Heart Flashcards
What is the cardiac cycle?
Events occuring from one heartbeat to the next.
Define end diastolic volume
Amount of blood in ventricles before systolic ( or filling in )
Define end systolic volume
Lowest volume of blood in ventricle during cardiac cycle, at end of contraction.
Ejection fraction
fraction of EDV ejected per cardiac cycle
Describe the electrical conduction pathway in the heart
SA node –> AV node –> Bundle of His –> Bundle Branch –> purkinje fibers
Describe intercalated disc:
Heart cells connected by discs working as one functional organ in synchronization.
Describe a gap junction
Intercellular connection between cells that connects cytoplasm of 2 cells to allow electrical impulses to pass directly.
What is the Frank-Starling Mechanism?
Heart automatically pumps incoming blood . The amount pumped is determined by the rate of blood flow into the heart.
Increase volume of blood stretches ventricles causing cardiac muscle to contract more forcefully.
What is preload?
Pressure as ventricles fill with blood at end of diastole.
What is afterload?
Afterload refers to the forces that oppose ejection of blood out of the chamber.
Name 2 similarities of Cardiac and Skeletal Contraction
Both striated with myosin/actin.
Both have the t-tubule mechanism acting on sarcoplasmic reticulum.
Name 3 differences of Cardiac and Skeletal Contraction
T tubule Mechanism has direct diffusion of Ca++ for larger amounts of storage.
Action potential has cardiac muscle plateau for longer time of contraction than skeletal mm.
Strength of contraction varies and is dependent on extracellular Ca++.
Ability of cardiac muscle to depolarize and contract is extrinsic or intrinsic?
Intrinsic
Does the SA node have small or large fibers?
Small diameter
Are there contractile muscle fibers in the SA node?
Almost none.
Where does the SA node connect to?
Atrial muscle fibers.
Cell membranes of the SA node are naturally ____ to NA+ and CA++? Why?
LEAKY. Less negative resting membrane potential for easier SELF excitation.
SA node and AV node make up which part on an ECG?
P-wave
Bundle branches make up which part on an ECG?
Q aspect
Purkinje fibers make up which part on an ECG?
QRS
Events that occur within the cardiac cycle are..
1) Chamber and vessel blood volume changes
2) Chamber and vessel blood pressure changes
3) Electrical activity
4) Heart sounds occur
5) Valve opening/closing
What is the p-wave?
depolarization of atrial tissue
What is the QRS complex?
depolarization of ventricular tissue, repolarization of atrial tissue
What is the t-wave?
repolarization of the ventricles; relaxation
Atrial contraction causes how much additional ventricle filling? Also known as a primer pump
20%, unnecessary except during vigorous exercise
Define both isolvolumnic contraction and isovolumnic relaxation.
Periods of time when the ventricles have no net change of volume during contraction and relaxation due to the AV valves being closed.
What type of energy metabolism does the heart use primarily?
Heavy reliance on aerobic (oxidative) @ 70-90% coming from fatty acids.
Lactate and glucose (10-30%) as well.
Heart pumps how much liters per minute? And how much does this number increase by during heavy exercise?
4-6 liters, 4-7x increase during heavy exercise
Blood volume pump controlled by what 2 factors?
Intrinsic cardiac regulation (Frank Starling) , and Extrinsic Autonomic Nervous system
What is released to regulate the cardiac pump in the ANS
Sympathetic Nervous System affected by norepinephrine for fight/flight response. –> increases cardiac output and pacemaker fires faster.
What inhibits cardiac output as a part of the ANS?
Parasympathetic Nervous system. Acetylcholine hyperpolarizes membrane of cells by opening K+ channels. Reduces HR
Heart SA node receives ANS innervation when?
Continuously.
Heart is said to have _____ tone
Vagal; dominant influence is inhibitory.
What allows the SA node to self-excite?
ANS
Does the heart pump out all of the blood from the ventricles per beat?
No, roughly 2/3 of the EDV
If afterload is increased, what happens to stroke volume?
Stroke volume will decrease, as their is more pressure against the outgoing blood from the heart.
If afterload is decreased what happens to stroke volume?
Stroke volume will increase, more blood ejected per beat.
