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)
Pulmonary Circuit (Right side)
Systemic Circuit (Left side)
right atrium receives blood from body (deoxygenated). Right ventricle sends blood to lungs.
left atria receives blood rom lungs (oxygenated). Left ventricle sends blood to body.
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)
(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.
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.
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)
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
pressure when heart relaxes (80mmHg)
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.
Conduction system, atria, and ventricle
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)
Sympathetic constriction of smooth muscle
-Veins hold less blood > more goes back to heart
Muscle pump: rhythmic skeletal muscle contraction
-compress veins > push blood back to heart
doesn't work well when standing
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.
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)
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.