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
Total Body Circulatory Readjustments During Exercise–2
- Increase in Mean Arterial Pressure results from ______________of metarterioles and small arteries in nonworking areas and an increase in mean systemic filling pressure caused by the contraction of the veins.
• Mean arterial pressure increases 20-80 mmHg during exercise.
• The increase in arterial pressure is dependent on exercise intensity. Jogging or swimming may only raise it 20 mmHg but high intensity exercise like a maximal bench press may raise it 80 mmHg or more.
• This increase in MAP will also cause a stretch in the walls of the blood vessels thus assisting with signaling vasodilation. This stretch on the walls to cause vasodilation is one of the most important factors for ___________ blood flow to the working muscles.
vasoconstriction
increasing
Total Body Circulatory Readjustments During Exercise –3
- Increase in Cardiac Output—the increase in CO is in proportion to the ___ demand of exercise.
• Increased CO provides O2 and nutrients to the working muscles and this is just as (if not more) important than the need to increase HR and force of contraction.
• An untrained individual can increase CO by 4 fold while a trained endurance athlete can increase CO 7 fold and an elite athlete 9 fold or more.
O2
Coronary Circulation and Ischemic Heart Disease
- ___% of all deaths in industrialized (primarily, Western) countries are due to heart disease (as compared to 22% due to cancers).
- 33% of all deaths result from coronary artery disease (CAD).
- Almost all elderly people have some level of CAD.
45
Risk factors for CAD
Irreversible x 3…name them.
- Aging
- Male
- Genetic predisposition
Risk factors for CAD
name 6 that are REVERSIBLE:
Reversible 1. Cigarette smoking— doubles risk of MI 2. Hypertension 3. High LDLs from high saturated fat diet 4. Physical Inactivity 5. Obesity 6. Diabetes if from lack of exercise and obesity
Control of Coronary Blood Flow—1
- Local Muscle Metabolism—arteriole __________occurs in response to increased nutrient needs of cardiac muscle.
***This is similar to control of local blood flow of
other tissues.
vasodilation
Control of Coronary Blood Flow–2
- O2 Demand—the heart’s need for ___ is a major
regulator of coronary blood flow. Normally, 70% of the O2 is removed as the blood flows through the coronary blood vessels. Therefore, blood flow must _________ in proportion to O2 demand.
When ATP degrades to ADP, AMP and then adenosine,
adenosine is a major vasodilator substance.
Other vasodilators in the heart are K+, H+, CO2 and
nitric oxide.
O2
increase
Control of Coronary Blood Flow–3
- Nervous Control—nervous stimulation comes
from the autonomic nervous system:
a. ___________ –release of acetylcholine from vagus nerves slows heart rate and decreases force of contraction.
b. ______________—norepinephrine and epinephrine cause the blood vessels to vasoconstrict and increase HR and force of contraction. Epicardial cells have receptors so vasoconstrict intramuscular arterioles have ß receptors so vasodilate. More influence from vasoconstrictors—people with ischemia have chest pain (angina) during times of significant vasoconstriction.
Parasympathetic
Sympathetic
Energy Supply for Heart
- ___% from lipid (fat) metabolism
- Glycolysis (glucose) must be used under anaerobic or ischemic conditions to produce ATP.
• _____________glycolysis uses lots of glucose and forms lots of lactic acid which may contribute to the angina in ischemic conditions.
70
Anaerobic
Ischemic Heart Disease
Definition—insufficient coronary blood flow
______________—the most frequent cause of diminished blood flow in the coronary arteries. Cholesterol deposits collect beneath the endothelium of the damaged blood vessel walls. These deposits are invaded by fibrous tissue and become calcified forming plaque. The plaque protrudes into the lumen of the blood vessel and either partially or completely blocks blood flow. The most common place for this to form is first few cm of the __________ arteries.
Atherosclerosis
coronary
Acute Coronary Occlusion—most frequently occurs in people with underlying atherosclerosis.
- If the plaque breaks through the endothelium, it comes in direct contact with the flowing blood. Since the plaque has an unsmooth surface, platelets adhere to it, fibrin is deposited and RBCs get trapped forming a blood clot. This blood clot is called a_______________
- If the blood clot breaks away and travels via the blood to a smaller branch of the artery, it causes a coronary ____________ in the more distal part of the blood vessel.
thrombus.
embolus
Collateral Circulation—in the heart, the smaller coronary arteries have____________. When an occlusion occurs in a large coronary artery, the anastomoses begin to
dilate immediately. This is why people with atherosclerosis don’t know it until the plaque build up is
excessive and the collateral circulation is not enough. Heart’s ability to pump is severely compromised.
anastomoses.
Myocardial Infarction (MI)—immediately after an acute coronary occlusion, blood does not flow beyond the occluded area except for the small amount of collateral circulation. The area of the heart that receives little or no blood supply is said to be \_\_\_\_\_\_\_\_\_\_\_\_
Soon after the occlusion, collateral circulation increases but the blood flow to this area becomes stagnant. The cardiac muscle uses all the O2 so the deoxygenated hemoglobin caused the infarcted area to take on a bluish-brown color.
infarcted.
Function of Heart After Recovery from an MI:
- The most important factors in treating a patient after an MI is complete body rest during the recovery process.
- The heart has the potential to recover to full functional capacity. However, most often the heart’s pumping capabilities are compromised below that of a healthy heart.
- Even with a compromised heart, under resting conditions, the heart can pump enough blood to make most day-to-day activities comfortable.
- The normal heart is capable of pumping 300-400% above resting (called______ ________). Even with a 100% cardiac reserve, the person can perform most daily activities.
cardiac reserve
Drug Treatments x 2
1– ____________ drugs such as nitroglycerin and other nitrates
2 – Beta Blockers such as propranolol (block sympathetic
receptors)
Surgical Treatments x 4
1– Angioplasty –balloon-tipped catheter
2– Stents—stainless steel mesh
3– Laser beam from tip of catheter—dissolves the plaque
4– By-Pass Surgery using a subcutaneous vein from leg as a graft
Vasodilator
Four Causes of Death After Acute Coronary Occlusion:
- Decreased Cardiac Output—if the cardiac muscle fibers cannot contract normally, then cardiac output decreases.
- _____ __________occurs when the dead or nonfunctional area develops pressure from the inside of the ventricle therefore, the pumping capacity of the left ventricle is diminished.
- When the heart is incapable of pumping enough blood through the arterial tree, cardiac failure and tissue death occurs.
- When there is not enough blood for the heart to receive nutrients, it goes into _____ _______
Systolic Stretch
cardiac shock.
Four Causes of Death After Acute Coronary Occlusion:
- Damming of Blood in the Venous System—if the heart isn’t pumping blood forward, it is damming in the atria, pulmonary vessels and the veins.
• Not noticeable initially after MI but within a few days, this decreased CO means less blood flow to the kidneys so urine production is diminished as well. This leads to increased blood volume.
• This leads to ________ and which produces
congestive heart failure.
edema
Four Causes of Death After Acute Coronary Occlusion:
- Ventricular Fibrillation—usually after a large infarct but can also occur after a small occlusion.
• Two dangerous periods after an MI when V-fib is most likely to occur:
– Within the first 10 minutes of the MI
– Another beginning an hour or so later and lasting a few hours
• Acute decrease in blood flow to the cardiac muscle causes an rapid decrease of K+ which increase K+ in the extracellular fluids. This increase in extracellular K+ causes _________
fibrillation.
Four Causes of Death After Acute Coronary Occlusion:
- Rupture of the Infarcted Area—does not occur within
the first few days after an MI.
• A few days after the MI, the cardiac muscle begins to
degenerate and the dead muscle bulges outward with
each contraction.
• This systolic stretch becomes greater until the heart
ruptures.
• When the heart ruptures, the loss of blood flow into
the pericardial space causes cardiac ________ by blood collecting in the pericardial cavity.
• Because of the compression on the heart, blood cannot
flow into the right atrium and the individual dies suddenly because there is no CO.
tamponade
