Cardiovascular Flashcards
Not completed! Goes up until the topic of the Pressure-volume curve
What is Ohm’s law related to hemodynamics?
- F = ∆P/R
F = flow
∆P = pressure difference between two fixed places
R = resistance to flow
To have blood flow, what must occur?
Pressure must being greater than resistance
Define
Hydrostatic pressure
Pressure exterted by a fluid
What happens when there in no pressure difference?
There is no flow
Where does blood pressure from?
Contraction of heart chambers and pressure of blood on the walls of the blood vessels and heart chambers
What determines resistance to blood flow?
- Viscosity: friction between molecules of a flowing fluid
- Length and diamter of blood vessel: determines the amount of contact between moving blood and stationary wall of vessel
What is poiseuille’s equation?
Equation to determining resistance
Define
Laminar flow
Flow characterized by fluid particles following smooth paths in layers, with each layer moving smoothly past the adjacent layers with little or no mixing.
What are the functions of the cardiovascular system? (5)
- To deliver oxygen and nutrients
- Removed waste products of metabolism
- Fast chemical signalling to cells by circulating hormones or neurotransmitters
- Thermoregulation
- Mediation of inflammatory and host defense responses against invading microorganisms
What are the main components of the cardiovascular system? (3)
- Heart (Pump)
- Blood vessels (Pipes)
- Blood (the fluid to be moved)
What are the vessels in the cardiovascular system? (5)
- Arteries
- Arterioles
- Capillaries
- Venules
- Veins
What are arterioles?
Small branching vessels with high resistance; branches off from arteries
What are arteries?
Larger vessels which move away from the heart; typically carry oxygenated blood
What are veins?
Larger vessels that carry blood towards the heart
What are capillaries?
Small vessels that transport bood between small arteries and venules; where the exchange of materials occurs
What are venules?
Small branching vessels (capillaries to veins) with low resistance
What is the benefit of a closed circulatory system?
It generates greater pressure
What are the four chambers of the heart?
- Right atria
- Right ventricle
- Left atria
- Left ventricle
Describe atria
- Thin-walled
- Low pressure chambers
- Receives blood returning to the heart
Describe ventricles
- Thick-walled
- Involved in forward propulsion of blood
- Receives blood from the atrias, to bring back to the body
What divides the heart?
Septa
What is the interartial spetum?
The septum that separates the left and right atria
What is the interventricular septum?
The septum that separates the left and right ventricles
How does the heart work as a dual pump?
- First pump: carries oxygen-poor blood to the lungs, and then delivers oxygen-rich blood back to the heart
- Second pump: delivers oxygen-rich blood to the body
What is pulmonary circulation?
- Blood to and from the gas exchange surfaces of the lungs
- Blood entering lungs = poorly oxygenated blood
- Oxygen diffuses from lung tissue to blood
- Blood leaving lungs = oxygenated blood
What is systemic circulation?
- Blood to and from the rest of the body
- Oxygen diffuses from blood to body tissues
- Blood entering tissues = oxygenated blood
- Blood leaving tissues = poorly oxygenated
What is the path of blood flow in the left heart?
Receives blood from pulmonary circulation and pumps to systemic circulation
What is the path of blood flow in the right heart?
Receives blood from systemic circulation and pumps to pulmonary circulation
What is the path for pulmonary circulation?
- Pulmonary trunk
- Pulmonary arteries
- Pulmonary arterioles
- Capillaries of lungs
- Pulmonary venules
- Pulmonary veins
- Enters left heart
What is the path of blood flow in systemic circulation?
- Aorta
- Arteries
- Arterioles
- Cappillaries
- Venules
- Veins
- Venae cavae
- Enters the right heart
Where does series flow occur in the cardiovascular system?
At the heart level; blood must pass through the pulmonary and systemic circuits in sequence
Where does parallel flow occur in the cardiovascular system?
At the organ level; each organ is supplied by a different artery and flow is independently regulated
How does the distribution of blood flow change during exercise?
The skeletal muscles get a higher flow than abdonimal organs; this is compared to the flow distribution at rest
When does the distribution of blood flow differ?
- Rest
- Exercise
- Emergency situations
What is the pericardium?
Fibrous sac surrounding the heart and roots of great vessels
What are the functions of the pericardium? (4)
- Stabilization of the heart in the thoracic cavity
- Protection of the heart from mechanical trauma/infection
- Secretes pericardial fluid to reduce friction
- Limits overfilling of the chambers, preventing sudden distension
What are the three layers of the pericardium?
- Fibrous pericardium
- Partietal pericardium
- Visceral (epicardium)
What reduces friction within the pericardial cavity?
Pericardial fluid
What is pericarditis?
Inflammation of pericardium
What is a cardiac tamponade?
Compression of heart chambers due to excessive accumulation of pericardial fluid; this causes decreases in ventricular filling
Which ventricle has a thicker wall? higher pressure?
The left ventricle has a thicker wall, which means it develops higher pressure
What is epicardium?
The visceral pericardium; it covers the outer surface of the heart
What is the myocardium?
The muscular wall of the heart; contains the cardiac muscle cells, blood vessels, and nerves
What is the endocardium?
The endothelium covering inner surfaces of the heart and heart valves
What are myocytes?
- Cardiac muscle cells
- Branched (“Y”) and joined longitudially
- Striated
- One nucleus
- Many mitochondria
What are intercalated disks?
- Interlocking region of attachment
- Include desmosomes and gap junctions
What are desmosomes?
- Structures that anchor cells together in tissues subject to considerable stretching
- Mechanically couples cells
What are gap junctions?
- Communicating junctions
- Transmembrane channels that link adjacent cells
- Electrically couple cells
- Allows movement of APs, and molecules/ions
What are leaflets/cusps?
Thin flaps of flexible, endothelium-covered fibrous tissues attached at the base to the valve rings; made of collagen
What are valve rings?
Dense fibrous connective tissue that is at the site of attachment for the heart valaves
What are the four valves of the heart?
- Left AV valve
- Aortic valve
- Pulmonary valve
- Right AV valve
How do the heart valves function?
- Open/close passively due to pressure gradients
- This means there is unidirectional flow of blood through the heart
What are atrioventricular (AV) valves?
- Valves between artia and ventricles
- Prevent the backflow of blood into atria when ventricles contract
- Tricuspid is the right, bicuspid is the left
What are the components of the AV valve apparatus?
- Cusps
- Chordae tendineae
- Papillary muscles
What are the Chordae tendineae?
- Tendinous-type tissue
- Extend from the edges of each leaftlet to the papillary muscle
What are the papillary muscles?
- Cone shaped muscles
- Contraction of papillary muscles causes the chordae tendineae to become taut
What is the function of the AV valve apparatus?
- Prevents eversion of the AV valves into the atria during contraction of the ventricles
How do the AV valves open and close?
Pressure gradients; not from the contraction and relaxation of papillary muscles
What are the arterial (semilunar) valves?
- Valves between the ventricle and artery
- Have 3 cusps
- No chordae tendineae, or papillary muscles
What is the purpose of the arterial valves?
To prevent the backflow of blood from the arteries into ventricles when ventricles relax
Where is the right arterial valve?
At the pulmonary valve
Where is the aortic valve?
At the aorta in the left ventricle
What is the cardiac skeleton?
The fibrous skeleton of the skeleton that serves as the point of attachment for the valve leaflets and myocardium
Is the cardiac skeleton conductive?
No; it is electrically inactive
What is coronary circulation?
Movement of blood through tissues of the heart
Where do the coronary arteries originate?
At the aortic sinuses at base of the ascending aorta
Where do the coronary veins terminate?
They drain into the coronary sinus, which empties into the right atrium
What is the coronary sinus?
A collection of veins joined together to form a large vessel that collects blood from the myocardium
What is systole?
Contraction of the heart
What happens to myocardial blood flow during systole?
It almost ceases
What is diastole?
Relaxation of the heart
What happens to myocardial blood flow during diastole?
It peaks
What is synctium?
When myocytes communicate with each other, and act together; if one cell is excited, it spreads across the atria/ventricles
How does cardiac synctium relate to APs?
- APs lead to the contraction of cardiac myocytes
- Syncytium is an all-or-nothing property
What is automaticity?
When cardiac myocytes contract in the absence of neural or hormonal stimulation; it is a result of APs it generates itself
What are the two types of cardiac myocytes?
- Contractile cells: does the mechanical work of pumping, propel blood; do NOT initiate APs
- Conduction cells: initiate and conduct the APs responsible for contraction of the contractile myocytes
How many cardiac myocytes are conducting cells?
1%
What are the components of the conduction system? (6)
- Sinoatrial (SA) node
- Internodal pathways
- Atrioventricular (AV) node
- Bundles of His
- Bundle branches (left and right)
- Purkinje fibres
What is the electrical connection between atria and ventricles?
AV node and Bundle of His; the only connection
Where is the SA node?
The top of the right atrium
What is the function of the SA node?
- Acts as the cardiac pacemakers
- Initiates APs and sets the heart rate
What is the role of the internodal pathways?
- Passing stimulus from the SA node to the contractile cells of both atria and to the AV node
What is the AV nodal delay? (time)
100 msec
What is the purpose of the AV nodal delay?
- Emsures atria depolarize and contract before the ventricles
- This way the valves do not close, preventing blow flow
- Allows ventricles time to fill completely before they contract
What do the left and right bundle branches travel long, to get to the ventricles?
The interventricular septum
What do the Purkinje fibers allow to happen?
- Fast conduction velocity
- Left and right ventricular myocytes depolarize and contract nearly simultaneously
What is the sequence for the conducting system of the heart?
What is Wolff-Parkinson-White Syndrome?
A relatively common heart condition that causes the heart to beat abnormally fast for periods of time
How does Wolff-Parkinson-White syndrome work?
- Due to an accessory pathway, electrical signals bypass the AV node and move from the atria to the ventricle faster than usual
- This results in a rapid heart rate
What does fast action potential look like?
What does slow action potential look like?
Where in the heart are there fast action potentials?
- Atrial myocardium
- Ventricular myocardium
- Bundle of His, bundle branches, Purkinje fibers
Where do slow action potentials occur in the heart?
- SA node
- AV node
What are the phases of the cardiac action potential associated with?
Changes in permeability of the cell mainly to Na+, K+, and Ca2+ ions
What is the permeability of K+ in the myocyte?
Greater in
What is the permeability of Ca2+ in the myocyte?
Greater out
What is the permeability of Na+ in the myocyte?
Greater out
What are the channels involved in pacemaker potential?
- K+ channels
- F-type channels (Na)
- T-type channels (Ca)
What channels are involved in the depolarization of pacemaker potentials?
L-type channels (long lasting); Ca2+
What does a SA node action potential look like?
What do ventricular muscle cell action potentials look like?
What is an electrocardiogram?
- Graphic recording of electrical activity of the heart detected on the surface
- Used to diagnose problems with the heart’s conduction system
What is the placement of electrodes in the 12 lead ECG?
What is the P wave?
The spread of depolarization across atria
What is the QRS complex?
Spread of depolarization across ventricles
What is the T wave?
Ventricular repolarization
What is the relationship between an ECG and action potentials graph>
What does an ECG look like in a partial AV node blcok?
- Every second P-wave is not followed by QRS complex
What does a complete AV node block look like on the ECG?
- No synchrony between atrial and ventricular electrical activities
What controls ventricular contraction in a complete AV node block?
The slower bundle of His
What is the sarcolemma?
The cell membrane of muscle cells
What is the sacroplasmic reticulum?
Structure that stores calcium ions for contraction
What are T-tubules?
- Transverse-tubules
- Invaginations of sacrolemma; transmit depolarization of membrane into interior of muscle cell
What ion regulates the contraction of cardiac muscle?
Calcium ions
What is calcium-dependent calcium release?
When calcium ions from the cytosol bind to ryanodine receptors, releasing calcium from sacroplasmic reticulum
What are the steps of calcium release in excitation-contraction coupling (ECC)?
What occurs in ECC during relaxation?
- Influx of calcium stops as L-type channels close
- SR is no longer stimulated to release calcium
- SR takes up cytosolic calcium by Ca2+ ATPase
- Calcium removed from cell by Na-Ca exchanger
- Reduced calcium binding to troponin
- Sites for interaction between myosin and actin are blocked
- Relaxation of myofibrils
What is the refractory period?
Period of time in which a new AP cannot be initiated
* Involves the inactivation of sodium channels
What are the two components of the cardiac cycle?
- Systole: ventricular contraction and blood ejection
- Diastole: ventricular relaxationa and blood filling
What is stroke volume?
Volume of blood ejected from each ventricle during systole
How much of the ventricles is filled passively?
The atria is relaxed and not contracted, AV valve is open
70%
