Cardiovascular and Circulatory System Pt.2 Flashcards
Electrical communication in the heart beings with ____________
An action potential in an autorhythmic cell
How does depolarization spread to adjacent cells?
Through gap junctions in the intercalated discs
Electrical communication in the heart creates wave of depolarization in __________
Contractile myocardium
Electrical signals move through the heart in the following coordinated manner ___________
- Sinoatrial (SA) node
- Internodal pathway
- Atrioventricular (AV) node
- AV bundle (bundle of his)
- Left and right bundle branches
- Purkinje fibers
The SA node originates
The action potential
The SA node spreads _________ and _______
Rapidly through internodal pathways and spreads more slowly via contractile cells of atrium
The SA node cannot spread
Directly from atrium to ventricle due to fibrous tissue
The AV node moves
Signal atrium to ventricle
From the AV node spreads
To apex of the heart via AV bundle and left and right bundle branches
Small purkinje fibers rapidly
Transmit impulses, contractile cells of apex contract almost simultaneously
The AV node pathway directs electrical signals
To the apex of the ventricles first
The AV node slows down the
Transmission of action potentials (AV node delay), which allows atrium and ventricle to contract
The SA node is the primary pacemaker of the heart (sets the heartbeat) BUT
- Other conducting cells can spontaneously generate action potential, but have slower rhythm
- If the SA node is disrupted, other nodes can set heartbeat
An electrocardiogram (ECG) shows _________
The summed electrical activity generated by cells of the heart, this is not the same as an action potential which is for an individual cell
What are electrocardiogram (ECG) measured by ___________
Leads,
1. One positive electrode
2. One negative electrode
3. One inactive
An upward deflection on an electrocardiogram (ECG) means _________
Depolarization
A downward deflection on an electrocardiogram (ECG) means __________
Repolarization
In an electrocardiogram (ECG) upward vs downward deflection represents ________
Movement towards vs from positive electrode
ECG has three waves (movements below or above the baseline) what are they?
- P wave
- QRS complex
- T wave
P wave
Depolarization of the atria
QRS complex
Wave of the ventricular depolarization (atrial repolarization is part of QRS)
T wave
Repolarization of the ventricle
What are the two major segments (sections between waves) in an ECG?
- P-R segment
- T-P segment
P-R segment
AV nodal delay
T-P segment
Ventricular and atrial releaxtion
Heart rate is
Time between two P waves or two Q waves
A faster-than-normal heart rate is called?
Tachycardia
A slower-than-normal heart rate is called?
Bradycardia
An irregular rhythm is called __________
Arrhythmia
Atrial fibrillation (Arrhythmia) is ____________
Rapid and irregular beating originating in the atria
Ventricular fibrillation (Arrhythmia) is ____________
Rapid and irregular beating originating in ventricles
A heart block is
Action potentials from SA node failed to be transmitted through AV node
The cardiac cycle is
A single contraction-relaxation cycle
Mechanical events lag behind electrical events: contraction follows ___________
Action potential
Due to periods of contraction and relaxation of atria and ventricles _______
Diastole and systole
Diastole is
Cardiac muscle relaxation (filling)
Systole is
Cardiac muscle contraction (pumping)
What are the five phases of the cardiac cycle?
- Late diastole
- Atrial systole
- Isovolumic ventricular contraction
- Ventricular ejection
- Isovolumic ventricular relaxation
Late diastole is the heart
At rest
Atrial systole is the
Completion of ventricular filling
EDV
End-diastolic volume
Isovolumic ventricular contraction is
High ventricular pressure, no blood in or out
Ventricular ejection is
Heart pumps
ESV
End systolic volume
Isovolumic ventricular relaxation is
Low ventricular pressure, no blood in or out
Av valves open when ________
Ventricular pressure drops below atrial pressure, causing the cycle to begin again
The wigger diagram follows ________
Heart pressure,left ventricular volumes, and the ECG
Stroke volume (SV) is
The amount of blood pumped by one ventricle during a contraction (mL per beat)
What is the average stroke volume (SV)?
Average= 70 mL (70-kg man at rest)
Cardiac output (CO) is
The volume of blood pumped by one ventricle in a given period of time (in L/min)
What impacts stroke volume (SV)?
- Contractility
- Length-tension
- Venous return
What is contractility?
The intrinsic inability of a cardiac muscle fiber to contract
What is length-tension? Frank-starling law?
Increased blood in the ventricle (preload) leads to a stronger contraction and the Frank-starling law of the heart states that stroke volume is proportionate to EDV
What is venous return?
The amount of blood entering the heart
What does the autonomic nervous system do?
Modulates heart rate
Sympathetic division ____________
Increases heartrate
Sympathetic division activates _______ and ______
-Activates Beta1-adrenergic receptors on the autorhythmic cells
-Depolarizes cell
Parasympathetic division ___________
Decreases heart rate
Parasympathetic division activates _____ and _____
-Activates acetylcholine receptors on the autorhythmic cells
-Hyperpolizes cell
A polygraph measures ________________
Physiological variables, like heart rate, while a person answers a series of questions
What do beta blockers do?
Bind and block beta1-adrenergic receptors
