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Flashcards in The Heart Deck (32):

What is the SA node

it's the pacemaker of the heart, it provides a constant supply of action potentials, and it causes contraction of the atriums. made up of p cells


What is the AV node

it's the Atrioventricular node which then passes the signal to ...


What is the bundle of his

it's the conduction cords between the ventricles


What is the perkinge fibers

they are the fibers that cause contraction of the ventricles.


what is the pathway of action potentials in t heart

1 Sa node
2 av node
3 bundle of his
4 perkinge fibers


What are the steps for the action potentials of the Sa node

1. -70mV the funny channels open, allows Na+in
2. -60mV the T type voltage gated Ca+ channels open
3. -50mV = threshold - L type voltage gated Ca+ channels open
4. at complete depolarization the Ca+ channels close and a K+ channel opens
5. once back to -70mv the cycle starts again.


how many AP's/min from sa node



how many AP's/min from av node



how many AP's/min from perkinge system



what i are the conductive velocities of
1. AV node
2. perkenje system
3. ventricular muscle fibers

1. slow
2. fast (allows for whole ventricle to contract simultaneously
3. slow


what is the whole process of cardiac action potential conduction

1. p cells depolarize causing an action potential
2. AP passes through cells via gap junctions, and through the interatrial pathway. (both atria contract simultaneously)
3. impulse is delayed at the AV node
4. impulse rapidly passes through bundle of his and purkinje fibers (so they can contract simultaneously)
5. ventricular muscle contracts from top to bottom.


why does AP pause at AV node

to allow blood to enter ventricles before they contract


What do gap junctions do

they allow the AP to pass from one cell to another


what are the differences between AP/contraction in cardiac muscle as compaired to skeletal muscle

1. in cardiac the action potential lasts almost as long as the contraction


what is autorythmicity

the fact that the heart doesn't require innervation from any neurons


how does excitation-contraction work in the heart

1. action potential travels down the t-tubule and opens up the L-type Ca+ channel
2. the Ca+ goes into the cytoplasm and binds to the ryanodine receptor. this opens up the sarcoplasmic reticulum, allowing more Ca+ into the cytosol (calcium induced Calcium release)
3. then the Ca+ is pumped back out


How is Ca+ pumped out of the cytosol in cardiac

1. SERCA pumps
2. Plasma Membrane Ca++ atpase
3. Na + and Ca++ exchanger on plasma membrane


What is an Electrocardiogram

(ECG) measuring of the hearts electrical impulses


Parts of the ECG and what they represent
1. P wave
2. QRS complex
3. T wave
4. P-R segment
5. QT segment
6. T-Q segment

1.atrial depolarization
2. Ventricular depolarization
3. ventricular repolarization
4. AV nodal delay
5. ventricular contraction and emptying
6. Ventricular relaxation and filling


how is an ECG measured

a triangle is formed with the heart in the middle, then you pick up the electric cignals from the heart


What is SV

Stroke volume, the amount of blood ejected by the ventricles with each beat


What is EDV

end diastolic volume, volume of blood in ventricle after filling is complete


What is ESV

end systolic volume, volume of blood left in the ventricle after contraction


What is CO (q)

Cardiac output, Heart rate x stroke volume


CO = x * X

heart rate * stroke volume


How do you find stroke volume



what is the effect of the sympathetic nervous system on the heart

1. triggers the Sa node to fire more ( increase in heart rate)
2. increases stroke volume

Uses Norepinephrine


what is the affect of the parasympathetic on the heart

1. decreases heart rate

uses ACH


what are the factors that affect stroke volume

1. ventricular contractility
2. End diastolic volume


What is the Frank-sterling law for the heart

the greater the filling, the stronger the contraction, and the smaller the end systolic volume


What does the sympathetic release of NE do for stroke volume

it increases stroke volume because it increases contraction strength


what determines end diastolic volume

1. duration of diastole
2. venous return