heart contraction physiology Flashcards
What is the resting potential of the heart cells?
When ___ enters, it causes muscle cell
rapid depolarization.
-85mV
Na+
After depolarization, the membrane potential is maintained, what is this phase known as?
Why does this happen? (hint: Ca2, Na+, and K+ channels)
Plateau phase
Voltage gated Ca2+ channels open for Ca2+ to enter cell
Na+ channels close
Some K+ channels open for K+ slowly exit
What is the phase called when the cell returns to resting potential?
How does this happen?
Repolarization phase
All K+ channels open and K+ rapidly leaves the cell.
All Ca2+ channels close
What is an EKG
an external measurement of electrical change in the heart
What does the P wave represent
atrial depolarization
What does the QRS wave represent
Ventrical depolarization
What does the T wave represent
ventrical repolarization
What indicates the heart rate on an EKG
distance from P wave to P wave
What is a does first degree heart block look like on an EKG
What is the physiological result?
More time between P and QRS wave
The conduction in the heart is slowed
AKA “AV block”
What does a second degree heart block look like on an EKG
What does this mean physiologically
more Ps than QRSs
some impulses are not conducted throughout the heart, “dropped beats”
AKA “2:1”
What does a third degree block look like on an EKG?
What does this mean physiologically
P and QRS waves are not coordinated
no impulses from SA node to AV node. atria and ventricles pace independently, which causes incomplete filling of the heart
AKA “complete block”
asynchronous contraction of muscle fibers so that chambers cannot pump
atrial and ventricular fibrilation
strong brief shock resets conduction system led by SA node
defibrillation, give a stringer shock to act as the orginal signal that should have been given by the SA node
Name the AV valves
What do they separate
Bicuspid: Left atrium/ventricle
Tricuspid: Right atrium/ventricle
Name the semilunar valves
What do they separate
Aortic semilunar valve: left ventricle and aorta
Pulmonary semilunar: right ventricle and pulmonary trunk
what process causes the first heart sound (lubb)?
AV valves closing
what process causes the second heart sound (dubb)?
semilunar valves closing
what is systole
contraction (think: squeze)
what is diastole?
relaxation (think: destress or dilation)
What is the first step of the cardiac cycle? (hint: first wave of EKG)
P wave
atrial depolarization which leads to atrial contraction (atrial systole).
Blood is “squeezed” out atria into ventricles
What is the second step of the cardiac cycle? (hint: second wave of EKG)
QRS wave
ventricular depolarization which leads to ventricular contraction (ventricular systole).
ventricular pressure increases and the AV valves close (first heart
sound)
papillary muscles contract, pulling chordae tendineae to keep valves closed.
No blood has moved out yet.
what is step 3 of the cardiac cycle? (hint: where does the blood go next? how does this happen?)
ventricular pressure > aortic pressure
semilunar valves open and blood ejected from the ventricle
What is the fourth and final step of the cardiac cycle? (hint: final wave of EKG)
T wave
ventricular repolarization leads to ventricular muscle relaxation
(ventricular diastole).
aortic pressure > ventricular pressure, semilunar valves
shut (second heart sound and brief spike in aortic pressure = dicrotic notch)
no more blood exits ventricle (end systolic volume).
End diastolic volume (blood in the ventricles before the heart contracts) – end systolic
volume (blood in the ventricle at the end of the systolic ejection phase =___
stroke volume
Once atrial pressure > ventricular pressure, the ____ valves will open and blood will pass from atria to ventricles for new cycle
AV
