Cardiovascular phsyiology ( Heart and Blood Vessels) chapter 20

Question 1

Describe the cardiac events that occur with the different parts of the ECG (P wave, QRS wave, T wave) and what electrical event causes each.

Answer 1

• P wave = caused by the depolarization of the cells of the atria
• QRS wave = repolarization of atria and depolarization of ventricles
• T wave = repolarization of ventricles

Question 2

Define diastole (in the heart).

Answer 2

A period of relaxation in a chamber of the heart, as part of the cardiac cycle

Question 3

Define systole (in the heart).

Answer 3

A period of contraction in a chamber of the heart, as part of the cardiac cycle

Question 4

Describe how pressure changes in the heart chambers cause the flow of blood through the heart (the “cardiac cycle”).

Answer 4

1) blood is returning to the heart into the atria.
2) the tricuspid and mitral valves are open so blood flows into the ventricles
3) this occurs because the pressure in the atria(returning venous blood) is greater than the ventricles which are relaxing and getting bigger. Eventually the ventricles reach maximum relaxation but continue filling up with blood
4) resulting in atrial contraction

Question 5

Define/describe isovolumetric contraction

Answer 5

During the time period between the closure of the AV valves and the opening of the aortic and pulmonic valves, ventricular pressure rises rapidly without a change in ventricular volume (i.e., no ejection occurs). Ventricular volume does not change because all valves are closed during this phase. Contraction, therefore, is said to be “isovolumic” or “isovolumetric.”

Question 6

Define/describe isovolumetric relaxation

Answer 6

When pressure in left ventricles is less than pressure in vessels , causing aortic and pulmonic valves to close
Ventricular blood volume is constant and atrial pressure rises due to venous return

Question 7

Describe the cause of each of the two main heart sounds.

Answer 7

Lupp = recoil of blood due to AV valves closing (ventricles contracting)
Dupp = recoil of blood due to Semilunar valves closing*(start of ventricles filling)

Question 8

Define stroke volume

Answer 8

avg = 70-80 mL
the volume of blood pumped out of a ventricles during each beat ( contraction )
difference between end diastolic volume and end systolic volume

Question 9

describe the relationship between stroke volume, enddiastolic volume and end-systolic volume.

Answer 9

you get the largest stroke volume when EDV is as large as it can be and ESV is as small as it can be.
SV = EDV - ESV

Question 10

what is end-diastolic volume

Answer 10

end-diastolic volume is the amount of blood in each ventricle at the end of diastole.

Question 11

what is end-systolic volume

Answer 11

end-systolic volume is the amount of blood left over at systole

Question 12

Describe how stroke volume can be affected by filling time

Answer 12

filling time= how much time was available for the ventricle to fill up with blood
longer filling phase means more blood can enter ventricles resulting in a greater EDV and larger stroke volume

Question 13

Describe how stroke volume can be affected by venous return

Answer 13

venous return = how much blood is flowing through the veins back toward the heart.
if venous return is high (lots of blood coming to veins to the heart ) you will be able to fill it up more resulting in a greater EDV therefore greater stroke volume

Question 14

Describe how stroke volume can be affected by preload

Answer 14

preload = the amount of stretch the muscle cells are undergoing
if increased preload than As ventricle fills up it stretches and causes conditions for a more efficient contraction allowing more blood out therefore stroke volume will increase

Question 15

Describe how stroke volume can be affected by contractility

Answer 15

contractility = how efficient cells contract
example having more calcium available will increases the efficiency of contraction . therefore high contractility will decrease ESV (more blood out) and stroke volume will be higher

Question 16

Describe how stroke volume can be affected by afterload

Answer 16

afterload = the amount of force you need to open up semi lunar valves and eject blood
increased by factors that restrict blood flow through arterties ex: blockage in the arteries. Therefore increasing ESV and decreasing stroke volume

Question 17

define cardiac output

Answer 17

amount of blood pumped by each ventricle in one minute.

Question 18

describe the relationship between cardiac output,

stroke volume, and heart rate

Answer 18

cardiac output can be altered by changes in heart rate or stroke volume .
how many times your heart beats per minute and how much blood is pumped every time it beats. a person needs a certain amount of blood pumped out over time.
(you can have a really high stroke volume to meet cardiac output need but if your stroke volume wasn’t efficient then maybe your heart rate would have be higher to compensate for that to pump more frequently to get the same volume of blood pumping out. )