, increased max force |
| What are examples of fusiform muscles? | Sternocleidomastoid, rectus abdominis, biceps brachii |
| What are some examples of pennate muscles? | Semimembranosus (unipennate), gastroc (bipennate), deltoid (multipennate) |
| What are the 4 properties of muscles? | Irritability Contractibility Extensibility Elasticity |
| What is irritability? | The ability of a muscle to respond to stimulation; muscle is stimulated by chemical neurotransmitters |
| What is the only tissue more sensitive to muscle tissue? | Nerve tissue |
| What is contractibility? | Ability to shorten when sufficient stimulation is received |
| What is extensibility? | Ability to lengthen out or stretch beyond resting length |
| What is extensibility determined by? | Connective tissue found in perimysium, epimysium, and fascia surrounding a muscle |
| What is elasticity? | Ability to return to resting position once stretch is removed |
| What is elasticity determined by? | Connective tissue |
| What's the difference between muscle spindles and GTOs? | Location |
| Muscle is excited by impulses from what? | Alpha motor neurons |
| What are series elastic components? | Tissues that lie in series with the active proteins (titin) |
| What are parallel elastic components? | Noncontractile tissues in parallel with the active proteins (perymysium) |
| What are the 3 type of motor units? | Fast fatigable (Type IIX) Fast fatigue-resistance (Type IIA) Slow (Type I) |
| What is the recruitment order for motor units? | Type I, Type IIA, Type IIX |
| What is the order of recovery after exercise from slowest to fastest? | Type IIX, Type IIA, Type I |
| If tension is generated at a slow rate, where would the injury most likely occur? | Tendon-bone junction |
| If the tension is generated at a fast rate, where would the injury most likely occur? | Within a tendon |
| What are the functions of muscles? | Movement production Position maintenance Joint stabilization Support/protect viscera Control body entrance/exits Produce head |
| What is an agonist? | Muscle that actively contracts to produce a desired movement (AKA: Prime mover) |
| What is a stabilizer? | Muscle acting on a segment to allow motion at an adjacent joint to occur |
| What is a neutralizer? | Muscle that contracts to eliminate an undesired joint action of another muscle |
| What is an antagonist? | Muscle that acts in opposition to another |
| What is a synergist? | Muscle that cooperates with another to produce a desired movement |
| According to the force-velocity curve, during a concentric contraction, as the load increases the maximal contraction velocity of a muscle does what? | Decreases |
| According to the force-velocity curve, during an eccentric activation, speed of lengthening does what as a greater load is applied? | Increases |
| What is the take home message regarding the force-velocity curve during a concentric contraction? | The slower you go (to a point) the more force you can produce |
| What is the take home message regarding the force-velocity curve during an eccentric contraction? | At maximum lengthening velocity is when you will produce the most amount of force |
| What muscle fibers enhances power? | Fast-twitch fibers |
| What is the stretch-shortening cycle? | When a concentric contraction is preceded by an eccentric contraction (Plyometrics) |
| By doing a concentric contraction preceded by an eccentric contraction, what does this allow once to do? | Generate greater force |
| How does the stretch-shortening cycle work? | At the end of a pre-stretch, concentric muscle acivity is enhanced by stored elastic energy |
| How long is the stored energy good for before the shortening cycle? | 0-.9 secs |
| If the stored elastic energy is lost, what happens to it? | Converted to heat |
| What is strength? | Max force or power produced by a muscle or muscle group during a maximal voluntary effort |
| How are strength gains commonly quantified? | 1RM |
| What is the SAID principle? | Specific adaptations to imposed demands |
| What does hypertrophy result from? | Increased protein synthesis within muscle fibers and therefore, an increase in the physiologic cross-sectional area of the muscle |
| What is hyperplasia? | Increase in the actual number of fibers |
| Where else can you see strength gains from? | Nervous system more towards the beginning |
| How does tension build during passive stretch? | As an exponential function |
| What is the ideal resting length of a muscle fiber or individual sarcomere? | Length that allows the greatest number of cross-bridges and therefore, the greatest potential force |
| What happens to the number of potential cross bridges as the sarcomere is lengthened OR shortened from it's resting length and what effect does this have on the muscle? | It decreases so that lesser amounts of active force are capable of being generated |
| What does the resulting active length-tension curve look like? | Inverted U-shape with its peak at the optimal resting length (90 degrees elbow flexion) |
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