Patho 1&2 > Cardio > Flashcards

Cardio Flashcards

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1
Q

The coronary arteries course through the epicardium and branch progressively as they descend into the myocardium. Unlike all other tissue the blood flows during diastole and is retarded during systole as the myocardium contracts around the arterioles.

A
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2
Q
A
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3
Q

What does the right coronary artery supply

A

The inferior portion of the left ventricle and the right ventricle

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4
Q

What does the left anterior coronary artery divide into

A

The left anterior descending artery and the circumflex artery

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5
Q

What does the left anterior descending artery supply

A

The anterior left ventricle and the septum

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6
Q

What does the circumflex artery supply

A

The posterior left ventricle

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7
Q

When does most ventricular filling occur

A

During diastole

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8
Q

What causes passive blood flow from the atria to the ventricles during diastole

A

The pressure in the atria is greater than the pressure in the relaxed ventricles

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9
Q

Which valves are open during passive ventricular filling

A

The tricuspid valve on the right and the mitral valve on the left

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10
Q

What happens in late diastole to complete ventricular filling

A

The atria contract to push the last blood into the ventricles

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11
Q

What happens during systole

A

The ventricles contract and push blood into the pulmonary artery and aorta

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12
Q

What initiates the rapid ejection phase of systole

A

Left ventricular pressure exceeds aortic pressure

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13
Q

What causes the aortic and pulmonic valves to close

A

Ventricular pressure falls below the pressure in the aorta and pulmonary artery

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14
Q

What happens in the atria while the ventricles are contracting

A

The atria are passively filling from the veins

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15
Q

What initiates the next cardiac cycle after passive atrial filling

A

Atrial contraction squeezes the remaining blood into the ventricles to complete filling

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16
Q

What is diastole

A

When the ventricles relax

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17
Q

What is systole

A

When the ventricles contract

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18
Q

What causes the first heart sound S1

A

Closure of the bicuspid mitral and tricuspid valves

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19
Q

What causes the second heart sound S2

A

Closure of the aortic and pulmonic valves

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20
Q

Where does the electrical impulse of the heart begin

A

In the sinoatrial SA node

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21
Q

What does the electrical signal travel through after the SA node

A

Through the atrial fibers to the atrioventricular AV node

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22
Q

Where does the electrical signal go after the AV node

A

Into the bundle of His

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23
Q

Where does the bundle of His divide

A

Into the left and right bundle branches

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24
Q

Where do the bundle branches terminate

A

In the Purkinje fibers

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25
How does the electrical impulse spread from cell to cell in the myocardium
Through hemichannels between adjacent myocardial cells
26
Why is the myocardium considered syncytial tissue
Because many cells act in concert as one functional unit
27
How does the electrical current move through the heart
As a wave passing through each part of the conduction system and through adjacent myocardial cells
28
What creates the diffusion potential for potassium in cardiac cells
The much higher intracellular potassium concentration compared to extracellular 130 to 4
29
What happens as potassium diffuses out of cardiac cells
It carries positive charge out creating a more negative intracellular electrical potential
30
When is resting membrane potential reached
When the electrical potential equals the diffusion gradient so cation entry equals cation exit
31
What is the approximate resting membrane potential of cardiac cells
Negative sixty millivolts
32
Why is potassium always effluxing out of the cell
To create a greater intracellular electronegativity
33
Do all cardiac cells have the same resting membrane potential
No different cells have different resting membrane potentials
34
What is the resting membrane potential of the electrical conduction system cells
Negative sixty millivolts
35
Why is the resting membrane potential in myocytes unstable
Potassium channels close and sodium channels open at rest
36
What does sodium entry cause in conduction cells
Slow depolarization making the membrane potential less negative
37
What happens when potassium channels close in conduction cells
Slow sodium channels open allowing positive ions to enter
38
What happens at negative forty millivolts in conduction cells
Calcium channels open and calcium floods in rapidly depolarizing the cell
39
What happens once the membrane potential becomes slightly positive
Calcium channels close and potassium channels open to repolarize the cell
40
Which node normally sets the heart rhythm
The sinoatrial SA node
41
What happens if the SA node fails
The atrioventricular AV node takes over at a slower rate
42
What happens if the AV node is blocked or fails
Ventricular pacemaker cells take over at an even slower rate
43
What is the intrinsic firing rate of the SA node
About sixty to eighty beats per minute
44
What determines the rate of SA node depolarization
The rate of sodium channel mediated depolarization
45
What is the intrinsic firing rate of the AV node
About forty to fifty beats per minute
46
What is the intrinsic firing rate of ventricular pacemaker cells
About thirty beats per minute
47
Why does the SA node override the AV and ventricular nodes
Because it has a faster depolarization rate which suppresses the slower pacemakers
48
What does the EKG record
Depolarization waves passing through the electrical system of the heart
49
Where are EKG leads attached
To the extremities as limb leads and to the chest wall as precordial leads
50
What does a positive or upright deflection on EKG represent
Depolarization moving toward the lead
51
What does a negative or downward deflection on EKG represent
Depolarization moving away from the lead or repolarization moving toward the lead
52
Why is the main EKG deflection upright
Because depolarization proceeds toward the left side of the body
53
What does the P wave represent
Depolarization of the atrial fibers
54
What does the Q wave represent
The delay between atrial and ventricular signals at the AV node
55
What does the QRS complex represent
Ventricular depolarization and simultaneous atrial repolarization
56
What does the T wave represent
Ventricular repolarization
57
What pattern do we see in normal EKG rhythm
A regular sequence of P Q R S T waves
58
What kind of striations do muscle cells have
Both vertical and horizontal striations
59
What is the resting membrane potential of myocardial cells
Approximately negative ninety millivolts
60
What triggers depolarization of myocardial cells
An electrical stimulus through the cardiac conduction system or adjacent myocytes
61
What happens first during myocyte depolarization
Sodium channels open and rapidly depolarize the cell almost instantly
62
What happens after sodium entry in myocyte depolarization
Transient potassium channels open causing minor repolarization
63
What happens after minor repolarization in myocytes
Voltage gated calcium channels open allowing calcium influx balanced by rectifier potassium efflux
64
Why is repolarization delayed in myocytes
Calcium entry brings in positive charge which opposes repolarization
65
What causes repolarization to complete in myocytes
Calcium channels close and resting membrane potential is restored
66
What causes contraction of myocytes
Calcium in the cytoplasm
67
How is myocyte depolarization different from SA and AV nodal cells
Myocytes rely on sodium influx for rapid depolarization while nodal cells use slow sodium and calcium channels
68
What are sarcomeres
Bundles of repetitive protein structures that divide the cell
69
What creates the striations seen in myocytes
Alternating and overlapping protein structures within sarcomeres
70
What organelles permeate the sarcomeres
Transverse tubules and sarcoplasmic reticulum
71
What defines the boundaries of a sarcomere
It extends from one Z disc to another Z disc
72
What are the regions within a sarcomere
I band A band H zone and M line
73
What is found in the H zone
Transverse bands of myosin
74
What is found in the A band excluding the H zone
Overlapping myosin and actin fibers
75
What is found in the I band
Longitudinally arranged actin fibers
76
What happens during contraction at the filament level
Myosin heads pull the actin fibers across release reconnect and pull again
77
What triggers actin exposure during contraction
Increased intracellular calcium binds to troponin C
78
What does troponin C do when it binds calcium
It moves tropomyosin away from the actin to expose the binding sites
79
What happens after actin binding sites are exposed
Actin can interact with the heads of the myosin fibers
80
What facilitates the interaction between actin and myosin
ATP
81
What happens to ATP during contraction
It is hydrolyzed to provide energy for the myosin heads to cock
82
What do the myosin heads do when cocked
Pull the actin and myosin fibers across each other to contract the muscle cell
83
What causes muscle relaxation
The binding of new ATP which releases the myosin heads from actin
84
What stops the contraction cycle
The decrease in calcium which allows tropomyosin to cover actin again
85
What is the primary source of calcium for cardiac muscle contraction
The endoplasmic reticulum of the sarcomere
86
How are calcium levels restored after contraction
Calcium pumps return calcium back into the endoplasmic reticulum
87
Can calcium also enter from outside the cell
Yes through calcium channels on the cell membrane
88
How do catecholamines affect calcium handling
They stimulate beta adrenergic receptors to increase the force and frequency of contraction
Patho 1&2
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