Chapter 14.2 Flashcards
P wave
The SA node depolarizes and then the atria
Q-wave
The SA node depolarizes and then the bundle branches located in the septum
Q-wave
The SA node depolarizes and then the bundle branches located in the septum
R wave
The Purkinge fibers depolarize (located in the apex and outer walls of the heart)
Electrocardiogram
Shows summed electrical activity generated by all the cells of the heart
Electrocardiogram
Shows summed electrical activity generated by all the cells of the heart
ECG components
Waves: deflections above or below baseline.
Segments: sections of baseline between waves.
Intervals: combinations of waves and segments
P QRS T
Atrial Depolarization
Ventricular depolarization & atrial repolarization
Ventricular repolariation
P QRS T
Atrial Depolarization
Ventricular depolarization
Ventricular repolariation
PR segment
Time between end of atrial depolarization and onset of ventricular depolarization.
Conduction through the AV node and continuing Atrial Contraction.
ST Segment
Time between end of ventricular depolarization and onset of ventricular repolarization.
Continuing Ventricular Contraction
Pulse rate
time between pressure waves in an artery
Systolic Pressure
Highest pressure in the ventricles and arteries.
Occurs during ventricular systole
Diastolic Pressure
Lowest pressure in the ventricles and arteries.
Occurs during ventricular diastole.
Pulse Pressure
Difference between the systolic & diastolic pressures
Pulse Pressure = SYS-DIA
What does each wave represent
AN electrical event of cardiac cycle
What comes first, Electrical/Mechanical Events?
Electrical
What comes first, Electrical/Mechanical Events?
Electrical
Where do action potentials originate
SA node
Pathway of electrical signals
SA node - internodal pathway - AV node - into the AV bundle - bundle branches - terminal Purkinje fibers - myocardial contractile cells
SA node job
To set pace for heart rate, and AV takes over if anything goes wrong
Systole and Diastole
Systole is the contraction phase;
Diastole is the relaxation phase
What is the heart rate?
Heart rate: time between two R waves or two P waves
Faster than normal: tachycardia
Slower than normal: bradycardia
5 stages of cardiac cycle
1) Heart is at rest, all chambers are in diastole
-Atria are filling, and AV opens causing ventricles to fill
2) Ventricles filled, Atrial systole
- Atrials contract, EDV (volume in ventricle when relaxed)
3)Early ventricular contraction & first heart sound
- AV closure causes “lub” sound
- isovolumic ventricular contraction (blood stays put)
4) Heart pumps: blood leaves ventricles
- Semilunar valves open, in arteries
- ESV (volume in ventricle at the end of ventricular contraction)
5) Ventricular relaxation and 2nd heart sound
- “dub”
5 stages of cardiac cycle
1) Heart is at rest, all chambers are in diastole
-Atria are filling, and AV opens causing ventricles to fill
2) Ventricles filled, Atrial systole
- Atrials contract, EDV (volume in ventricle when relaxed)
3)Early ventricular contraction & first heart sound
- AV closure causes “lub” sound
- isovolumic ventricular contraction (blood stays put)
4) Heart pumps: blood leaves ventricles
- Semilunar valves open, in arteries
- ESV (volume in ventricle at the end of ventricular contraction)
5) Ventricular relaxation and 2nd heart sound
- “dub”
Parasympathetic nerves on heart rate
Decreases heart rate
decreased rate of depolarization
K+ permeability increases
Sympathetic nerves on heart rate
Increases heart rate
Increased rate of depolarization
β1-adrenergic receptors in node
Na+ and Ca++ permeability increases
Autorythmic (intrinsic firing) HR
heart rate
Parasympathetic control = 70
Symohathetic = 220-age
What causes increase in pacemaker depolarization?
Epi and Norepinephrine act on B1-receptors
What hyperpolarizes the pacemakers
Acetylcholine on muscarinic receptors
Stroke volume
Avg=70mL
The amount of blood pumped by one ventricle during one contraction
SV= EDV-ESV
End Diastolic Volume - End Systolic Volume
end-diastolic volume
volume of blood at the end of ventricular filling
what happens during isovolumic contraction
ventricular blood volume does not change, but pressure rises.
When do the semilunar valves open?
When ventricular pressure exceeds arterial pressure
When do the semilunar valves open?
When ventricular pressure exceeds arterial pressure
end-systolic volume
The volume of blood in the ventricles at the end of contraction
end-systolic volume
The volume of blood in the ventricles at the end of contraction
what creates heart sounds
1- Closure of the AV valves
2- the semilunar valves close
Cardiac output
Avg=5L/min
Volume of blood pumped per ventricle during a given period of time.
- indicates total blood flow through circulation
- Measures cardiac performance.
Q or CO =HRxSV
Ejection Fraction
% of EDV ejected with a single contraction.
EF = SV/EDV x100
eg. EF = 70 ml/beat ÷ 135 ml × 100 =
EF = 52%
Homeostatic changes in cardiac output
varying heart rate, stroke volume, or both
Homeostatic changes in cardiac output
varying heart rate, stroke volume, or both
Starling law of the heart
SV is proportional to EDV
Venous return is affected by
skeletal muscle pump
respiratory pump
sympathetic innervation of veins
Factors that Effect SV
1) Preload -initial stretching of the cardiac muscle cells prior to contraction
2) Contractility - intrinsic strength of the cardiac muscle independent of preload
3) Afterload -‘load’ to which the heart must pump against.
length and tension of sarcomere
Longer it is the greater tension there will be
intropic Agent
medicine that changes the force that your heart contracts
(norepinephrine increases stroke volume)
Catacholamines
Definition, eg, binding site, effects
Increases cardiac contractions (eg. Epi/Norepinepherine)
Bind to - B1-receptors
effects - increased voltage-gated Ca+ channels, and phospholamban
How to increase stroke volume
Increase End Diastolic Volume.
- More blood in the ventricle to be ejected.
- Preload.
Increase Ejection Fraction.
- More of the blood in the ventricle is ejected.
- Contractility.
how to increase Blood Volume in ventricles? (EDV)
Increased Venous Return
- The amount of blood that returns to the heart from venous circulation.
- Venous return is affected by:
- - Skeletal Muscle Pump.
- - Respiratory Pump.
- - Venous constriction.
What does contraction of muscles help with?
compresses veins and pushes blood toward the hear
Venous Constriction
Cause
Increased sympathetic activity causes veins to constrict.
- Volume of blood in vein decrease
Hyoertension (increased blood pressure)
Associated with increased afterload
what indicates afterload?
Mean Arterial pressure
