Chapter 5A, 2

Question 1

Cardiac ….: cardiac events that occur from the beginning of one heartbeat to the
beginning of the next.

Answer 1

cycle

Question 2

1. A cardiac action potential arises in the SA node, continues down to the AV node. As the atrial contractile fibers depolarize, the ….. appears in the ECG.

Answer 2

p wave

Question 2

The cardiac cycle consists of a period of relaxation called ….stole, during which the
heart fills with blood, followed by a period of contraction called …tole

Answer 2

dia
sys

Question 3

2. After the P wave begins, the atria contract (atrial
   …tole). Conduction of the action potential slows at the AV node because the fibers there have much smaller diameters and fewer gap junctions. The resulting delay gives the atria time to contract, thus adding to the volume of blood in the ventricles, before ventricular systole begins.

Answer 3

sys
(P wave ends)

Question 4

3. The action potential propagates rapidly again after entering the AV bundle. After the P wave, it has propagated through the bundle branches, Purkinje fibers, and the entire ventricular myocardium.

Re/depolarization progresses down the septum,
producing the …… At the same time, atrial
re/depolarization is occurring, but it is not usually evident in an ECG because the larger QRS complex masks it.

Answer 4

depolarization
QRS complex
repolarization

Question 5

4. Contraction of ventricular contractile fibers (ventricular …tole) begins shortly after the QRS complex appears and continues during the ….. As contraction proceeds, blood is
   squeezed upward toward the semilunar valves

Answer 5

sys
S–T segment

Question 6

5. Re/depolarization of ventricular contractile fibers begins and spreads. This produces the …. in the ECG after the onset of the P wave.

Answer 6

Repolarization
T wave

Question 7

6. Shortly after the T wave begins, the ventricles start to relax (ventricular …stole). Then, ventricular re/depolarization is complete and ventricular contractile
   fibers are relaxed

Answer 7

dia
repolarization

Question 8

The heart valves open and close actively/passively

Answer 8

passively, because of pressure
differences on either side of the valve

Question 9

Blood flows from lower/higher to lower/higher pressure.

Answer 9

higher to lower

Question 10

Cardiac output = (definition)

Answer 10

amount of blood pumped by the heart/minute

Question 11

Cardiac output = (formula)

Answer 11

CO = HR (heart rate) x SV (stoke volume)

Question 12

Heart rate = (definition/ ..)

Answer 12

beats/min

Question 13

SV = (… / …)

Answer 13

ml/beat

Question 14

A …..cardia is defined as a rate greater
than 100 beats/min.
* A …..cardia is defined as a rate less
than 60 beats/min (or <50 beats/min
during sleep).

Answer 14

tachy
Brady

Question 15

• Several factors contribute to regulation
  of heart rate:

1. Autonomic nervous system
2. Somatic nervous system
3. Chemicals: hormones and cations
4. Others

true/false

Answer 15

false, not the somatic, which is about voluntary movements

Question 16

Nervous system regulation of the heart originates in the ….. center in the
medulla oblongata (lowest portion of the brainstem).

Answer 16

cardiovascular

Question 17

The cardiovascular center in the medulla receives input from:
1. Sensory receptors: propioceptors (monitor position of limbs and muscles),
chemoreceptors (monitor chemical changes in blood), ……receptors (monitor
the stretching of major arteries and veins caused by the pressure of the blood
flowing through them).
2. Higher brain centers: limbic system and cerebral cortex.

Answer 17

baro

Question 18

The cardiovascular center directs appropriate output by increasing or decreasing
the frequency of nerve impulses in only the
parasympathetic branches (vagus nerves) of the ANS

true/false

Answer 18

False, also sympathetic (cardiac accelerator nerves)

Question 19

What two chemicals regulate heart rate?

Answer 19

Hormones (epinephrine and norepinephrine)
and cations

Question 20

Cations:
Excess potassium speeds/slows the heart rate
Excess of calcium ions speeds/slows the heart rate

Answer 20

pot: slows
Calcium: speeds

Question 21

OTHER FACTORS REGULATING HEART RATE?

Answer 21

age, gender, fitness, body temp

Question 22

The end-diastolic volumen or EDV (preload) is a measure of the filling/emptying of the ventricle,

Answer 22

filling

determined by ventricular distensibility and the ventricular filling pressure.

Question 23

The end-systolic volumen or ESV (afterload) is the volume left in the heart at the end
of systole.

true/false

Answer 23

true

Question 24

Stroke Volume = end-diastolic volume - end-systolic volumen
SV = EDV - ESV
* According to this formula, how can we increase SV?

Answer 24

1. Increasing the end-diastolic volumen (EDV) (preload)
2. Decreasing the end-systolic volumen (ESV) (afterload)

Question 25

Three factors regulate stroke volume and ensure that the left and right ventricles
pump equal volumes of blood:

(1) Preload: the degree of stretch on the heart before it contracts.

(2) Afterload: the pressure that must be exceeded before ejection of blood from the
ventricles can occur.

(3) Contractility or inotropy: the forcefulness of contraction of individual ventricular
muscle fibers

Answer 25

ok

Question 26

Preload: Effect of Stretching or Frank–Starling law of the heart:

the more it fills, the greater the force of contraction

Answer 26

ok

Question 27

Afterload: ejection of blood from the heart begins when pressure in the right
ventricle exceeds the pressure in the pulmonary trunk (about 20 mmHg), and
when the pressure in the left ventricle exceeds the pressure in the aorta

true/false

Answer 27

true

Question 28

• The pressure that must be overcome before a semilunar valve can open is termed
  the preload

true/false

Answer 28

false, afterload

Question 29

increase in afterload causes stroke volume to in/decrease, so that more blood
remains in the ventricles at the end of systole

Answer 29

decrease

Question 30

Myocardial contractility or inotropy: the strength of contraction at any given
(constant) pre/afterload.

Answer 30

pre