Cardiovascular System

cardiovascular system is the heart and two circulator systems

pulmonary and systemic

What does the cardiovascular system do?

deliver oxygen and nutrients to the tissues and remove waste products

the myocardium does not contract synchronously but...

in a wave; right atria and ventricle; left atria and ventricle

pulmonary circulation

right ventricle -> pulmonary artery -> lungs (pulmonary capillaries -> pulmonary veins -> left atria

systemic circulation

left ventricle -> aorta -> arteries -> arterioles -> capillaries -> venules -> veins -> vena cava (great veins -> right atria

systolic blood pressure

pressure the blood exerts against the vessel while the heart is contracting; push against the wall

diastolic blood pressure

pressure the blood exerts against the vessel while the heart is relaxing

mean arterial blood pressure

average pressure the blood exerts against the vessel during a cardiac cycle (systole and diastole)

MABP = ?

1/3 (SBP-DBP) + DBP

normal blood pressure at rest is

120/80 mmHg

high blood pressure (hypertension) at rest is typically defined as

> 140/95 mmHg

SBP during exercise

increases linearly with an increase in exercise intensity (to ≥ 200mmHg at max); 220,240 ish

MABP during exercise

increases linearly with an increase in exercise intensity (to ≥ 140-150mmHg at max)

DBP during exercise

slight increase or decrease with an increase in exercise intensity

Conduction system of the heart

SA node, AV node, bundle of His, bundle branches, and Purkinje fibers

SA node (1)

at right atrium; AP sends depolarization across

AV Node (2), Bundle of His (3), Bundle Branches (4)

between the ventricles

Purkinje Fibers (5)

around the ventricles

Normal Electrocardiogram (ECG)

P wave, QRS complex, T wave

P wave

depolarization of the atria (atrial contraction)

QRS complex

depolarization of the ventricles (ventricular contraction)

T wave

repolarization of the ventricles (ventricular relaxation)

Heart can beat on its own until

it runs out of ATP

sympathetic nervous system (SNS)

catecholamines (NE and E) increase the heart rate and myocardial contractility

increased heart rate

tachycardia

decreased heart rate

bradycardia

parasympathetic nervous system (PNS)

acetylcholine decreases heart rate

training results as a ____ in SNS activation resulting in

decrease; a decrease in resting heart rate; drop in E and NE bc SV increases.

peripheral input to control heart rate

baroreceptors & proprioceptors; cardiovascular center in the medulla (brainstem)

baroreceptors

located at carotid sinus and aortic arch; activated by change in blood pressure

proprioceptors

Sensory receptors, located in the muscles and joints, that provide information about body position and movement.

vasoconstriction

stiffening of the blood vessels by contraction of arteriole smooth muscle due to NE release (SNS)

vasodilation

relaxation of the smooth muscle around the blood vessels due to acetylcholine release (decrease in NE)(PNS)

what else regulates blood flow

several local metabolites, circulating hormones, and neural mechanisms

lots of ATP = ____ blood flow

don't need as much

lots of ADP/AMP = _____ blood flow

need!

______ increase from rest to max HR

linear

training causes a ___ in Hr at rest, and at every work rate to max, but _____max HR

decrease (decrease SNS and decrease NE and E); similar (stays!)

stroke volume (ml/beat)

amount of blood pumped by the heart during one beat

stroke volume increases ______ with increasing work rates

curvilinearly; from 80ml/b at rest to 140ml/b

stroke volume plateaus at

40-50% VO2 max; bc BF can't fill faster

training increases SV at all work intensities bc

chamber size increases

maximal SV in elite athletes can be

200ml/b (bc bigger hearts)

females have lower SV than males

bc body size smaller = smaller hearts

why does stroke volume decrease with age?

bc heart will stiffen

cardiac output (L/min)

amount of blood pumped by the heart per minute (SVxHR)

CO has no change with training at any given work rate up to max bc

increase SV with training but that will decrease HR

Maximal cardiac output (Q) is greater with training due to

increased stroke volume

maximal Q =

20-25 L/min in untrained and 30L/min in trained (bc increased SV)

5-6L/min increase in Q with each

1L/min increase in VO2

regulation of stroke volume (three steps)

1. end-diastolic volume

2. average aortic blood pressure

3. ventricular contractility

end-diastolic volume (preload)

volume of blood in the left ventricle at the end of diastole; how much blood we pump per beat depends on how much blood we put in the chamber before contraction

average aortic blood pressure

Pressure the heart must pump against to eject blood (afterload)

ventricular contractility

the amount of force produced by the contracting ventricles

increase volume = increased stretch of cardiac muscle fibers =

increased contractility = increased stroke volume

how does rate of venous return influence EDV

better blood returns to heart, better fill, more blood that fills, more stretch in cardiac fibers, more force in contraction

aortic blood pressure (after load)

pressure to overcome to eject blood; left ventricular pressure must be greater than aortic pressure; inversely related to SV

cardiac contractility; increased force of contraction

increased by circulating E and NE; increased by direct sympathetic stimulation; mechanism via increased Ca++ available in cell for myocardial contraction

atrial-venous O2 difference

difference between O2 [ ] in arterial and venous blood; how much o2 did muscle use?

atrial-venous O2 difference depends on

aerobic metabolism at muscles and blood flow to muscles

atrial-venous O2 difference increases with

increasing exercise intensity ; the greater the difference the more O2 was taken up by muscles for aerobic metabolism

Fick Equation

VO2 = cardiac output x a-vO2 difference

shunting of blood from GI tract to exercising tissues (skeletal muscle and heart)

control of blood flow distribution as a result of autonomic stimulation (SNS and PNS)

in active skeletal muscle the effect of _____ _____ overrides the SNS vasoconstrictor effect

vasodilator metabolites (best at local spot) good bc exercising muscles need BF

since BF to muscles increases during exercise we must

increase venous return to the heart

three ways we increase venous return to heart during exercise

vasodilation of the skeletal muscle beds; vasoconstriction; the action of the skeletal muscle pump

vasoconstriction during exercise

constriction of veins to quickly move BF up to heart

the action of the skeletal muscle pump during exercise

contract, squeeze capillaries into veins to move blood back to heart

blood flow during exercise end result

increased ventricular filling and an increased stroke volume

Frank-Starling Law of the Heart

the more the heart fills with blood during diastole, the greater the force of contraction during systole; any increase in VR will increase ventricular filling during diastole

increase in end-diastolic volume stretches the myocardial fibers improving

myocardial contractility and results in an increased stroke volume

FSL: the effect of training results in changes that are mostly the result of

central adaptations (C-V) and secondarily due to alterations at the periphery (increase in SV)

throughout exercise (and rest), the most important variable the human body will always attempt to maintain is

Mean arterial blood pressure (MABP) bc brain needs BF

MABP must be maintained since

pressure is required to perfuse the various tissue beds

MABP =

Q x TPR