Cardiovascular Physiology Flashcards
Chronotropy
Heart rate
Ex: if the heart is inhibited, it’s “negative chronotropy”
If the heart rate is increased, it’s “positive chronotropy”
Ionotropy
Effects (contractile strength, rate of pressure development and ejection velocity)
Bathmotropy
Influence on excitability
Ex: the SA node contributes
Dromotropy
Velocity of conduction
“Positive dromotropy” is under the influence of the sympathetic system; “negative dromotropy” is under the influence of the parasympathetic system
The vagal effect is mediated by
Acetylcholine (Ach); acts on M3
The sympathetic nerve fiber mediated by nor-adrenaline is released from
Postganglionic fibers terminating on the heart; acts on B1
Heart rate
Number of heart beats per minute
Bradycardia
Decrease in heart rate
Tachycardia
Increase in heart rate
Flutter or Fibrillation
Dramatic increase in heart rate “heart is racing”
Flutter is manageable
Fibrillation is not manageable
Want to use M3 agonist to decrease the heart rate
Ventricular systole
This is the period of ventricular contraction; blood is ejected from the ventricles
Ventricular Diastole
This is the period during which the ventricles relax and refill with blood
End Diastolic Volume
The quantity of blood remaining after ventricular systole and that following ventricular refilling (diastole) called end diastolic volume
Ventricular Preload
The pressure within the ventricles during diastolic filling
Isovolumetric Contraction
The contraction of the ventricles when both atrio-ventricular and pulmonary and aortic valves are closed
Stroke volume
“Systolic discharge” or the “pulse volume”
Cardiac Output
The output of each ventricle per minute, aka the “minute volume of circulation”
Cardiac output is given as:
C.O. = Stroke volume
S.V x Heart rate
If the stroke volume drops lower than normal…
The ventricles are weak, the systemic and pulmonary circulation drops, leading to hypotension
Excessive ventricular contraction could be caused by
Hypertrophy, the stroke volume increases
