Question 1

Stretching cardiac muscle results in an increase in the force of contraction as a result of:

Accepted Answer

A) Activation of K+ channels. 
B) An increase in the sensitivity of actin-myosin interactions to Ca++. 
C) Phosphorylation of the ryanodine receptor. 
D) Increased phosphorylation of troponin I. 
E) Increased Ca++ influx through the Na+-Ca++ antiporter. 
A) Activation of K+ channels. 
B) An increase in the sensitivity of actin-myosin interactions to Ca++. 
C) Phosphorylation of the ryanodine receptor. 
D) Increased phosphorylation of troponin I. 
E) Increased Ca++ influx through the Na+-Ca++ antiporter. B

Question 2

Relaxation of cardiac muscle typically requires:

Accepted Answer

A) Myosin light-chain dephosphorylation. 
B) Activation of the ryanodine receptor. 
C) Ca++ uptake by the sarcoplasmic reticulum (SR). 
D) Phosphorylation of phospholamban. 
E) Activation of the dihydropyridine receptor. 
A) Myosin light-chain dephosphorylation. 
B) Activation of the ryanodine receptor. 
C) Ca++ uptake by the sarcoplasmic reticulum (SR). 
D) Phosphorylation of phospholamban. 
E) Activation of the dihydropyridine receptor. C

Question 3

The mechanisms underlying the development of cardiac hypertrophy are complex,although relaxation abnormalities that result in chronic elevation of cytosolic Ca++ level appear to promote the development of hypertrophy through:

Accepted Answer

A) Stimulation of the sarcolemmal Ca++ pump. 
B) Ca++ binding to troponin I. 
C) Activation of calcineurin. 
D) Inhibition of Ca++/calmodulin-dependent protein kinase. 
E) Opening of Ca++-activated K+ channels. 
A) Stimulation of the sarcolemmal Ca++ pump. 
B) Ca++ binding to troponin I. 
C) Activation of calcineurin. 
D) Inhibition of Ca++/calmodulin-dependent protein kinase. 
E) Opening of Ca++-activated K+ channels. C

Question 4

Cardiac muscle cells in the atria are capable of contracting spontaneously because of a spontaneous depolarization that results from:

Accepted Answer

A) An inward current through a hyperpolarization-activated channel. 
B) Cyclic changes in the activity of Na+,K+-ATPase. 
C) Slow leak of Ca++ through the dihydropyridine receptor. 
D) Cyclic changes in the activity of the sarcolemmal Ca++ pump. 
E) Cyclic changes in the activity of SERCA. 
A) An inward current through a hyperpolarization-activated channel. 
B) Cyclic changes in the activity of Na+,K+-ATPase. 
C) Slow leak of Ca++ through the dihydropyridine receptor. 
D) Cyclic changes in the activity of the sarcolemmal Ca++ pump. 
E) Cyclic changes in the activity of SERCA.

Question 5

Epinephrine increases the force of contraction of cardiac muscle by:

Accepted Answer

A) Increasing the amount of Ca++ in the SR for release to the cytosol. 
B) Increasing the level of myosin light-chain phosphorylation. 
C) Inhibiting the ryanodine receptor. 
D) Increasing Ca++ extrusion through the sarcolemmal Ca++ pump. 
E) Shortening the duration of the action potential. 
A) Increasing the amount of Ca++ in the SR for release to the cytosol. 
B) Increasing the level of myosin light-chain phosphorylation. 
C) Inhibiting the ryanodine receptor. 
D) Increasing Ca++ extrusion through the sarcolemmal Ca++ pump. 
E) Shortening the duration of the action potential.

Question 6

Contraction of cardiac muscle typically requires:

Accepted Answer

A) Ca++ influx through voltage-gated Ca++ channels to trigger a rise in cytosolic [Ca++]. 
B) Ca++ influx through voltage-gated Ca++ channels,which is sufficient to support contraction. 
C) Activation of myosin light-chain kinase (MLCK). 
D) Phosphorylation of myosin heavy chain. 
E) Ca++ influx through the Na+-Ca++ antiporter. 
A) Ca++ influx through voltage-gated Ca++ channels to trigger a rise in cytosolic [Ca++]. 
B) Ca++ influx through voltage-gated Ca++ channels,which is sufficient to support contraction. 
C) Activation of myosin light-chain kinase (MLCK). 
D) Phosphorylation of myosin heavy chain. 
E) Ca++ influx through the Na+-Ca++ antiporter.

Question 7

Mutations in the cardiac ryanodine receptor have been associated with cardiac arrhythmias.Specifically,a mutation in the cardiac ryanodine receptor that increases Ca++ efflux from the SR promotes the development of delayed afterdepolarizations by:

Accepted Answer

A) Decreasing the activity of calcineurin. 
B) Increasing Ca++ efflux through the Na+-Ca++ antiporter. 
C) Increasing mitochondrial Ca++ uptake. 
D) Decreasing actin-myosin interactions. 
E) Increasing the activity of K+ channels. 
A) Decreasing the activity of calcineurin. 
B) Increasing Ca++ efflux through the Na+-Ca++ antiporter. 
C) Increasing mitochondrial Ca++ uptake. 
D) Decreasing actin-myosin interactions. 
E) Increasing the activity of K+ channels.

Question 8

The force of contraction of cardiac muscle is typically increased by:

Accepted Answer

A) An increase in Ca++ extrusion by the Na+-Ca++ antiporter in cardiac muscle. 
B) An increase in myosin phosphorylation in cardiac muscle. 
C) A decrease in cytosolic [Ca++] in the cardiac muscle. 
D) β-Adrenergic stimulation of the cardiac muscle. 
E) Recruitment of more cardiac muscle cells. 
A) An increase in Ca++ extrusion by the Na+-Ca++ antiporter in cardiac muscle. 
B) An increase in myosin phosphorylation in cardiac muscle. 
C) A decrease in cytosolic [Ca++] in the cardiac muscle. 
D) β-Adrenergic stimulation of the cardiac muscle. 
E) Recruitment of more cardiac muscle cells.

Question 9

Calsequestrin in cardiac muscle:

Accepted Answer

A) Acts as a high-affinity Ca++ buffer in the cytosol. 
B) Acts as a low-affinity Ca++ buffer in the SR lumen,near the ryanodine receptor. 
C) Promotes Ca++ accumulation by the mitochondria. 
D) Increases the Ca++ affinity of the sarcolemmal Ca++ pump. 
E) Facilitates myosin binding to the actin thin filament. 
A) Acts as a high-affinity Ca++ buffer in the cytosol. 
B) Acts as a low-affinity Ca++ buffer in the SR lumen,near the ryanodine receptor. 
C) Promotes Ca++ accumulation by the mitochondria. 
D) Increases the Ca++ affinity of the sarcolemmal Ca++ pump. 
E) Facilitates myosin binding to the actin thin filament.

Exam 13: Cardiac Muscle

Stretching cardiac muscle results in an increase in the force of contraction as a result of:

Relaxation of cardiac muscle typically requires:

The mechanisms underlying the development of cardiac hypertrophy are complex,although relaxation abnormalities that result in chronic elevation of cytosolic Ca++ level appear to promote the development of hypertrophy through:

Cardiac muscle cells in the atria are capable of contracting spontaneously because of a spontaneous depolarization that results from:

Epinephrine increases the force of contraction of cardiac muscle by:

Contraction of cardiac muscle typically requires:

Mutations in the cardiac ryanodine receptor have been associated with cardiac arrhythmias.Specifically,a mutation in the cardiac ryanodine receptor that increases Ca++ efflux from the SR promotes the development of delayed afterdepolarizations by:

The force of contraction of cardiac muscle is typically increased by:

Calsequestrin in cardiac muscle:

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

Skeletal Muscle Physiology

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

The mechanisms underlying the development of cardiac hypertrophy are complex,although relaxation abnormalities that result in chronic elevation of cytosolic Ca⁺⁺ level appear to promote the development of hypertrophy through:

Mutations in the cardiac ryanodine receptor have been associated with cardiac arrhythmias.Specifically,a mutation in the cardiac ryanodine receptor that increases Ca⁺⁺ efflux from the SR promotes the development of delayed afterdepolarizations by: