Muscle Physiology

What is the role of acetylcholine in calcium release?

Stimulates cellular contraction by opening voltage-gated ion channels

The term that means a continued mild or partial contraction of a muscle that keeps it healthy and ready to respond is muscle _________.

Tone

When muscle contracts upon stimulation, calcium ions bind to______. Which exposes the binding sites for the myosin cross-bridges to attach to.

Troponin

Lactic acid, a byproduct of cellular respiration, is typically produced during _______ respiration.

Anaerobic

What is the cause of rigor mortis

Calcium influx into the sarcoplasm after death

Which one of the following binds calcium ions in a smooth muscle, causing contraction?

Calmodulin

Which of the following statements about smooth muscle is true?

Fibers are small and spindle-shaped

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

All of the above

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

All of the above are true

Which of the following is true about muscle structure?

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

The sequence if electrical changes that occurs along the sarcolemma when a muscle fiber is stimulated is known as the _______.

Action potential

Select the trait that does not characterize muscle tissue in general.

All of these are traits of muscle

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

Calcium

Which of the following does NOT occur during skeletal muscle contraction?

Calcium binds to myosin heads

When the cross-bridges bind to actin. They will pivot in such a manner to cause the actin filaments to slide. This pivoting action causes the actin filaments to slide __________.

Closer together

All of the following terms refer to the ability to receive and respond to a stimulus, EXCEPT _______.

Contractility

The force of a tetanic contraction if greater than that of a twitch contraction because: A. The muscle action potentials are smaller during a tetanic contraction. B. The muscle action potentials travel faster along the transverse tubules. C. More acetylcholine is released at the neuromuscular junction per nerve impulse. D. More Ca2+ is released in a tetanic contraction

D. More Ca2+ is released in a tetanic contraction

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

Diaphragmatic paralysis

Which of the following statements is INCORRECT?

Skeletal muscles are responsible for the pumping action of the heart

Which of the following allows recoil of the muscle fiber when contraction ends?

Elastic filaments

Individual fibers of skeletal muscle have fine sheath of connective tissue called a(n) _________.

Endomysium

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 following correctly identifies muscle components in order from largest to smallest?

Fasciculus, muscle fiber, myofibril

ATP can be made in muscles from stored glucose. In muscles, glucose is stored in the form of __________.

Fat

"Cross bridges" that links between the thick and thin filaments are formed by the ________.

Globular head of thick filaments

In regard to the cross-bridge (CB) 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 following is NOT a characteristic of skeletal muscle contraction

It can contact for long periods of time without tiring

Which of the following substances increases in quantity during repetitive muscle contraction during oxygen deficit?

Lactic acid

The sarcoplasmic reticulum does not:

Make up about 85% of the contents of a muscle fibre.

A motor neuron and all the muscle fibers it supplies is called a(n) ______.

Motor unit

We would expect to find smooth muscle in all of the following EXCEPT:

Myocardial tissue

A sarcomere is part of a(n)

Myofibril

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

Myofibril

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

Myosin

The sensitivity of the smooth muscle contractile apparatus to calcium is known to increase in the steady-state under normal conditions. This increase in calcium sensitivity can be attributed to a decrease in the levels of which of the following substances?

Myosin light chain phosphatase (MLCP)

Each skeletal muscle fiber is controlled by a neuron at a single _______.

Neuromuscular junction

During one cross-bridge (CB) cycle:

One molecule of ATP is used

The alternating contraction and relaxation of opposing layers of smooth muscle is referred to as ______.

Peristalsis

In order to make ATP (adenosine triphosphate) in muscles, creatine phosphate (CP) transfers ______ to adenosine diphosphate (ADP).

Phosphate

Elasticity refers to the ability of a muscle fiber to

Recoil and resume its resting length after being stretched

The refractory period in which the muscle will NOT contract if stimulated occurs during _______ of the muscle cell.

Repolarization

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 fibre shortens, the following also shortens:

Sarcomere

What is the membranous network that surrounds each myofibril?

Sarcoplasmic reticulum

Which of the following 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 following 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 following muscles is voluntary?

The muscle that extends the arm at the elbow

Calcium ions are released from the sarcoplasmic reticulum to initiate muscle contraction and are reabsorbed upon muscle relaxation. Which of the following occurs if calcium ions are not completely reabsorbed?

The next muscle contraction will be greater than the previous muscle contraction

What is the role of tropomyosin is muscle contraction?

To prevent myosin from continuing to slide up the actin filament

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

Within each muscle fibre, more cross-bridges are attached to actin at a given time

The ends of the actin filaments are anchored (attached) to the:

Z-line