BMS 108 Ch. 14 Cardiac Output, Blood Flow and Blood Pressure

Question 0

What is stroke volume? Heart rate? Total blood volume?

Answer 0

Volume of blood ejected from each ventricle per beat ~80 ml/beat

Beats per min ~70 bpm

Total blood volume is about 5.5L

Question 1

What is cardiac output? What is the equation for calculating cardiac output?

Answer 1

volume of blood pumped/min by each ventricle; CO=SV x HR

Question 2

How long does it take for blood to circulate through the body?

Answer 2

about a minute

Question 3

What factors regulate cardiac output?

Answer 3

1. SA node

2. Sympathetic and Parasympathetic input

Question 4

What is the main controller of HR?

Answer 4

SA node

Question 5

How to Sympathetic and Parasympathetic regulate cardiac rate?

Answer 5

modifying the rate of spontaneous depolarization

Question 6

Where does ANS input to the heart originate?

Answer 6

Cardiac control center in the medulla

Question 7

Describe the mechanism by which sympathetic input increases HR.

Answer 7

1. NE binds to B1 adrenergic receptors
2. 2nd messenger system increases the number of cyclicnucleotides
3. This increases the number of open HCN channels
4. which causes HR to increase because SA node is depolarizing faster

Question 8

Describe the mechanism by which parasympathetic input decreases HR.

Answer 8

1. ACh binds to mAChR activating a 2nd messenger system
2. Causing more K+ channels to open
3. More K+ leaves the cell as Na+ is entering the cell
4. Cell reaches threshold slower, effectively decreasing HR

Question 9

What are the three components that determine cardiac output?

Answer 9

1. End diastolic volume (EDV)
2. Total peripheral resistance (TPR)
3. Contractility

Question 10

What is End diastolic volume?

Answer 10

Volume of blood in the ventricles at the end of diastole (aka preload)

Question 11

What is Total peripheral resistance?

Answer 11

Frictional resistance to blood flow in arteries (aka afterload)

Question 12

What is contractility?

Answer 12

Strength of ventricular contraction.

Question 13

What is the relationship between EDV and Stroke Volume? TPR and SV? Contractility and SV?

Answer 13

increase EDV = increase SV
increase TPR = decrease SV
increase Contractility = increase SV

Question 14

What is the Frank Starling Law of the Heart?

Answer 14

States that strength of ventricular contraction varies directly with EDV

Question 15

Why is EDV directly tied to SV?

Answer 15

As EDV increases, myocardium is stretched more, causing greater contraction and SV

Question 16

Why does this stretch effect have a greater impact in cardiac muscle than skeletal muscle?

Answer 16

Due to the increased sensitivity of cardiac muscle to the stimulatory effects of Ca++

Question 17

If EDV is an intrinsic control on contractility of the heart, what are extrinsic controls?

Answer 17

Sympathetic and Parasympathetic input.

Question 18

How does Sympathetic and Parasympathetic input control contractility?

Answer 18

By increasing Ca++ in sarcomeres

Question 19

What factor influences EDV?

Answer 19

Venous return of the blood

Question 20

What is Venous return of blood influenced by?

Answer 20

1. Blood volume and venous pressure
2. Vasoconstriction (Symp)
3. Skeletal muscle pump
4. Pressure drop during inhalation

Question 21

What is Ejection Fraction of the Heart? What is a normal %?

Answer 21

% EDV ejected/contraction; normal = 80ml/130ml = 60%

Question 22

Distribution of ECF between blood and interstitial compartments is in a state of ________ _______.

Answer 22

dynamic equilibrium

Question 23

What drives movement of fluid out of capillaries in the capillary bed?

Answer 23

hydrostatic pressure - pressure exerted against the capillary walls

Question 24

Other than hydrostatic pressure, what else drives the movement of ECF between blood and interstitial fluid?

Answer 24

Colloid osmotic pressure - the pressure exerted by proteins in blood plasma

Question 25

What is the difference between osmotic pressures in and outside of capillaries that affect fluid movement called?

Answer 25

oncotic pressure

Question 26

Are blood proteins able to diffuse through capillary walls?

Answer 26

no

Question 27

What determines overall fluid movement in capillary beds?

Answer 27

Determined by net filtration pressure and forces opposing it (Starling forces).

Question 28

What percetage of the ECF that leaks out of the capillary beds is reabsorbed by the venules?

Answer 28

80%

Question 29

How many liters of interstitial fluid is absorbed by the lymphatic system per day?

Answer 29

3L

Question 30

Is interstitial fluid static?

Answer 30

no

Question 31

What is an edema?

Answer 31

Excessive accumulation of interstitial fluid resulting from:

1. High arterial blood pressure
2. Venous obstruction
3. Excess proteins into interstitial fluid
4. Low plasma protein levels resulting from liver disease
5. Obstruction of lymphatic drainage