Lab 5 Flashcards
Action potential in cardiac muscle
Rapid depolarization
Na+
Plateau phase
Depolarization
Ca2+
Repolarization
K+
Hyperpolarization
Electrocardiogram
ECG or EKG
Pattern of electrical activity recorded at bodys surface
P-wave
Sinoatrial node generates action potential
Atrial contraction: 0.1 second after P wave begins, atria contracts
Sinoatrial node doesnt work = no P-wave
Lasts 0.08 seconds
Depolarization of the atria
QRS wave/complex
Action potential travels down atrioventricular node, atrioventricular bundle, bundle branches, and Purkinje fibers
Ventricular depolarization
Ventricular contraction
Atrial repolarization
Lasts approximately 0.8 seconds
T-wave
Ventricular relaxation
Bipolar Limb Lead II
Gives completed representation of heart on an electrocardiogram reading
Cardiac Cycle
1) Heart relaxed: Passive ventricular filling
2) Atrial systole: active ventricular filling
3) Ventricular systole: Period of isovolumetric contraction
4) Ventricular systole: period of ejection
5) Ventricular diastole: Period of isovolumetric relaxation
Depolarization
Systole
Contraction
Repolarization
Diastole
Relaxation
Isovolumetric contraction
Both valves are closed simultaneously
Pacemaker cells
Specialized non-contractile cells that conduct the electrical activity of the heart
1) Sinoatrial node (SA node)
2) Atrioventricular node (AV node)
3) Atrioventricular bundle:
4) Bundle branches
5) Purkinje fibers
If SA node cannot work
AV node will contract heart but at a much slower pace; Considered a pacemaker cell
Heart’s Conduction System
Sinoatrial node (SA node): Natural pacemaker
Located in right atrium
Initiates the electrical pulse
Atrioventricular (AV) node: Delays impulse to allow atrial contraction before passing the signal to the ventricles
Bundle of His: Transmits the signal from the AV node to the ventricles; Carries impulse down interventricular septum; No gap junctions
Purkinje Fibers: Distribute the impulse throughout the ventricles causing contraction
Path of electrical signal ensures coordinated heart contractions, maintaining an efficient heartbeat and circulation
Cardiac Output
Amount of blood pumped out of each ventricle in one minute
CO = SV * HR
Stroke volume
Volume of blood pumped out by one ventricle with each beat
Correlates with strength of ventricular contraction
SV = EDV - ESV
End diastolic volume
Amount of blood that collects in ventricle during diastole
Higher than systole volume
End systole volume
Amount of blood remaining in ventricle after it has contracted
Stages of Wiggers diagram
Stage 1) AV valves open and aortic and pulmonary valves closed; Ventricular filling; P-wave
Stage 2a) Isovolumetric contraction; Both valves closed; QRS complex
Stage 2b) Ventricular ejection phase; AV valves closed and aortic and pulmonary valves open; T-wave
Stage 3) Isovolumetric relaxation; Both valves closed
Lub sound
Low sound from low pressure
Closure of Atrioventricular valves
First sound in heartbeat
Dup sound
High sound from high pressure
Closure of aortic and pulmonary valves
Second sound in heartbeat
Diastole
Period of relaxation of ventricles
While ventricles fill with blood returning from the veins in preparation for the next systole, blood continues to flow out of arterial system into capillaries
Arterial pressure decreases
Systolic pressure
The peak pressure reached during the cardiac cycle
Diastolic pressure
When arterial blood pressure is at its lowest immediately before contracting ventricle pushes blood into arteries again
Dicrotic notch
Small plateau or dip in the pressure wave
Caused through following events:
1) Aortic valve closes when ventricles relax and blood tries to go backwards to low pressure ventricle
2) Backwards flow of blood snaps semilunar valves shut and blood bouncing off the closed semilunar valve will follow initial pressure wave out to circulation
3) Produces dicrotic arch
Blood moves from high pressure to low pressure, so heart creates pressure differences so the blood will flow in coordinated fashion through body
