34 Questions
What happens at 0mV in the heart cells?
Both Ca++ and K+ channels close
What is the role of slow Ca++ channels during the heart's action potential?
Allow for the plateau phase
If not for endocrine control, how many times per minute would the SA node fire?
80 - 100 times
Which part of the heart would fire around 20 - 30 times per minute?
Atrioventricular bundle
What is the purpose of an Electrocardiogram (ECG)?
Record electrical signals of the heart
What is the function of the atria in the heart?
Collect blood and push it into lower chambers
Where is the base of the heart located?
Superior and medial to the apex
Which layer of the heart produces lubricating fluid?
Epicardium
What is the main function of the ventricles in the heart?
Pump blood out to the body or lungs
Which structures attach at the base of the heart?
Superior and inferior vena cava, aorta, and pulmonary trunk
What is the role of the auricles in the heart?
Thin walled structures that can hold blood
What is the main function of an artificial pacemaker?
Delivers electrical impulses to ensure effective heart contractions
During which phase of the cardiac cycle does atrial contraction occur?
Atrial systole
What is the main purpose of an Automatic External Defibrillator (AED)?
Corrects fibrillations in the heart
Which wave corresponds to the repolarization of the ventricles?
T wave
What happens to the semilunar valves during ventricular systole?
They open
What is the normal amount of blood pushed out by the ventricles in one stroke called?
Stroke volume
Which layer lines the chambers filled with blood, covers heart valves, and is continuous with the lining of blood vessels?
Endocardium
What type of muscles do the atrioventricular valves close due to?
Papillary muscles
What separates the heart into chambers, and are physical extensions of myocardium?
Septum
What structure separates the right atrium from the right ventricle?
Tricuspid valve
What is the primary function of purkinje fibers in the heart?
Spread the impulse around the ventricles for contraction
Which cells in the heart have a long refractory period to prevent tetany?
Cardiac muscle cells
What is responsible for creating a spontaneous depolarization in cardiac conductive cells?
$Na^{+}$ channels
Which feature characterizes myocardial contractile cells during depolarization?
$Ca^{++}$ channels open and $Na^{+}$ channels close
What is the main cause of heart murmurs?
Turbulent blood flow
Which event marks the closing of atrioventricular valves?
S1
What happens in the ventricle when blood is being pushed into a stiff or hypertrophic ventricle?
S4 sound is heard
What is the normal percentage range for ejection fraction?
50% – 70%
What is the formula for calculating Cardiac Output (CO)?
CO = HR * SV
What does the Baroreceptor reflex primarily respond to in order to regulate heart function?
Pressure and stretch changes in the vessels
Which substance releases acetylcholine (ACh) to slow heart rate?
Norepinephrine
What condition can decrease heart rate among the following options?
Excess hydrogen ions (acidosis)
What effect does caffeine have on heart rate?
Increases heart rate
Study Notes
Heart Function and Structure
- At 0mV in heart cells, the resting potential is reached, and the cell is not permeable to sodium.
- Slow Ca++ channels play a crucial role in the heart's action potential, specifically in the plateau phase.
Heart Rate Regulation
- Without endocrine control, the SA node would fire around 100 times per minute.
- The AV node would fire around 40-60 times per minute without regulation.
- The atrial rate would be around 20-30 times per minute without regulation.
Electrocardiogram (ECG)
- An ECG is used to measure the heart's electrical activity.
Heart Structure
- The atria are the upper chambers of the heart, responsible for receiving blood.
- The base of the heart is located at the top of the heart, where the atria meet.
- The epicardium produces lubricating fluid to reduce friction between the heart and surrounding tissues.
- The ventricles are the lower chambers of the heart, responsible for pumping blood throughout the body.
Blood Flow
- The atrioventricular valves close due to muscle contractions.
- The semilunar valves close during ventricular diastole.
- The stroke volume is the normal amount of blood pushed out by the ventricles in one stroke.
Heart Layers
- The endocardium lines the chambers filled with blood, covers heart valves, and is continuous with the lining of blood vessels.
Heart Conduction
- The atrioventricular valves separate the heart into chambers and are physical extensions of myocardium.
- The septum separates the right atrium from the right ventricle.
- Purkinje fibers have a primary function of conducting electrical signals rapidly, allowing for coordinated contraction.
Cardiac Cycle
- Atrial contraction occurs during the atrial systole phase of the cardiac cycle.
- The T-wave corresponds to the repolarization of the ventricles.
Cardiac Assistive Devices
- An artificial pacemaker is used to regulate heart rhythm.
- An Automatic External Defibrillator (AED) is used to restore normal heartbeat in cardiac emergencies.
Heart Function Abnormalities
- Heart murmurs are primarily caused by abnormal blood flow through the heart valves.
- The closing of atrioventricular valves marks the end of diastole and the start of systole.
- A stiff or hypertrophic ventricle increases blood pressure, making it harder for the heart to pump blood.
Cardiac Output and Blood Pressure
- The normal ejection fraction range is 55-70%.
- Cardiac Output (CO) is calculated using the formula: CO = Heart Rate x Stroke Volume.
- The Baroreceptor reflex primarily responds to changes in blood pressure to regulate heart function.
- The vagus nerve releases acetylcholine (ACh) to slow heart rate.
Test your knowledge on the physiology of cardiac muscle including topics like repolarization, calcium channels, refractory period, conduction system, and endocrine control of heart rate.
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