Cardiovascular System

Cardiovascular System

Composed of the heart, blood vessels, and blood, responsible for transporting essential materials throughout the body (O2, fuel molecules, hormones) and collecting waste materials (CO2, lactate, urea)

Pulmonary Circuit

Blood vessels going to and from the lungs, with the right ventricle pumping through this circuit.

Systemic Circuit

Blood vessels going to and from the rest of the tissues of the body, with the left ventricle pumping through this circuit.

Heart

Has 4 chambers (atria and ventricles) that are muscular pumps propelling blood. Atria are the two upper chambers, ventricles are the two lower chambers

Septum

Divides the left and right sides of the heart, separating the two pumps.

Valves

Control the direction of blood flow through the heart, preventing backflow. carry blood against the force of gravity especially veins in the leg

Myocardium

Specialized type of muscle, specifically cardiac muscle, where all fibers are interconnected for coordinated action.

Conduction System of the Heart

Heart’s inherent contractile rhythm originates in an area of specialized tissue located in the posterior wall of the right atrium. SA Node has autorhythmic cells and spontaneously fire. It fire at set frequency and normal pacemaker of the heart

Electrocardiogram (ECG)

Records the wave of depolarization as it passes across the heart, with components including P wave, QRS wave, and T wave.

Arrhythmias

Irregularities in the rhythm of the heartbeat, diagnosed by analyzing heart rate, amplitude, shapes of ECG components, and time intervals.

Blood Supply to the Heart

Supplied by the left and right coronary arteries, with the large veins of the heart emptying into the right ventricle. Cardiac muscle is higher dependent on aerobic metabolism and must have a rich blood supply.

Arteries

Blood vessels that carry blood away from the heart, ranging in size from the aorta to arterioles, with less elastic tissue and more smooth muscle in the walls. Large arteries > medium-sized arteries > small arteries > arterioles, less elastic tissue in the wall of the artery and more smooth muscle.

Capillaries

Tiny, thin-walled vessels where exchange of nutrients and gases between blood and tissues occurs. All other organs of the circulatory system exist only to serve the capillary beds. Has a very large surface area and length

Veins

Vessels that convey blood back to the heart, thinner-walled than arteries, with valves to prevent backflow. there’s both superficial and deep veins. Smooth muscle allow them to change their diameter. Venules and veins constitute the low-pressure apart of the circulatory system

Blood

Composed of specialized cells (red blood cells, white blood cells, and platelets) suspended in plasma. Plasma makes up 50-60%of blood by volume

Gas Exchange and Transport

Involves diffusion of gases across the alveolar-capillary membrane in the lungs and tissue-capillary membrane in tissues.

Partial Pressure of Gas

The pressure of a specific gas in a gas mixture, dependent on the total pressure and fractional concentration of that gas.

Lung Diffusing Capacity

Volume of gas that crosses the alveolar-capillary membrane per minute per mmHg between alveolar air and pulmonary capillary blood.

Gas Transport

98% of oxygen is carried in red blood cells in chemical combination with hemoglobin, with the majority of oxygen transported as oxyhemoglobin.

Oxyhemoglobin Dissociation Curve

Plots the percent saturation of hemoglobin with oxygen against the partial pressure of oxygen, indicating the affinity of hemoglobin for oxygen.

Hemoglobin

A protein in red blood cells that acts as a tissue oxygen buffer system.

Oxyhemoglobin dissociation curve

A graph showing the relationship between the partial pressure of oxygen (PO2) and the saturation of hemoglobin with oxygen.

Plateau portion of Oxyhemoglobin dissociation curve

The range of PO2 (60-100 mm Hg) where the saturation of hemoglobin with oxygen remains relatively constant.

Steep portion of Oxyhemoglobin dissociation curve

The range of PO2 (0-40 mm Hg) where the saturation of hemoglobin with oxygen declines rapidly.

Bohr Effect

The shift of the oxyhemoglobin dissociation curve to the right due to increased body temperature, increased pCO2, and decreased pH, resulting in more oxygen release at the tissue for a given PO2.

Total Blood O2

The total amount of oxygen in the blood, which includes dissolved oxygen and oxygen bound to hemoglobin.

PO2

Partial pressure of oxygen in ambient air (159 mm Hg).

PAO2

Partial pressure of alveolar oxygen (104 mm Hg).

PaO2

Partial pressure of arterial oxygen for blood leaving the left ventricle (95 mm Hg).

PvO2

Partial pressure of venous oxygen (40 mm Hg).

PCO2

Partial pressure of carbon dioxide in ambient air (0.1 mm Hg).

PACO2

Partial pressure of alveolar carbon dioxide (40 mm Hg).

PaCO2

Partial pressure of arterial carbon dioxide (40 mm Hg).

PvCO2

Partial pressure of venous carbon dioxide (45 mm Hg).

Walls of the ventricles

The wall of the left ventricle is thicker than the right as the systemic circulation required to force a greater volume of blood farther through the body than the pulmonary circuit

Heart Murmur

Valve in the heart is damaged and doesn’t close properly. The blood regurgitates causing noise

Functional Syncytium

Individual cells work together with adjacent cells for coordinated action. When 1 fiber contracts and all fibers contract. Heart contracts in sync and cardiac muscle must all fire

Intercalate disk with gap junctions

Link cells together, major portal for cardiac cell to cell communication. Required for coordinated muscle contraction and maintenance of circulation

Path Way of conduction of the wave of depolarization

Atrial muscle fibers > contraction of atria > Internodal pathway (only electrical connective atria to ventricle) > AV node > AV bundle > left and right bundle branches > Purkinje fibers travel throughout the ventricles > simultaneous contraction of the left and right ventricle

Delay of the AV Node

Delay in wave of depolarization is delayed to give the atria time to contract and empty their contents into the ventricles

P Wave

Atrial depolarization

QRS Wave/Complex

Represents ventricular depolarization

Diagnosing arrhythmias

Look at heart rate, amplitude and shapes of the components of the ECG waveform and the time intervals

Tacchycardia

HR is faster than normal

Bradycardia

HR is slower than normal

Fibrillation

ECG is disorganized

Atrial Fibrillation

Atria reacts irregularly, heart is still functional as a mump and needs a pace maker

Ventricular fibrillation

Ventricle beats irregularly and Heart doesn't function as an effective pump. Can't bring enough blood to the brain/body and Must defibrillate to reset electrical activity

Blood Supply to the Heart at Rest vs Exercise

At rest the normal blood flow to the myocardium is 4% of the total cardiac output. During exercise, the flow to the myocardium is still 4% but since the cardiac output increase with exercises which increases. 70-80% of the oxygen is extracted from blood flowing in the coronary vessels compared to the average 30% in other tissue

Arterioles

arterioles under 0.5mm in diameter. contracting or relaxing the thick layer of smooth muscle in the walls of arteries causes the increasing and decreasing of blood flow to capillaries. During exercise, arterioles leading to working muscles are dilated, directing blood flow to active muscle where oxygen and fuel for contraction are required. Arteries and arterioles constitute the high pressure part of the circulatory system

Venules

small vessels which conducts venous blood from capillaries to veins, pressure is lower compared to arterious side

Pulse Pressure

Difference between systolic and diastolic pressure readings in arteries

Systolic Pressure

Pulse pressure, pressure in the artery when your heart beats

Diastolic Pressure

Pressure in artery when heart relaxs

Mechanisms involved in return of blood to the heart

Pressure, skeletal muscle pump, and respiratory pump

Driving Pressure

Difference between left ventricle and right atrium. 120 mm Hg - 3 mm HG = 117 mm Hg driving pressure

Skeletal muscle pump

Active muscles squeeze the veins and push the blood towards the heart

Respiratory Pump

Decreased pressure in thoracic cavity during inspiration. Easier for blood to return from lower portions of body via inferior vena cava > Thoracic cavity > Right atrium of heart

Blood Volume

Blood volumed of an average adult with a normal body composition is about 8% of body mass. Blood volume is greater for larger, more endurance trained and heat acclimatized people.  A person with a body mass of 70kg has a blood volume of 5.6L

Plasma

Composed of about 90% water and 10% solutes

Red Blood Cells

Biconcave discs, about 5-6 million RBC per cubic mm of blood. Continuously being formed in red bone marrow at the end of long and flat bones. The lifespan is 120 days and contains Hemoglobin

Hematocrit

Ratio of volume of blood cells to the total volume of blood, expressed as a percentage. 37-47% in females and 43-52% in males

Hemoglobin

4 subunits, each one contains an iron molecule. Transports oxygen and Carbon dioxide. 140-160mg per 1L of blood in men and 120-140g per 1L of blood in females

Blood Doping

Increasing the RBC count and/or oxygen carrying capacity of the blood though blood transfusion, EPO (stimulate products), synthetic oxygen caries. To increase RBC count naturally: hypoxic Tents, altitude training

Diffusion

Molecules move from areas of high concentration to low, driven by concentration gradient. Movement of molecules across the respiratory membrane are driven by diffusion

Rate of diffusion is increased by

• Higher concentration gradient

• Shorter diffusion distance (thinner)

• Higher temperature (more kinetic energy)

• Greater surface area (more area to diffuse)

Sites of gas exchange

Alveolar-capillary membrane in lung and Tissue-Capillary membrane in tissue

Partial pressure of gas

The pressure of a specific gas in a gas mixture is dependent on - The total (barometric) pressure. The fractional concentration of that gas

Composition of dry ambient air at sea level

O2 - 20.93%; N2 79.04%; CO2 0.03%

Functional residual capactiy

serves as a damper so that each incoming breath of air only has a small effect on the composition of the alveolar air. Partial pressure of gases in the alveoli remains relatively stable

Henry’s Law

The amount of gas that dissolves in a fluid is a function of 2 factors: The pressure of the gas above the fluid and the solubility coefficient of gas (CO2 is 20.3 times more soluble in water than O2)

Diffusing capacity can be affected by many factors

1. Pressure gradient

2. Thickness of respiratory membrane - length of diffusion path

3. Number of red blood cells or hemoglobin concentration

4. The surface area of the respiratory membrane available for diffusion

Diffusing capacity during heavy aerobic exercise

Increase lung volumed during exercise > increase surface area for diffusion and Opening up of more capillaries in the lung and greater volume of blood flowing through the lung

O2 carrying capacity of hemoglobin

1g of hemoglobin is saturated when combine with 1.34mL of O2.

Percent saturation of hemoglobin with O2 (%SO2)

Related the amount of O2 actually combined with hemoglobin to the max O2 capacity of hemoglobin

Arteriovenous Oxygen Different (a-v)O2

Represents how much oxygen is extracted or consumed by the tissues for each 100mL of blood perfusing them