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Flashcards in Section 7 Deck (47):

Functions of the CV system (5)

1. deliver O2 to tissue
2. deliver deoxygenated blood to lungs
3. transport heat from core to skin
4. deliver nutrients to tissues
5. transport hormones to tissues


Describe heart structure (2)

striated lattice-like.
Pulmonary Circuit (Right side)
Systemic Circuit (Left side)


Pulmonary Circuit

Right side;

right atrium receives blood from body (deoxygenated). Right ventricle sends blood to lungs.


Systemic Curcuit

Left side;

left atria receives blood rom lungs (oxygenated). Left ventricle sends blood to body.


Arterial System

aorta, arteries, and arterioles

moves blood front heart to tissues.
High pressure w/ elastic recoils.
Endothelial lining (lack of is an early sign of cardiovascular disease), smooth muscle, and connective tissue (anchors it into place).


Cardiorespiratory System (3)

Arterial System
Capillaries system
Venous System


Capillaries System

(fiber type dependent)

Store quite a bit of blood.
Exchange vessel are 7-10 m in diameter.
Contain 6% of total blood volume.
Pre-capillary sphincters regulate flow.


Venous System

coronary sinus, venules, and veins

Blood movement from tissue to heart (assisted by one-way valves).
Low pressure, thinner-walled collection and return tubes. Serve in capacitance role (about 2/3 of blood on the venous side).
When sitting, 60-65% of our blood is between our hips and downward.



Contractile portion of the heart responsible for force. Intercalated discs intercellular connections that permit the transmission of electrical impulses between fibers. The heart contracts as a unit (“functional syncytium”). Highly aerobic with high capillary and mitochondrial density.
Heart muscle receives blood from the R and L coronary arteries.


Myocardial Circulation

Coronary arteries branch off the ascending aorta.
Right coronary artery (RCA) supplies predominantly the right atrium and ventricle.
The left coronary artery (LCA) supplies the left atrium and ventricle and small portion of the right ventricle.


Myocardial O2 use at REST

~70-80% available O2.

Myocardium has higher mitochondrial density than Type 1 fiber.

This allows heart to utilize: glucose, lactate (fuel for heart), and fatty acids (produce more ATP at rest).

Lactate>pyruvate>Acetyl-CoA>combusts thru Krebs and ETC

Endurance exercise increases: use of lactate and FFA for fuel, which decreases use of carbs


Myocardial O2 use during EXERCISE

flow must increase to meet O2 demand

flow may increase 4-6x during strenuous-near max exercise.

Increase in CO= heart is working very hard


Myocardial Workload Assessment

Rate - Pressure or Double Product: Systolic Blood Pressure (SBP) x HR.
If this number is high, that means the heart is working hard.
MAP = DBP + 1/3PP


Electrical Conduction System (5)

1. SA node initiates the action potential, which sweeps across the atria.
2. Slight delay at the AV node to allow the atria to finish pumping blood.
3. Impulse is then transmitted to the AV bundle.
4. Impulse spreads to contractile fibers of the ventricle.
5. Ventricular contraction begins.

Parasympathetic stimulation- decreased heart rate (slower NA influx)
Sympathetic stimulation- increased heart rate (less K efflux)


Auto Rhythmicity

it refers to the electrical activity of the heart & how the heart contracts rhythmically as a result of APs that it generates by itself


Components of blood (5)

Plasma: watery portion consisting of ions, proteins, and hormones.
Cells: red bloods cells, platelets, WBCs.
RBCs: contains hemoglobin for O2 transport
Platelets: blood clotting
WBCs: immune function



Hematocrit: percentage of blood that’s RBC. Varies person to person (42% males, 38% females).
Hematocrit increase = Viscosity increases.


2 phases of the cardiac cycle and how they relate to BP

Diastolic BP (relax)
Systolic BP (contraction)

maintains blood pressure and keeps blood flowing to organs


Diastolic BP


pressure when heart relaxes (80mmHg)


Systolic BP


the pressure exerted on the arteries when the heart contracts (120 mmHg).


What is blood pressure and what factors influence it?

Combined effects of arterial blood flow per minute and resistance to that flow in the peripheral vasculature (BP = cardiac output x total peripheral resistance).

Cardiac output: product of HR and SV
Total peripheral resistance: the amount of resistance to blood flow in the system (BP = SV x HR x TPR)


What regulates Heart Rate?

sympathetic (excitatory) and parasympathetic (inhibitory) nervous systems. Branches innervate different areas.


Sympathetic NS

excitatory (norepinephrine).
Conduction system, atria, and ventricle


Parasympathetic NS

inhibitory (acetylcholine).
Conduction system and mainly atria.


What regulate Stroke Volume? (3)

End-Diastolic Volume (Preload)
Aortic BP (Afterload)


End-Diastolic Volume (Preload)

volume of blood in ventricles at the end of diastole.
Frank Starling Law of the heart (More stretch = greater SV)
Increased EDV = Increased stretch of cardiac fibers.
Stretch is more optimal so “better” alignment of actin and myosin = more cross-bridges = increased force of contraction
Venous return increase = EDV increase


Aortic BP (Afterload)

pressure in the aorta
In order to eject blood, the pressure generated by the left ventricle must exceed the aortic pressure
SV is inversely related to aortic pressure
Afterload minimized during exercise by arteriole dilation
(makes it easier for heart to pump blood)



Greater force of contraction= myocardium squeezes harder and ejects more blood (systole).

In skeletal muscle SR-released Ca2+ saturates troponin.
In cardiac muscle SR release DOES NOT saturate troponin.
An increase in calcium release causes a greater contraction.
Increased force of contraction; myocardium squeezes harder and ejects more blood


EDV: Venous Return during exercise (3)

Muscle pump
Respiratory pump



Sympathetic constriction of smooth muscle

-Veins hold less blood > more goes back to heart


Muscle pump

Muscle pump: rhythmic skeletal muscle contraction

-compress veins > push blood back to heart
doesn't work well when standing


Respiratory pump

rhythmic pattern of breathing provides a mechanical pump > promotes venous return from abdominal region


Factors that impact peripheral resistance (3)

Viscosity of blood
Vessel length: changing vessel length is key to diverting blood away from inactive tissues to the active muscle when needed
Radius: primary factor of blood flow regulation)

Resistance = (Length Vessel x Viscosity of Blood)/


Flow is proportional to ? and inversely related to?

Proportional to pressure (more pressure forced outward, more pressure from resistance).
Inversely proportional to resistance (one increases, the other decreases)


Fick Equation variables, hormones, and purpose of increased HR

Fick Equation= VO2 = CO x A-VO2 diff (amount of O2 extracted by tissues)
Hormones? Epinephrine and norepinephrine
Purpose of increased HR? Push out more blood


Describe age and maximal HR

As we age, our Max HR decreases

Maximal HR is “Function of Age”

Estimation equations (Others exist)
Max HR = 220 – age (10-12 bpm)

Only way to find true maximal HR is via maximal exercise test (stress test)

If max HR decreases, we don’t push out as much blood and struggle with extraction


Describe exercise and SV

Volume of blood pushed out with each beat

SV plateaus during the exercise intensity continuum

Estimated around 50-60% VO2max in untrained

Not linear with VO2

Aerobic training: plasma volume expansion


Describe the distribution of cardiac output during rest and exercise using some specific values

Rest: 14% CO
Exercise: 4% CO, but absolute blood flow is increased.

Skeletal Muscle:
Rest: 20% cardiac output (1000 mL) and only 25% O2 extraction.
Exercise: 80-85% cardiac output (21,000 mL). Exercise = increased blood flow and increased % O2 extraction.

Rest: 4% CO, extracts 70-80% 02.
Exercise: only way to get large increase in O2 to heart is to increase blood flow during exercise. Same percentage cardiac output during max exercise (4%), but absolute blood flow is increased (200 v. 1000 mL perfuses the myocardio).


Sympathetic NS on blood flow

activates at the beginning of exercise and causes system-wide vasoconstriction via increased sympathetic response.
If the SNS response drives up HR, increases SV, and creates vasoconstriction, then we push out and return more blood to the heart.

Increased metabolic rate changes within muscles during exercise: decreased O2: increased CO2; increased NO, K+, adenosine, decreased pH.


Metabolites on blood flow

override sympathetic influence in active regions
-results in vasodilation of arterioles (more blood) feeding active skeletal muscle (called autoregulation)


A-VO2 Difference during rest

Resting metabolism consumes ~5 mL O2 from 20 mL O2 in each deciliter of arterial blood (50 mL/L) that passes through the tissue capillaries.

This equals an a-vO2 diff of 5 mL O2 per deciliter of blood that perfuses the tissue-capillary bed.

Thus, 15 mL O2 or 75% of blood’s original O2 load still remains bound to hemoglobin at rest.


A-VO2 Difference during exercise

Arterial: doesn’t change much from 20mL O2 throughout exercise (bc there’s less venous O2 due to extraction)

Venous: O2 content decreases from 12-15mL/dL (rest) to 2-4mL/dL (max exertion)


Cardiac Output

ability to get blood out of the heart



amount of O2 consumed


Relationship between CO and VO2

Low VO2 = low COmax; High VO2 = high COmax (ratio of 5-6L CO: 1L VO2 above resting value; 5-6:1).
This relationship essentially remains unchanged regardless of activity.


Genetic influence of CO and VO2 relationship

high levels of VO2max and CO provide distinguishing characteristics for preadolescent and adult endurance athletes.


A-v02 diff

Measured difference in O2 between arterial and venous blood