BIO 163 Chapter 7 Muscular System Test(?) Questions

Collectively, the biceps femoris, semitendinosus, and semimembranosus make up __________.

the hamstrings

Which of the following is the layer of collagen fibers that surrounds the entire muscle?

Epimysium

What are the five primary functions of skeletal muscle?

Move the skeleton, maintain posture and body position, support soft tissues, guard entrances and exits, and maintain body temperature.

Which of these pathways produces carbon dioxide as a by-product?

Aerobic metabolism

What occurs during the latent period of these isometric contractions?

All the steps of excitation-contraction coupling occur

The striated appearance of skeletal muscle results from

actin and myosin arrangement.

What kind of striated muscle tissue is under involuntary control?

cardiac

Unlike skeletal tissue, cardiac muscle tissue __________.

is involuntary, and contains branched cells and intercalated discs

Skeletal muscle is connected to bones by

Tendons

Describe the latent period

The latent period begins at stimulation and the action potential sweeps across the sarcolemma, causing calcium ions to be released by the sarcoplasmic reticulum.

An action potential in a motor neuron triggers the release of which neurotransmitter?

acetylcholine

The graded depolarization in the skeletal muscle fiber that is elicited in response to one action potential from the motor neuron is called

an EPP (end-plate potential)

What is the principle action of the vastus lateralis and the other quadriceps muscles?

extension of the knee

Which of the following is not a phase of a skeletal muscle twitch?

hyperpolarization phase

The term used to describe muscular growth in response to usage is

hypertrophy

What is the role of ATP in cross bridge cycling?

it breaks the myosin-actin cross-bridge, freeing the myosin for the next contraction.

What kind of nervous cells provide support to neurons?

neuroglia

The gastrocnemius is what to the soleus?

posterior

The basic repeating unit of a muscle fiber is called the __________.

sarcomere

The major cause of malignant hyperthermia is uncontrolled release of calcium into the sarcoplasm of muscle cells. What intracellular organelle functions to store and release calcium?

sarcoplasmic reticulum

Skeletal muscles are composed of hundreds to thousands of individual cells called

Fibers

What organelle stores calcium in muscles cells?

Sarcoplasmic reticulum

At the threshold stimulus, do sodium ions start to move into or out of the cell to bring about the membrane depolarization?

Sodium ions move into the cell to bring about the membrane depolarization.

Which muscle dorsiflexes the foot?

tibialis anterior

Describe the contraction phase

In the contraction phase, tension rises to a peak. Throughout this period the cross-bridges are interacting with the active sites on the actin filaments.

List all the metabolic pathways that function to synthesize ATP for skeletal muscle contraction.

Phosphorylation of ADP by creatine phosphate, anaerobic glycolysis, and aerobic metabolism.

Explain how calcium functions to cause contraction of a skeletal muscle cell.

When calcium ions bond to troponin, the protein changes shape, swinging the tropomyosin away from the active sites. Myosin-actin binding can then occur, and a contraction begins. Calcium binding to troponin triggers it to change shape and pivot. This action pulls tropomyosin off the actin binding sites for myosin on the thin myofilament. This sets the stage for cross bridge formation. At this point, the myosin heads have already been activated by the hydrolysis of ATP before cross bridges can form.

What happens when the diaphragm contracts?

When the diaphragm contracts and flattens; it creates more space in the thoracic cavity while reducing the space in the abdominopelvic cavity.

What is the neurotransmitter that is responsible for triggering contraction of muscle fibers?

acetylcholine (ACh)

Malignant hyperthermia causes a high demand for ATP within the muscle cells. Which of the following ATP-consuming events causes skeletal muscles to relax?

active transport of Ca2+ back into the terminal cisterns

During David's hyperthermic crisis, Dr. Hodges reports that he has an elevated level of exhaled carbon dioxide. Which ATP-generating metabolic pathway produces carbon dioxide as a by-product?

aerobic metabolism

the term skeletal muscle fiber refers to

an individual skeletal muscle cell

Which of the following is NOT a muscle for chewing food?

buccinator

David's body temperature rises far above normal during his surgery. Which of the following structures plays a role in regulating body temperature?

both skin and skeletal muscle

Dantrolene is the only drug available to treat malignant hyperthermia. It works by inhibiting calcium channels of the terminal cisterns of the sarcoplasmic reticulum. Explain how this inhibition helps to terminate skeletal muscle contraction. What effect would this have on David's body temperature?

A muscle contraction begins when stored calcium ions in the terminal cistern of the sarcoplasmic reticulum are released into the cytosol of the sarcoplasm, but, if the calcium channels of the terminal cisterns are inhibited, no calcium will be released, therefore muscle contractions will cease. Without muscle contractions, no energy is being converted to heat, meaning David's body temperature would decrease.

What is the role of acetylcholine in a skeletal muscle contraction?

Acetylcholine binds to receptors in the motor end plate, initiating a change in ion permeability that results in the end-plate potential

Describe the process of excitation-contraction coupling in skeletal muscle fibers

An action potential in a motor neuron triggers the release of ACh from its terminal. ACh then diffuses onto the sarcolemma and binds to receptors in the motor end plate, initiating a change in ion permeability that results in a graded depolarization of the sarcolemma (the end plate potential). Depolarization of the end plate leads to an increase of calcium released by the sarcoplasmic reticulum, and more calcium is used by the actin and myosin of sarcomeres to cause contraction.

Describe the relaxation phase

During the relaxation phase, muscle tension falls to resting levels as calcium levels drop, active sites are being covered, and the number of cross-bridges declines.

Will changes to the stimulus voltage alter the duration of the latent period?

No

The drug Dantrolene treats malignant hyperthermia by blocking calcium release into the sarcoplasm and terminating skeletal muscle contractions. Which of the following statements best describes why skeletal muscle relaxes in the absence of calcium?

The active site on actin is blocked by tropomyosin.

Which of the following correctly matches the twitch phase with its definition?

The contraction phase: the time between the end of the latent period and peak muscle tension

What is the role of ATP in generating a resting membrane potential?

When ATP binds to the myosin head, the link between the myosin head and the active site on the actin molecule is broken, breaking the cross-bridge and ending a muscle contraction.

What is the role of ATP in maintaining calcium concentration gradients?

When calcium ions are reabsorbed by the sarcoplasmic reticulum, the tropomyosin returns to its normal position and causes muscle contraction to end. This process is fueled by ATP.

This muscle allows you to do a "pull-up," or pull yourself up from a hanging position.

biceps brachii

A twitch is

one contractile response to a single action potential

The term motor unit refers to

one motor neuron and all of the skeletal muscle fibers it innervates

What is the name of the bone cell that secretes acids and enzymes that dissolve the bony matrix and release the stored minerals through osteolysis?

osteoclast

What is the period of time that elapses between the generation of an action potential and the start of muscle tension development in a muscle fiber?

the latent period

the motor neuron and muscle fiber intersect at what is called

the neuromuscular junction

Which of the following is the large, superficial muscle covering the upper back and portions of the neck?

trapezius

Skeletal muscle contraction is calcium dependent. The protein ________ binds calcium and is part of the _________ myofilament.

troponin; thin