Muscles Flashcards
What are the functions of muscles?
- Movement (muscles produce movement by pulling on bones as muscles contract)
- Posture (a continuous, low-strength muscle contraction called tonic contraction (muscle tone) enables us to maintain body position)
- Heat production (contraction of muscle fibres produces most of the heat required to maintain normal body temperature)
3 types of muscles
- Skeletal - Voluntary, striated
- Smooth - Involuntary, non striated
- Cardiac - involuntary, striated
Regions of a skeletal muscle
- origin (attachment to the bone that remains relatively STATIONARY or fixed when movement at the joint occurs)
- insertion (point of attachment to the bone that MOVES when a muscle contracts)
- Body (main part of the muscle)
What attaches muscle to bone?
Tendons
What are muscle cells called?
Muscle fibers
What is needed for muscle contraction to occur?
- Myosin
- Actin
Which myofilaments contain myosin?
Thick ones
Which myofilaments contain actin?
Thin ones
What is the basic functional contractile unit called?
A sarcomere (separated by Z lines)
What is happening when muscles contract?
Thick and thin myofilaments slide past each other
What 2 things are required for muscle contraction?
Calcium and ATP molecules
What 3 things happen for muscle contraction?
1 - nerve impulse travels to a muscle fiber through a motor neurone
2 - the impulse triggers the release of calcium ions
3 - calcium ions bind to thin filaments and permit actin to react with myosin
What is a motor unit?
A combination of a motor neurone with the muscle fibres it controls
What is a neuromuscular junction?
Point of contact between a nerve ending and the muscle fiber
What is a motor neuron?
the specialized nerve that transmits an impulse to a muscle, causing contraction
What is the difference between a twitch and tetanic contractions?
Twitches are single involuntary muscle contractions, whereas tetanic contractions are CONSTANT MUSCLE CONTRACTIONS
What are isotonic contractions?
Contractions that produce movement at a joint because the muscle changes length
- further broken down into concentric contractions (muscle shortens at the insertion end of the muscle to move toward the point of origin)
and
-eccentric contractions (muscle lengthens under tension, thus moving the insertion from the origin)
What are isometric contractions?
Contractions that do not produce movement; the muscle as a whole does not shorten. Although no movement occurs, tension within the muscle increases
(i.e. wall sit)
What is fatigue and what causes it?
- Fatigue is reduced strength of muscle contraction caused by repeated muscle stimulation without adequate periods of rest
What systems contribute to movement and fatigue?
- Respiratory, circulatory, nervous, muscular, and skeletal
What is flexion and extension?
- flexion = decreasing the angle
- extension = increasing the angle
What is abduction and adduction?
- abduction = away from the midline
- adduction = toward the midline
- rotation = around an axis
What is rotation and circumduction?
- rotation = around an axis
- circumduction = move distal end of a part in a circle
What is supination and pronation?
- Hand positions that result from twisting the forearm, supination = up, pronation = down
