control of the heart
Terms
undefined, object
copy deck
-
The Frank-Starling Mechanism
involves a _________ in myocardial fiber ______. -
sustained change
lengths -
increase Venous Return (Sustained)
leads to - Venous Return > Cardiac Output
-
Venous Return > Cardiac Output
leads to - Increased ventricular EDV and ESV (over several cardiac cycles)
-
Ventricular EDV and ESV (over several cardiac cycles)
leads to - Ventricular Myocardial Fiber Lengths (Preload)
-
Ventricular Myocardial Fiber Lengths (Preload)
leads to - increased Force of Myocardial Contraction
-
increased Force of Myocardial Contraction
leads to - increased Ventricular Systolic Pressure Development
-
increased Ventricular Pressure Development
leads to - increase in Ventricular Stroke Volume
-
increase in Ventricular Stroke Volume
leads to -
increase in Cardiac Output to Equal increase Venous Return
(New Steady State) - Both EDV and ESV remain increased as long as ___is elevated.
- VR
- Equality of VR and ___ is restored, after a transient inequality
- CO
- Increased _____ ventricular CO increases VR to the ____ ventricle, resulting in a subsequent increase in ventricular CO by the same mechanisms outlined in diagram above.
-
right
left
left -
Response to a sudden increase in total peripheral resistance (afterload). Assume constant venous return and HR:
increase TPR (sustained)
leads to - Ventricle initially unable to pump normal SV against the increased TPR
-
Ventricle initially unable to pump normal SV against the increased TPR
leads to - Initial decrease in SV and CO
-
Initial decrease in SV and CO
leads to - Venous Return > Cardiac Output
-
increased Ventricular EDV and ESV (over several cardiac cycles)
leads to - increased Ventricular Myocardial Fiber Lengths (Preload)
-
increased Ventricular Myocardial Fiber Lengths (Preload)
leads to - increased Force of Myocardial Contraction
-
increased Ventricular Systolic Pressure Development
leads to - increased Ventricular Stroke Volume
-
increased Ventricular Stroke Volume
leads to -
Cardiac Output to Equal Venous Return
(New Steady State) - Both EDV and ESV remain increased as long as ____ is elevated and VR is constant.
- TPR
- An increase in afterload results in an increase in _____, under the conditions specified above.
- preload
- The initial decrease in SV is reversed and CO = ___ once again.
- VR
-
bradycardia (assume constant VR and TPR)
leads to -
(Venous Return > Cardiac Output)
increased Diastolic Ventricular Filling Time -
increased Diastolic Ventricular Filling Time
leads to - increased EDV and Myocardial Fiber Lengths (Preload)
-
increased EDV and Myocardial Fiber Lengths (Preload)
leads to - increased Ventricular Pressure Development and Stroke Volume
-
increased Ventricular Pressure Development and Stroke Volume
leads to -
Cardiac Output to Equal Venous Return
(New Steady State) - Changes in EDV and fiber lengths are sustained as long as ___ change is sustained and VR and TPR are constant.
- HR
- Increased HR would result in the opposite responses due to _____ time for ventricular filling.
- decreased
- In normal humans, these mechanisms operate only transiently. Other control mechanisms normally help prevent large changes in ventricular volume. Large, rapid changes in ventricular volume are also normally prevented by an intact ________ .
- pericardial sac
- If extrinsic control mechanisms (see below) fail, or the pericardial sac is surgically opened, the ____________ relationship becomes more important.
- Frank-Starling
- However, even in normal hearts, the Frank-Starling mechanism is very important in continuously matching the output of one ventricle with the other as _______ and ________ fluctuate.
-
venous return
ventricular afterloads - The Frank-Starling relationship is not confined to a single ventricular performance vs. preload curve in each heart. That is, "families" of curves for each heart can be generated under different conditions. For example, infusion of norepinephri
- positive inotropic effect
- The relationship between LV stroke work and end diastolic pressure (Fig. 4-19) is one form of _________ and still is an expression of the basic Frank-Starling relationship, with cardiac fiber length depending on end diastolic volume and pressure.
-
"ventricular function curve" - The force of cardiac muscle contraction in the _______ is directly related to heart rate, within certain limits.
- steady state
- As the interval between beats decreases from 20 sec to 0.5 sec, _____ tension development progressively increases
- steady state
- The changes in steady state tension development occur despite constant diastolic fiber _____. (I.e., not a result of the Frank-Starling mechanism.)
- length
- Following an increase in heart rate, several contractions are required to reach a new steady state, and tension development _______ gradually ("treppe", i,e., a non-steady state; Fig. 4-21 A). The opposite responses occur following a decrease i
- increases
- The beat following a premature ventricular systole is delayed, but more forceful than normal. This may occur in the absence of any change in diastolic fiber length or EDV. (Contractions A, B and C in Fig. 4-23 are isovolumic and are not occurring during
-
Postextrasystolic potentiation - Postextrasystolic potentiation in an otherwise normal heart also involves an increase in ventricular filling and ____ during the pause after the premature beat. This and the volume-independent mechanism mentioned above both produce the increased _______
-
EDV
pressure - Since rate-induced regulation involves a change in cardiac performance without a sustained change in diastolic cardiac fiber length, these responses involve changes in myocardial ______ or inotropic state.
- contractility
- Increases in cardiac performance at constant diastolic fiber lengths must ultimately result from increased availability of ____ ions to the contractile proteins, or changes in myofilament sensitivity to ____.
-
Ca2+
Ca2+ -
In sympathetic Cardiac Innvervation:
The right branches innervate primarily the ___ node and ____ atrial and ventricular muscle. -
S-A
right -
In sympathetic Cardiac Innvervation:
The left branches innervate primarily ___ node and ____ atrial and ventricular muscle. Overlap may occur. -
AV
left - peak ventricular pressure, dP/dt max and rate of relaxation _______ .
- increase
-
Effect of left sympathetic stimulation on left ventricular performance (right stimulation has less marked effect):
ventricular function curves shift __________; - upward to the left
- Effect of left sympathetic stimulation on left ventricular performance (right stimulation has less marked effect): force-velocity curves shift _______
- upward to the right,
- Effect of left sympathetic stimulation on left ventricular performance (right stimulation has less marked effect): Vmax _______
- increases
- Effect of sympathetic stimulation on heart rate (chronotropy): Stimulation of _____ sympathetics has a marked cardioacceratory effect, since these fibers innervate the SA node. ____ sympathetics have less effect on heart rate.
-
right
Left - Sympathetic activation also increases action potential conduction velocity(_______ ).
- (dromotropy
- Neurotransmitter: _________ stimulates beta adrenergic receptors
- Norepinephrine