Cardiovascular System Overview

The volume of blood pumped by the left ventricle per beat.

The amount of blood pumped by the heart per minute. A healthy resting cardiac output is about 5 liters/minute.

The two upper chambers of the heart that receive blood returning from the body.

The two lower chambers of the heart that pump blood out to the body and lungs.

Valves located between the atria and ventricles that prevent blood from flowing backward.

The phase of the heart cycle when the heart muscle is relaxed and chambers fill with blood.

The phase of the heart cycle when the ventricles contract and pump blood out of the heart.

The specialized cells in the heart that initiate and conduct electrical impulses, triggering heartbeats.

During intense exercise, the body produces more CO2 and lactate, leading to a decrease in blood pH. This is because the body relies on anaerobic metabolism, creating lactic acid.

The point during exercise where ventilation increases exponentially faster than oxygen uptake. This signifies the shift to anaerobic metabolism.

The threshold where lactate production exceeds the body's clearance rate. This triggers a shift to anaerobic metabolism.

The primary function is to circulate blood, which carries oxygen, nutrients and removes waste, throughout the body.

The cardiovascular system monitors and adjusts blood pressure through feedback loops. It achieves this by controlling blood vessel diameter (vasoconstriction/dilation) and heart output.

Cardia Output (CO) = Heart Rate (HR) x Stroke Volume (SV)

Mean Arterial Pressure (MAP) = Cardiac Output (CO) x Systemic Vascular Resistance (SVR)

The systematic circulation distributes blood to the whole body, including skeletal muscles, skin, digestive system, liver, kidneys, and brain.

The heart requires about 5% of the body's total blood flow.

At rest, the heart extracts more oxygen from the blood than skeletal muscle.

At maximum exercise, the heart extracts almost all oxygen from the blood.

The increased metabolic demand during exercise causes dilation of coronary vessels, allowing more blood flow to the heart.

Increased aortic pressure during exercise forces a greater volume of blood into the coronary circulation, further increasing heart blood flow.

Myocardial metabolism is three times more efficient than skeletal muscle due to a higher concentration of mitochondria.

The heart relies heavily on free fatty acids for energy at rest.

The heart uses a significant amount of lactate (produced by muscles during exercise) as fuel during intense exercise.

A network of tiny blood vessels that allow for the exchange of oxygen and nutrients between blood and tissues. Muscle tissue is highly dense with capillaries due to its high metabolic needs.

The venous system is responsible for returning blood to the heart. It holds the majority of blood volume at rest and can regulate blood distribution by adjusting its tone.

Valves within veins prevent backflow of blood, ensuring efficient return to the heart. Muscle contractions further help this process.

Skeletal muscles function as pumps when contracting, squeezing veins to move blood towards the heart. This is essential for venous return.

Weak or damaged veins can lead to blood pooling in the lower limbs, resulting in visible, enlarged veins. Regular exercise helps maintain blood flow and prevent this.

When standing for extended periods, blood can pool in the legs due to gravity, reducing venous return. This can cause dizziness or fainting.

Hematocrit refers to the percentage of red blood cells in total blood volume. It can vary and indicate health conditions like anemia or polycythemia.

Blood pressure is the force exerted by blood on arterial walls. It is measured as systolic and diastolic pressures. Hypertension is a chronic condition with serious health consequences.

A drop in blood pressure that occurs after exercise, particularly in individuals with low blood volume, dehydration, or high exercise intensity.

The body's ability to deliver enough oxygen to meet the increased demands of physical activity.

The process of directing blood flow to different areas of the body depending on their needs during exercise.

Blood flow to the skin decreases during the initial phase of exercise to prioritize oxygen delivery to working muscles.

Blood flow to the skin increases during prolonged or sustained exercise to help regulate body temperature.

Blood flow to the skin decreases again at maximum exercise intensity to ensure adequate oxygen supply to the highly active muscles.

A gradual increase in heart rate during sustained, sub-maximal exercise. It's often caused by a decrease in stroke volume.

Intense or isometric contractions cause a sharp rise in blood pressure, which can increase the workload on the heart.

The SA node is the natural pacemaker of the heart, located in the posterior right atrium. It spontaneously depolarizes and repolarizes to generate a regular heart rhythm, typically between 60 and 100 beats per minute (bpm).

The AV node is located at the junction of the right atrium and ventricle. It receives electrical signals from the atria and transmits them to the ventricles, ensuring coordinated contraction. If the SA node fails, the AV node can act as a backup pacemaker, though at a slower rate.

The P-wave represents atrial depolarization, indicating the electrical activity that triggers the contraction of the atria. The QRS complex represents ventricular depolarization, the electrical activity that precedes ventricular contraction. The T-wave reflects ventricular repolarization, signifying the return of the ventricles to a resting state.

During exercise, the sympathetic nervous system (SNS) is activated, increasing heart rate and blood pressure. The parasympathetic nervous system (PsNS) withdraws its influence, allowing for increased heart rate. This is known as a feed-forward reaction, where increased activity leads to further increases.

The cardiovascular control center, located in the ventrolateral medulla, regulates heart rate and blood pressure. It receives input from various sensors and integrates this information to adjust autonomic nervous system output.

Exercise training has numerous cardiovascular benefits, including reduced blood pressure, decreased inflammation, increased baroreflex sensitivity, improved cardiovascular risk factors, enhance autonomic function, and increased cardiorespiratory capacity.

Atherosclerosis is a condition where plaque builds up inside arteries, narrowing them and restricting blood flow. This can lead to complications like heart attack and kidney failure.

The resting membrane potential of a heart cell is maintained by the sodium-potassium pump. This pump actively transports potassium ions (K+) into the cell and sodium ions (Na+) out, creating an electrical imbalance.