9-17c Cardiac Physiology I Flashcards
Biomedical
What are the atrioventricular valves? What side of the heart is each one on?
The valves draining blood from the atria to the ventricles (part of diastole)
Mitral valve: left
Tricuspid valve: right
Trace the path of an RBC from vena cava to vena cava
SVC/IVC > R atrium > Tricuspid Valve > R ventricle > Pulmonary Valve > Pulmonary Arteries > Pulmonary circulation > Pulmonary Veins > L atrium > Mitral Valve > L ventricle > Aortic Valve > Aorta > Systemic Circulation > SVC/IVC
When do arteries carry deoxygenated blood?
Systemic veins > Pulmonary arteries
What are the main functions of the cardiovascular system?
Deliver O2 and nutrients, remove waste
Deliver enough blood to satisfy metabolic needs
Metabolic need at rest? At exercise?
250 mL O2/min
5000 mL O2/min
How do you measure Cardiac Output (CO)?
Heart Rate (HR) * Stroke Volume (SV)
What drive the signal that causes the heart to beat? What distinguishes a normal heart beat?
Depolarization of cardiac myocytes
“Automaticity” due to the unstable resting potential of nodal tissue
The SA node dominates the pacemaking of the heart via overdrive suppression
Normal sinus rhythm is regular at 60 to 100 bpm with a normal ECG shape
Describe how the movement of charged particles Na, K, and Ca affect electrochemical concentration gradients/action potential in skeletal m.
A cell begins with an internal Voltage of -90mV, with more Na+ outside the cell (a little more Ca++ outside) and more K+ inside the cell due to the pumping of the Sodium Potassium Pump;
If an electric current is big enough for an action potential (meets threshold), Na+ rushes in and depolarizes the cell.
Na+ channels opening cause upstroke, and those channels closing and the K+ opening cause downstroke
What are two main differences b/w cardiac and skeletal m.?
- skeletal m. action potential is over in a couple milliseconds, while cardiac m. action potential lasts ~300 milliseconds. Upstroke is the same (Na+ rushing inside), but plateau is created by:
the opposition of slow acting Ca++ channels opening and bringing Ca++ into the cell while K+ is leaving the cell. The downstroke happens when enough K+ leaves the cell to bring it back down to -90mV - Cardiac m. does not need nerves to contract
How does Cardiac m. contract without innervation?
Automaticity
The conducting pathway is made up of nodal cells that generate the depolarization that leads to the action potential by having an upward-sloping membrane potential that eventually reaches threshold
This action potential then spreads to the other force-producing cells (myocytes)
How does Automaticity work?
via a “funny current:” an unstable resting membrane potential from a gradual opening of Na+ and Ca++ channels into the cell that eventually reaches threshold for the action potential
SA Node role and action
Dominate pace-maker of the heart under normal conditions
causes depolarization of the atria to allow blood to flow into relaxed ventricles
The heart contracts in a coordinated manner
What is different about the different nodal tissue in the heart?
they beat at a different intrinsic rate
SA Node beats at 60-100 bpm and has a higher slope to reach threshold
What is a refractory period? Overdrive suppression? Ectopic foci?
The period of time before the action potential can be fired again
SA node has the fastest rate so it can fire again fastest
Ectopic foci become pacemakers in pathological states
What is one of the main jobs of the AV node?
To slow down conduction of the action potential impulse so there is time for the atria to contract and have ventricle filling maximized
What does the p wave correspond to on the ECG?
Spread of AP from SA node to atria m. for atrial depolarization
What does the QRS complex correspond to on the ECG?
ventricular depolarization; AP moves through bundle of hys, bundle branches, purkinjie fibers, and ventricular m.
What does the t wave correspond to on the ECG?
ventricular repolarization
What is “Normal Sinus Rhythm” defined by?
regular rhythm
rate b/w 60 and 100 bpm
“normal” waveform shape
What is Sinus Tachycardia?
Fast-beating heart
What is Sinus Bradycardia?
Slow-beating heart
What is Premature ventricular contraction?
Different region is playing pacemaker
Ventricular fibrillation
wavy line
Atrial fibrillation
no p wave
What does the coupling of the electrical signal and the mechanical response cause (during systole)?
Excitation-Contraction Coupling causes Calcium induced Calcium Release from AP (release of Ca inside the SR)
What happens to the Ca++ after it is released from the SR (during systole)?
binds to troponin, causes a shift in troponin; myosin and actin interaction and contraction
What happens to Ca++ during diastole?
Levels fall as it’s transported out of the cytoplasm; it moves into the SR via a SERCA pump, and it is pumped out of the cell as well
How do you calculate Stroke Volume?
End diastolic volume - end systolic volume
How do you calculate ejection fraction?
stroke volume/end diastolic volume
What can go wrong with heart beat?
Stenosis: Narrowing of valve opening
Regurgitation: Valve allows backflow of blood
Decreased contractility during systole: Systolic dysfunction
Decreased relaxation during diastole: Diastolic dysfunction
