Muscle Chapt. 10

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the following is a function of skeletal muscle

produce movement, maintain posture.

the contractions of skeletal muscles pull on tendons and move bones of the skeleton, skeletal muscles are responsible for
controlling the openings of the digestive and urinary tracts

skeletal muscles support the weight of some internal organs, muscle contractions help maintain body temperature

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


nerves and blood vessels that service the muscle fibers are located in the connective tissues of the


the delicate connective tissue that surrounds the skeletal muscle fibers and ties adjacent muscle fibers together is the


the bundle of collagen fibers at the end of a skeletal muscle that attaches the muscle to bone is called a


muscle fibers differ from "typical" cells in that muscle fibers

have many nuclei

the advantage of having many nuclei in a skeletal muscle fiber is

the ability to produce large amounts of the enzymes and structural proteins needed for contraction

skeletal muscle fibers are formed from embryonic cells called


the cell membrane of skeletal muscle is called the


the cytoplasm of a skeletal muscle fiber is called the


the series of membranous channels that surround each myofibril is the

sarcoplasmic reticulum

the functional unit of a skeletal muscle fiber is the


interactions between actin and myosin filaments of the sarcomere are responsible for

muscle contraction

in a sarcomere, thick fillaments are linked laterally by filaments of the

M line

thin filaments at either end of the sarcomere are attached to the

Z line

the area of the sarcomere containing the thick filaments is the

A band

the area of the sarcomere that contains only thin filaments is the

I band

the area in the center of the A band that contains only thick filaments is the

H band

each thin filament consists of

a pair of protein strands wound together

the sarcoplasmic reticulum stores

calcium ions

the skeletal muscle complex known as the triad consists of

a transverse tubule and terminal cisternae

cross-bridges are portions of

myosin molecules

at rest, active sites on the actin are blocked by

tropomyosin molecules

at rest, the tropomyosin molecule is held in place by

troponin molecules

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

neuromuscular junction

the space between the neuron and the muscle is the

synaptic cleft

receptors for acetylcholine are located on the

motor end plate

action potentials are conducted into a skeletal muscle fiber by

transverse tubules

active sites on the actin become available for binding when

calcium binds to troponin

in response to action potentials arriving from the transverse tubules, the sarcoplasmic reticulum releases

calcium ions

which of the following acts as an ATPase during the contraction cycle of muscle?

myosin cross-bridges

when calcium ion binds to troponin,

tropomyosin moves out of the groove between the actin molecules.

the most important factor in decreasing the intracellular concentration of calcium ion after contraction is

active transport of calcium into the sarcoplasmic reticulum

when sarcomeres are fully shortened, contraction cannot occur, when sarcomeres are slightly less than fully shortened, contraction connot occur

when the muscle is fully stretched, contraction cannot occur, all sarcomeres in a muscle fiber contract and relax together.

calcium ions are released from the sarcoplasmic reticulum during the

latent period and the contraction phase

the type of contraction represented by a single stimulus/contraction/relaxation sequence is

a twitch

when a muscle is stimulated repeatedly for several seconds with a constant stimulus, the amount of tension gradually increases to a maximum. This phenomenon is called

wave summation

a muscle producing peak tension with rapid cycles of contraction and relaxation is said to be in

incomplete tetanus

if a second stimulus arrives before the relaxation stage has ended, a second, more powerful contraction occurs. This is called

wave summation

a muscle that is stimulated so frequently that the relaxation phase is completely eliminated is said to exhibit

complete tetanus

the increase in muscle tension that is produced by increasing the number of active motor units is called


the type of contraction in which the muscle fibers produce increased tension but do not shorten is called


a resting muscle generates most of its ATP by

aerobic respiration

creatine phosphate

acts as an energy reserve in muscle tissue

during anaerobic glycolysis

ATP is produced, pyruvic acid is produced, lactic acid is produced if pyruvic acid accumulates.

at peak levels of muscle exertion the mitochondria can supply

only about 1/3 of the energy required by the muscle

when energy reserves in a muscle are exhausted and lactic acid levels increase,

fatigue occurs

during the recovery period following exercise, all of the following is true:

lactic acid is removed from muscle cells, the muscle actively produces ATP, oxygen is consumed, heat is generated

during the Cori cycle in the liver,

glucose is produced from lactic acid

during the recovery period the body's need for oxygen is increased because

additional oxygen is required to metabolize the lactic acid produced during exercise

fast fibers

produce powerful contractions

the type of muscle fiber that is most resistant to fatigue is the

slow fiber

contractions that utilize anaerobic ATP production

require maximal contraction of muscles for short periods of time

during activities requiring aerobic endurance

most of the muscle's energy is produced in mitochondria

fast muscle fibers can develop a larger number of mitochondria in response to

repeated, exhaustive stimulation

which of the following statements are true regarding human muscles:

eye and hand muscles are composed of fast fibers, back muscles are mostly composed of endurance fibers.

Each of the following changes in the skeletal muscles is a consequence of aging

muscle fibers become smaller, less elastic, fatigue more rapidly, and there is a steady decrease in number of satellite cells

heat energy produced from muscle contraction is released through the

integumentary system

cardiac muscle cannot be summated, skeletal muscle contractions may be summated, skeletal muscle control is neutral, cardiocytes are interconnected through intercalated discs


Neurons that innervate smooth muscle are under involuntary control, smooth muscles are uninucleate

smooth muscles do not contain sarcomeres, the thin filaments of smooth muscle fibers are attached to dense bodies

functions of smooth muscle: altering diameter of respiratory passageways, elevating hairs on the arm,

moving food materials along digestive tract, forcing urine out of urinary tract

the ability of smooth muscle to function over a wide range of lengths is called


muscle tissue, one of four primary types of tissue, consists chiefly of muscle cells that are highly specialized for


the types of muscle tissue include all of the following: striated, cardiac, smooth


at each end of the muscle, the collagen fibers of the epimysium, perimysium, and endomysium come together to form either a bundle known as

a tendon or a broad sheet called a aponeurosis

in order for a muscle to contract properly, it requires

energy, oxygen, nutrients, adequate blood supply

skeletal muscle contracts only under stimulation from

the central nervous system

differences between skeletal muscle cells and typical cells include

sketetal muscle cells are larger than normal cells, and are multinucleate

each skeletal muscle fiber contains

hundreds to thousands myofibrils

when a skeletal muscle fiber contracts

the H zones and I bands get smaller, the zones of overlap get larger, the Z lines get closer together, the width of the A band gets constant

knowing that the myofibrils are attached at the Z line of the sarcolemma and at either end of the muscle fiber, when myofibrils get shorter, the muscle fiber


the pull called tension is

an active force

The cytoplasm of the synaptic terminal contains mitochondria and vesicles filled with molecules of the neurotransmitter


knowing the five steps that occur causing a neuron to stimulate a muscle fiber, if there is a problem with the release of calcium ions in the third step,

the acetylcholine does not bind to the motor end plate

ATP metabolism normally provides

95% of the ATP demands of a resting cell.

in a isotonic contraction

tension rises and the skeletal muscle length changes

the contraction of a muscle exerts a pull on a bone because

muscles are attached to bones by tendons

large diameter, densith packed myofibrils, large glycogen reserves, and a few mitochondria are characteristics of

fast fibers

when contraction occur,

the H and I bands get smaller, the Z lines move closer together, the width of the A band remains constant.

which of the following hormones directly stimulates growth of muscle tissue and increased muscle mass


because skeletal muscle contractions demand large quanities demand large qualities of ATP, skeletal muscles have

a rich vascular supply

during muscle contraction, all of the following occur, except

hemoglobin concentration in muscle fibers increases

Physical evidence that supports the sliding filament theory of muscle contraction includes

decreased distance between Z lines during contraction

when myosin cross-bridges bind to the active sites on actin,

they pivot toward the M line.

the following is a list of the events that occur during a muscle contraction

calcium ion is released from the sarcoplasmic reticulum, calcium ion binds to troponin, myosin cross-bridges bind to the actin, the myosin head pivots toward the center of the sarcomere, the myosin head binds an ATP molecules and detaches from the actin, the free myosin head splits ATP

after death, muscle fibers run out of ATP and calcium begins to leak from the sarcoplasm reticulum into the sarcoplasm. This results in a condition known as

rigor mortis

how would blocking the activity of acetylcholinesterase affect skeletal muscle--

it would cause spastic paralysis (muscles are contracted and unable to relax)

when acetylcholine binds to receptors at the motor end plate, the muscle membrane becomes

more permeable to sodium ions

each of the following factors would increase the probability of skeletal muscles contracting:

increased permeability of the muscle membrane to calcium ions, increased amounts of acetylcholine in the synaptic cleft, increased permability of the muscle membrane to sodium ion, increased numbers of acetylcholine receptors at the motor end plate

the following ratio of neurons to muscle fibers are the greatest :

muscles that control the eye

which of the following muscles would contract more forcefully-

a muscle receiving 10 to 15 action potentials per second

a muscle with 20 motor units active

would produce the greater tension

increased blood flow to a muscle could result in all of the following:

fatigue, oxygen debt, shift to more anaerobic glycolysis in the muscle, an increase in intracellular lactate

increased oxygen consumption would accompany all of the following:

increased heat production, increased conversion of lactate to glucose, increased aerobic respiration by muscle cells, increased muscle activity

how would an elevated level of thyroid hormone in the body affect skeletal muscles:

it would simulate atrophy, hypertrophy, decrease heat production by muscle tissue, increase muscle mass

How does a drug that competes with acetylcholine for receptors at the motor end plate affect skeletal muscle--

it would cause flaccid paralysis (relaxed and unable to contract)

if a person is suffering from severe hyperkalemia, you would expect

the potassium ion concentration of the interstital fluid to be less than normal, muscle weakness and increased strength of twitch contractions

The bacterium that causes tetanus produces a toxin that affects the central nervous system and skeletal muscles producing a powerful tetanic contractions of the skeletal muscles. the toxin probably acts by

making the cell membranes more permeable to calcium ions

athletes go through a warmup period before engaging in an event. the reason for this is to take advantage of

wave summation

satellite cells

are scattered between the endomysium and muscle fibers and function in the repair of damaged muscle tissue

communication between nerve and muscle fibers occur at specialized junctions called

neuromuscular junctions

on either side of a transverse tubule, the individual tubules of the sarcoplasmic reticulum fuse, and form expanded chambers called the

terminal cisternae

the theory that explains how a muscle fiber contracts is called the

sliding filament theory

the sequence of events that forms the link between electrical activity in the sarcolemma and the initiation of a contraction is called

excitation-contraction coupling

thyroid hormone

elevates the rate of energy consumption in resting and active skeletal muscles


primary sex hormone in males


stimulates muscle metabolism and increases duration and stimulation of the force of contraction


gives red pigment to slow fibers


interacts with calcium ions and activates myosin light chain kinase

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