Chap 21

Question 1

How many ml/min do coronary arteries supply to the myocardium?

Answer 1

200-250 ml/min

Question 2

% of blood supply the left coronary artery delivers to the myocardium?

Answer 2

85%

Question 3

Connections between arterioles that provide backup circulation on the myocardium

Answer 3

Anastomoses

Question 4

% of volume needed in the right ventricle to make the right atrium contract?

Answer 4

70%

Question 5

% of blood pumped under stress

Answer 5

300-400%

Question 6

Phases of the cardiac cycle

Answer 6

Phase 1: ventricular filling (middle of late diastole)

Phase 2: ventricular systole (atria relaxes & the ventricles begin contracting)

Phase 3: isovolumetric relaxation (early diastole)

Question 7

Isovolumetric contraction phase

Answer 7

0.02-0.03 seconds, the moment the ventricles are completely closed chambers & blood volume in the chambers remain constant

Question 8

Stroke volume

Answer 8

Amount of blood ejected from the heawith each ventricular contraction

Question 9

Preload

Answer 9

Volume of the blood returning to the heart

Question 10

After load

Answer 10

Resistance against which the heart muscle must pump

The pressure within the aorta before ventricular contraction

Question 11

Myocardial contractibility

Answer 11

The performance of the cardiac muscle

Question 12

End diastolic volume

Answer 12

Volume of blood returning to each ventricle (normally 120-130ml)

Question 13

End systolic volume

Answer 13

50-60 ml as the ventricles empty during systole

Question 14

Average adult stroke volume (amount of blood ejected during each cardiac cycle)

Answer 14

About 70ml

Question 15

Ml’s the end systolic volume is reduced to during the strong contraction of a healthy heart via exercise

Answer 15

10-30 ml

Question 16

Healthy heart, volume of end diastolic volume if large amount of blood flow into the ventricles during diastole?

Answer 16

As much as 200-250 ml

Question 17

Starling law

Answer 17

Myocardial fibers contract more forcefully when they are stretched

Question 18

Cardiac output

Answer 18

Amount of blood pumped by the ventricles in 1 minute

Stroke volume x heart rate

Question 19

Ways vagus nerve may be stimulated

Answer 19

Valsalva maneuver

Carotid sinus massage

Pain

Distention of the urinary bladder

Question 20

Beats/min heart rate is decreased with strong parasympathetic stimulation

Answer 20

20 or 30 beats/min

(Has little effect on stroke volume)

Question 21

How is stroke volume affected by a decreased heart rate?

Answer 21

Increased,
because the longer interval between heartbeats allows the heart to fill with a larger amount of blood and thus contract more forcefully (startling law)

Question 22

Epi’s effect on cardiac muscle & body

Answer 22

Increases the rate and force of contraction.

Causes blood vessels to constrict in the skin, kidneys, GI tract, & other visceral organs.

Causes dilation of skeletal & coronary blood vessels.

Takes longer to act on heart than does direct sympathetic innervation, but effects last longer

Question 23

Norepinephrine’s effect on the body

Answer 23

Causes constriction of peripheral blood vessels in most areas of the body & stimulates cardiac muscle

Question 24

Specialized cells of the electrical conduction system

Answer 24

Responsible for the formation & conduction of electrical current

Question 25

Working myocardial cells

Answer 25

Have the property of contractility & perform the actual pumping of blood

Question 26

What do separated particles with opposing charges have that is similar to the force of attraction similar to that of an electrical magnet?

Answer 26

Potential energy

Question 27

How is the electrical charge (potential difference) expressed?

Answer 27

Millivolts (1mV equals 0.001 volt)

Question 28

When is electrical charge’s potential energy released?

Answer 28

When the cell membrane appearing the ions becomes permeable

Question 29

Resting membrane potential

Answer 29

The electrical charge difference when the cell is in its resting state

Question 30

Synonym of POTENTIAL used in the electrical sense?

Answer 30

Voltage

Question 31

How is the membrane potential recorded?

Answer 31

From the inside of the cell

(-70 to -90 mV)

Question 32

What is the resting membrane potential a result from?

Answer 32

The balance between 2 opposing forces

Question 33

Reentry & what causes it?

Answer 33

The reactivation of myocardial tissue for the second or subsequent time by the same impulse

The progression of an electrical impulse is delayed or blocked (or both) in one or more segments of the electrical conduction system of the heart

Question 34

P wave

Answer 34

Represents Atrial depolarization

Duration: 0.10 seconds or less

Amplitude: 0.5 to 2.5 mm

Question 35

PR interval

Answer 35

The time required for an electrical impulse to be conducted through the atria & the AV node up to the instant of ventricular depolarization

Duration: 0.12-0.20 seconds (3 to 5 small squares(

A normal PR interval indicates that the electrical impulse has been conducted from the atria through the AV node normally

Question 36

QRS complex

Answer 36

Represents ventricular depolarization

Rapidly transmitted through the bundle of his

Duration: 0.08-0.10 seconds (2-2.5 small squares)

Amplitude: less than 5 mm - no more than 15 mm

Question 37

What does it mean when a QRS complex is 0.11 seconds?

Answer 37

Indicates a partial or incomplete bundle branch block (IBBB) where there is an intraventricular conduction delay.

Although abnormal, it’s not always pathologic.

Can be seen in healthy people or as a normal variation between beats.

Can also be seen in:
- Congenital heart disease (especially atrial septal defects)
- myocarditis
- pulmonary emboli
- right ventricular hypertrophy
- induced syndrome following cardiac surgery