Lecture 9 - Cardiovascular System Flashcards
What is the cardiovascular system composed of? (3)
- heart
- blood vessels
- blood
What is the function of the circulatory system?
- transport essential materials (oxygen, fuel molecules, hormones, etc.) throughout the body to cells where they are needed and to collect cell products (carbon dioxide, lactate, urea, etc.) generated by metabolic activity
What are the 2 sections that the circulatory system is divided into? Describe them briefly.
Circulatory system is divided into two sections:
(a) Pulmonary circuit - blood vessels going to and from the lungs
(b) Systemic circuit - blood vessels going to and from the rest of the tissues of the body
Describe the heart
- a four chamber muscular pump which propels body through the blood vessels
Define: atria
- the two upper chambers of the heart
Define: ventricles
- the two lower chambers
Define: septum
- divides the left and right sides of the heart
How do the left and right ventricles of the heart differ? (2)
- The right ventricle pumps blood through the pulmonary circuit while the left ventricle pumps blood through the systemic circuit.
- The wall of the left ventricle is thicker than the wall of the right ventricle because the systemic circulation is a much higher-pressure system than the pulmonary circulation.
What controls the direction of bloodflow through the heart?
- valves
Describe a heart murmur
- noise created by blood regurgitating due to damaged valve
Describe: myocardium
- muscle of the heart
How do the cells of the cardiac muscle differ from the skeletal muscle?
Unlike skeletal muscle, all of the fibers or cells in cardiac muscle are anatomically interconnected - functional syncytium. When one fiber contracts, all fibers around it contract.
How do the fibers of the atria differ from the fibers of the ventricles?
The fibers of the atria are electrically separate from the fibers of the ventricles.
Where does the heart contractile rhythm originate?
- posterior wall of the right atrium where the SA node is located
State the pathway of conduction of the wave of depolarisation (cardiac impulse) across the heart
- S-A node (pacemaker)
- Atrial muscle fibers → contraction of atria
- Internodal Pathway (only electrical connection atria to ventricle)
- A-V node → A-V bundle → left and right bundle branches
- Purkinjie fibers travel throughout the ventricles
- simultaneous contraction of the left and right ventricles.
The wave of depolarisation is delayed in the A-V node for approximately .10 seconds. WHy?
gives the atria time to contract and empty their contents into the ventricles.
Give the function of Electrocardiography (ECG)
- record the wave of depolarization as it passes across the heart using electrodes on the surface of the body.
State the components of a normal ECG waveform and give what they represent
- P wave - represents atrial depolarization
- QRS wave - represents ventricular depolarization
- T wave - represents ventricular repolarization
- be able to draw and label a normal ECG!
define: arrhythmia; how are they diagnosed?
- an irregularity in the rhythm of the heartbeat
- look at heart rate, amplitude and shapes of the components of the ECG waveform, and time intervals
State the different examples of arrhythmias and explain them briefly(5).
- atrial fibrillation: atria contract irregularily
- AV block: electrical conduction is impaired
- ventricular fibrillation: erratic electrical impulses cause ventricles to quiver uselessly, serious medical issue
- Bradycardia: HR is slower than normal
- Tachycardia: HR is faster than normal
Give the name of the 2 major arteries that originate from the aorta; hint: these supply the heart with blood
- left coronary artery
- right coronary artery
Where do the large veins of the heart converge and empty?
- right atrium
Fill in the blank: Since cardiac muscle is highly dependent on ________, it has a _________
- aerobic metabolism
- rich blood supply
At rest, normal blood flow to the myocardium is about ___% of total cardiac output. How does this change with exercise?
- 4%
- Blood flow to heart stays around 4% of total output but the cardiac output increases substantially
Compare oxygen extraction from the blood flowing in coronary vessels vs from other tissues
- 70-80%
- 30%
define: arteries
- diameter of aorta
- compare the composition of arteries as they get smaller (large arteries, medium, small, arterioles)
- blood vessels that carry blood away from the heart
- 25mm
- less elastic tissue in the walls of the artery and more smooth muscle
define: arterioles
- how do arterioles increase or decrease blood flow to the capillaries?
- what do the arterioles do during exercise?
- arteries under 0.5 mm in diameter
- constricting/ relaxing the thick layer of smooth muscles in the walls of the arterioles
- the arterioles leading to working muscle are dilated, directing blood to flow to active muscle where the oxygen and fuel for contraction are required.
define: capillaries
- explain their diameter, SA, length, and mass
- very tiny (5-10 microns diameter), thin-walled vessels where the exchange of nutrients and gases between the blood and tissues occur
- 6000 sq meters
- 100 000 km long end to end
- twice the mass of the liver
define: venules
- small vessels which conduct venous blood from capillaries to veins
define: veins
- explain their composition
- compare veins to arteries
- vessels that convey blood toward the heart
- smooth muscles in the walls, allowing them to change their diameter
- veins have a greater diameter but thinner walls in comparison to arteries
When graphing the systemic blood pressure, there is a high BP portion and a low BP portion, explain which blood vessels are responsible for each portion
- high bp: arteries and arterioles
- low bp: venules and veins
- see graph from notes! understand and be able to draw (figure 20. 10)
What is the purpose of valves found in veins
carry blood against the force of gravity, especially in the leg veins
What mechanisms are involved in the return of blood to the heart? (3)
- pressure difference between the left ventricle and right atrium (117 mmHg 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 makes it easier for blood to return from lower portions of the body via the inferior vena cava to the right atrium of the heart)
State the blood composition (4); For an average adult, what % of body mass is blood?
- red blood cells
- white blood cells
- platelets
- plasma
- 8%
What type of people have a greater blood volume?
- Larger, more endurance trained, and altitude acclimatised people
Explain the composition of plasma
- 90% water, 10% solutes (proteins, nutrients, hormones, etc)
What is the other name for red blood cells? Explain the shape, diameter and the average amount per cubic mm of blood
- erythrocytes
- biconcave discs 7 microns in diameter
- 5-6million/mm^3 of blood
define: hematocrit
- state the % in the average female and male
- ratio of volume of blood cells to total volume of blood expressed in a percentage
- 37-47% in females
- 42-52% in males
Red blood cells
- where are they formed?
- lifespan
- contains? define what it contains
- function
- red bone marrow at the ends of long bones and flat bones
- 120 days
- hemoglobin; protein that binds with oxygen
- transports oxygen and carbon dioxide around the body
Define: diffusion
- molecules move from an area of high concentration to low concentration; driven by concentration gradient
Where are the 2 sites of gas exchange in the body? Explain the net diffusion of O2 and CO2 in both these sites.
- alveolar- capillary membrane in the lungs
(O2: alveoli –> blood)
(CO2: blood –> alveoli) - tissue capillary membrane in tissues
(O2: blood –> tissue)
(CO2: tissue –> blood)
What is the pressure of a gas in a gas mixture dependent on? (2)
- total pressure
- fractional concentration of that gas
What is the most important factor that determines gas exchange?
- partial pressure gradient of the gases involved
Explain functional residual capacity and its purpose
- FRC: the volume of air present in the lungs at the end of passive expiration
- exists so that each incoming breath of air has only a small impact on the composition of alveolar air and thus partial pressure of gases in the alveoli remain stable
Explain Henry’s Law (2 parts)
- the amount of gas that dissolves in a fluid is a function of two factors:
- Pressure of the gas above the fluid
- Solubility
Explain the meaning of the diffusing capacity for oxygen
the volume of oxygen that crosses the alveolar-capillary membrane per minute per millimeter mercury pressure between the alveolar air and pulmonary capillary blood
What can diffusing capacity be impacted by (4)?
- partial pressure gradients
- The thickness of the respiratory membrane - length of the diffusion path. Diffusing capacity is decreased in restrictive lung diseases such as pulmonary fibrosis or pneumonia.
- The number of red blood cells or their hemoglobin concentration or both
- The surface area of the respiratory membrane available for diffusion - diffusing capacity is decreased in emphysema.
Diffusing capacity can increase up to 3x resting values during heavy aerobic exercise. What are the mechanisms that allow for this (2)?
- Increased lung volumes during exercise, more alveoli are ventilated–> increased surface area for diffusion
- Opening up of more capillaries in the lung and greater volume of blood flowing through the lung due to an increase in cardiac output.
How is oxygen carried in the blood?
- 98% of oxygen is carried by red blood cells in combo with hemoglobin (HbO2 oxyhemoglobin)
- 2% dissolved in plasma
State the carrying capacity hemoglobin
- 1g of hemoglobin to 1.34ml of O2
What does the arteriovenous oxygen difference represent?
- how much oxygen is extracted or consumed by tissues for each 100mL of blood perfusing them. (see notes for how to do calculations)
What is the oxyhemoglobin dissociation curve? Can you draw it?
- a plot of the % saturation of hemoglobin vs partial pressure of oxygen
- see notes for drawing
Explain the Bohr effect
- increased body temperature, increased CO2 pressure, and decreased pH shift the oxyhemoglobin dissociation curve to the right
- results in more released oxygen at the tissues for a given PO2
Give the normal values for gas partial pressure at rest at sea level for:
PAO2 - partial pressure of alveolar oxygen
PAO2 - partial pressure of arterial oxygen for blood leaving the left ventricle
PVO2 - partial pressure of venous oxygen
- 100mmHg
- 95mmHg
- 40mmHg
Give the normal values for gas partial pressure at rest at sea level for:
PACO2 - partial pressure of alveolar carbon dioxide
PACO2 - partial pressure of arterial carbon dioxide
PVCO2 - partial pressure of venous carbon dioxide
- 40mmHg
- 40mmHg
- 40mmHg
Draw how pressure changes as blood travels from the left ventricle, arteries, arterioles, capillaries venules, veins, right atrium
- see google doc notes!
