Cardiovascular System Notes

Chapter 4 Overview: The Cardiovascular System

Key Concepts

• Structure and Function: Understanding the anatomy and physiology of the cardiovascular system.

• Cardiovascular System During Exercise: How the system responds to varying intensities of physical activity.

• Thermoregulation: The role of the cardiovascular system in regulating body temperature.

3 Key Knowledge

• The structure and function of the cardiovascular system, including the heart, blood, blood vessels, and blood flow around the body at rest and during various intensities of physical activity, sport, and/or exercise.

• The role of the cardiovascular system in thermoregulation, including vasodilation and vasoconstriction of the blood vessels to regulate blood distribution at rest and during physical activity, sport, and/or exercise.

• The relationship between stroke volume, heart rate, and cardiac output at rest, and submaximal and maximal exercise intensities.

Key Skills

• Apply and use anatomical terminology to identify the structures and functions of the cardiovascular and respiratory systems.

• Use primary data to measure and analyze the changes to the cardiovascular and respiratory systems at rest compared with various exercise intensities.

• Examine the role and process of thermoregulation through participation in physical activity, sport and/or exercise.

Structure and Function of the Cardiovascular System

The cardiovascular system consists of:

• The heart

• Blood vessels (arteries, veins, and capillaries)

• Blood

Functions:

• Transportation of gases and fuels

• Immunity

• Cellular repair and regrowth

• Thermoregulation

Two Main Circuits:

• Systemic Circuit: Transports oxygen and fuels to the major muscles and organs of the body.

• Pulmonary Circuit: Transports oxygen between the heart and the lungs.

Pulmonary Circulation

• Involves only the heart and lungs and the major blood vessels that connect them.

• Blood moves from the heart to the lungs and back, becoming oxygenated.

• The right ventricle pumps deoxygenated blood into the right and left pulmonary arteries.

• Oxygenated blood returns from the lungs through the pulmonary veins to the left atrium.

Systemic Circulation

• Transports blood to and from all the tissues of the body, providing oxygen and fuels and removing wastes.

• The left atrium pumps oxygenated blood to the left ventricle, then into the aorta.

• Major arteries branching off the aorta supply the head and upper body.

• The aorta also branches downwards to supply the lower body.

Structure and Function of the Heart

The heart has four chambers:

• Two upper chambers: atria (singular: atrium)

• Two lower chambers: ventricles

Blood is pumped from the atrium to the ventricle below and then out of the heart.

The heart contains one-way valves that ensure blood flows in the right direction, preventing backflow.

Blood Vessels

Three Major Types:

• Arteries: Carry oxygen-rich blood away from the heart to the body.

• Capillaries: Small blood vessels that allow for the exchange of gases (oxygen and carbon dioxide), water, nutrients, and waste products.

• Veins: Carry blood (low in oxygen) back to the heart.

Blood vessels make up the vascular network through which all blood flows.

Arteries

• Carry blood away from the heart; elastic walls allow them to expand and contract.

• The aorta subdivides into smaller arteries and arterioles, eventually becoming capillaries.

• Each division increases the cross-sectional area, allowing for greater exchange.

Capillaries and Veins

• Arteries branch into arterioles, which become capillaries.

• Capillaries are thin, allowing for exchange of:

  • Nutrients and fuel sources

  • Oxygen

  • Carbon dioxide

  • Waste products

  • Metabolic by-products

• Capillaries converge into venules, which transport blood back to the heart via veins.

• Veins have lower blood pressure than arteries and rely on muscular contractions to return blood to the heart.

Blood Vessel Characteristics

Composition and Functions of Blood

• Red Blood Cells: Produced in bone marrow, contain hemoglobin to carry oxygen.

• White Blood Cells: Fight infection, produced in bone marrow, lymph tissue, and the spleen.

• Platelets: Help form blood clots, produced in bone marrow.

• Blood Plasma: Carries nutrients, transports waste products, assists with their removal. 90% water, contains fibrinogen for blood clotting.

Functions of Blood

• Transportation of gases, fuels, and minerals

• Protection against dehydration

• Maintenance of equilibrium (homeostasis) via enzyme and hormone regulation

• Thermoregulation

• Carrying cells and antibodies that fight infection

• Bringing waste products to the kidneys and liver

During exercise, plasma and red blood cells respond to increased demands, while white blood cells and platelets are vital for the immune system and clotting.

Cardiovascular System During Rest and Exercise

Cardiac Output

• Cardiac Output (Q): Amount of blood pumped out of the heart per minute.

• Stroke Volume: Amount of blood squeezed out of the heart each beat (systole).

  • Average adult stroke volume at rest: 70-90 mL.

  • Increases during exercise by about 40\%.

• Equation: Q = stroke \ volume \times heart \ rate

Stroke volume reaches its maximum at around 50-60 \% of maximal heart rate, while heart rate continues to increase with exercise.

Redistribution of Blood During Exercise

• The brain redirects blood flow from organs like the stomach and kidneys to the muscles.

• The sympathetic nervous system stimulates vasoconstriction (blood vessel contraction) in most areas but causes vasodilation (blood vessel widening) in the muscles due to metabolic by-products.

Thermoregulation Assisted by the Cardiovascular System

Thermoregulation maintains the body's optimum operating temperature around 37 degrees Celsius.

Mechanisms:

• Radiation: Heat transfer from blood vessels to the skin and air.

• Evaporation: Cooling via conversion of liquid (sweat) to gas.

• Conduction: Heat transfer between two solids in contact (e.g., ice vest).

• Convection: Heat transfer by circulation of fluid or gas (e.g., water, air).

Sweating

• Primary mechanism for cooling.

• Warm blood is shunted to the skin via vasodilation.

• Reduces blood flow to working muscles, decreasing oxygen and fuel supply and waste removal, leading to decreased performance intensity.

Interesting Facts

• A 0.3 degree Celsius increase in core temperature can initiate vasodilation and sweating.

• Hair becomes raised to release hot air at the skin's surface, an example of radiant heat loss.