Unit 3

Which of these structures conduct(s) action potentials the slowest?

AV node

The ________ is the regulation of blood flow by local mechanisms within a capillary bed.

Autoregulation

Why does tetany not occur in cardiac muscle?

Cardiac muscle has a long refractory period that continues until relaxation is well under way. As a result, another action potential cannot arrive quickly enough for summation to occur, and thus tetany cannot occur.

Which of the following can be heard with a stethoscope most easily?

Closing of atrioventricular valves

The beginning of the QRS complex of the electrocardiogram (ECG) immediately precedes which of the following events?

Closing of the atrioventricular valves The QRS complex is a recording of ventricular depolarization. This depolarization begins just prior to the ventricular contraction it initiates. As the ventricles contract, the increase in ventricular pressure closes the atrioventricular valves, beginning isovolumetric contraction. As ventricular pressure increases above the corresponding blood vessel, only then do the semilunar valves open, initiating ventricular ejection.

The ________ lines the chambers of the heart, covers the heart valves, and is continuous with the endothelium.

Endocardium

P-R interval

Period from start of atrial depolarization to start of ventricular depolarization

Which chamber receives blood from the superior and inferior vena cavae?

Right Atrium

Which part of the intrinsic conduction system normally initiates the depolarizing impulse that causes a heartbeat?

SA Node

The volume of blood ejected from each ventricle during a contraction is called the

Stroke Volume

Resting heart rate

Varies with age, general health, physical conditioning Normal range is 60-100 bpm

V fib

Ventricular fibrillation a chaotic quivering of the heart muscle, is the most common dysrhythmia that results in sudden cardiac arrest (SCA). In V-Fib, the heart is not beating effectively and is not pumping blood; therefore, the patient will not have a pulse.

V-tach

Ventricular tachycardia (an increased ventricular heart rate).

Cardiac arrhythmias

abnormal patterns of cardiac electrical activity About 5% of healthy people experience a few abnormal heartbeats each day

During a period of moderate exercise:

arterioles to the skeletal muscles dilate

coronary artery disease

atherosclerosis of the coronary arteries that reduces the blood supply to the heart muscle

P wave

atrial depolarization (contraction)

During the isovolumetric contraction phase of ventricular systole, the

atrioventricular valves and semilunar valves are closed.

cardiac regurgitation

backflow of blood due to imperfect closure of the heart valves

What do semilunar valves prevent?

backflow of blood into the ventricles

Which of the following is not associated with the right side of the heart?

bicuspid valve

Exchange between a blood vessel and the cells that surround it can occur only in

capillaries

Vessels that allow exchange of materials to occur between blood and surrounding tissues are the:

capillaries

One of two factors that determine mean arterial pressure is:

cardiac output

Why is ventricular fibrillation fatal?

causes the condition known as cardiac arrest fatal because the ventricles merely quiver and do not pump blood into the systemic circulation.

Blood flow through the coronary circuit is maintained by

changing blood pressure and elastic rebound

Atherosclerosis

condition in which fatty deposits called plaque build up on the inner walls of the arteries

An increase in sympathetic stimulation of the heart would increase stroke volume by increasing __________.

contractility

Venous return is aided by:

contraction of skeletal muscles one-way valves thoracic pressure ***All of the above***

valvular heart disease

disorders involving valves of the heart that impact the heart's ability to pump blood effectively to the lungs or tissues of the body and cause the heart to work harder

cardiac tampanade

excess accumulation of pericardial fluid - heart fills with fluid so it can't expand

True or False: The AV node serves as a "bridge" that transmits the depolarization wave from the ventricles to atria.

false because the AV node transmits signals from the atria to the ventricles

Purkinje fibers

fibers in the ventricles that transmit impulses to the right and left ventricles, causing them to contract

atrial fibrillation

rapid, random, ineffective contractions of the atrium

electrocardiogram

record of the electrical activity of the heart

isovolumetric contraction

refers to the short period during ventricular systole when the ventricles are completely closed chambers

cardiac skeleton

reinforces the myocardium internally and anchors the cardiac muscle fibers

Which heart chamber pumps unoxygenated blood out the pulmonary trunk?

right ventricle

The pressure within the large arteries of the systemic circulation:

rises if the cardiac output is increased

Mediastinum

space or region in thorax between the two pleural cavities (between the lungs)

As a result of the long refractory period in the cardiac action potential, cardiac muscle cannot exhibit

tetany

If the cells of the SA node failed to function, how would the heart rate be affected?

the heart would still continue to beat, but at a slower rate; the AV node would act as the pacemaker

Heart rate (HR)

the number of heart beats per minute

End Systolic Volume (ESV)

the volume of blood in one ventricle after contraction

End Diastolic Volume (EDV)

the volume of blood in one ventricle before contraction

Stroke Volume (SV)

the volume of blood per heart beat pumped out by one ventricle

Venous Return (VR)

the volume of blood per minute flowing into one atrium

Cardiac Output (CO)

the volume of blood per minute pumped out by one ventricle

The heart is actually (one, two, or three) pumps?

two pumps

Which of the following refers to a decrease in vessel diameter due to smooth muscle contraction?

vasoconstriction

The amount of blood returning to the heart is the

venous return

QRS complex

ventricular depolarization Larger wave due to larger ventricle muscle mass

phases of cardiac cycle

ventricular filling isovolumetric contraction ventricular ejection isovolumetric relaxation

T wave

ventricular repolarization

Heart Sounds: S3 and S4

very faint; rarely heard in adults S3—blood flowing into ventricles S4—atrial contraction

End Diastolic Volume (EDV)

volume of blood in each ventricle at end of ventricular diastole

End Systolic Volume (ESV)

volume of blood remaining in each ventricle after systole

heart sounds: S1 (Lubb)

when AV valves close; marks start of ventricular contraction

Heart Sounds: S2 (Dub)

when semilunar valves close

Cardiac Muscle vs Skeletal Muscle

​Intercalated discs = branching interconnections between cells

the heart wall has 3 layers

pericardium, myocardium, endocardium

Damage to the semilunar valve on the right side of the heart would affect blood flow to which vessel?

pulmonary trunk

The difference between the systolic and diastolic pressures is called the ________ pressure.

pulse

when ventricles are relaxed

*Diastole* they fill AV valves are open Semilunar are closed

when ventricles are contracted

*systole* they empty AV valves are closed Semilunar are Open

Left coronary artery supplies

-Left Atrium -Left Ventricle -Interventricular septum

Components of conducting system:

-Sinoatrial node (SA node) action potential generated -Internodal pathways -Atrioventricular node (AV node) -AV bundle and bundle branches -Purkinje fibers

Right coronary artery supplies

-right atrium -most of the right ventricle -part of the left ventricle -the SA and AV nodes

Match the cardiac components in the left column to the blanks near their functions on the right.

1. AV node: Delay(s) occurs here while atria contract 2. SA node: Set(s) the pace for the entire heart 3. AV bundle : Electrical link(s) between atria and ventricles 4. Purkinje fibers: Convey(s) the impulse throughout the ventricular walls 5. Bundle branches: Convey(s) the impulse down the interventricular septum 6. Internodal pathways: Link(s) between the SA node and AV node

Tachycardia

Heart rate faster than normal (>100 bpm)

Bradycardia

Heart rate slower than normal (<60 bpm)

In cardiac muscle, the fast depolarization phase of the action potential is the result of ________ membrane permeability to ________ ions.

Increased; Sodium

internodal pathways

Interconnect the SA Node with the AV Node, conducts impulses through to the atrial working cells.

Pericardium

Membrane surrounding the heart

Premature atrial contractions (PACs)

Often occur in healthy people Normal atrial rhythm momentarily interrupted by "surprise" atrial contraction Increased incidences caused by stress, caffeine, various drugs that increase permeability of the SA pacemakers

Blood flowing into the heart from the venae cavae flows next through the ________ valve.

Tricuspid

Q-T interval

Time for ventricles to undergo a single cycle

heart failure

a chronic condition in which the heart is unable to pump out all of the blood that it receives

The force of contraction of the left ventricle is

greater than that of the right ventricle

arteriosclerosis

hardening of the arteries

Why is it important for impulses from the atria to be delayed at the AV node before they pass into the ventricles?

if the impulses from the atria were not delayed at the AV node, they would be conducted through the ventricles so quickly by the bundle branches and Purkinje cells that the ventricles would begin contracting immediately, before the atria had finished their contraction. As a result, the ventricles would not be as full of blood as they could be, and the pumping of the heart would not be as efficient, especially during activity.

Which of the following factors will not increase cardiac output?

increased parasympathetic stimulation.

pericarditis

inflammation of the pericardium

endocardium

innermost layer of the heart

Right and left atria are separated by the

interatrial septum

Right and left ventricles are separated by

interventricular septum (much thicker)

In which direction would fluid move between the interstitial fluid (fluid around cells) and the capillary at the venule end of the capillary?

into the capillaries

two phases of ventricular systole

isovolumetric contraction phase and ejection phase

Why can cardiac tamponade be a life-threatening condition?

it interferes with the performance of the heart that if left untreated results in dangerously low blood pressure, shock and death.

The purpose of a stent is to

keep an artery open

coronary ischemia

lack of blood flow to the heart muscle due to a blockage

Which heart chamber receives blood from the pulmonary veins?

left atrium

The pulmonary veins carry blood to the

left atrium of the heart

Which chamber pumps oxygenated blood out the aorta to the systemic circuit?

left ventricle

The space between the pleural cavities containing only the heart, great vessels, thymus, trachea and esophagus is called the

mediastinum

Myocardium

muscular, middle layer of the heart

interventricular septum

partition between the right and left ventricles