Cardiovascular Physiology 1 (9/17b) [Biomedical Sciences 1]

Question 1

Path of RBC from vena cava to vena cava

Answer 1

Vena cava
Right atrium
-Tricuspid Valve
Right Ventricle
-Pulmonary Valve
Pulmonary Circulation
-Pulmonary artery → vein
Left atrium
-Mitral/Bicuspid Valve
Left Ventricle
-Aortic Valve
Systemic circulation
-Aorta → Vena Cava

Question 2

Atrioventricular valves

Answer 2

tricuspid and mitral valves

Question 3

Semilunar valves

Answer 3

aortic and pulmonary valves

Question 4

When do arteries carry deoxygenated blood?

Answer 4

Pulmonary artery carries deoxygenated blood to the lungs to get oxygenated

Question 5

Main functions of cardiovascular system

Answer 5

Deliver enough blood to satisfy metabolic needs

Deliver O2 and nutrients, remove waste

Redistribute cardiac output

Question 6

Range of metabolic demand

Answer 6

measure respiration/oxygen consumption rate to understand metabolic demand

Resting = about 250 mL O2/min

Exercise = about 5000 mL O2/min

Question 7

Cardiac Output (CO)

Answer 7

measure cardiac output (L/min) by Heart Rate (beats/min) x Stroke Volume (mL/beat)

CO = HR * SV

Question 8

Cardiac output increases as heart rate does, but not enough to keep up with oxygen consumption. What is needed?

Answer 8

redistribution of blood

Question 9

During heavy exercise, more of cardiac output will be directed to ___ ___ ___

Answer 9

active skeletal muscle

Question 10

___-____ fold increase in blood flow to active muscle

Answer 10

20-30

Question 11

Sodium-Potassium (Na+/K+) pump

Answer 11

sets up electrochemical gradients

Lots of K+ inside cell, little outside → pumped out

Lots of Na+ outside cell, little inside → pumped in

Creates an electrical potential of about -90 mV in a resting cardiac/muscle cell

An electric current is needed to depolarize the current → action potential

Question 12

Na+/K+ pump creates an electrical potential of about ___ mV in a resting cardiac/muscle cell

Answer 12

-90 mV

Question 13

Action Potential - Skeletal Muscle (Myocytes)

Answer 13

Threshold reached → Na+ channels open quickly and Na+ rushes in (upstroke)

Depolarizes the cell, brings it up a little past neutral

Na+ channels close → K+ channels open and K+ rushes out (downstroke)

All of this happens in about 1-2 milliseconds

Question 14

Action Potential - Cardiac Muscle (Nodal Cells)

Answer 14

Slow calcium (Ca2+) channels open and calcium comes in while potassium is leaving → they oppose each other and makes it a slow process → creates a plateau

Calcium has positive charge, so it keeps depolarizing the membrane; but potassium leaving hyperpolarizes it

Once Ca2+ channels close → membrane potential brought back to -90 mV

Upstroke rapid influx of Na+, plateau is balanced influx of Ca2+ and efflux of K+, downstroke is efflux of K+

happens in about 300 milliseconds

Question 15

Contraction Ability - Skeletal vs Cardiac Muscle

Answer 15

Skeletal muscle → needs innervation to cause contraction, some electrical stimulation needed

Cardiac muscle → could beat on its own without innervation, has sinus or AV nodal cells

Question 16

Automaticity

Answer 16

Nodal cells have an unstable resting potential → creates automaticity (able to beat on its own)

Gradual inward current of Na+ creates funny current

Once threshold is reached → action potential spreads to other myocytes

Question 17

Flow of Signal Conduction

Answer 17

Sinoatrial (SA) node (60-100 bpm)

Atrioventricular (AV) node (40-60 bpm)

Bundle of His (15-40 bpm)

Bundle branches

Purkinje fibers

Question 18

Overdrive suppression

Answer 18

high intrinsic rate of SA node makes it the dominant pacemaker

Ectopic foci can become pacemakers in pathological states

Question 19

AV node delay allows time for…

Answer 19

atrial contraction and ventricular filling

aka leads to coordinated heart beat

Question 20

How do we evaluate the signal of the heart?

Answer 20

with an ECG

Question 21

Normal sinus rhythm is defined by

Answer 21

Regular rhythm

rate between 60-100 bpm

normal shape of waveform (shape of P, QRS, T waves) (duration of PR, ST, and QT intervals)

Question 22

What do P, QRS, and T segments of ECG correspond to in the heart?

Answer 22

P = atrial depolarization

QRS complex = ventricular depolarization (also partly atrial repolarization) (mitral valve closing)

T wave = ventricular repolarization

Question 23

What parts of ECG correspond to ventricular systole and diastole?

Answer 23

Ventricular Systole → beginning QRS complex to end of T wave

Ventricular Diastole → end of T wave to beginning of next QRS complex

Question 24

ECG abnormalities

Answer 24

Sinus tachycardia → fast rhythm

Sinus bradycardia → slow rhythm

Triplet Premature Ventricular Contraction → ectopic foci, wide bizarre signals

Ventricular fibrillation → wavy line with no distinct rhythm/shapes

Atrial fibrillation → lacks P wave

Question 25

The signal that makes the heart beat

Answer 25

the depolarization of cardiac myocytes

Question 26

How does the signal produce a heart beat?

Answer 26

Excitation-Contraction Coupling (E-C Coupling)

Question 27

E-C Coupling - Contraction/Systole

Answer 27

Ca2+ influx during action potential triggers release of Ca2+ from sarcoplasmic reticulum (SR)
(Calcium-induced calcium release)

Ca2+ binds to troponin, causing it to shift, allowing myosin-actin interaction and contraction

Question 28

E-C Coupling - Relaxation/Diastole

Answer 28

Ca2+ falls as it is transported

• Into SR via SERCA pump (requires ATP)
• Out of cell by membrane Ca2+ pump and Na+/Ca2+ exchanger

Fall in Ca2+ causes troponin to shift back, blocking actin-myosin interaction and contraction

Question 29

Echocardiography

Answer 29

uses sound waves to image the heart and evaluate the beat

provides info about stroke volume and ejection fraction

Question 30

Stroke Volume (SV)

Answer 30

the volume of blood ejected each beat

SV = End Diastolic Volume (EDV) - End Systolic Volume (ESV)

Question 31

Ejection Fraction (EF)

Answer 31

the fraction of end diastolic volume ejected each beat

normal is about 50-70%

EF = SV/EDV

Question 32

Issues with heart response

Answer 32

Valve disease (stenosis and regurgitation)

Decreased contractility during systole → systolic dysfunction

Decreased relaxation during diastole → diastolic dysfunction

Question 33

Valve Disease - Stenosis

Answer 33

narrowing of valve opening

Question 34

Valve Disease - Regurgitation

Answer 34

valve allows backflow of blood

Question 35

Phases of Cardiac Cycle

Answer 35

Ventricular Systole (contraction)

• Isovolumetric contraction
• Ejection of blood into aorta

Ventricular Diastole (relaxation)

• Isovolumetric relaxation
• Passive filling of ventricle
• Active filling of ventricle → atrial systole (“atrial kick”)

Question 36

How can the autonomic nervous system charge heart rate?

Answer 36

The sympathetic and parasympathetic systems change the slope of the resting membrane potential by changing Na+/K+ levels, impacting the funny current

Question 37

Cardiac Regulation - Sympathetic

Answer 37

Positive Chronotropic effect → increases slope

Norepinephrine acts on beta-1 receptors in SA node to increase HR

Question 38

Cardiac Regulation - Parasympathetic

Answer 38

Negative Chronotropic effect → decreases slope

Acetylcholine released from vagus nerve acts on muscarinic receptors to decrease HR

Question 39

As HR increases (above ~150 bpm), diastole duration decreases, reduces time for ___ ___

Answer 39

ventricular filling

Question 40

To increase cardiac output, increased HR is accompanied by increased ventricular filling, but how?

Answer 40

Venoconstriction by sympathetic nervous system

Muscle pump - muscles in our legs contract, squeeze veins, push blood back up to heart

Question 41

Factors that affect stroke volume

Answer 41

Preload (increases)
Afterload (decreases)
Contractility (increases)

Question 42

Preload

Answer 42

volume of blood in ventricles at the end of diastole

Directly correlated with SV → increased preload = increased SV

Increased preload → increased stretch on myocyte → stronger contraction → increased stroke volume

Length-tension relationship (Frank-Starling Curve)

Venous return and duration of diastole affect preload

Question 43

Afterload

Answer 43

resistance the ventricle must overcome to eject blood

The left ventricle must overcome aortic pressure

Inversely correlated with SV → increased afterload = decreased SV

Hypertension and aortic stenosis increase afterload, hypotension decreases afterload

Question 44

Contractility

Answer 44

strength of myocardial contraction, calcium dependent

Directly related with SV → increased contractility = increased SV

Inotropy (+/-)affects calcium concentration in myocyte

Question 45

Positive (+) Inotropy

Answer 45

Positive inotropy → increased calcium concentration → stronger contraction → increased stroke volume

SNS → norepinephrine acts on β-1 receptors to increase calcium concentration

Cardiac glycosides (digitalis) also increases calcium concentration

Question 46

Negative (-) Inotropy

Answer 46

Negative inotropy → decreased calcium concentration → weaker contraction → decreased stroke volume

Calcium channel blockers (diltiazem) decrease calcium concentration

Question 47

At the beginning of ___ ___, mitral (on left) and tricuspid (on right) valves close

Answer 47

isovolumetric contraction

Question 48

At the beginning of ___ ___, the aortic valve closes when ventricular pressure falls below aortic pressure

Answer 48

isovolumetric relaxation