Cardiac Physiology and Electrophysiology

the right atrium receives blood from…

vena cava

the right ventricle receives blood from…

right atrium

the left atrium receives blood from…

pulmonary veins

the left ventricle receives blood from…

left atrium

the vena cava receives blood from…

systemic veins

the pulmonary trunk (artery) receives blood from…

right ventricle

the pulmonary vein receives blood from…

veins of the lungs

the aorta receives blood from…

left ventricle 

the right atrium sends blood to…

right ventricle

the right ventricle sends blood to…

lungs

the left atrium sends blood to…

left ventricle

the left ventricle sends blood to…

body except for lungs

the vena cava sends blood to…

right atrium

the pulmonary trunk (artery) sends blood to…

lungs

the pulmonary vein sends blood to…

left atrium

the pulmonary vein sends blood to…

left atrium

the aorta sends blood to…

systemic arteries

where do ascending arteries go to?

1. head and brain

2. arms 

where does the abdominal aorta go to?

trunk

where does the hepatic artery go to?

liver

where do the descending arteries go to?

1. digestive tract

2. kidneys

3. pelvis

4. legs

convection

substances move along in the blood because they are dissolved or contained within it

bulk flow requires a ______ gradient

pressure

flow rate equation and units

1. Q = deltaP / R

2. Q = flow rate 

3. deltaP = pressure difference 

4. R = resistance

flow depends on the pressure ______ not on the _______ pressure

gradient, absolute

resistance to blood flow by Poiseuille’s Law (and units)

1. R = 8ln / pir^4

2. r = radius of tube

3. l = length of tube 

4. n = viscosity of liquid 

Poiseuille Equation (blood flow)

Q = deltaP * ( pir^4 / 8ln )

role of the right heart

1. provides the energy necessary to move blood through the pulmonary vessels

2. allows for oxygenation and removal of carbon dioxide

role of the left heart

provides the energy necessary to move blood through the systemic organs

tricuspid valve

between right atrium and right ventricle

pulmonic valve

between right ventricle and pulmonary artery

mitral valve

between left atrium and left ventricle

aortic valve

between left ventricle and aorta

systole

phase of cardiac cycle where cardiac muscle cells are contracting (can be either atrial or ventricular)

diastole

phase of cardiac cycle where cardiac muscle cells are at rest (can be atrial or ventricular)

where does the interstitial fluid come from?

plasma that leaks from capillaries

pulmonary and system circulation run in _______

parallel

blood that leaves the left side of the heart is _____

oxygenated

blood that enters the right side of the heart is _______

deoxygenated 

the left and right heart handle the _____ volume of blood at the ____ rate

same

each organ system can control blood flow ______ of others

independently

blood conditioning organs

1. modifies the blood as it moves through the tissue 

2. receive increased blood flow compared to their metabolic needs 

meaning of cardiac output

amount of blood pumped per minute from each ventricle

cardiac output formula

CO = SV x HR

what is stroke volume SV?

volume of blood ejected per beat

preload

1. represents the filling of the ventricle that occurs during diastole 

2. reflects Starling’s law, where the more ventricular stretch the more tension that can be generated 

afterload

1. pressure that the heart is working against

2. reflects values within the aorta that the heart must overcome to efficiently eject blood forward 

what is a measure of the heart’s efficiency as a pump?

cardiac output

at rest, the _______ branch of the ANS dominates control of the heart

parasympathetic

as preload increases, so does the strength of the heart’s _______

contraction

the stretch of the ventricle’s cardiac muscle is indicated by ventricular ________

end-diastolic volume 

the force of a ventricle’s cardiac muscle is indicated by _______

stroke volume

positive inotropy is a result of stimuli that increase _______ availability within cardiac muscle cells 

calcium

what effect does hypertension have in terms of afterload?

this creates extra stress on the heart to provide a stronger contraction to overcome the the aortic pressure 

5 requirements for an effective heart as a pump

1. synchronized and regular contractions of individual cardiac cells 

2. valves fully open

3. non-leaky valves

4. muscle contractions are forcefail 

5. ventricle exhibit compliance 

function of arteries

elastic and act as a pressure reservoir

function of arterioles

high resistance and direct blood flow to individual tissues

function of capillaries

leaky vessels that allow for exchange of materials between plasma,ISF, and ICF

function of veins

capacitance vessels that act as a volume reservoir from which the blood can be sent to the arterial side of circulation 

total peripheral resistance TPR

the contraction or relaxation of vascular smooth muscle that modifies overall resistance in the circuit

mean arterial blood pressure MAP formula

MAP = CO x TPR

what are the two phases of the cardiac cycle?

1. diastole (filling)

2. systole (contraction and eventual blood ejection)

left heart cardiac cycle: diastolic phase

valves that separate the atria from ventricles (mitral valve) must passively open in response to ventricular pressure falling blow atrial pressure 

the filling of the ventricle occurs if there is…

1. an appropriate cardiac return

2. ability of AV valves to open fully

3. ability of the ventricular wall to expand passively with little resistance (high compliance)

atrial depolarization (leading to contraction) is captured as what on an EKG recording?

p wave

during normal resting conditions, ________ is not essential for ventricular filling

atrial contraction

what causes the left cardiac cycle: systolic phase?

the movement of an action potential from atrial to ventricular leading to muscle contraction 

ventricular cardiac muscle cells develop tension that result in the following chronological events:

1. mitral valve closes and intraventricular pressure increases in a closed system (isovolumetric contraction)

2. early and rapid ejection period once intraventricular pressure exceeds that in the aorta 

3. peak systolic pressure 

after peak systolic pressure, strength of the contraction diminishes and intraventricular pressure falls which leads to… 

1. closure of aortic valve (dicrotic notch)

2. isovolumetric relaxation phase where pressure falls again below atrial values 

what do the axes of the left heart cardiac pressure volume loop represent?

1. x axis: intraventricular volume 

2. y axis: intraventricular pressure 

what does the bottom left point represent?

1. mitral valve opens

2. ventricle is at lowest volume 

what does the bottom dotted line represent?

ventricular filling, with constant pressure due to stretching (compliance)

what does the bottom right point represent?

1. end-diastolic volume

2. equivalent to preload 

3. mitral valve closes 

what does the right vertical line represent?

1. isovolumetric contraction

2. closed system 

3. the ventricle depolarizes and creates a contraction to produce increasing pressure 

what does the upper right point represent? 

1. aortic valve opens

2. ventricular pressure exceeds aorta 

what does the top arrow represent? 

blood is ejected into aorta 

what does the top left point represent?

1. end-systolic volume 

2. contraction is over 

3. aortic valve closes 

what does the left line represent?

1. isovolumetric relaxation 

2. closed system 

3. ventricular pressure is decreasing as it expands 

what does the width of this graph represent? 

stroke volume 

formula for stroke volume SV

SV = EDV - ESV

what does the ejection fraction indicate?

how much of the filled volume in the left ventricle will be ejected into the aorta 

ejection fraction formula EF

EF = SV / EDV

a ventricle that lacks contractile strength to force blood into the aorta will cause an increase in ________

end-systolic volume

what influences stroke volume ( and ejection fraction)?

1. starling’s law of the heart

2. changes in ventricular afterload 

3. changes to cardiac muscle contractility 

cardiac electrophysiology flow chart

1. SA node

2. internodal pathways

3. AV node

4. AV bundle

5. bundle branches

6. purkinje fibers

the SA node demonstrates _______ over heart rate

dominance

what neurotransmitter causes positive inotropy (or increased contractility of the heart)?

norepinephrine 

what neurotransmitter causes negative inotropy (or decreased contractility of the heart)?

acetylcholine

sympathetic nerves release norepinephrine onto ______ of the _____

B1 receptors, SA node

vagal terminals release acetylcholine onto ______ of the ______

M2 receptors, SA node

location of SA node

upper right atrium

location of AV node

bottom right atrium 

internodal pathways

allows signal from SA node to travel to the AV node, leading to excitation and depolarization of the atrial tissue during travel

bundle branches

allows signal from AV node down into the ventricle

purkinje cells

carries signal to apex of heart and around walls of the ventricles, allowing for depolarization of contraction of the ventricle 

as a result in patients with mutations to gap junction proteins, _____ may result

arrhythmias

the ECG represents the _________ activity of all cells recorded from the surface of the body

summed electrical 

p wave

atrial depolarization

PR segment

conduction through AV node and AV bundle

QRS complex

ventricular depolarization