Ch 20--Cardiac Output & Venous Return & CH 21--Muscle Blood Flow and CO During Exercise & Coronary Circulation and Ischemic Heart Disease Flashcards
______ _____—the volume of blood pumped out of the heart per minute.
_________ ________—the volume of blood returning from the superior and inferior vena cava into the Right Atrium each minute.
Cardiac Output (CO)
Venous Return (VR)
CO = __? except for the few beats it takes to make the adjustment. Although HR, SV and cardiac contractility influence CO, the most influence on CO is ___ (the volume of blood returning to the heart has the most influence on how much will be pumped out).
VR
VR
Ultimately, the most influence on CO (and VR) is ______ _________ Resistance—the total amount of resistance for blood flow
Total Peripheral
Cardiac Output • The average resting CO for adults is usually expressed as about___L/min
5
CO varies depending on several factors:
- Size of the body (surface area—so height and weight)
- Level of ___ __ at rest (basal metabolic rate or BMR)
- Metabolic rate during __________
- Age—the decline in CO with age is indicative of decline in activity level and declining _______ ________
body metabolism
exercise
muscle mass
Frank-Starling Mechanism-1
_________ _______ circulation usually determines CO more than the heart itself. In essence, the factors that affect the amount of blood returning to the heart (VR) are the primary controllers of CO.
Peripheral (tissue)
Frank-Starling Mechanism-2
Frank-Starling Mechanism (Law) is an ___________mechanism that signals the heart to automatically pump out the same amount of blood that was returned to the right atria.
- The mechanism works on this basis:
- ↑ VR (pre-load) → ↑ STRETCH of cardiac muscle fiber →↑ in CONTRACTILITY fibers (force of contraction) →↑ __
So with an increase in VR, there is the same increase in __
autoregulatory
SV
CO
Frank-Starling Mechanism-3
Another factor is the stretching of the cardiac muscle fibers also increases HR because the stretch also affects the SA node in the wall of
the ________ atrium.
right
Frank-Starling Mechanism-4
The stretched right atrium initiates the\_\_\_\_\_\_\_\_\_ Reflex which passes information via the vagus nerves to the vasomotor center (VMC) located in the \_\_\_\_\_\_\_\_\_ of the brain. This vagal nerve stimulus signals the sympathetic nervous system to increase HR.
Bainbridge
medulla
Frank-Starling Mechanism-5
The increase in HR prevents ‘________” of the blood in the veins, atria and pulmonary system.
Under normal resting conditions, \_\_ is controlled by peripheral circulation (the sum of all local tissue blood flows) which determines VR. Therefore, \_\_ is the “sum of all local blood flow regulations.”
damming
CO
CO
CO varies inversely with ___
Ohm’s Law:
CO = ________ pressure/ TPR
TPR
arterial
Chronic Conditions that Cause↓TPR—1
__________—caused by insufficient vitamin B1 (thiamin) in the diet. This vitamin is needed in the metabolic pathway so if ATP isn’t made, the cell’s reaction is to need more nutrients, thus more blood so local blood vessels dilate which ↓TPR.
Beriberi
Chronic Conditions that Cause↓TPR—2
______________—tissue metabolism increases so O2 need increases. To increase local blood flow, blood vessels dilate which ↓TPR.
Hyperthyroidism
Chronic Conditions that Cause↓TPR—-3
________—decrease in blood viscosity and with decrease in RBCs is a decrease in O2 delivery. To increase
O2 delivery, local blood vessels dilate which ↓TPR
Anemia
Factors Related to HYPEReffective Heart (increased plateau)
- Nervous System Excitation:
a) Sympathetic Stimulation
b) Parasympathetic Inhibition - _________—as with skeletal muscle, long-term aerobic exercise will increase the mass and contractile strength of the heart muscle (myocardium).
Hypertrophy
***This increased pumping volume
(CO) is considered one of the most
important training effects of
aerobic (endurance) training.
Factors Related to HYPOeffective Heart
(decrease the plateau)
- Low Pumping Effectiveness: When the heart becomes
severely damaged, the ability to pump blood to the tissues is severely compromised.
a. Severe coronary artery blockage leading to an MI
b. Severe valve disease
c. Myocarditis
d. Cardiac _________
e. Cardiac _________ - Interference with VR = Anything that ↓VR will lead to a
↓CO
a. Decreased blood volume—results most often from ____________
b. Acute venous __________—results from fainting.
c. Decrease in tissue mass (skeletal muscle)—results from aging and inactivity.
tamponade
shock
hemorrhaging
dilation
Muscle Blood Flow and CO During Exercise—1
- When exercise begins, the shift (_________) in blood flow to the skeletal muscles is needed to bring O2 and nutrients to the muscles and carry CO2 and waste products away.
- Blood flow to the exercising muscles can increase
___-_____ fold depending on the intensity of exercise and the aerobic capacity of the individual.
vasodilation
25-50
Muscle Blood Flow and CO During Exercise—2
Blood flow fluctuates during exercise—during the contraction phase of exercise, the contracted muscles compress the blood vessels so blood flow ______. During the relaxation phase, the blood vessels are wide-open so blood flow. Example of running—foot on ground contraction, foot in air, relaxed.
decreases
increases
Muscle Blood Flow and CO During Exercise—3
During exercise, dormant capillaries open to increase capillary surface area ___ to ________fold
two to threefold.
Local Control of Muscle Blood Flow During Exercise
The significant increase in blood flow to the exercising
muscles is caused mainly by the following chemicals
acting directly on arterioles causing them to vasodilate:
- ↓O2 content in the tissue fluid because it is used rapidly during exercise—causes dilation of arteriole walls which signals the release of _________ substances.
- _________- is one of the vasodilator substances but it cannot stimulate enough blood flow.
- Other vasodilator substances—K+, LA, ↑CO2
vasodilator
Adenosine
Sympathetic and Hormonal Regulation During Exercise–1
Along with the local vasodilator substances, the sympathetic nervous system and hormones also have a role in ________ blood flow to the exercising muscles.
increasing
Sympathetic and Hormonal Regulation During Exercise–2
Releases _____________(alpha- receptors) which vasoconstricts blood vessels in non-exercising areas so reduces blood flow to the kidneys and gut by 1/3 to ½ of resting values.
noreponephrine
Sympathetic and Hormonal Regulation During Exercise–3
Adrenal medulla releases norepinepherine and epinepherine which works as a ___________ on ß receptors in skeletal muscle.
vasodilator
Total Body Circulatory Readjustments During Exercise –1
- Mass Sympathetic Discharge—at the onset of exercise, voluntary signals to the brain cause :
(1) muscle contractions,
(2) the Vasomotor Center (VMC) initiates the sympathetic discharge to the whole body, and
(3) inhibition of parasympathetic signals to the heart.
a. Heart is stimulated to increase HR and force of contraction.
b. Most of the _____________in the body are strongly contracted except for those involved in exercise. Redistribution of blood from nonmuscular areas to the skeletal muscles. (Cardiac and cerebral blood vessels have limited capacity to vasoconstrict and to maintain blood flow during exercise).
c. The walls of the veins contract which increases VR.
arterioles