Module 5: Cardiac Physiology Flashcards
List the 5 functions of the circulatory system
- Gas exchange
- Nutrient and Water delivery and absorption
- Removal of head and metabolic waste
- Immunity and defence
- Cell communication
T/F
The circulatory system is a closed loop system
True
How is blood both serial and parallel?
System as a whole is serial
Systemic circulation is parallel
Describe series flow (in terms of electrons)
Electrons can only flow down one path in a clockwise direction
Describe parallel flow (in terms of electrons)
Electrons can flow down many paths in a counter clockwise direction, but can flow down intermediate pathways
The septum of the heart does what?
Separates the left and ride sides of the heart
The heart consists of how many pumps?
2
Each pump is divided into how many chambers? what are they called?
- An upper chamber: the atrium. And a lower chamber: the ventricle
T/F
Veins only carries deoxygenated blood
False!
It carries blood TOWARDs the heart
See the pulmonary vein for example
Describe the flow of blood throughout the body
- O2 rich blood is pumped from the left ventricle to the aorta
- O2 rich blood is delivered to the tissues and organs
- nutrients are removed from the blood while waste is added into the blood
- oxygen poor blood circulated into the veins and into the right atria via the vena cavae
- Blood is pumped into the right ventricle then through the pulmonary artery to the lungs
- CO2 is removed form blood and O2 is added back
- O2 rich blood flows through pulmonary vein into left atria where it is pumped into the left ventricle
When there is greater pressure behind a cardiac valve, what happens?
It opens
When there is greater pressure in front of a cardiac valve, what happens?
It closes
Where is the atrioventricular valve located?
Between the atria and ventricles
To prevent inversion of the valves, what are they connected to?
The papillary muscles of the ventricular walls via the chordae tendinae
The right AV valve is also called what?
The tricuspid valve
The left AV valve is also known as what?
The bicuspid valve and mitral valve
Where are the semilunar valves located?
Between the ventricles and arteries that leave them
Where is the pulmonary valve lcoated?
Between the right ventricle and the pulmonary artery
Where is the aortic valve located?
Between the left ventricle and the aorta
T/F
Semilunar valves contain chordae tendinae to prevent inversion
False
Inversion is prevented solely on their shape
Valvular heart disease (VHD) is the dysfunction of what?
The valves in the heart
VHD arises in which two forms
Either regurgitation or stenosis
What characterizes regurgitation
Occurs when a valve does not close properly
Describe regurgitation
Valves do not close properly leading blood flowing back into the compartment in which is came from. Can occur in any of the 4 valves
Regurgitation can lead to what?
Irregular heart rhythms and unnecessary stress on the walls
Can lead to heart failure
What characterizes stenosis
The narrowing of the valve due to thickening/inflammation of the valve
Describe stenosis
Can occur in any of the heart valves
Inhibits flow of the blood out of the ventricle/atria
Intercalated discs are composed of what?
Desmosomes and gap junctions
What are the function of desmosomes in intercalated discs?
To mechanically hold the cells together
What are the function of gap junctions in intercalated discs?
To allow cells to communicate and spread action potentials from cell-cell
What is the function of intercalated discs?
To allow the chambers of the heart to coordinate a contraction and efficiently push out blood
Describe the structure of the pericardial sac
A double membrane consisting of the fibrous and serous layer
What is the function of the pericardial sac?
To protect the heart from the rest of the chest cavity
What is the function of the fibrous layer?
To anchor the heart to the surrounding walls, keeping it in place during movement
To prevent it from overfilling with blood
What is the structure of the serous layer?
Divided into the parietal and visceral pericardium
What is the function of the serous layer?
To lubricate the heart with pericardiac fluid and prevent friction during activity
T/F
The heart is a mechanical organ
False!
It’s an electro-mechanical organ
u goon
What are cardiac auto-rhythmic cells?
Specialized cardiac muscle cells that can generate action potentials
Where are cardiac auto-rhythmic cells located?
In the:
sinoatrial (SA) node
atrioventricular (AV) node
Bundle of His
Purkinje fibres
Describe the location of the SA node
Located in the right atrial wall near the opening of the superior vena cava
Describe the location of the AV node
Located in the right atria where the right atria and right ventricle come together
Describe the location(s) of the Bundle of His
Cells arise from the AV node and divide into two bundle branches that travel down each side of the septum to the bottom of the heart where they curve around and travel back towards the atria
Where do purkinje fibres originate from and go to
Branch off of the Bundle of His and spread along the inner surface of the ventricles
What are the pacemaker cells?
The auto-rhythmic cells in the SA node
What would happen if there were no pace maker cells?
The heart wouldn’t beat
What do pacemaker cells do?
They control heart rate, keeping it at about 70-80 bpm
T/F
Atrial contraction accounts for 80% of total ventricular filling
False!
It passive filling accounts for that.
The other 20% is from atrial contraction
What requirements need to be met for a successful cardiac excitation?
Atrial excitation and contraction should be complete before the onset of ventricular contraction
Excitation of the cardiac muscle fibres need to be coordinated
The pair of atria and the pair of ventricles must be functionally coordinated
If the ventricles were to contract at the same time as the atria, what would occur?
Incomplete ventricular filling
Uncoordinated depolarization of the cells in the ventricles is also called what?
Ventricular fibrillation
What is the function of interatrial and internodal pathways?
They move the wave of excitation faster than possible by gap junctions alone
Describe the interatrial pathway: it’s location and function
Extends from the right atrium to the left atrium
Ensures that the wave of excitment spreads across both atria at the same time
Describe the function of the internodal pathway
Connects the SA node to the AV node
What is the purpose of the AV node delay?
To ensure that the atria have fully contracted before the ventricles contract. This ensures maximal atrial emptying
T/F
The ventricles rely more on the bundle of His and purkinje fibres than the atria to transmit their electrical signal
True
What is the resting membrane potential for a cardiac myocyte?
80mV
When a cardiac myocyte becomes excited, what channels open?
What does the membrane depolarize towards?
Voltage-gated Na+ channels
50mV
The opening of the sodium ion channel triggers a potassium channel creating a balance of membrane potential. What is this called?
Plateau potential
T/F
L-type Ca2+ channels in the T tubules open during the plateau phase
True
What is the refractory period?
The period during which a cardiac myocyte cannot be re-stimulated. Occurs during the plateau phase
Who invented the ECG?
Williem Einthoven
In the first ECG, where were the electrical leads and ground electrode placed?
Electrical leads on the right and left arm, and left leg
Ground electrode on the right leg
Lead I recorded electrical activity where?
From the right to left arm
Lead II recorded electrical activity where?
From the right arm to left leg
Lead III recorded electrical activity where?
From the left arm to the left leg
How many leads are in the modern day ECG. How many are physical?
12 total
9 are physical
How are the remaining leads determined?
Mathematically from leads I II and II
What does an ECG measure?
The changes of electrical potentials that originate in the heart but are transmitted through the body
ECGs allow us to identify what medical thing?
Cardiac abnormalities
The standard ECG graph is from what lead?
Lead II
Observed upward detections in the graph are caused from what?
Depolarization
Observed downward reflections in the graph are from what?
Repolarizations
What characterizes the P wave?
The atria’s depolarization
What characterizes the QRS complex?
The wave of excitation traveling down the bundle of His and purkinje fibres to depolarize the ventricles
What characterizes the T wave?
Where the ventricles repolarize
The PR segment represents what?
The AV node delay
The ST segment represents what?
The time during which the ventricles are contracting and emptying
The TP segment indicates what?
The time during which the ventricles are relaxing and filling
The QT segment indicates what?
The electrical depolarization and repolarization of the ventricles
What is tachycardia?
Heart rate exceeding 100bpm
What can tachycardia be due to?
Exercise, caffeine, or an electrical abnormality within the heart
What is the affect of tachycardia on CO and ventricular filling
Can cause decreased CO and decreased ventricular filling
The kind of tachycardia (either wide or narrow) is identified by what part of the ECG graph?
The QRS complex
What is extrasystole?
A heartbeat initiated by the purkinje fibres rather than the SA node
What is happening with the ventricles and atria in someone experiencing extrasystole?
Their ventricles are contracting before the atria
What is Ventricular fibrillation (V-fib)
When the heart is quivering rather than pumping due to abnormal electrical activity within the ventricles
What does the ECG look like in patients experiencing V-fib?
Irregular QRS complex with no clear P waves
What occurs in complete heart block?
The impulse generated by the SA node does not travel to the ventricles
What does the ECG look like in someone experiencing Complete heart block
- Continuous P wave occurs
- QRS complex occurs that doesn’t follow a P wave
What is systole?
Contraction
What is diastole?
Relaxation
HELLO
this card is a reminder to look at the mechanical activity of the heart. Looks like a good short answer question. U should know its details.
Describe isometric contraction
Contraction in the left ventricle that creates enough pressure to close the AV valve, but not yet strong enough to open the aortic valve
When using a stethoscope, what is the first heart sound from? What does it sound like? What does it signal the beginning of?
Occurs when the AV valve closes
Sounds like “lub”
Signals the beginning of ventricular systole
When using a stethoscope, what is the second heart sound from? What does it sound like? What does it signal the beginning of?
Occurs when the semilunar valves close
Sounds like “dub”
Signals the onset of ventricular diastole
What is a heart murmur?
When a valve is not functioning properly and the typical lub-dub sounds are altered
Describe an aortic stenosis murmur
Occurs in the stenotic valve
Valve does not open fully
Causes whistling-like sound
Describe a mitral valve regurgitation murmur
Valve does not close properly
Called a leaky valve
Allows backwards flow of blood
Creates a swishing/gurgling type sound
What is cardiac output?
The volume of blood pumped out by each ventricle over a minute
How do you calculate cardiac output?
Heart rate * Stroke volume
What is stroke volume?
The amount of blood ejected by ventricle contraction
How does the parasympathetic system innervate the heart
Innervates via the vagus nerve
Mainly innervates onto the atria (specifically SA and AV nodes)
How does the sympathetic system innervate the heart
Mainly innervates the ventricles (but will also innervate the atria)
List how the parasympathetic system regulates the heart
Slows heart rate
Reduced the AV nodes excitability
Shortens atrial action potentials
How does the parasympathetic system reduce heart rate
Releases acetylcholine at the SA node
Increases K+ permeability, which hyperpolarizes the cell
How does the parasympathetic system reduce AV node excitability?
Increases K+ permeability, hyperpolarizing it
How does the parasympathetic system shorten atrial action potentials?
Increases K+ permeability, creating a shorter plateau phase, where the Ca2+ usually enters to create a strong contraction
List how the sympathetic system regulates the heart
Increases heart rate
Increases AV node excitability
Enhances conduction speeds
Increases contractibility of cardiac muscles
How does the sympathetic system increase heart rate?
Releases norepinephrine at the SA node
Hoe does the sympathetic system increase AV node excitability?
Decreases the AV node delay
How does the sympathetic system increase contractibility of cardiac muscles
Increased Ca2+ permeability during the plateau phase allows for more calcium ions to pass into the cell, increasing contractility
What are some of the ways heart rate can be activated to increase or decrease?
Injury to the vagus nerve
Activity
Fever
Give an example of extrinsic control of stroke volume
The sympathetic nervous system
Give an example of intrinsic control of stroke volume
The volume of blood in the ventricle at the end of diastole
What is the Frank-Starling Law?
That increasing end-diastolic volume increases SV
The greater the diastolic filling, the greater the systolic emptying
What is preload also known as?
Venous return
What is preload?
The amount of blood returning to the ventricle
What is afterload?
The force that the ventricle is pushing against
(if there is increased pressure in the aorta then the left ventricle is contracting against this extra load
What is ejection fraction?
The amount of blood that is pumped out of the ventricles relative to the amount of blood that was in the ventricles before contraction
What is the calculation for ejection fraction?
Stroke volume / end diastolic volume
The left coronary artery branches off into what?
The left anterior descending artery and the circumflex artery
What is the purpose of coronary circulation?
To supply oxygen rich blood to the cardiac muscle
T/F
The amount of blood that can flow through the coronary arteries decreases during systole
True
What is the primary fuel source of the heart? Why?
Free fatty acids
Because they are slow burning and easily stored
What is the primary fuel source of the heart? Why?
Free fatty acids
Because they are slow burning and easily stored
