Lecture 10

SV+IV, RA, tricuspid valve, RV, pulmonary valve, pulmonary trunk, R/L pulmonary arteries, lungs, R/L pulmonary veins, LA, mitral/bicuspid valve, LV, aortic valve, aorta, rest of the body

what is the pathway of blood

contractile and pacemaker cells

what are the two kinds of cardiac muscle cells (myocytes)

contractile cells

responsible for contraction: push/pump blood

pacemaker cells

noncontractile cells that spontaneously depolarize; do not need nervous system stimulation.

true

is it true that all cardiomyocites contract as a unit, or none contract at all. contraction of all cardiac myocytes ensures effective pumping action

presence of gap junctions

coordinated heartbeat is a function of what?

c

Which of the following statements is true?

a) All arteries transport oxygen rich blood.

b) The right side of the heart is the systemic

circuit pump

c) Equal volumes of blood are pumped to the

pulmonary and systemic circuits at any

moment

d) The left side of the heart pumps blood to the

lungs

independently

how do skeletal muscles contract

intrinsic cardiac conduction system

network of specialized cells (noncontractile cells) that are electrically connected to cardiac muscle cells via gap junctions. this system initiates the heartbeat and helps spread an action potential rapidly throughout the heart.

pacemaker cells

which cells initiate the action potential

SA node, av node, av bundle (bundle of his), R and L bundle branches, purkinje fibers

what is the sequence of excitation in which the cardiac pacemaker cells pass impulses

B because if it’s damage, that when the AV node takes over so it still beats, it’s just slower

A patient has damage to the SA node. Which of the following is most likely to occur?

A. The ventricles stop contracting completely
B. The heart rate slows, but contraction still occurs
C. The atria contract faster than normal
D. Electrical signals cannot reach the ventricles

B

A blockage occurs at the AV node. What is the most likely outcome?

A. Atria and ventricles contract together normally
B. Ventricles will not receive signals from the atria
C. SA node stops functioning
D. Blood flow increases

A, because the AV bundle is only one that is responsible for the electrical connection to ventricles

A patient has damage to the AV bundle (Bundle of His). What happens?

A. Electrical signal cannot reach the ventricles efficiently
B. Atria stop contracting
C. SA node stops generating impulses
D. No effect on heart function

A

A patient has damage to the AV bundle (Bundle of His). What happens?

A. Electrical signal cannot reach the ventricles efficiently
B. Atria stop contracting
C. SA node stops generating impulses
D. No effect on heart function

SA node because it is the pacemaker that generates impulses

Question 4

Which structure is responsible for initiating the heartbeat?

A. AV node
B. Purkinje fibers
C. SA node
D. Bundle branches

B

A patient has a condition where the ventricles contract too slowly. Which structure is most likely malfunctioning?

A. SA node
B. AV node
C. Purkinje fibers
D. Atria

C

Electrical signals are generated normally, but ventricles contract in an uncoordinated way. Which structure is likely affected?

A. SA node
B. AV node
C. Purkinje fibers
D. Atria

B

A patient’s EKG shows that the atria contract, but ventricles do not follow properly. Where is the problem?

A. SA node
B. AV node
C. Purkinje fibers
D. Bundle branches

B

Which structure ensures that the ventricles contract AFTER the atria?

A. SA node
B. AV node
C. Bundle branches
D. Purkinje fibers

AV node problem

if atria work but ventricles don’t

SA node problem

if heart is slow but still beating

purkinje fibers problem

if ventricles are uncoordinated whose problem is it

AV bundle problem

if electrical signal can’t reach ventricles

bundle branches problem because they supposed to contract at the same time

one ventricle contracts later than the other

sa node

pacemaker that generates impulses about 75x/min

calcium

what ion causes depolarization in pacemaker cells

repolarization

k+ channels open, allowing efflux of K+, and cell becomes more negative. Potassium pouring outside of the cell

Artificial pacemaker

if AV node is defective, it may cause a heart block. Would be too slow to maintain adequate circulation. What should you do to treat this? It will help to recouple the atria and ventricles

ensures efficient ejection of blood

what is the benefit of longer action potential and contraction

contractile muscle fibers

make up bulk of heart muscle and are responsible for pumping action

depolarization

action potential of contractile cardiac muscles. due to Na+ influx through fast voltage gated sodium channels. a positive feedback cycle rapidly opens many Na+ channels, reversing the membrane potential. Channel inactivation ends this phase.

plateau phase

is due to calcium influx through slow calcium channels. this keeps the cell depolarized because most K+ channels are closed. happens only in contractile cells

repolarization

is due to calcium channels inactivating and K+ channels opening. this allows k+ efflux, which brings the membrane potential back to its resting voltage

P wave

atrial depolarization, initiated by the SA node. depolarization of SA node and atria

QRS wave

ventricular depolarization begins at apex, causing this to occur. Atrial repolarization also occurs

t wave

ventricular repolarization

P-R interval

beginning of atrial excitation to beginning of ventricular excitation

s-t segment

entire ventricular myocardium depolarized

q-t interval

beginning of ventricular depolarization through ventricular repolarization

electrocardiogram (ecg or ekg)

composite of all action potentials at given time, not a tracing of a single AP

enlarged ventricles

enlarged r waves may indicate what?

cardiac ischemia

elevated or depressed s-t segment indicates what problem?

ventricular arrhythmias

prolong q-t interval reveals a repolarization abnormality that increases risk of what?

systole

period of heart contraction and blood ejection

diastole

period of heart relaxation and blood filling

cardiac cycle

blood flow through heart during one complete heartbeat

a

in a normal heart, which of the following structures is responsible for setting the heart’s pace

a. sinoatrial node

b. atrioventricular node

c. atrioventricular bundle

d. purkinje fibers

cardiac output

amount of blood pumped by the heart per minute

ventricular fibrillation

electrical activity is disorganized. Action potentials occur randomly throughout the ventricles. results in chaotic, grossly abnormal ECG deflections. seen in acute heart attack and after an electrical shock

d

damage to cells of the AV bundle would prevent the cardiac impulse from reaching this:

a. sa node

b. atria

c. av node

d. ventricles

c

Predict the nature of an ECG recording when the

atrioventricular node becomes the pacemaker.

a) There would continue to be a normal sinus rhythm.

b) The P wave would be much larger than normal.

c) The rhythm would be slower.

d) The T wave would be much smaller than normal.

electrical and then contraction happens

which happens first: electrical or mechanical events

before

do atria contract before or after ventricles

atrial diastole/systole

which occurs first atrial diastole/systole or ventricular diastole/systole

fill; pump

Atria contract first to ___ ventricles, then ventricles contract to ___ blood out.

cardiac cycle

represents series of pressure and blood volume changes

end diastolic volume

volume of blood in each ventricle at end of ventricular diastole before being pumped out by ventricular systole

isovolumetric ventricular contraction

first part of systole, in which the ventricles are contracting, but blood cannot leave them, since all of the valves are close

ventricular; aorta; pulmonary trunk

I am looking for four words: period of ventricular contraction, in which blood is forced out of ventricles, into the ___ and _____ ______

pressure

aortic and pulmonary valves are forced open by rising ___ in the ventricles

stroke volume

is the volume of blood ejected from each ventricle during systole

ventricular systole

they don’t clash or do the same thing at the same time. So atrial diastole equals

ventricular diastole

they don’t clash or do the same thing at the same time. so atrial systole equals

AV valves

rising ventricular pressure in the isovolumetric contraction phases causes the closing of what valves in order for the blood to not backflow into the atria

AV valve

between atria and ventricles

SL valves

when ventricular pressure exceeds pressure in large arteries, which valves will open.

semilunar valves

between ventricles and arteries

isovolumetric ventricular relaxation

First part of diastole, in which the ventricles

begin to relax, the aortic and pulmonary valves

close, and no blood is entering or leaving the

ventricles. The AV valves are also closed, and ventricular

volume is not changing.

• following ventricular repolarization (T wave), ventricles relax

• end systolic volume

• ventricular pressure drops causing backflow of blood from aorta and pulmonary trunk that triggers the closing of the semilunar valves because now ventricular pressure does not exceed the pressure in large arteries

• ventricles are completely closed chambers momentarily

end systolic volume

the amount of blood left remaining in each ventricle after systole

ventricular filling

the av valves then open, and blood flows from the atria into ventricles. The atria contract at end of ventricular diastole, but 80% of this occurs passively before atrial contraction.

atrial systole

Contraction of the atrial myocardium

is called this:

lub; av

the first heart sound is caused by ___ valves closing at the beginning of ventricular systole

dup; semilunar

the second heart sound is caused by ___ valves closing. occurs between the second heart sound and the first heart sound of the next cycle. or you could say at the beginning of ventricular diastole

lub-dup

what are the two heart sounds associated with the closing of heart valves

b

•During the period of ejection in the cardiac cycle, the AV valves are ___ and the semilunar valves are _____.

• a. closed, closed

• b. closed, open

• c. open, closed

• d. open, open

av valves close, semilunar valves close, heart murmurs (volume problem), pressure problem

what is s1, s2, s3, s4

hr x sv

what is the cardiac output formula

incompetent valve

fails to close completely, allowing backflow of blood. causes a swishing sound as blood regurgitates back from the ventricle into atria

stenotic valve

fails to open completely, restricting blood flow through valve. Causes high pitched sound or clicking as blood forced through narrow valve.

EDV - ESV

what is the stroke volume formula

bradycardia

HR slower than 60 beats per minute

tachycardia

HR greater than 100 beats/min

preload, contractility, and afterload

what are the three main factors that affect stroke volume

preload

how much the ventricle is filled (EDV) (the volume of blood in the ventricles just before contraction)

contractility

how hard the heart squeezes. it is affected by the sns (epinephrine) and excess calcium. this will mean the stronger the contraction the more blood it pushes out, and less blood left behind.

afterload

the arterial pressures against which the ventricles pump. the pressure the heart must push against. if resistance is high, it will be harder to push blood out. so having higher of this will mean more effort to push out and stroke volume doesn’t like that, less blood would be ejected because of it.

frank-starling mechanism

the ventricle contracts more forcefully during systole when it has been filled to a greater degree during diastole. The greater the EDV, the greater the stretch and the more forceful the contraction

lower stroke volume

high afterload means ___ stroke volume

higher

high contractility means ____ stroke volume

high

high preload means ____ stroke volume

venous return

the flow of blood from the veins into the heart

venous return

an increase in this will automatically force an increase in cardiac output by increasing end diastolic volume and, therefore, stroke volume

increases stroke volume because then it will eject more blood

what does increased contractility do to stroke volume

exercise and slow heartbeat

what increases venous return

increased contractility

what is caused by sympathetic epinephrine release stimulates increased ca2+ influx , leading to more cross bridge formations

hypertension

what increases afterload, resulting in increased ESV, and reduced stroke volume

congestive heart failure

cardiac output is so low that blood circulation is inadequate to meet tissue needs

coronary atherosclerosis

clogged arteries caused by fat buildup; impairs oxygen delivery to cardiac cells. heart becomes hypoxic, contracts inefficiently.

persistent high blood pressure

causes myocardium to exert more force