Cardiac Muscle

Question 1

What are the two types of myocardium cells?

Answer 1

1. Automaticity Cells

2. Contractile Cells

Question 2

Automaticity cells, which set the pace of the heart, include what?

Answer 2

1. Pacemaker (SA Node)
2. AV Node
3. AV bundle of His
4. Purkinje fibers

Question 3

Contractile cells, which generate force in the heart, include what?

Answer 3

1. Actin and Myosin
2. Other contractile proteins
3. Sarcoplasmic reticulum

Question 4

Which 4 myocardial cells lack actin and myosin?

Hint: automaticity cells do not have actin/myosin

Answer 4

1. SA node
2. AV node
3. Bundle of His
4. Purkinje fibers

(Hint: automaticity cells do not have actin/myosin)

Question 5

The 3 major types of cardiac muscle are ____ (contractile), _____ (contractile) and _____ (non-contractile or nodal)

Answer 5

1. atrial
2. ventricular
3. excitatory and conductive muscle fibers

Question 6

What are the 2 similarities of contractile tissue to skeletal muscle?

Answer 6

1. Striated

2. Myofibrils which contain actin and myosin

Question 7

What are the 3 main differences of contractile tissue to skeletal muscle?

Answer 7

1. Lattice network
2. Intercalated discs to form “communicating” gap junctions
3. Syncytium

Question 8

What is the syncytium?

Answer 8

interconnected heart cells; when one becomes excited, the AP spreads to all cells throughout the latticework interconnections

Question 9

What are the 2 types of syncytium?

Answer 9

1. Atrial

2. Ventricular

Question 10

The 2 syncytiums are separated by ___ tissue that surround the ___ valvular openings

Answer 10

fibrous; AV

Question 11

Cardiac action potentials last ____x longer in cardiac muscle vs. skeletal muscle because it is _____ms long (much slower than skeletal 2-5ms)

Answer 11

15x; 200-300ms

Question 12

What are the phases of action potentials? (in order)

Answer 12

4 = resting membrane potential (-90mv)\

0 = opening of fast V-gated Na+ channels (-70mV)
= opening of slow V-gated Ca2+ channels (-40mV)

1 = closing of V-gated Na+ channels
= opening of V-gated fast K+ channels

2 = slow Ca2+ channels are OPEN (-40mV)
= decreased K+ permeability

3 = Ca2+ channels close
= K+ channels remain open

Question 13

At what phase of the AP do the V-gated Na+ channels close and the V-gated fast K+ channels open?

Answer 13

1

Question 14

At what phase of AP do the Ca2+ channels close and the K+ channels remain open?

Answer 14

3

Question 15

At what phase of AP is the membrane at resting potential?

Answer 15

4

Question 16

At what phase of AP are the slow Ca2+ channels open and there is decreased K+ permeability?

Answer 16

2

Question 17

What happens at phase 1 of the AP?

Answer 17

1 = closing of V-gated Na+ channels

= opening of V-gated fast K+ channels

Question 18

What happens at phase 2 of the AP?

Answer 18

2 = slow Ca2+ channels are OPEN (-40mV)

= decreased K+ permeability

Question 19

What happens at phase 3 of the AP?

Answer 19

3 = Ca2+ channels close

= K+ channels remain open

Question 20

What happens at phase 4 of the AP?

Answer 20

4 = resting membrane potential (-90mv)

Question 21

At what phase(s) is the membrane potential at -40mV?

Answer 21

0 (opening of slow V-gated Ca2+ channels) and 3

Question 22

At what phase is the membrane potential at -90mV?

Answer 22

4

Question 23

At what phase is the membrane potential at -70mV?

Answer 23

0 (specifically the opening of fast V-gated Na+ channels)

Question 24

At what phase is the membrane potential at +20mV?

Answer 24

1

Question 25

At what phase is the membrane potential at +10mV?

Answer 25

2

Question 26

Excitation-Contraction Coupling is a mechanism by which the action potential causes the _____ of the muscle to ____

Answer 26

myofibrils; contract

Question 27

The AP spreads to the interior of the cardiac muscle fiber along the membranes of what?

Answer 27

t-tubules

Question 28

T-tubules AP act on membranes of the longitudinal ______ tubules to cause release of ___ ions into the sarcoplasm from the SR

Answer 28

sarcoplasmic; ca2+

Question 29

Ions diffuse into the myofibril to catalyze reactions for binding of ___ and ___ to produce muscle ___

Answer 29

actin; myosin; contraction

Question 30

What is less developed in the cardiac muscle in comparison to skeletal muscle and does not store enough calcium to provide a full contraction?

Answer 30

sarcoplasmic reticulum

Question 31

Strength of the cardiac muscle contraction is dependent on the extracellular ____ concentration

Answer 31

calcium

Question 32

AP of pacemaker cells include phases ___, ___ and ___

Answer 32

``` 4 = membrane potential (-60mV) 0 = calcium channels open at AP threshold 3 = calcium channels close, potassium channels open ```

Question 33

At what phase of the pacemaker AP do the calcium channels open?

Answer 33

0

Question 34

At what phase of the pacemaker AP do the calcium channels close?

Answer 34

3

Question 35

At what phase of the pacemaker AP do the potassium channels open?

Answer 35

3

Question 36

At what phase of the pacemaker AP is the resting membrane potential -60mV?

Answer 36

4

Question 37

In order for passive filling to occur in the heart, blood collects until ____ drops and ____ open

Answer 37

pressure; valves

Question 38

The atria is considered the ____ pump for the ____

Answer 38

primer; ventricles

Question 39

80% of blood flows directly through the ____ and into the ___ even before the atria contract (passive process)

Answer 39

atria; ventricles

Question 40

Passive filling increasing the ventricular pumping effectiveness by ___%

Answer 40

20%

Question 41

Right atrial pressure is ___ than left atrial pressure

Answer 41

less ``` right = 4-6mmHg left = 7-8mmHg ```

Question 42

Left ventricular pressure rises above __ mmHg and right ventricular pressure rises above ___ mmHg

Answer 42

80; 8

Question 43

When the R/L ventricular pressures rise, the semilunar valves ___ and blood pours into where?

Answer 43

open; the aorta and pulmonary arteries

Question 44

The first heart sound is the closure of what?

Answer 44

AV valves

Question 45

The second heart sound is the rapid closure of what?

Answer 45

semilunar valves

Question 46

In the volume-pressure diagram, phase I is the period of ____, phase II is the ____ contraction, phase III is the period of ____ and phase IV is the period of ____ relaxation

Answer 46

filling isovolumetric contraction ejection isovolumetric relaxation

Question 47

The systolic pressure curve shows that _______ filaments of cardiac muscle fibers are pulled far apart and strength of the cardiac fiber contraction becomes what?

Answer 47

actin-myosin; less than optimal

Question 48

The diastolic pressure curve shows that ___ tissue in the heart will stretch no more and the ____ becomes filled nearly to its limit

Answer 48

fibrous; pericardium

Question 49

Preload is the ____ pressure the the ____ has become filled

Answer 49

end-diastolic; ventricle

Question 50

Afterload is the pressure in the ____ leading from the ____

Answer 50

aorta; ventricle

Question 51

Increase in ____ will increase stroke volume, while increase in ____ will decrease stroke volume

Answer 51

preload; afterload

Question 52

At rest, cardiac output (CO) is ___L/min. During exercise however, CO is ____x this amount

Answer 52

4-6L/min; 4-7x

Question 53

There is an intrinsic cardiac regulation of pumping in response to changes in ______ of the blood flowing into the heart from the _____

Answer 53

volume; veins

Question 54

Stretch of the ____ wall directly increases the ____ by 10-20%

Answer 54

atrial; heart rate

Question 55

As atrial pressure for each side of the heart INCREASES, the ____ work output for that side also increases until it reaches the limit of the ____ pumping ability

Answer 55

stroke; ventricle's

Question 56

The ____ fill in response to higher atrial pressures

Answer 56

ventricles

Question 57

Each ventricular volume and strength of the cardiac muscle contraction _____, causing the heart to pump ____ quantities of blood into the arteries

Answer 57

increase; increased

Question 58

Sympathetic activation stimulation increases the ____ and increases the force of ____

Answer 58

heart rate; contraction

Question 59

Sympathetic activation inhibition ___ heart rate and ___ force of contraction

Answer 59

decreases; decreases

Question 60

Parasympathetic activation causes the heart rate to ____ and the force of contraction to ____

Answer 60

decrease; decrease

Question 61

Hyperkalemia is an ___ of K+ (potassium) in the blood, muscle ____, _____, ______, arrhythmias, nausea, and can even lead to cardiac ____ and death.

Answer 61

``` increase fatigue weakness paralysis arrest ```

Question 62

Hypokalemia is a ___ of K+ (potassium) in the blood, muscle _____, weakness, ____, paralysis, abnormal _____, low ____, and even ____ failure

Answer 62

``` decrease twitches cramps heart rhythms blood pressure respiratory ```

Question 63

High amounts of K+ ion concentration cause the heart rate to _____

Answer 63

slow

Question 64

High amounts of K+ ion concentration in large enough quantities can block the conduction of _____ from the atria to the ventricles through the ____ bundle

Answer 64

cardiac impulse | AV

Question 65

Hypercalcemia is the increased amount of ____ in the blood which can cause ____ contractions

Answer 65

calcium; spastic

Question 66

Hypocalcemia is the decreased amount of _____ in the blood and can cause ____ weakness

Answer 66

calcium; cardiac

Question 67

When the body drops to 60-70F, what happens?

Answer 67

hypothermia

Question 68

The alterations of which two ions will effect the cardiac pump?

Answer 68

potassium and calcium