54 Questions
What is the focus of the next lecture after covering electrical activity in the heart?
ECG and its diagnostic applications
What is the function of the endogenous group of cells in the heart?
To function as the normal pacemaker in non-pathological situations
What does the electrical axis of the heart indicate?
The general direction of electrical activity flow in the heart
What will be covered in the next lecture after discussing the ECG?
Cardiovascular physiology
What is the primary focus of today's lecture on cardiovascular physiology?
Electrical activity in the heart
What is the purpose of an ECG in relation to the heart?
To diagnose disease or abnormal states
What is the function of cardiac output?
To measure the amount of blood the heart puts out per unit of time
Which equation represents the calculation for cardiac output?
$CO = HR imes SV$
What is the primary function of cardiovascular regulatory mechanisms?
To prevent blood pressure from falling too low
Which factor can affect blood pressure?
Blood volume
What is the function of peripheral resistance in the cardiovascular system?
To regulate the resistance to blood flow within the circulatory system
What does stroke volume represent in the cardiovascular system?
The amount of blood pumped per beat
What is the primary role of arterioles in the cardiovascular system?
To regulate the resistance to blood flow within the circulatory system
How can adjustments in the cardiovascular system affect blood pressure levels?
By affecting heart rate, stroke volume, and peripheral resistance
What is the main function of diuretics in treating high blood pressure?
To decrease fluid retention and reduce blood volume
What is cardiac output a function of?
Heart rate, stroke volume, and peripheral resistance
What does pulmonary mechanics primarily involve?
The pressure and volume changes associated with inspiration and expiration
What is alveolar ventilation primarily modified by?
Changing breathing rate and tidal volume
What causes the large upswing in depolarization during the cardiac action potential?
Opening of voltage-gated sodium channels
What is the duration range of the cardiac action potential in contractile muscle cells?
250 to 300 milliseconds
What causes the plateau phase during the cardiac action potential?
Opening of inward-rectifying potassium channels
What is the resting membrane potential during the cardiac action potential in contractile muscle cells?
-90mV
What leads to the large repolarization in phase 3 of the cardiac action potential?
Activation of delayed-rectifying potassium channels
What process marks the beginning of repolarization during the cardiac action potential?
Phase 1
What closes during phase 1, trapping positively charged potassium in the cell?
Inward-rectifying potassium channels
What leads to the elevated level of membrane potential during phase 2 of the cardiac action potential?
Activation of inward-rectifying potassium channels
What marks phase 0 in the cardiac action potential?
The large upswing in depolarization caused by opening of voltage-gated sodium channels.
What causes the wave of depolarization that stimulates the contractile muscle cells?
Large increase in sodium permeability and opening of voltage-gated sodium channels.
What is the role of calcium during the cardiac action potential?
It contributes to the large upswing in depolarization.
What are inward-rectifying potassium channels responsible for in phase 1?
Trapping positively charged potassium in the cell.
What prevents the atria from contracting and pushing blood into the ventricles while the ventricles are also contracting?
The slight increase in resistance caused by the AV node
Which part of the heart's conduction system is our endogenous pacemaker?
SA node
What happens if the SA node fails as the pacemaker of the heart?
AV node takes over as pacemaker
What is an ectopic pacemaker?
Any area functioning as a pacemaker that is not 'normal'
What happens if the AV node becomes the pacemaker of the heart?
It can't spread electrical activity upwards because those muscles are in a refractory period
Why are modern pacemakers computerized?
To sense heart rate and stimulate the heart as needed
What is the equilibrium potential for sodium in pacemaker cells?
+60 mV
Which ion moves to get the average membrane potential to be -94 mV in pacemaker cells?
Potassium ions
What drives the depolarization in pacemaker cells?
Increased sodium permeability and decreased potassium permeability
"Funny" channels, allowing both sodium and potassium through, open during which phase of the pacemaker potential/action potential?
(1) First phase
What continues the depolarization after "funny" channels begin to close during the pacemaker potential/action potential?
T-type calcium channels begin to open.
What happens after all of the ventricles depolarize during the action potential in pacemaker cells?
The heart contracts, from bottom to top.
What is the function of the interventricular septum?
To separate the two ventricles
Why does the left ventricle have substantially greater muscle than the right ventricle?
To pump blood to the systemic circulation, which has rather high resistance
What is the primary role of the SA node in the heart's electrical conduction system?
To generate electrical activity causing the heart muscle to depolarize and contract
Why is the slowing down of the wave of depolarization as it reaches the AV node important?
To allow the atria to finish contracting before the ventricles begin to contract
What is the function of Purkinje fibers in the heart's conduction system?
To originate at the bottom of the heart and move upward into the contractile muscle
What is the main function of cells within the heart's conduction pathway system?
To pass waves of depolarization onto the contractile cells
What is responsible for rapidly transferring electrical activity between cardiac muscle cells?
Gap junctions
Why is continual stretching of the heart undesirable?
It can lead ultimately to heart failure
What is a function of desmosomes in the heart?
Help to resist stretching in the heart
What is responsible for causing cardiac hypertrophy if stretched too far over a long period of time?
High blood pressure
What is an important aspect of electrical conduction through internodal pathways in the atria?
Low resistance to current flow due to large cell size
What is a distinguishing feature of pulmonary circulation compared to circulation throughout the rest of the body?
Having substantially less pressure and resistance during blood flow
Test your knowledge of the human heart anatomy and circulation with this quiz. Explore the pathways of blood flow through the heart and the functions of the ventricles and septa.
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