Cardiac
Cardiovascular system
Structure and function:
● Heart structures
○ Four chambers
○ Endocardium: inner lining
○ Myocardium: muscle layer
○ Epicardium: outer layer
● Heart valves
● Blood flow
The conduction system
● Sinoatrial Node
○ Right atrium
○ Primary pacemaker of the heart
■ 60-100 beats per minute
● AV Node
○ Receives impulse from SA nodes
○ Allows time for atria to empty into ventricular contraction
○ Backup pacemaker of the heart
■ 40-60 beats per minute
● Bundle of His
● Left & Right Bundle Branches
, ● Purkinje fibers
● Components of the Conduction System—as impulses travel through this pathway,
depolarization occurs in the atrial and ventricular chambers, resulting in contraction.n
○ Located throughout the heart
○ What keeps all the structures from firing at the same time?
○ Absolute Refractory—no stimulus, no matter how large
○ Relative Refractory—If the stimulus is large enough can cause firing
● Ventricular
○ Bundle of His: Electrical connection between atria and ventricle transmits to the
bundle branches
○ Right and Left Bundle Branches
○ Purkinje Fibers/Ventricular tissue
■ Relays the impulse to the ventricular myocardium
○ May initiate electrical impulses at 20-40 beats/min
○ Ventricles are stimulated to contract
● Automaticity: Specialized cells in the conduction system can fire/generate impulses
spontaneously
● Cardiac cells in the conduction system have a special quality called automaticity.
● Normal heart rate is? What is the term for a heart rate that is less than 60? Greater than
100?
● What do you think might happen if the SA node stops generating impulses? Or maybe
generates impulses at a rate slower than 60?
○ The atrioventricular node will begin generating impulses.
Waveform Analysis
● Depolarization = Contraction
● S1-closure of mitral & tricuspid valve
● S2-closure of aortic and pulmonic valves
Cardiac output
● Cardiac Output (CO): Amount of blood pumped by each ventricle in one minute
○ CO = SV x HR
○ Normal range: 4-8 L/min (at rest)
● What affects stroke volume?
○ Preload: volume of blood stretching the ventricles at the end of diastole before
contraction
○ Contractility: the “strength” of the heart contraction
○ Afterload: peripheral resistance
● Blood Pressure = CO x SVR
○ Measure of force exerted by blood against the walls of the arterial system
○ Normal 120/80 mmHg
● Frank-Starling: the greater the stretch, the greater the force of the contraction.
, ● Afterload anything that opposes ejection of blood: blood pressure, valve resistance,
blood volume
Hypertention
● High blood pressure or hypertension is one of the most important modifiable risk factors
for cardiovascular disease.
○ Text says around 45% of adults in the US meet criteria for diagnosis.
Blood Pressure Regulation
● Sympathetic nervous system
○ Increases HR (chronotropic)
○ Increases contractility (inotropic)
○ Baroreceptors: send inhibition vs activation signals to SNS
● Vascular Endothelium
○ Regulate & maintain vasoactive substances
● Renal System
○ Renin secreted bythe kidneys converts Angiotensin I to Angiotensin II (potent
vasoconstrictor.
○ Aldosterone secretion (Sodium retention, Fluid retention)
● Baroreceptors are found in the carotid sinus and aortic arch; they are sensitive to
stretching.
○ Angio II stimulates the adrenal cortex to secrete aldosterone
● Primary Hypertension: elevated BP without identified cause (many contributing factors)
● Secondary Hypertension: elevated BP with a specific cause
Cardiovascular system
Structure and function:
● Heart structures
○ Four chambers
○ Endocardium: inner lining
○ Myocardium: muscle layer
○ Epicardium: outer layer
● Heart valves
● Blood flow
The conduction system
● Sinoatrial Node
○ Right atrium
○ Primary pacemaker of the heart
■ 60-100 beats per minute
● AV Node
○ Receives impulse from SA nodes
○ Allows time for atria to empty into ventricular contraction
○ Backup pacemaker of the heart
■ 40-60 beats per minute
● Bundle of His
● Left & Right Bundle Branches
, ● Purkinje fibers
● Components of the Conduction System—as impulses travel through this pathway,
depolarization occurs in the atrial and ventricular chambers, resulting in contraction.n
○ Located throughout the heart
○ What keeps all the structures from firing at the same time?
○ Absolute Refractory—no stimulus, no matter how large
○ Relative Refractory—If the stimulus is large enough can cause firing
● Ventricular
○ Bundle of His: Electrical connection between atria and ventricle transmits to the
bundle branches
○ Right and Left Bundle Branches
○ Purkinje Fibers/Ventricular tissue
■ Relays the impulse to the ventricular myocardium
○ May initiate electrical impulses at 20-40 beats/min
○ Ventricles are stimulated to contract
● Automaticity: Specialized cells in the conduction system can fire/generate impulses
spontaneously
● Cardiac cells in the conduction system have a special quality called automaticity.
● Normal heart rate is? What is the term for a heart rate that is less than 60? Greater than
100?
● What do you think might happen if the SA node stops generating impulses? Or maybe
generates impulses at a rate slower than 60?
○ The atrioventricular node will begin generating impulses.
Waveform Analysis
● Depolarization = Contraction
● S1-closure of mitral & tricuspid valve
● S2-closure of aortic and pulmonic valves
Cardiac output
● Cardiac Output (CO): Amount of blood pumped by each ventricle in one minute
○ CO = SV x HR
○ Normal range: 4-8 L/min (at rest)
● What affects stroke volume?
○ Preload: volume of blood stretching the ventricles at the end of diastole before
contraction
○ Contractility: the “strength” of the heart contraction
○ Afterload: peripheral resistance
● Blood Pressure = CO x SVR
○ Measure of force exerted by blood against the walls of the arterial system
○ Normal 120/80 mmHg
● Frank-Starling: the greater the stretch, the greater the force of the contraction.
, ● Afterload anything that opposes ejection of blood: blood pressure, valve resistance,
blood volume
Hypertention
● High blood pressure or hypertension is one of the most important modifiable risk factors
for cardiovascular disease.
○ Text says around 45% of adults in the US meet criteria for diagnosis.
Blood Pressure Regulation
● Sympathetic nervous system
○ Increases HR (chronotropic)
○ Increases contractility (inotropic)
○ Baroreceptors: send inhibition vs activation signals to SNS
● Vascular Endothelium
○ Regulate & maintain vasoactive substances
● Renal System
○ Renin secreted bythe kidneys converts Angiotensin I to Angiotensin II (potent
vasoconstrictor.
○ Aldosterone secretion (Sodium retention, Fluid retention)
● Baroreceptors are found in the carotid sinus and aortic arch; they are sensitive to
stretching.
○ Angio II stimulates the adrenal cortex to secrete aldosterone
● Primary Hypertension: elevated BP without identified cause (many contributing factors)
● Secondary Hypertension: elevated BP with a specific cause
