A&P Muscular System Study Guide

Step 8 of muscle contraction

The myosin heads link to the active sites on actin.

T or F: The amount of oxygen needed to repay the oxygen debt includes the amount of oxygen that muscle cells need to resynthesize ATP

True

The type of smooth muscle in which all of the cells contract together is ________ smooth muscle.

Visceral

A contractile response of a single muscle fiber to a single muscle impulse is called:

a twitch

The chemical used at the junction with a skeletal muscle is ______

acetylcholine

The neurotransmitter that is release at neuromuscular junctions and that stimulates skeletal muscle to contract is ______.

acetylcholine

Binding sites for myosin

actin

Muscle relaxation sequence

1. Nerve impulses no longer arrive at neuromuscular junction 2. Acetylcholine is no longer released. 3. Acetylcholinesterase decomposes ACh, and the muscle fiber is no longer stimulated. 4. Calcium ions are actively transported from the sarcoplasm into the sarcoplasmic reticulum. 5. Troponin and tropomyosin shift, blocking the further interaction between myosin and actin. 6. Muscle fiber relaxes.

The events that occur at a muscular junction

1. Some vesicles release acetylcholine. 2. acetylcholine diffuses across a synaptic cleft. 3. acetylcholine binds to receptors on the motor end plate. 4. membrane permeability to sodium is increased (opening of sodium channel) 5. sodium enters the muscle cell 6. Triggers an electrical impulse along sarcolemma.

after prolonged muscle use, muscle fatigue occurs due to...

A decrease in ATP levels, Electrolyte imbalance (possible answer)

Step 1 of muscle contraction

A nerve impulse arrives at the distal end of a motor neuron axon.

Define/describe muscle tone

A response to nervous stimulation that originates repeatedly from the spinal cord and stimulates only a few muscle fibers at a time

A person feels out of breath after vigorous exercise because of oxygen debt, what helps explain this phenomenon?

A. Conversion of lactic acid to glucose occurs in the liver and requires energy B. Anaerobic respiration increases during strenuous activity (another possible answer) C. Priority in energy use is given to ATP synthesis (another possible answer)

Describe at least 3 roles of acetylcholinesterase in stimulation of a muscle fiber. (4)

A. it is the enzyme found in the axon ending that catalyzes the production of acetylcholine. B. Enzyme breaks down acetylcholine in synaptic cleft, ending stimulation of muscle fiber. C. inactive form of acetylcholine found stored in synaptic vesicles of the neuromuscular junction. D. type of receptor found in motor end plate that binds acetylcholine initiating an electrical impulse.

the striations seen in skeletal muscle consist of alternating dark bands, called the _____ bands, and light bands called the ______bands.

A; I

Step 3 of muscle contraction

ACh binds to receptors on the motor end plate.

As strenuous activity begins, muscle cells first use the ____ molecules present in their cytoplasm as their source of energy. the supply of this molecule, however, is limited. It must be produced by other means in order for exercise to continue.

ATP

Step 2 of muscle contraction

Ach is released into the synaptic cleft.

During skeletal muscle contraction, myosin cross bridges attach to active sites of:

Actin filaments

Step 4 of muscle contraction

An electrical impulse travels across the sarcolemma and into transverse tubules.

Step 6 of muscle contraction

Calcium ions diffuse out of sarcoplasmic reticulum and bind to troponin.

___________ diffuse from the sarcoplasmic reticulum into the sarcoplasm. These ions bind to _______ molecules.

Calcium ions; troponin

In order to produce more ATP, the muscle cells next start to use ______, also present in the cytoplasm, to form new ATP. This is done by moving a phosphate and its energy from this molecule to ADP to form new ATP.

Creatine phosphate

What describes smooth muscle contraction but not skeletal muscle contraction?

Hormone can inhibit muscle contraction

Of the energy released during cellular respiration, less than half is used to produce ATP. What is the fate of the rest of the released energy?

It becomes heat

The inability of a muscle to contract after rigorous exercise is the definition of:

Muscle fatigue

Muscle fiber contractions called _______________ result from a single stimulus to a muscle fiber. Each contraction generates the same force. These contractions aren't physiologically useful.

Muscle twitches

Place the following muscle components in order from largest to smallest.

Muscle, fascicle, muscle fiber, myofibirl, protein filament.

During the contraction cycle, what is the result of ATP binding to myosin?

Myosin heads release from the binding site on actin.

Name the type of synapse that occurs between a motor neuron and a muscle fiber

Neuromuscular junction

Step 10 of muscle contraction

The muscle fiber shortens as a contraction occurs.

The ion necessary to allow linkage of myosin and actin

calcium

What best describes myofibrils?

comprised of thick and thin filaments

therefore, layers of _________ enclose and separate all parts of a skeletal muscle.

connective tissue

Skeletal muscles

contraction only in response to nervous stimulation, only response to stimultion is contraction, stretching results in reflexive contraction

What is the equation that best represents how the muscle cell can replenish ATP when ATP levels are low?

creatine phosphate + ADP → creatine + ATP

Each Muscle fiber within a fascicle lies within a layer of connective tissue in the form of a thin covering called_______

endomysium

the layer of connective tissue that closely surrounds a skeletal muscle is called the ________

epimysium

T/F: The cells of visceral smooth muscles function as separate units, independent of neighboring cells.

false

Which muscle fiber type is fatigable?

fast-twitch fibers

Two mechanisms can be used to cause contractions of greater force. One involves increasing the _________ of stimulation. The result is _________ in which each successive contraction is a bit stronger

frequency; summation

As exercise continues, the cells now bein to use __________ as a fuel to produce ATP. Initially, the anaerobic pathway called ____________ uses this fuel to produce 2 ATP and molecules of pyruvic acid.

glucose; glycolysis

The metabolic process that generates two ATP molecules in the cytosol of a muscle fiber is called:

glycolysis

At what level of organization is a skeletal muscle, such as the biceps brachii?

organ

Within a skeletal muscle, fascicles are separated from each other by connective tissue called the _________, and muscle fibers are separated from each other by connective tissue called the _______.

perimysium; endomysium

another layer of connective tissue, called the _____________, extends inward from the epimysium and separates the muscle tissue into small sections. These sections contain bundles of skeletal muscle fibers called __________.

perimysium; fascicles

site of ATP production

mitochondria

The chemicals then bind to receptors located on the _________, a specialized area of the sarcolemma.

motor end plate

At this junction, the _________ releases a type of chemical called a _______.

motor neuron; neurotransmitter

Muscle contraction can cause....

movement of bones, pumping of blood, squeezing of intestinal contents.

threadlike bundles of thick and thin filaments

myofibril

forms cross bridges

myosin

The union between a nerve fiber and a muscle fiber is the _____.

neuromuscular junction

The strength of a muscle contraction in response to different levels of stimulation is determined by the __________.

number of motor units stimulated

The oxygen debt required by muscle and other tissues during _____________. This oxygen is used by the __________ to convert lactic acid into _________ by the ______________ to resynthesize _________________ and creatine phosphate; and by the _________ to restore previous levels of oxygenation.

recovery from vigorous activity; liver cells; glucose ; muscle cells; ATP; blood

Another way of increasing force of contraction is by the process of ___________ during which an increasing number ____________ are stimulated to contract.

recruitment; motor units

The major function of the sarcoplasmic reticulum is skeletal muscle contraction is to:

regulate intracellular calcium concentration

plasma membrane of muscle fiber

sarcolemma

functional unit of contraction within muscle fiber

sarcomere

Thin (actin) filaments are pulled toward the center of the _______ by myosin cross-bridges. The muscle fiber ______ and contracts.

sarcomere; shortens

Name the functional units of contraction in a muscle fiber.

sarcomeres

cytoplasm of muscle fiber

sarcoplasm

Site for storage of calcium

sarcoplasmic reticulum

Muscles respond to the neurotransmitter acetylcholine

skeletal and smooth muscle

According to the sliding-filament mechanism, thin filaments ________.

slide toward the H zone

Smooth Muscles

slow to relax and contract, can be stretched and still maintain tension, contractions include peristalsis, contraction in response to acetylcholine or norepinephrine

muscles are slower to contract and relax than the other muscle type

smooth muscle

muscles can respond to neurotransmitters with inhibition of contraction

smooth muscle

muscles respond to the neurotransmitter norepinephrine

smooth muscle

In a muscle fiber at rest, calcium ions are________

stored in sarcoplasmic reticulum

If the frequency of stimulation is fast enough, a __________ contraction results. This is called _________, during which no relaxation occurs.

sustained; tetanus

Compared to skeletal muscle, smooth muscle:

takes longer to contract and can stay contracted longer

Name the cordlike structures that connect muscles to bone

tendons

muscles respond to hormones

Smooth muscle

Step 5 of muscle contraction

The impulse causes calcium channels to open in the sarcoplasmic reticulum.

T or F: Muscle fatigue is due in part to decreased ATP levels in muscle cells

True

Place the following layers associated with skeletal muscles from superficial to deep.

Epimysium, perimysium, endomysium, sarcolemma, fascia.

As the electrical impulse reaches the ________, permeability of the cisternae to calcium increase

Sarcoplasmic Reticulum

An electrical impulse traveling along the sarcolemma and into transverse tubules causes calcium ions to diffuse from the __________ into the ___________.

Sarcoplasmic reticulum; sarcoplasm

Muscles release calcium into the cytosol when stimulated

Skeletal and smooth muscle

Muscles rely on actin and myosin during contraction

Skeletal and smooth muscle

Muscles have regularly aligned thin and thick filaments

Skeletal muscle

Creatine phosphate (CP) functions within the muscle cells by:

Storing energy that will be transferrred to ADP to resynthesize ATP as needed.

In general, oxygen debt develops as a result of:

Strenuous exercise

The site where the neuron communicates with the muscle fiber is called the ________.

Synapse

These chemicals diffuse across a small gap between the neuron and muscle fiber called the _________.

Synaptic cleft

Step 9 of muscle contraction

Thin filaments are pulled toward the center of the sarcomere by myosin.

the smallest stimulus strength that triggers a contraction of a muscle fiber is called a(n)_______ stimulus

Threshold

The binding of the chemicals to the muscle cell causes an electrical impulse to travel across the sarcolemma and down the __________ tubules.

Transverse

Step 7 of muscle contraction

Tropomyosin molecules move to expose binding sites on actin.

In order for a skeletal muscle to contract, calcium must bind to...

Troponin

After nervous stimulation of a skeletal muscle has ceased, the calcium:

is reabsorbed into the sarcoplasmic reticulum

if little or no oxygen is available, pyruvic acid is converted to _________. If however, oxygen is available, the pyruvic acid molecules enter the aerobic respiration pathways.

lactic acid

The minimal strength stimulus needed to elicit contraction of a single muscle fiber is called a(n) ______.

threshold stimulus

After a muscle fiber is stimulated by a motor neuron, an electrical impulse travels along the sarcolemma and deep into the fiber via _______ tubules.

transverse

channel formed by invagination of plasma membrane

transverse tubule

Blocks myosin binding sites

tropomyosin

Interactions between troponin and ________ results in exposure of binding sites on actin. Then, _______ bind to these sites.

tropomyosin; myosin heads

binding sites for calcium

troponin

T or F: Muscle contraction leads to movement of blood, intestinal contents, and limbs.

true