Physiology Exam 1: Cardiac Dynamics

Front 1

The volume of blood ejected by EACH ventricle per unit of time is the definition of?

Back 1

Cardiac Output

Front 2

What is the measurement of Cardiac Output at rest?

Back 2

5-6 L/min

Front 3

What are the percentages of Cardiac Output for:
Brain
Cardiac Muscle
Kidneys

Back 3

Kidneys: 20-25%
Brain: 13%
Cardiac Muscle: 4%

Front 4

What is normal heart rate?

Back 4

80 bpm

Front 5

What is the difference for the SV in the ventricles?

Back 5

Usually the same for both ventricles

Front 6

Which ventricle is Cardiac Output usually referring to?

Back 6

Left Ventricle

Front 7

What is the normal SV?

Back 7

70-80 mL/systole

Front 8

What 3 factors is the SV affected by?

If these remain constant, what is SV determined by?

Back 8

Venous Return
Peripheral Resistance
Autonomic Nervous System

If all those remain constant, Force of Contraction determines SV. (Basis of Frank-Starling Law)

Front 9

What happens to the SV and CO if the HR increases between 90-140 bpm ?

Back 9

CO increases proportionally
SV will decrease due to less filling time

Front 10

If the HR increases beyond 140 bpm, how does Cardiac Output respond?

Back 10

It will now decrease because the SV decreases faster than the increase in HR.

Front 11

Will the heart automatically eject ALL the blood that enters it over a broad range of volume?

Back 11

Yes, ALL of it.

Front 12

What makes it possible for the heart to automatically eject ALL the blood that eneters it over a broad range of volume?

Back 12

The striated nature of the cardiac muscle.
It's force of contraction is proportional to the degree of stretch (up to a limit!....!!...!!!!!)

Front 13

What is the force of contraction of the cardiac muscle proportional to?

Back 13

Degree of Stretch
Length of the Ventricular Muscle Fibers

Front 14

What does the proportionality of the force of contraction with the length of the ventricular muscle fibers imply?

Back 14

That ALL the extra blood resulting from increased venous return is pumped out.

Front 15

What determines the initial LENGTH of the Ventricular Muscle Fibers ?

Back 15

The quantity of blood in the ventricles just prior to their contraction. This is called the End Diastolic Volume.

Front 16

What determines the degree of TENSION of the cardiac muscle when it begins to contract?

Back 16

The Pre-load, which is determined by the End Diastolic Volume.

Front 17

According to the Frank-Starling Law, what does any change in the Venous Return have a direct effect on?

Back 17

Stroke Volume and therefore, the Cardiac Output

Front 18

What is the pathway of an increase in venous return?

Back 18

Increased Venous Return = Increase in strength of contraction = increased SV = Increased CO

Front 19

Does increasing the Blood Pressure have a similar effect as an increase in the Venous return on Cardiac Output?

Back 19

Yes, but indirectly.
Increased BP = Increased Resistance = Decreased SV = Increased EDV = Increased strength of myocardial contraction = Increased SV = Increased CO

Front 20

After the initial adjustment by the Frank-Starling Law, what takes over and begins to regulate the strength of contraction (and thus Cardiac Output)?

Back 20

Homeometric Regulation takes over the heart so the muscular stretch returns to normal.

Front 21

Does the metabolism of the myocardium depend on the degree of stretch of the myocardium?

Back 21

No

Front 22

What are the valves called between the Atrium and Ventricles?

Back 22

Cuspid Valves

Front 23

What are the valves called between Ventricles and great Arteries?

Back 23

Semi-Lunar Valves

Front 24

What is the cause for the heart Lub-Dup sounds?

Back 24

Closing of heart valves.
The first sound is the closure of the Cuspid valves, and the second with a higher frequency is due to the closure of the Semi-lunar valves.

Front 25

What are the leaflets of the valves covered with?

Back 25

Endothelial Tissue

Front 26

What are the divisions between the cusps called?

Back 26

Commissures

Front 27

What two things do the Chordae Tendinae anchor together? What is this meant to prevent?

Back 27

The A-V valves (cuspid) have their ventricular surface anchored to the Ventricular wall.
This prevents blood reflux (heart murmur)

Front 28

The Cardiac cycle is marked from where to where?

Back 28

Beginning of one cycle (THE END OF SYSTOLE when both atria are being filled with returning blood, and all valves are closed) to the beginning of the next

Front 29

How is each cardiac cycle initiated?

Back 29

By SPONTANEOUS generation of an action potential in the SA node.

Front 30

What is the pathway from the beginning of the Action potential in the Atria?

Back 30

A-V node
Bundle of HIS
Bundle Branches
Purkinje Fibers
FInally all the cardiac fibers

Front 31

In regards to the Action Potential, what contributes to effective ventricular filling?

Back 31

The delay of the impulse going from the atria to the ventricles

Front 32

What is the function of the conductive system's Specialized Muscle Tissue?

Back 32

Impulse generation and transmission.

(NOT CONTRACTION)

Front 33

How fast are all the 4 components of the cardiac cycle accomplished?

Back 33

Less than 1 second, due to the HR being ~70 bpm

Front 34

What type of process is the opening and closing of the valves?
What determines this?

Back 34

It is a Passive Process.

This is determined by the Pressure Gradient across them.

Front 35

What prevents the closure of the AV valves and helps with ventricular filling?

Back 35

Atrial Contraction, as soon as the intraventricular pressure is higher than the atrial pressure.

Front 36

Does atrial contraction increase the ventricular pumping efficiency?

Back 36

Yes, by 40-50%

Front 37

Can the heart function effectively without the aid of Atrial Contraction increasing the Ventricular Pumping Efficiency?

Back 37

Yes

Front 38

What are the 4 phases of Systole and Diastole?

Back 38

Systole: Contraction Phase (I) & Ejection Phase (II)
Diastole: Relaxation Phase (III) & Filling Phase (IV)

Front 39

List the 3 phases of ventricular pumping during Systole

Back 39

1. Isometric Contraction
2. Rapid Ejection
3. Reduced Ejection

Front 40

List the 5 phases of ventricular pumping during Diastole

Back 40

1. Protodiastole
2. Isometric Contraction
3. Rapid Inflow
4. Diastasis
5. Atrial Systole

Front 41

What are the sensors that respond to distension of the artery wall as a result of increased blood pressure?

Back 41

Baroreceptors

Front 42

Where do the Baroreceptors send impulses to?
What happens as a result?

Back 42

Cardiac Center - Medulla Oblongata - specifically the cardioinhibitor center.
This results in the activation of the Parasympathetic System.

Front 43

When the Baroreceptors activate the PNS in the Medulla Oblongata, what are the effects on the heart?

Back 43

Decreased:
HR and Contraction
Cardiac Output
Blood Pressure

Front 44

Where are the Baroreceptors located and what are they innervated by?

Back 44

Aortic Arch: Called the Aortic Sinus, innervated by the Vagus.

Carotid Artery: Called the Carotid Sinus, located at the bifurcation of each common carotid, innervated by the Carotid Sinus Nerves (Nerves of Herring)

Front 45

How does the heart respond to a decrease in blood pressure?

Back 45

The SNS acts through a cardioacceleration center

Front 46

How do Chemoreceptors differ from Baroreceptors?

Back 46

Chemoreceptors don't respond to changes in pressure, rather by changes in the concentration of pO2 and pCO2 in the blood.

Front 47

Where are the Chemoreceptors located?

Back 47

Aortic Bodies: Scattered in the tissue between the Aorta and the Pulmonary Arteries.
Carotid Bodies: Immediately close to the bifurcation of each common carotid artery.

Front 48

What is the term for the value that adjusts the cardiac output to the individual person's body size by representing blood flow relative to a square meter of body surface area?

Back 48

Cardiac Index

Front 49

What is the normal adult range for Cardiac Index?

Back 49

4.2 L/min/m2

Front 50

State the equation for Cardiac Index

Back 50

Cardiac Index = Cardiac Output / Body surface area

(Body Surface Area = (Height x Weight) / 3600)

Front 51

The amount of blood that passes a given point in the circulation in a given period of time is called?

Back 51

Blood Flow (change in Pressure / Resistance)

Front 52

The rate of blood flow is expressed in what Law?

Back 52

Poiseulle's Law
Proving the diameter is the most important factor in determining blood flow.

Front 53

What is the term describing the impediment to blood flow, and what is the term describing the measure of the blood flow through a vessel for a given deltaP?

Back 53

Resistance is impediment to blood flow
Conductance is the measure of the blood flow through a vessel for a given change in Pressure.

Front 54

When the cardiac system is working properly, the atria contract how much sooner than the ventricles?

Back 54

1/6th second

Front 55

What ability of the myocardium causes automatic rhythmical discharge and contraction?

Back 55

Capacity of Self-Excitation

Front 56

Which fibers of the heart represent the capability of Self-Excitation to the greatest extent?

Back 56

The fibers of the conductive system with the SA node

Front 57

What is the potential for the SA fibers between discharges compared to the Ventricular muscle fibers?
What is the reason for the difference?

Back 57

SA fibers = -55 -> -60mV
Ventricular fibers = -85 -> -90mV

Due to the SA fibers being naturally leaky to Na+.

Front 58

What are the 3 types of membrane channels that play an important role in causing the voltage changes of the action potential?

Back 58

1. Fast Na+ Channels
2. Slow Ca2+/Na+ Channels
3. Potassium Channels

Front 59

Which membrane ion channel is responsible for bringing the membrane back to its resting level?

Back 59

Potassium Channels

Front 60

Which membrane ion channel is responsible for the response to the spike-like onset of the action potential in the ventricular muscle?

Back 60

Fast Na+ Channels

Front 61

Which membrane ion channel is responsible for the plateau of the ventricular action potential?

Back 61

Slow Ca2+/Na+ Channels

Front 62

Which channels are permanently closed at the S-A node? Which are open?

Back 62

Fast Na+ Channels are closed.
Slow Ca2+/Na+ Channels are open.

Front 63

What does the high extracellular Na+ and high (-) intracellular charge do to the Na+ ions?

Back 63

It gives them a tendency to leak into the cell.
Naughty Sodium.

Front 64

How do the Slow Ca2+/Na+ Channels get activated at the S-A node? What does this result in?

Back 64

The gradual leaking of Na+ into the SA node cells causes a further increase of the potential from -55mV to -40mV.
-40mV is the Threshold Voltage of the SA node.

Once it reaches -40mV, the Slow Ca2+/Na+ Channels are activated, allowing entrance of Ca2+ and Na+.

This results in an Action Potential.

Front 65

What is the Threshold Voltage of the S-A fibers?

Back 65

-40mV.
This is generated from Na+ leaking into the cells.

Front 66

What is the cause of the Self-Excitation of the S-A fibers?

Back 66

The natural leakiness of the Na+ in the SA fibers causes their Self-Excitation.

Front 67

How long after opening do the Slow Ca2+/Na+ Channels close? What is happening at the almost at the same time?

Back 67

It takes only 100-150ms for the Slow Ca2+/Na+ Channels to close.
Many K+ Channels open at the same time, forcing more K+ outside the cell.

Front 68

What are the results of the K+ travelling out the cell?

Back 68

A temporary excess of (-) charge inside the cell.
Hyperpolarization, which initially carries the resting membrane potential down to -55 to -60mV at the end of the Action Potential.

Front 69

How is Rhythmicity possible in a Cardiac Action Potential?

Back 69

It's never (-) enough to keep all the channels closed.

Front 70

Where do the action potentials spread to, following the S-A node?

Back 70

Through the fused surrounding muscle fibers
To the entire Atrial mass
Eventually to the A-V node