Heart physiology.
Myocardial cells are short, branched, and interconnected by gap junctions.
Entire muscle that forms a chamber is called a myocardium.
AP's originating in any cell are transmitted to cells in that chamber
4 chambers are separated from each other by non conductive tissue.
Electroactivity of the heart
Located in inferior interatrial septum.
delays impulses by 0.1 seconds
allows atrial contraction
Inherent rate of 50X/minute.
Atriotventricular node (AV)
What are the 3 waves (parts) of EKG
P-wave atrial depolarization (sa node)
QRS Complex, ventricular depolarization and atrial repolarization
T-wave, ventricular repolarization.
Volume of blood pumped by the minute by each ventricle
Cardiac outpout
stronger contraction ejects more blood
contractility.
Cardiac muscle tissue has intrinsic ability to generate and conduct impulses.
signal these cells to contract rythmically
How does norepinephrine affect SA node
SA node drives heart rate. SNS/PNS influence HR.
SYMP-NORepi-Speed up HR
Norepinephrine causes pacemaker to fire more rapidly
repeating pattern of contraction and relation of heart.
blood flow throughout heart during one cycle.
series of pressure and blood volume changes in heart chambers.
The cardiac cycle.
Volume of blood pumped/beat by each ventricle
Stroke volume (SV)
States that strength of ventricular contraction varies directly with EDV.
Intrinsic property of myocardium.
EDV increases, myocardium stretches more, causing greater contraction and stroke volume.
Frank-Starling law of the heart
A series of specialized autorhythmic cardiac muscles
These initiate and distribute impulses, which coordinate depolarization and contraction of the heart
Pacemakers.
How does acetylcholine affect SA node?
Parasymp-AcH-slows down HR
AcH hyperpolarizes pacemaker cells by opening K+ channels, slowing down HR.
AV valves are open, semilunar valves close, pressure low in all chambers.
80% of blood flows passively through atria into ventricles.
atrial contraction occurs, delivering remaining 20% of blood to ventricles
Ventricular filling (cardiac cycle.)
Stroke Volume and Heart Rate affect what?
Cardiac outpout
What causes pacemaker potentials?
unstable resting membrane potentials, due to opening of slow Na+ channels.
composite of all AP's generated by nodal and contractile cells.
measures electric activity of the heart
NOT a measure of HR or contraction.
measures electric activity of heart in the cardiac cycle.
EKG or ECG.
atria relaxes, ventricles begin to contract.
all valves close
ventricular pressure exceeds pressure in larger arteries, forcing valves to open, bloods ejects from ventricles
Ventricular systole (cardiac cycle.)
Amount of blood in ventricles before contraction
EDV
Sets the inherent rate of contraction
Rythm can be altered by autonomic nervous system.
located in right atrial wall.
Impulse spreads across atria via gap junctions.
Sinoatrial node (SA)
Bi-polar reads: wrist and legs
lead 1: right arm-left arm
lead 2: right arm-left leg
lead 3: Left arm left leg
Types of EKG readings.
ventricles relax- atria fills with blood from systemic circuit-av valves closed.
backflow of blood in aorta and pulmonary trunk close Valves
atrial pressure exceeds in ventricles-AV valves open-cycle then begins at step 1.
Isovolumetric relaxation. (cardiac cycle)
Amount of blood left after contraction
ESV