Question 1

The ability to develop increasing levels of force in an intact muscle composed of both fast- and slow-twitch muscle fibers typically involves:

Accepted Answer

A) Recruitment of slow-twitch muscle fibers before fast-twitch muscle fibers. 
B) Tetany of fast-twitch muscle fibers at lower stimulus frequencies than those for tetany of slow-twitch muscle fibers. 
C) A progressive recruitment of more muscle fibers within a given motor unit. 
D) A progressive increase in the amplitude of the intracellular Ca++ transient. 
E) A progressive decrease in the threshold for an action potential in the skeletal muscle. 
A) Recruitment of slow-twitch muscle fibers before fast-twitch muscle fibers. 
B) Tetany of fast-twitch muscle fibers at lower stimulus frequencies than those for tetany of slow-twitch muscle fibers. 
C) A progressive recruitment of more muscle fibers within a given motor unit. 
D) A progressive increase in the amplitude of the intracellular Ca++ transient. 
E) A progressive decrease in the threshold for an action potential in the skeletal muscle. A

Question 2

Endurance training typically increases:

Accepted Answer

A) Ca++ influx into the muscle fiber. 
B) The oxidative capacity of the muscle. 
C) The conversion of slow-twitch muscle fibers into fast-twitch muscle fibers. 
D) The number of muscle fibers within a muscle. 
E) Ca++ extrusion from the muscle fiber. 
A) Ca++ influx into the muscle fiber. 
B) The oxidative capacity of the muscle. 
C) The conversion of slow-twitch muscle fibers into fast-twitch muscle fibers. 
D) The number of muscle fibers within a muscle. 
E) Ca++ extrusion from the muscle fiber. B

Question 3

Relaxation of skeletal muscle after contraction requires:

Accepted Answer

A) Ca++ release by the ryanodine receptor. 
B) Ca++ uptake by sarcoplasmic endoplasmic reticulum calcium-adenosine triphosphatase (SERC
A) . 
C) Ca++ efflux by the plasmalemmal Ca++ pump. 
D) Dephosphorylation of a myosin light chain. 
E) Activation of Rho kinase. 
A) Ca++ release by the ryanodine receptor. 
B) Ca++ uptake by sarcoplasmic endoplasmic reticulum calcium-adenosine triphosphatase (SERC
A) . 
C) Ca++ efflux by the plasmalemmal Ca++ pump. 
D) Dephosphorylation of a myosin light chain. 
E) Activation of Rho kinase. B

Question 4

Stretching a skeletal muscle beyond rest length reduces the force of contraction because of:

Accepted Answer

A) Increased Ca++ sensitivity of actin-myosin interaction. 
B) Increased Ca++ influx through stretch-activated channels. 
C) Decreased actin-myosin overlap. 
D) Decreased Ca++ uptake by the SR. 
E) Decreased intracellular pH. 
A) Increased Ca++ sensitivity of actin-myosin interaction. 
B) Increased Ca++ influx through stretch-activated channels. 
C) Decreased actin-myosin overlap. 
D) Decreased Ca++ uptake by the SR. 
E) Decreased intracellular pH.

Question 5

The speed of contraction of skeletal muscle is related to:

Accepted Answer

A) The oxidative capacity of the skeletal muscle fiber. 
B) The myosin adenosine triphosphatase (ATPase)activity of the skeletal muscle fiber. 
C) The level of β-adrenergic stimulation. 
D) The rate of Ca++ extrusion from the skeletal muscle fiber. 
E) The level of myosin light-chain phosphorylation within the muscle fiber. 
A) The oxidative capacity of the skeletal muscle fiber. 
B) The myosin adenosine triphosphatase (ATPase)activity of the skeletal muscle fiber. 
C) The level of β-adrenergic stimulation. 
D) The rate of Ca++ extrusion from the skeletal muscle fiber. 
E) The level of myosin light-chain phosphorylation within the muscle fiber.

Question 6

Malignant hyperthermia is a hereditary disorder that can increase surgical risk because temperature may be elevated during certain types of anesthesia.The cause of the increased temperature is an increase in cytosolic Ca++ level as a result of an anesthetic-induced:

Accepted Answer

A) Increase in Ca++ release from the SR,as a result of a mutation in the ryanodine receptor. 
B) Decrease in Ca++ uptake by the SR,as a result of a mutation in SERCA. 
C) Increase in frequency of the rupturing of skeletal muscle fibers. 
D) Decrease in Ca++ extrusion,as a result of hyperphosphorylation of the plasmalemmal Ca++ pump. 
E) Increase in Ca++ influx,as a result of a mutation in N-type Ca++ channels. 
A) Increase in Ca++ release from the SR,as a result of a mutation in the ryanodine receptor. 
B) Decrease in Ca++ uptake by the SR,as a result of a mutation in SERCA. 
C) Increase in frequency of the rupturing of skeletal muscle fibers. 
D) Decrease in Ca++ extrusion,as a result of hyperphosphorylation of the plasmalemmal Ca++ pump. 
E) Increase in Ca++ influx,as a result of a mutation in N-type Ca++ channels.

Question 7

During intense exercise,fatigue of skeletal muscle occurs because of:

Accepted Answer

A) Depletion of ATP within the skeletal muscle fiber. 
B) Ca++ overload by mitochondria within the muscle fiber. 
C) Inhibition of actin-myosin interaction. 
D) Stimulation of Ca++ release in the sarcoplasmic reticulum (SR) 
E) Increase in pH within the muscle fiber. 
A) Depletion of ATP within the skeletal muscle fiber. 
B) Ca++ overload by mitochondria within the muscle fiber. 
C) Inhibition of actin-myosin interaction. 
D) Stimulation of Ca++ release in the sarcoplasmic reticulum (SR) 
E) Increase in pH within the muscle fiber.

Question 8

The force of contraction of skeletal muscle can be increased by:

Accepted Answer

A) Activation of additional skeletal muscle fibers within a motor unit. 
B) Increase in the frequency of action potentials within a skeletal muscle fiber. 
C) Increase in β-adrenergic stimulation of the skeletal muscle. 
D) Increase in myosin light chain phosphorylation in the skeletal muscle. 
E) Increase in Ca++ extrusion from the skeletal muscle fiber. 
A) Activation of additional skeletal muscle fibers within a motor unit. 
B) Increase in the frequency of action potentials within a skeletal muscle fiber. 
C) Increase in β-adrenergic stimulation of the skeletal muscle. 
D) Increase in myosin light chain phosphorylation in the skeletal muscle. 
E) Increase in Ca++ extrusion from the skeletal muscle fiber.

Question 9

In the absence of extracellular Ca++,an action potential in a motor neuron fails to initiate contraction of the innervated skeletal muscle because of:

Accepted Answer

A) Inhibition of Ca++ influx into the innervated muscle. 
B) Inhibition of acetylcholine (ACh)binding to receptors on the muscle end plate. 
C) Stimulation of ACh degradation. 
D) Inhibition of ACh release from the motor neuron. 
E) Inhibition of Ca++ binding to troponin C in the innervated muscle. 
A) Inhibition of Ca++ influx into the innervated muscle. 
B) Inhibition of acetylcholine (ACh)binding to receptors on the muscle end plate. 
C) Stimulation of ACh degradation. 
D) Inhibition of ACh release from the motor neuron. 
E) Inhibition of Ca++ binding to troponin C in the innervated muscle.

Exam 12: Skeletal Muscle Physiology

The ability to develop increasing levels of force in an intact muscle composed of both fast- and slow-twitch muscle fibers typically involves:

Endurance training typically increases:

Relaxation of skeletal muscle after contraction requires:

Stretching a skeletal muscle beyond rest length reduces the force of contraction because of:

The speed of contraction of skeletal muscle is related to:

Malignant hyperthermia is a hereditary disorder that can increase surgical risk because temperature may be elevated during certain types of anesthesia.The cause of the increased temperature is an increase in cytosolic Ca++ level as a result of an anesthetic-induced:

During intense exercise,fatigue of skeletal muscle occurs because of:

The force of contraction of skeletal muscle can be increased by:

In the absence of extracellular Ca++,an action potential in a motor neuron fails to initiate contraction of the innervated skeletal muscle because of:

Principles of Cell Function

Homeostasis of Body Fluids

Signal Transduction, membrane Receptors, second Messengers, and Regulation of Gene Expression

The Nervous System: Introduction to Cells and Systems

Generation and Conduction of Action Potentials

Synaptic Transmission

The Somatosensory System

The Special Senses

Organization of Motor Function

Higher Functions of the Nervous System

The Autonomic Nervous System and Its Central Control

Cardiac Muscle

Smooth Muscle

Overview of Circulation

Elements of Cardiac Function

Properties of the Vasculature

Regulation of the Heart and Vasculature

Integrated Control of the Cardiovascular System

Structure and Function of the Respiratory System

Static Lung and Chest Wall Mechanics

Dynamic Lung and Chest Wall Mechanics

Ventilation

Oxygen and Carbon Dioxide Transport

Control of Respiration

Non-Physiologic Functions of the Lung: Host Defense and Metabolism

Functional Anatomy and General Principles of Regulation in the Gastrointestinal Tract

The Cephalic, oral, and Esophageal Phases of the Integrated Response to a Meal

The Gastric Phase of the Integrated Response to a Meal

The Small Intestinal Phase of the Integrated Response to a Meal

The Colonic Phase of the Integrated Response to a Meal

Transport and Metabolic Functions of the Liver

Elements of Renal Function

Solute and Water Transport Along the Nephron: Tubular Function

Control of Body Fluid Osmolality and Volume

Potassium, calcium, and Phosphate Homeostasis

Role of the Kidneys in the Regulation of Acid-Base Balance

Introduction to the Endocrine System

Hormonal Regulation of Energy Metabolism

Hormonal Regulation of Calcium and Phosphate Metabolism

The Hypothalamus and Pituitary Gland

The Thyroid Gland

The Adrenal Glands

The Male and Female Reproductive Systems

Filters

Malignant hyperthermia is a hereditary disorder that can increase surgical risk because temperature may be elevated during certain types of anesthesia.The cause of the increased temperature is an increase in cytosolic Ca⁺⁺ level as a result of an anesthetic-induced:

In the absence of extracellular Ca⁺⁺,an action potential in a motor neuron fails to initiate contraction of the innervated skeletal muscle because of: