Heart Week 1

Question 1

What is the sarcolemma?

Answer 1

The thin, continuous cell membrane that binds muscle cells.

Question 2

What is the Z band?

Answer 2

every 2.5 micrometers, the line that delimits the sarcomere.

Question 3

What is the A band? H band? I band?

Answer 3

A: region of myosin (thick filament)
H: portion of sarcomere that is free of thin filament
I: region without myosin, encompasses the Z line.

Question 4

What are T tubules?

Answer 4

Deep invaginations of the cell membrane which help to propagate the AP to deep fibrils.

Question 5

No T tubules equals what?

Answer 5

No contraction, even though the contraction machinery involves Ca++.

Question 6

What is held in the sarcoplasmic reticulum?

Answer 6

Ca++

Question 7

What does Ca++ bind to?

Answer 7

Troponin, allowing for cross bridges.

Question 8

What is SERCA?

Answer 8

Smooth Endo(sarco)plasmic Ca++. These are the pumps that return the Ca++ to the SR.

Question 9

What is the role of troponin and tropomyosin? How does Ca++ affect these proteins?

Answer 9

Troponin and Tropomyosin block cell contraction. Ca++ inhibits the inhibitor.

Question 10

What are the steps of the ATP/myosin action stroke?

Answer 10

1. ADP and Pi weakly bind to myosin to actin
2. loss of Pi leads to strong binding and power stroke
3. ADP is released
4. ATP binds and dissociates the actin/myosin bond.
5. ATP hydrolysis changes the head angle

Question 11

Do motor units fire synchronously or asynchronously? Why?

Answer 11

Asynchronously so that the summation maintains a constancy.

Question 12

What is the difference between TnT, TnI and TnC?

Answer 12

All are troponin.
TnT: links troponin to the actin and tropomyosin complex
TnI: inhibits the ATPase activity of the actin/myosin interaction
TnC: where Ca++ binds

Question 13

What is tropomyosin?

Answer 13

The wire-like structure that winds around actin and prevent myosin from binding to the actin.

Question 14

What is an example of a catecholamine?

Answer 14

Epinephrine.

Question 15

What type of G proteins are beta-adrenergic and muscarinic receptors attached to?

Answer 15

beta-adrenergic: Gs for stimulation of cAMP and activating protein kinases
muscarinic: Gi for inhibition of cAMP.

Question 16

What is the rate of the SA node, AV node, and Purkinje fibers?

Answer 16

SA: 60-100 bpm
AV: 50-60 bpm
Purkinje: 30-40 bpm

Question 17

How can beta-adrenergic receptors affect pacemaker cells?

Answer 17

They increase the probability that the pacemaker channels are open, leading to a steeper phase 4 slope, and more rapid firing.

Question 18

How does sympathetic activity affect pacemaker cells?

Answer 18

1. increases rate of depolarization

2. makes the threshold potential more negative

Question 19

What is an escape beat? Escape rhythm?

Answer 19

When the SA node slows it’s beat, another pacemaker can fire, making sure that the heart beat doesn’t become pathologically slow. Many escape beats make up an escape rhythm.

Question 20

What is an ectopic beat?

Answer 20

When a latent pacemaker begins to beat faster than the SA node. It is a premature beat.

Question 21

How can a myoctye become a pacemaker cell?

Answer 21

If they become leaky. They may lose ions quickly, never repolarize as much, and fire more rapidly than the SA node, making for ectopic beats.

Question 22

What is a conduction block? Name two types.

Answer 22

A region of the heart that is electrically unexcitable. It can be uni or bi-directional.

Question 23

What is the difference between the parietal and visceral layers of the heart?

Answer 23

Bunch a balloon…
Visceral: the surface touching your first (the heart)
Parietal: the outer surface.

Question 24

What is the endocardium?

Answer 24

Smooth membrane lining the inside of the chambers of the heart.

Question 25

What is the only ion that has a high intracellular concentration at rest?

Answer 25

K+

Question 26

How do Na+ channels work?

Answer 26

They have two gates each, and each gate must be open for Na to enter or exit.

Question 27

What maintains phase 2?

Answer 27

The influx of Ca++

Question 28

What leads to the repolarization?

Answer 28

K+ leaving the cell.

Question 29

What is the resting potential of myocytes as compared to pacemaker cells?

Answer 29

myoctytes: -90mV pacemakers: -60mV

Question 30

What determines the force of cardiac contraction?

Answer 30

intracellular Ca++ levels.

Question 31

What is the function and ratio of the Ca/Na exchanger?

Answer 31

Fxn: Pump Ca++ out of cell. Uses ATP. Depends on both concentration and electrical gradients. Ratio: 3 Na+ in and 1 Ca+ out.

Question 32

Tell me about the Ryanodine receptor.

Answer 32

Found on the sarcoplasmic reticulum, it facilitates calcium mediated calcium release. Needed for muscular contractions. It requires ATP.

Question 33

What are the two phases of systole?

Answer 33

1. Isovolumetric: both valves are closed, volume stays the same, pressure increases 2. Ejection: aortic/pulmonary valves open and blood flows out.

Question 34

What is diastole?

Answer 34

When the ventricle is relaxed.

Question 35

What are the three phases of diastole?

Answer 35

1. isovolumetric relaxation: just after ejection, both valves are closed, and pressure is releasing 2. Filling 1: mitral valve opens bc atrial pressure is greater than ventricular pressure, blood flows in passively 3. Filling 2: atrial contraction purges remaining blood with contraction

Question 36

What makes the "lub" sound?

Answer 36

closing of the AV valves (tricuspid and mitral)

Question 37

What makes the "dub" sound?

Answer 37

closing of the semilunar valves.

Question 38

What is the stroke volume? What is normal resting value?

Answer 38

Volume of blood pumped per beat of the heart. End Diast - End Syst = Stroke Vol Normal Resting = ~70ml (3 fl. oz or 2 shots of whiskey)

Question 39

What is ejection fraction? What is the normal resting value?

Answer 39

(stroke volume)/(end diastolic volume) = ejection fraction NRV = 0.5-0.7 (50-70%) NRV for ejection fraction increases with fitness and decreases with heart disease.

Question 40

What is Cardiac Output? What is the NRV?

Answer 40

stroke volume x heart rate = cardia output NRV = 5 L/min NRV for cardiac output scales up with size

Question 41

Where is norepi used?

Answer 41

In the sympathetic system, and only in the synapse between the post-ganglionic cell and the effector organ, everything else uses ACh.

Question 42

Where are the preganglionic neurons?

Answer 42

In the lateral horn.