The Heart Flashcards
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
- -70mV the funny channels open, allows Na+in
- -60mV the T type voltage gated Ca+ channels open
- -50mV = threshold - L type voltage gated Ca+ channels open
- at complete depolarization the Ca+ channels close and a K+ channel opens
- once back to -70mv the cycle starts again.
how many AP’s/min from sa node
70-80
how many AP’s/min from av node
40-60
how many AP’s/min from perkinge system
20-40
what i are the conductive velocities of
- AV node
- perkenje system
- ventricular muscle fibers
- slow
- fast (allows for whole ventricle to contract simultaneously
- slow
what is the whole process of cardiac action potential conduction
- p cells depolarize causing an action potential
- AP passes through cells via gap junctions, and through the interatrial pathway. (both atria contract simultaneously)
- impulse is delayed at the AV node
- impulse rapidly passes through bundle of his and purkinje fibers (so they can contract simultaneously)
- 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
- 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
- action potential travels down the t-tubule and opens up the L-type Ca+ channel
- 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)
- then the Ca+ is pumped back out
How is Ca+ pumped out of the cytosol in cardiac
- SERCA pumps
- Plasma Membrane Ca++ atpase
- 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
- P wave
- QRS complex
- T wave
- P-R segment
- QT segment
- T-Q segment
- atrial depolarization
- Ventricular depolarization
- ventricular repolarization
- AV nodal delay
- ventricular contraction and emptying
- 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
EDV - ESV
what is the effect of the sympathetic nervous system on the heart
- triggers the Sa node to fire more ( increase in heart rate)
- increases stroke volume
Uses Norepinephrine
what is the affect of the parasympathetic on the heart
- decreases heart rate
uses ACH
what are the factors that affect stroke volume
- 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
- duration of diastole
2. venous return
