Lesson 2 (ch. 9/10)

Question 1

Why can’t the heart be perfused during incisura?

Answer 1

Coronary arteries are blocked/compressed by aorta opening + twisting motion of the heart (blocks blood flow to myocardial tissue)

Question 2

Why is there a slight increase in aortic pressure after ventricular ejection?

Answer 2

Blood pushed out can’t fit into smaller vessels quick enough: pulse wave “bounces back”

Question 3

What records heart sounds?

Answer 3

phonocardiogram

Question 4

Heart sounds (lub-dup) are associated with:

Answer 4

closing of heart valves

Question 5

What is the first sound of the heart?

Answer 5

Atrioventricular (tricuspid/mitral) valves close: beginning of systole

Question 6

What is the second sound of the heart?

Answer 6

Semilunar (pulmonary & aortic) valves close: beginning of ventricular diastole

Question 7

When is the third sound of the heart heard?

Answer 7

Inc. ventricular vol (kids or pro athletes)

Question 8

What is another name for preload?

Answer 8

End diastolic volume

Question 9

What is another name for after load?

Answer 9

End systolic volume

Question 10

What is preload and afterload?

Answer 10

amt of blood in ventricles before/after contraction

Question 11

Stroke volume =

Answer 11

Preload - afterload

Question 12

What does the area under the work output of the heart represent?

Answer 12

amt of work from the heart

Question 13

What are the muscles doing during the period of filling of the heart?

Answer 13

Relaxed (nothing)

Question 14

What are the muscles doing during the isovolumic contraction of the heart?

Answer 14

Ventricles contract (beginning of systolic phase)

Question 15

What are the muscles doing during the period of ejection of the heart?

Answer 15

Ventricles still contracting

Question 16

What are the muscles doing during isovolumic relaxation?

Answer 16

ventricles relax

Question 17

What happens when you increase the preload?

Answer 17

• inc. stroke volume
• dec. heart rate
• inc. venous return
• no inc. in pressure

Question 18

Explain the Frank-Starling Mechanism

Answer 18

If cardiac muscle sarcomeres are stretched, within limits, they contract more forcibly (recoil)
- as sarcomeres are stretched, there are more sites available for cross-bridge interaction

Question 18

What happens if sarcomeres are stretched too much?

Answer 18

dec. # of cross bridges formed: dec. contraction force

Question 19

What happens when you increase afterload?

Answer 19

• dec. stroke volume
• ventricles work harder
• inc. pressure (ejection phase starts at a higher pressure)

Question 20

What happens to the left ventricular vol/pressure curve when you increase sympathetic innervation?

Answer 20

• inc. stroke volume
• dec. afterload
• inc. contractility
• inc. systolic BP

Question 21

What are the concentrations of K+ (and organic anions)

Answer 21

• High inside myocyte
• Low outside sarcolemma

Question 22

Where are Na+ (and Ca++ & Cl-) concentrated?

Answer 22

outside the cell

Question 23

The potential difference btwn the inside and outside is called

Answer 23

Diffusion potential

Question 24

The electro-chemical equilibrium give the

Answer 24

resting membrane potential

Question 25

The diffusion potential across a membrane develops depending on:

Answer 25

1) Polarity of electrical charge of each ion (compare Na+ to Ca++) 2) Permeability of membrane 3) Concentrations of respective ions on the inside and outside of membrane

Question 26

membrane potential is not a potential, it is:

Answer 26

the difference of 2 potentials: a voltage

Question 27

What is the sinus (sinoatrial node)?

Answer 27

- specialized cardiac muscle: flattened ellipsoid strip of cells in right atrium ("pacemaker cells") - no contractile filaments - inherent rate of 100bpm - electrically connected w/ atrial muscle fibers

Question 28

What causes self-excitation of sinus nodal fibers?

Answer 28

cell membranes of the sinus fibers have an inherent leakiness to sodium and calcium ions

Question 29

What is the resting membrane potential of the sinus nodal fiber?

Answer 29

-55 to -60mV

Question 30

What is the resting membrane potential of the ventricular muscle fiber?

Answer 30

-85 to -90mV

Question 31

How would you compare the atrial nodal action potential to the action potential of ventricular muscle?

Answer 31

it's slower

Question 32

Why does the sinus node control heart rhythmicity?

Answer 32

the discharge rate of the sinus node is faster than natural self-excitatory discharge rate of A-V node of Purkinje fibers

Question 33

What are abnormal/Ectopic pacemakers?

Answer 33

pacemaker in another place than the sinus node

Question 34

Under abnormal conditions what other parts of the heart can exhibit intrinsic rhythmical excitation in the same way as sinus nodal fibers?

Answer 34

A-V node and Purkinje fibers

Question 35

Why does the A-V node delay the AP from reaching the ventricles?

Answer 35

- allow atria to empty blood into ventricles (before ventricle contract) - A-V node has a lot LESS gap junctions

Question 36

What is the A-V bundle also known as?

Answer 36

His bundle

Question 37

T/F the A-V bundle has one-way conduction?

Answer 37

T

Question 38

Where does the His bundle conduct the AP signal to?

Answer 38

Right Bundle Branch (RBB) and Left Bundle Branch (LBB): towards apex of heart

Question 39

What do Purkinje fibers do?

Answer 39

lead signal from A-V node thru A-V bundle (His), into ventricles

Question 40

At the termination of Purkinje fibers, what happens to the impulse?

Answer 40

Travels RAPIDLY thru ventricular muscle fibers via gap junctions, from inside (endocardium) to outside (epicardium) - rapid propagation: important for effective contraction

Question 41

How do the SA and AV node APs compare to that of atrial or ventricular muscles?

Answer 41

Slower to develop (slope less steep)

Question 42

Can fast responses of normal myocardial fibers be slowed down?

Answer 42

Yes: either spontaneously or under experimental conditions (lack of blood supply)

Question 43

What is effective refractory period (ERP)

Answer 43

Same as absolute refractory period: another AP cannot happen

Question 44

What is relative refractory period (RRP)

Answer 44

AP possible w/ enough stimulus

Question 45

How does the refractory period of cardiac muscle compare to skeletal muscle?

Answer 45

Short in skeletal muscle: can undergo summation and tetanus via repeated stimulation

Question 46

What are the ways to diminish firing frequency of the pacemaker?

Answer 46

- reduction in slope of slow diastolic depolarization - inc. in threshold potential - inc. in magnitude of max diastolic potential

Question 47

What are the nerves the modify basic heart rhythm through extrinsic innervation?

Answer 47

- parasympathetic nerves - sympathetic nerves

Question 48

How do parasympathetic nerves affect the heart?

Answer 48

- only affects HR - releases acetylcholine - dec. heart rhythm and excitability - excitatory signals no longer transmitted into ventricles - inc. permeability to potassium ions (dec. resting membrane potential)

Question 49

How do sympathetic nerves affect the heart?

Answer 49

- affects HR and contraction - releases norepinephrine - inc. rate of sinus nodal discharge - inc. overall heart activity - inc. permeability of Na+ and Ca++ ions (reach threshold faster)

Question 50

Which nervous system modulates the frequency of depolarization of pacemaker?

Answer 50

autonomic NS

Question 51

What does sympathetic stimulation (norepinephrine) bind to?

Answer 51

beta1 receptors on SA nodal membranes

Question 52

What does parasympathetic stimulation (acetylcholine) bind to?

Answer 52

muscarinic receptors on nodal membranes (inc. conductivity of K+ and dec. conductivity of Ca++)

Question 53

What is atrial fibrillation?

Answer 53

- abnormal and usually very rapid heart rhythm

Question 54

What is superventricular tachycardia

Answer 54

- electric impulses travel from ventricle to atria - fast irregular heart beat

Question 55

What is ventricular tachycardia?

Answer 55

- ventricles do not have time to fill up properly - fast heart rate

Question 56

What is bradycardia

Answer 56

slow heart beat

Question 57

What is pacemaker implantation for?

Answer 57

Sends signal to heart when you have a faulty SA node