Muscles Flashcards
What three muscle types does the muscular system consist of?
Cardiac, smooth and skeletal.
Which is the most abundant tissue type?
Skeletal muscle (40-45% of total body weight)
How many skeletal muscle pairs does the human body have?
430 pairs, 80 of which produce the most vigorous movement.
What are the 5 key functions of muscular tissue?
- producing body movements
- stabilizing body positions
- regulating organ volume
- moving substances within the body
- producing heat
What are tendons?
Extensions of connective tissue beyond muscle fibers that attach the muscle to bone.
What are myofibrils?
A unit of a muscle cell containing thin and thick filaments.
What is the sarcolemma?
The plasma membrane surrounding muscle cells.
What are sarcomeres?
The arrangement of thick and thin fillaments in the myofibril.
What are thick and thin filaments composed of?
Thick filaments are composed of myosin, thin filaments are composed of actin, tropomyosin and troponin.
What is the sliding-filament mechanism?
The sliding of filaments and shortening of sarcomeres that cause the shortening of muscle fibers.
How is Ca2+ alongside ATP needed for muscle contraction?
An increase in the level of Ca2+ in the sarcoplasm, caused by the muscle action potential, starts the contraction cycle; a decrease in the level of Ca2+ turns off the contraction cycle.
What is the muscle action potential?
An electric signal delivered by a neuron to its muscle fibre that causes contraction.
What is a motor unit?
A single motor neuron along with all the muscle fibres that it stimulates.
What is the neuromuscular junction (NMJ)?
The synapse between a motor neuron and a skeletal muscle fibre. The NMJ includes the axon terminals and synaptic end bulbs of a motor neuron plus the adjacent motor end plate of the muscle fiber sarcolemma.
What is a myogram?
A record of a muscle contraction.
What are the three periods in a myogram?
Latent, contraction and relaxation
What is wave summation?
The increased strength of a contraction that occurs when a second stimulus arrives before the muscle has completely relaxed after a previous stimulus.
What produce unfused and fused tetanus?
Repeated stimuli and more rapidly repeating stimuli.
What is motor unit recruitment?
The process of increasing the number of active motor units.
What fibre types of motor units are there?
I (decreases force potential)
IIA and IIB (increase force potential)
How are skeletal muscles classified on the basis of their structure and function?
Slow oxidative (SO) fibers, fast oxidative-glycolytic (FOG) fibers, and fast glycolytic (FG) fibers.
What is the order of motor unit recruitment?
SO -> FOG -> FG
What is the average population distribution of fibre muscle types?
Type I - 50-55%
Type IIA - 30-35%
Type IIB - 15%
What are the three types of muscle contraction?
Concentric (shortening muscle)
Eccentric (lengthening muscle)
Isometric (contracts but doesn’t change shape)
