CV System: The Heart Flashcards
Similarities of cardiac and skeletal mechanism of contraction
Striated- myosin/actin mechanism
T-tubule mechanism-acting on sarcomas mic reticulum
T tubules store more/less Ca++ in the heart than skeletal
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What does the cardiac muscle plateau result in
Longer time of contraction
What is the strength of cardiac muscle dependent on
Extracellular Ca++
Order of conduction system
SA node, AV node, bundle of His, bundle branches, purkinje fibers
An increase in Ca++ permeability facilitates
Action potential
Increase in K+ permeability
Hypopolarizaiton
P wave
Atrial depolarization
QRS complex
Ventricular depolarization
T wave
Ventricular repolarization
Diastole
Relaxation, fills with blood
Systole
Contraction, ejects blood
Ejection fraction
Fraction of EDV ejected
P wave detail
Spread of depolarization through atrial tissue followed by contraction - increase in atrial pressure
QRS complex detail
Spread of depolarization through ventricular tissue followed by contraction - increase in ventricular pressure
T wave detail
Repolarization of ventricles which represents ventricular relaxation
Atrial pressure changes. (A,C,V waves)
A- during atrial contraction
C- onset of ventricular contraction
V- end of ventricular contraction
Preload
End-diastolic pressure when the ventricle is filled; amount of tension on the muscle when it begins to contract
After load
Pressure in the artery leading from the ventricle; load against which the muscle exerts its contractile force
10-30 % of energy derived from oxidative metabolism of ______, and majority 70-90% of ______
Lactose or glucose
Fatty acids
*can also use lactic acid generated by skeletal muscle activity
Amount of blood pumped determined primarily by rate of blood flow into heart
Frank-Starling Mechanism
Intrinsic regulation of heart pumping
Frank-starling mechanism
Extrinsic regulation of the cardiac pump
Norepinephrine released by the sympathetic nervous system in response to stressors such as fright, anxiety, or exercise; threshold reached more quickly
Parasympathetic extrinsic regulation of cardiac pump
Reduces HR when stressors removed by opening K+ channels and acetyloholine hyperpolarizes membranes of cells
*note this primarily affects HR rather than contractility
