ANATOMY MIDTERM REVIEW: Muscular System

a muscle fiber exposed to a series of stimuli of increasing frequency combines individual twitches (summation) which results in

a muscle fiber exposed to a series of stimuli of increasing frequency combines individual twitches (summation) which results in

complete sustained contraction

in a recording of a muscle twitch, the delay between the time a stimulus is applied and the time the muscle responds is called the

latent period

when a muscle undergoes atrophy in response to disuse…

the size of actin and myosin filaments decreases

smooth muscle has ——— and not troponin.

calmodulin

activities such as distance swimming and distance running will most likely stimulate development of

slow fatigue-resistant fibers

while examining a sample of muscle tissue under a microscope, you notice that the cells are multinucleated. they are long, unbranched, striated, and contain a developed transverse tubule system. which muscle type does this sample contain?

skeletal muscle

while examining a sample of muscle tissue under a microscope, you notice that the cells have a single nucleus. the fibers are striated and heavily branched. which muscle type does this sample contain?

cardiac muscle

compared to skeletal muscle, smooth muscle contracts

more slowly and relaxes more slowly

the increase in the number of motor units activated as a result of more intense stimulation is called

recruitment

myasthenia gravis is

an autoimmune disorder

the characteristic reddish brown color of skeletal muscle comes from which substance?

myoglobin

threshold stimulus is the

minimum strength of stimulation required to contract a muscle fiber

during muscle contraction, ATP supplies energy for

myofilament movement

people with myasthenia gravis have a deficiency of

acetylcholine receptors

a plank position is part of a yoga/pilates workout. the person supports the body on the floor in a prone position with the arms and feet supporting the body. it is a little similar to the “up” position of a pushup, held for 30-60 secs. Contraction of the abdominal muscles in a plank is most likely

isometric

when ATP levels are low, the relationship between ATP and creatine phosphate is that

creatine phosphate supplies energy to regenerate ATP from ADP and phosphate

oxygen debt in muscles may develop because of

the inability of respiratory and circulatory systems to supply enough oxygen to skeletal muscles when used strenuously for a minute or two

Actin filaments slide along…

myosin filaments

what is the first event in muscle fiber contraction?

acetylcholine is released from the end of the motor neuron

the muscle that opposes a particular action is called the

antagonist

steps of muscle fiber contraction:

1. the impulse arrives at the synapse and travels through the transverse tubules

2. the muscle impulse reaches the sarcoplasmic reticulum and calcium is released

3. calcium floods the sarcoplasm and binds to troponin molecules leaving active sites

4. myosin heads bind to exposed active sites on actin, forming cross-bridges

5. thin filaments are pulled over thick filaments

6. the muscle fiber shortens and contracts

cardiac muscle…

excites itself.

what enzyme degrades acetylcholine, keeping it from accumulating in the synapse?

acetylcholinesterase

the structures that connect cardiac muscle cells are

intercalated disks

both acetylcholine and norepinephrine can affect

smooth muscle contraction

at a neuromuscular junction…

neurotransmitters are released

the muscle that causes the action is the

agonist

the more movable end of a muscle

insertion

binding sites on the surface of actin allow the formation of cross-bridges with molecules of

myosin

at a neuromuscular junction, the muscle fiber membrane folds, forming a

motor end plate

the amount of oxygen liver cells require to support the conversion of lactic acid to produce glucose or glycogen is the

oxygen debt

a tendon is—-, whereas an aponeurosis is—-.

cordlike and connects muscles to bones; a broad sheet of dense connective tissue that connects muscles to muscles

neurotransmitters are stored in vesicles in

motor neuron endings

the functional unit of muscle contraction is

the sarcomere

T or F: ATP is necessary for muscle relaxation.

true

T or F: acetylcholine is released by the myofibril and crosses the synaptic cleft to bind to the motor neuron ending.

false

T or F: in the initiation of muscle fiber contraction, calcium ions bind to tropomyosin, exposing active sites on actin for cross-bridge formation.

false

T or F: a motor neuron and the muscle fibers that it controls constitute a motor unit.

true

muscles that assist an agonist are called —-.

synergists

the part of a sarcomere that is myosin only is the —- zone.

H