Nordgren Cardiac Physiology

Question 1

What is Starling’s Law of the Heart?

Answer 1

If cardiac filling increases during diastole, the volume ejected during systole also increases.

–the heart pumps what it recieves

Question 2

State the equation for resistance with respect to length (L), viscosity (n), and radius (r).

Answer 2

R = 8Ln/ (pi)r^4

Question 3

Stroke Volume = ?

Answer 3

EDV (end diastolic volume) - ESV (end systolic volume)

Question 4

Cardiac output = ?

Answer 4

SV x HR

Question 5

5 requirement for effective heart operation?

Answer 5

1. contractions of cardiac myocytes must be synchronized and occur at regular intervals (not arrhythmic)
2. The valves must open fully (not stenotic)
3. Valves must not leak (not insufficient or regurgitant)
4. Contraction must be forceful (not failing)
5. Ventricles must fill adequately during diastole

Question 6

Total blood volume in an average adult?

Answer 6

5 L ~ 8% total body weight

Question 7

Flow (Q) = ?

Answer 7

change in pressure / resistance

Question 8

What ion is responsible for rapid depolarization of myocardial contractile cells?

Answer 8

Na+

Question 9

What ion is responsible for rapid depolarization of myocardial pacemaker cells?

Answer 9

Ca2+

Question 10

What are the 5 phases of contractile cells?

Answer 10

4 -- resting potential (~ -90 mV)
0 -- depolarization (influx of Na+)
1 -- peak
2 -- plateau (slow influx of Ca2+)
3 -- rapid repolarization (K+ outflow)
4 -- resting again (K+ inward rectifier channels open)

Question 11

What are the 3 phases of pacemaker cells?

Answer 11

4 – funny current channels open (more Na+ in than K+ out, net depolarization but gradual), transient Ca2+ channels open (influx) **pacemaker potential
0 – long lasting Ca2+ channels open at threshhold of -30 mV –> depolarization
3 – K+ channels open –> repolarization
4 – funny current channels open again

Question 12

What is the pacemaker node and where is it?

Answer 12

SA node in right atrium

Question 13

Where is Bachman’s Bundle?

Answer 13

left atrium

Question 14

Where does the action potential go immediately after the AV node?

Answer 14

Bundle of His

Question 15

What structure allows passage of AP from cell to cell?

Answer 15

gap junctions

Question 16

Gap junctions and what other structure form intercalated discs?

Answer 16

desmosomes

Question 17

Anchoring sites for actin, connect to closest sarcomere:

Answer 17

Fascia Adherens

Question 18

join cells together by binding intermediate filaments:

Answer 18

Macula Adherens

Question 19

protein that forms gap junctions:

Answer 19

connexin

Question 20

Why does AP slow through AV node?

Answer 20

fewer gap junctions than SA node and atrial myocardium

Question 21

tissue with fastest conductance?

Answer 21

Bundle of His and Purkinje fibers– 4 m/sec

Question 22

nerve and NT in control of cardiac parasympathetic response:

Answer 22

vagus

Acetylcholine

**increase permeability of resting membrane to K+

**decrease diastolic funny current through HCN channels

Question 23

NT involved in cardiac sympathetic response:

Answer 23

norepinephrine

**increases diastolic funny current through HCN channels

**shortens time to depolarization

Question 24

Ca2+ enters myocyte via ________ channel.

Answer 24

L-type

Question 25

Ca2+ released from SR via _________ channels.

Answer 25

ryanodine receptor channels (RyR)

Question 26

Ca2+ ions bind to ______________ to initiate contraction.

Answer 26

Troponin

Question 27

Ca2+ exchange with Na+ via the ____________.

Answer 27

NCX antiporter

Question 28

passive/resting tension placed on cardiac muscle cells before contraction (a function of volume and pressure at the end of diastole):

Answer 28

Preload

Question 29

the active tension placed on cardiac muscle cells during contraction (a function of the resistance the left ventricle must overcome to circulate blood):

Answer 29

Afterload

Question 30

The total ventricular wall tension (T) depends on both intraventricular pressure (P) and the internal ventricular radius (r)— T = P x r

…this is known as:

Answer 30

The law of Laplace

Question 31

Positive chronotropic effect:

Answer 31

NE increases rate of spontaneous depolarization of membrane–shortens time to depolarization

increases HR

Question 32

Isometric contraction:

Answer 32

Activation of muscle whose ends are held rigidly

can develop tension

cannot shorten

Question 33

Isotonic contraction:

Answer 33

activation of unrestrained muscle causes it to shorten without force development because it has nothing to develop force against

Question 34

Inotrope:

Answer 34

influences the amount of tension a muscle can develop and the amount of shortening a muscle can achieve

ie: NE has a positive inotropic effect–increses afterloaded shortening, increases isometric tension

Question 35

Positive dromotropic effect:

Answer 35

an increase in the rate of action potential conduction

particularly evident in the AV node