6: Review of Exercise Physiology - Cardiovascular System

Veins

receives deoxygenated blood

Right Atrium

receives DEOXYGENATED blood

Tricuspid Valve

right AV valve

Right Ventricle

sends DEOXYGENATED blood to lungs

Pulmonic valve

semilunar valve

Pulmonary ____→ _____ → Pulmonary _____

Pulmonary artery → Lung → Pulmonary vein

Left Atrium

receives oxygenated blood from lung

Bicuspid Valve

Left AV valve

Left Ventricle

send oxygenated blood to the aorta/body

Aortic valve

semilunar valve

aorta

Main artery that carries oxygenated blood from the Left Ventricle to the body

diastole

• relaxation phase: ventricles FILL with blood

• atrioventricular valves are open

• aortic and pulmonic valves closed

systole

• contraction phase during which ventricles EXPEL blood

• atrioventricular valves are closed

• aortic and pulmonic valves open

intrinsic control *4

• autorhythmaticity

• sinoatrial node

• atrioventricular node

• purkinje fibers

autorhythmaticity

• ability to initiate impulse for contraction at regular intervals

• controlled by the SA node (pacemaker

sinoatrial node

pacemaker of cardiac contraction

atrioventricular node

delays impulse by 1/10 of second, allowing atria to contract before ventricles

purkinje fibers

rapidly spreads impulse to contract throughout ventricles

electrocardiogram (ECG)

records the electrical activity of the heart

P wave

atrial depolarization

QRS complex

• ventricular depolarizations

• atrial repolarization

T wave

ventricular repolarization

ECG abnormalities may indicate what?

Coronary heart disease

What 2 things can ST elevation indicate?

• sign of myocardial ischemia ← blockage of coronary artery

• myocardial infarction

What 3 things can ST depression indicate?

• sign of myocardial ischemia

• non-ischemic: ventricular hypertrophy, hypothermia, digoxin

• normal variant: hyperventilation

Diastole: Pressure in ventricles is ____

low

Diastole: Ventricles are _____

filling with blood from atria

Diastole: AV valves open when ___

ventricular pressure is less than atrial pressure

systole: pressure in ventricles ____

rises

systole: blood is ejected in _____

pulmonary and systemic circulation

systole: semilunar valves open when _____

ventricular pressure is greater than aortic pressure

first heart sound (lub)

closing of AV valves

second heart sound (dub)

closing of aortic and pulmonary valves

what is the equation for cardiac output?

Q = heart rate (HR) x stroke volume (SV)

What are the 2 types of control that regulate heart rate?

• intrinsic

• extrinsic

What are the 3 types of control that regulate stroke volume?

• end diastolic volume

• afterload

• contractility

What is an example of intrinsic control of heart rate?

Autorhythmaticity

What two systems regulate heart rate?

parasympathetic and sympathetic nervous system

how does the PNS affect heart rate?

• by the vagus nerve

• slows HR by inhibiting SA and AV node

how does the SNS affect heart rate?

• by the cardiac accelerator nerves

• increases HR by stimulating SA and AV node

what is parasympathetic tone?

baseline level of activity of the PNS → low resting HR

what causes an increase in HR at onset of exercise

parasympathetic withdrawal

What causes the later increase in heart rate during exercise (after ~100 beats/min)?

increased SNS stimulation

Name two types of sensory receptors involved in the extrinsic neural control of blood pressure and heart rate

• Baroreceptors

• Mechanoreceptors

Baroreceptors (sensory/afferent)

located in the carotid artery and aortic arch

Mechanoreceptors

detect beat to beat blood pressure

what do baroreceptors do if BP is high?

send signals to medulla oblongata

• to increase parasympathetic nervous activity (PNA)

• to decrease sympathetic nervous activity (SNA)

• decrease HR → reduced BP

end-diastolic volume (EDV)

volume of blood in the ventricles at the end of diastole (preload)

aortic blood pressure

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

strength of ventricular contraction (contractility)

enhanced by:

• circulating EPI and NE

• direct sympathetic stimulation of heart

frank-starling mechanism

greater EDV → more forceful contraction

• due to stretch of ventricles

what is EDV dependent on

venous return

what 3 factors increase venous return?

• venoconstriction (by SNS)

• skeletal muscle pump

• respiratory pump

skeletal muscle pump

• rhythmic skeletal muscle contractions force blood in the extremities toward the heart

• one-way valves in veins prevent backflow of blood

respiratory pump

changes in thoracic pressures pull blood toward heart

afterload

tension developed in the wall of the left ventricle during ejection

high afterload results in ____

decrease in stroke volume

• requires greater force generation by the myocardium to eject blood into the aorta

how does increased ventricular contractility affect stroke volume

results in higher stroke volume

what 2 factors enhance ventricular contractility?

• circulating EPI and NE

• direct sympathetic stimulation of heart

regulation of stroke volume equation

what 3 factors influence arterial BP?

• determinants of mean arterial pressure (MAP)

• short-term regulation

• long-term regulation

determinants of mean arterial pressure

• cardiac output

• total vascular resistance

• ABP = CO x TPR

short-term regulation

• sympathetic nervous system to heart and vasculature

• baroreceptors in aorta and carotid arteries

  • increase in BP → decreased SNS activity → normalizes BP

  • decrease in BP → increased SNS activity → normalizes BP

long-term regulation

kidneys by controlling blood volume

vasodilation’s relationship to resistance and BP

decreases both resistance and BP

vasoconstriction’s relationship to resistance and BP

increases both resistance and BP

regulation of blood pressure chart