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) |