anatomy Dynamic study

Which of the following is the dark band seen on myofibrils?

A band

What causes the myosin head to release its attachment to actin?

A new ATP molecule binds to the myosin head.

_______ is required to detach cross-bridges and reactivate the myosin head.

ATP

Layers of smooth muscle in the reproductive tract of the female are important for __________. All of the listed responses are correct. Unselected movement of oocytes Unselected delivery of a newborn during parturition Unselected movement of sperm if present

All of the listed responses are correct.

Which of the following may cause muscle atrophy? All of the listed responses are correct. Unselected A lack of regular stimulation of muscle fibers Unselected Wearing a cast on a broken limb Unselected Paralysis

All of the listed responses are correct.

Which of the following is NOT found in the endomysium? all of these are present in the endomysium. Unselected Capillary networks Unselected Nerve fibers Unselected Myosatellite cells

All of these are present in the endomysium.

What is the term for the ability of cardiac muscle cells to contract without neural stimulation?

Automaticity

What must bind to troponin in order to expose the active sites on actin?

Calcium ions

In smooth muscle cells, calcium binds to which regulatory protein to initiate contraction?

Calmodulin

The cardiovascular system uses which types of muscle?

Cardiac and smooth

What provides ATP for the first 15 seconds of a muscle contraction?

Creatine phosphate

Which of the following would NOT be an effective source of energy for muscle contraction?

DNA

Which of the following would NOT be an effective source of energy for muscle contraction? DNA Unselected Glycogen Unselected ATP Unselected Creatine phosphate

DNA

Which connective tissue layer wraps around the entire muscle?

Epimysium

Which of the muscle fiber types is best adapted for a rapid contraction but fatigues easily?

Fast fibers

What structure is responsible for the spread of action potential between visceral smooth muscle cells?

Gap junctions

Which of the following is an example of an isometric contraction?

Holding a heavy stack of books above the ground

What is the effect of acetylcholine on the motor end plate of the muscle cell membrane?

Increasing the permeability to Na+, causing Na+ to diffuse into the muscle cell

What is the name of the structure that contains gap junctions and desmosomes and joins the plasma membranes of two cardiac muscle cells together?

Intercalated discs

Pushing both hands against a nonmoving wall represents which type of muscle contraction?

Isometric

How does the release of calcium ions from the terminal cisternae initiate contraction?

It triggers the binding of myosin to actin.

What happens in the muscle fiber during the Cori cycle?

Lactic acid is shuttled to the liver and glucose is shuttled back to the muscle fiber from the liver.

Why is control over leg muscles LESS precise than control over the muscles of the eye?

Many muscle fibers in the legs are controlled by a single motor neuron.

The H band contains which structures?

Only myosin in the thick filaments

Which of the following is NOT a characteristic of smooth muscle tissue?

Presence of striations

Where is the site of calcium storage in the skeletal muscle fibers?

Sarcoplasmic reticulum

Which type of tissue is responsible for holding your head upright while you are reading this question?

Skeletal muscle tissue

What are the three types of muscle tissue?

Skeletal, cardiac, and smooth

Marathon runners rely on which muscle fiber type for endurance?

Slow fibers

Which of the following activities describes an isotonic eccentric contraction?

Slowly lowering a book out in front of you with the arm extended.

Structurally, how do smooth muscle cells differ from skeletal muscle cells?

Smooth muscle cells lack myofibrils and sarcomeres.

Which type of muscle tissue causes contraction of the urinary bladder, forcing urine out of the body?

Smooth muscle tissue

Cardiac muscle has the feature of automaticity, which is the ability to contract without neural stimulation. Which of the following statements accurately explains this feature?

Specialized pacemaker cells within the heart determine the rate of contraction of heart muscl

Which structure in a muscle fiber or muscle cell is continuous with the sarcolemma and carries the signal to contract deep into the muscle cells?

T tubules

The transmission of an action potential along the T tubules stimulates the release of calcium from which structure in the sarcomere?

Terminal cisterna

What is happening during the contraction phase of a single twitch?

The muscle is producing tension.

What causes the myosin head to reenergize itself once the power stroke has occurred?

The myosin head splits a fresh ATP molecule.

What happens during the power stroke?

The thin filaments slide toward the M line

What is a characteristic of cardiac muscle that is NOT true of skeletal muscle?

They lack terminal cisternae

What structures make up a triad?

Two terminal cisternae and a T tubule

When would we use the contractile proteins in our skeletal muscle cells to provide energy?

When our diet contains too few proteins or calories

Which of the following has been correlated with muscle fatigue?

a decline in pH within the muscle, which alters enzyme activities

Smooth muscle contractions in the respiratory passageways cause __________.

a decrease in diameter, making it harder for air to flow

The thin filaments consist of __________.

a pair of F-actin molecules twisted together

A single stimulation-contraction-relaxation sequence in a muscle fiber is known as ________.

a twitch

The thick filaments consist of __________.

about 300 myosin molecules twisted around one another

The neurotransmitter required to trigger skeletal muscle contraction is __________.

acetylcholine (ACh)

The sliding of __________ over ___________ causes shortening of skeletal muscle fibers.

actin; myosin

The length of time a muscle can continue to contract while supported by mitochondrial activities is referred to as __________.

aerobic endurance

What are the two mechanisms used to generate ATP from glucose?

aerobic respiration and glycolysis

What allows the contraction cycle to repeat so that shortening of the sarcomere happens? All of the choices are correct. Unselected Calcium levels remain high in the sarcomere. Unselected ATP is continuously supplied by the mitochondria. Unselected The active site on actin remains exposed.

all are correct

What can happen when multiple stimuli are applied to a muscle fiber before it completely relaxes and tension production is gradually increasing? All of the listed answers are correct. Unselected Incomplete tetanus Unselected Complete tetanus Unselected Wave summation

all are correct

A blending of epimysium, perimysium, and endomysium that forms a broad sheet at the end of a muscle is known as __________.

an aponeurosis

As a result of physical inactivity, muscle cell and myofibrils will be reduced in size and number, respectively. This condition is known as __________.

atrophy

Unlike skeletal muscles, cardiac muscle fibers do not require autonomic stimulation to depolarize and contract. This property is known as ___________.

automaticity

Mitochondrial activities are relatively efficient, but their rate of ATP generation is limited by the __________.

availability of oxygen

The first step in the contraction cycle in skeletal or cardiac muscles is when ______ binds to ________.

calcium; troponin

Depolarization of the skeletal muscles at the NMJ occurs as a result of acetylcholinebinding and opening the _____________.

chemically gated sodium channels

During __________, the muscle fiber is rapidly and continuously being stimulated and is never allowed to relax completely.

complete tetanus

The length of a sarcomere determines the degree of tension produced. For optimal contraction, the ideal range of sarcomere length is 75 percent to 130 percent of its normal length. This is because at this range, there is a maximal number of _______ that can be formed during contraction.

cross-bridges

In an isotonic contraction, __________.

cross-bridges must produce enough tension to exceed the load to be moved

After contraction, a muscle fiber returns to its original length because of __________.

elastic forces and the movement of opposing muscles

Excitation-contraction coupling forms the link between __________.

electrical activity in the sarcolemma and the initiation of a contraction

During the recovery period, the body's oxygen demand is __________.

elevated above normal resting levels

The connective tissue layer that surrounds a single muscle fiber and joins it to other muscle fibers is __________.

endomysium

Nerves and blood vessels are contained within the connective tissues of the __________.

epimysium, perimysium, and endomysium

The perimysium surrounds a bundle of muscle fibers called a __________.

fascicle

The primary source of energy in a resting muscle fiber is ___________.

fatty acids

Which of the following produces ATP from glucose anaerobically?

glycolysis

Voluntary control over swallowing, defecation, and urination is provided by muscles that __________.

guard entrances and exits

A muscle producing almost peak tension during rapid cycles of contraction and relaxation is said to be in __________.

incomplete tetanus

The process of complete tetanus is reached by __________.

increasing the rate of stimulation until the relaxation phase is completely eliminated

What is the type of contraction in which the muscle does not change length and the contraction does not produce tension that exceeds the load?

isometric

During anaerobic muscle metabolism, _______ is produced as the end product of glycolysis.

lactate

When glycolysis produces pyruvic acid faster than it can be used by the mitochondria, the pyruvic acid is converted to __________, which lowers the pH of body fluids.

lactic acid

Heat released from contracting muscles functions to __________.

maintain body temperature

All the muscle fibers and the single motor neuron that innervates them are called a __________.

motor unit

Inherited disorders that produce progressive muscle weakness and deterioration within muscles are called ______________.

muscular dystrophies

One of the distinct features of the skeletal muscle fibers is that they are multinucleated. The multinucleation is the result of the fusion of embryonic cells called __________.

myoblasts

Skeletal muscles develop from the conjoining of a group of embryonic cells knows as _______.

myoblasts

Presence of _______ in the sarcoplasm provides a ready supply of oxygen for aerobic respiration in muscle tissue.

myoglobin

Which of the following is NOT found in a thin filament? Myosin Unselected Troponin Unselected Tropomyosin Unselected Actin

myosin

What structure below is part of the crossbridge?

myosin head

The amount of tension produced by an individual muscle fiber ultimately depends on the __________.

number of pivoting cross-bridges

Skeletal muscles generate maximum tension when the maximum number of cross-bridges can form in the zone of _______.

overlap

The connective tissue layer that surrounds a bundle of skeletal muscle fibers is called __________.

perimysium

The wave-like contraction created by smooth muscle cells is known as ________.

peristalsis

When lifting a heavy weight, more motor neurons are called into action to overcome the weight by creating a greater tension. This phenomenon is known as _________.

recruitment

Myofibrils are formed as a result of repeating functional units called __________.

sarcomeres

The repeating functional units seen in the myofibrils are __________.

sarcomeres

A high blood concentration of the enzyme creatine phosphokinase (CPK) usually indicates __________.

serious muscle damage

Extensive blood vessels, mitochondria, and myoglobin are found in the greatest concentration in __________.

slow fibers

The type of skeletal muscle fiber best suited for endurance-type activities is __________.

slow fibers

What type(s) of muscle tissue do(es) NOT contain sarcomeres?

smooth

The connective tissue fibers of the epimysium, perimysium, and endomysium extend beyond the skeletal muscle cells to form a bundle of connective tissue that joins the muscle cells to a bone. This bundle is called a(n) __________.

tendon

The regulatory protein responsible for elasticity of skeletal muscles is _________.

titin

The regulatory protein responsible for binding to calcium for contraction to proceed is _____.

troponin