Muscle Physio

an entire skeletal muscle is surrounded by

epimysium

the dense layer of collagen fibers that surround an entire skeletal muscle is the

epimysium

which of the ff correctly identifies muscle components in order from largest to smallest?

fasciculus, muscle fiber, myofibril

which of the ff statements about smooth muscle is true?

fibers are small and spindle-shaped

the sarcoplasmic reticulum does not:

make up about 85% of the contents of a muscle fiber

a motor neuron and all the muscle fibers it supplies is called a

motor unit

we would expect to find smooth muscle in all of the ff except:

myocardial tissue

a sarcomere is part of a

myofibril

in the sliding filament model of muscle contraction, the myofilaments slide over each other, resulting in the overlapping of actin and ____

myosin

each skeletal muscle fiber is controlled by a neuron at a single _____

neuromuscular junction

eccentric contractions are stronger than isometric and concentric contractions partly because, in eccentric contraction:

within each muscle fiber, more cross-bridges are attached to actin at a given time

the ends of the actin filaments are anchored to the

z - line

the refractory period in which the muscle will NOT contract if stimulated occurs during _____ of the muscle cell

repolarization

cross bridges that link between the thick and thin filaments are formed by the

"globular head of thick filaments"

the alternating contraction and relaxation of opposing layers of smooth muscle is referred to as _____

peristalsis

elasticity refers to the ability of a muscle fiber to _____

recoil and resume its resting length after being stretched

select the trait the does not characterize muscle tissue in general

-irritability -extensibility -contractility

concentric contraction are weaker than isometric and eccentric contraction partly because, in concentric contractions:

-some attached CB may exert a "drag" effect on the actin filament -there is a smaller number of CB bound to actin at any time -there may be a small decrease in the force per CB

in regard to the force-length relationship it is true that:

-the muscle length at which maximal active force occurs is called optimal length -total force is equal to the sum of active and passive force -beyond resting length, passive force increases from short to long muscle lengths

the force of a tetanic contraction is greater than that of a twitch contraction because:

More Calcium is released in a tetanic contraction

which of the ff is true about muscle structure?

actin filaments are arranged so that 6 actin filaments surround each myosin filament

the sequence of electrical changes that occurs along the sarcolemma when a muscle fiber is stimulated is known as the _____

action potential

what is the ion released from the terminal cisternae that combines the with troponin and removes the blocking action of tropomyosin, resulting in the formation of cross bridges

calcium

which of the ff does NOT occur during skeletal muscle contraction?

calcium binds to myosin heads

which one of the ff binds calcium ions in a smooth muscle, causing contraction?

calmodulin

all of the ff terms refers to the ability to receive and respond to a stimulus EXCEPT:

contractility

Curare is a naturally-occuring compound that competitively binds to nicotinic acetylcholine receptors on muscle cells. Which of the ff symptoms might be seen in a patient who has been exposed to curare?

diaphragmatic paralysis

which of the ff allows recoil of the muscle fiber when contraction ends?

elastic filaments

individual fibers of skeletal muscle have fine sheath of connective tissue called an

endomysium

what is the cause of rigor mortis?

high levels of sodium in the cell after death

in regard to the cross bridge power stroke, it is true that:

in concentric contractions, the CB power stroke pulls the actin filament toward the center of the sarcomere, causing sarcomere shortening

the type of muscle contraction in which the muscle fibers produce increased tension, but the muscle neither shortens nor lengthens, is called ____

isometric

which of the ff is NOT a characteristic of skeletal muscle contraction?

it can contract or long periods of time without tiring

which of the ff substances increases in quantity during repetitive muscle contraction during oxygen deficit?

lactic acid

which is most likely to extend the entire length of a muscle fiber

myofibril

during one CB cycle:

one molecule of ATP is used

the functional unit of contraction in a skeletal muscle fiber is the _____

sarcomere

the space between two Z lines constitutes the:

sarcomere

when a muscle fiber shortens, the ff also shortens:

sarcomere

what is the membranous network that surrounds each myofibril

sarcoplasmic reticulum

which of the ff statements is incorrect?

skeletal muscle are responsible for the pumping action of the heart

what is the role of acetylcholine in calcium release

stimulates cellular contraction by opening voltage-gated ion channels

which of the ff is NOT innervated by the autonomic nervous system?

striated skeletal muscle cell

the space between the neuron and the muscle is the ___

synaptic cleft

which of the ff best describes the composition of the structure known as a TRIAD in a skeletal muscle fiber

terminal cisterna, transverse tubule, and terminal cistern

which of the following characteristics is unique to smooth muscle?

the absence of striations

in excitation-contraction coupling:

the muscle action potential propagates along the sarcolemma and down the transverse tubules

which of the ff muscles is voluntary?

the muscle that extends the arm at the elbow

what is the role of tropomyosin in muscle contraction?

to prevent myosin from continuing to slide up the actin filament

the term that means a continued mild or partial contraction of a muscle that keeps it healthy and ready to respond is muscle ____

tone