189:. Inhibition of the Na/K causes extra sodium to accumulate inside the cell. The buildup the Na concentration inside the cell will cause the gradient from inside the cell to the outside of the cell to decrease slightly. This action will make it more difficult for calcium to leave the cell via the Na/Ca antiporter.
310:
By this model, if myocardial performance changes while preload, afterload, heart rate, and conduction velocity are all held constant, then the change in performance must be due to a change in contractility. However, changes in contractility alone generally do not occur. Other examples:
130:. When it's phosphorylated by PKA, levels of calcium stored in the sarcoplasmic reticulum are increased, allowing a higher rate of calcium being released at the next contraction. However, the increased rate of calcium sequestration also leads to an increase in
200:
Decreasing contractility is done primarily by decreasing the influx of calcium or maintaining lower calcium levels in the cytosol of cardiac myocytes during an action potential. This is done by a number of mechanisms:
31:
of contraction of a given heart. The ability to produce changes in force during contraction result from incremental degrees of binding between different types of tissue, that is, between filaments of
223:, the heart cells will enter a state of dysfunction and not work properly. Correct sarcomere crossbridges will not form the heart becomes less efficient (leading to myocardial failure).
429:
67:
Increasing contractility is done primarily through increasing the influx of calcium or maintaining higher calcium levels in the cytosol of cardiac myocytes during an
185:
can act as a positive inotropic agent by inhibiting the Na/K pump. High Na concentration gradient is necessary to pump out sarcoplasmic calcium via the Na/Ca
59:
of cardiac muscle cells. The factors causing an increase in contractility work by causing an increase in intracellular calcium ions (Ca) during contraction.
652:
422:
1021:
415:
366:
247:
A measurable relative increase in contractility is a property of the myocardium similar to the term "inotropy". Contractility may be
205:
322:
565:
149:
942:
697:
675:
937:
682:
763:
84:
48:
967:
924:
914:
790:
770:
734:
657:
617:
438:
291:
785:
775:
665:
68:
972:
904:
849:
750:
670:
554:
532:
145:
512:
909:
899:
813:
559:
517:
127:
104:
266:
that enhance contractility are considered to have a positive inotropic effect. The ancient herbal remedy
758:
227:
178:
to keep up with the sodium influx at the higher frequency of action potentials at elevated heart rates
318:
An increase in contractility tends to increase stroke volume and thus a secondary increase in preload.
507:
490:
296:
274:
properties that have been recorded encyclopedically for centuries and it remains advantageous today.
854:
692:
687:
522:
495:
76:
962:
827:
580:
24:
598:
570:
550:
362:
231:
947:
542:
112:
100:
386:
315:
An increase in sympathetic stimulation to the heart increases contractility and heart rate.
282:
Under one existing model , the five factors of myocardial performance are considered to be
797:
527:
407:
336:
171:
108:
75:
Sympathetic activation. Increased circulating levels of catecholamines (which can bind to
957:
882:
874:
468:
455:
259:
248:
174:; treppe; frequency-dependent inotropy). This is probably due to the inability of Na/K-
80:
20:
1015:
575:
485:
478:
463:
234:
wall dies off, that portion cannot contract and there is less force developed during
119:
52:
989:
979:
952:
841:
832:
629:
603:
329:
271:
164:
152:
to calcium, allowing more calcium into the myocyte cells, increasing contractility.
123:
994:
984:
712:
707:
702:
613:
263:
212:
932:
717:
607:
590:
473:
286:
186:
138:
92:
55:, which is a process that determines the concentration of calcium ions in the
192:
Increase the amount of calcium in the sarcoplasm. More calcium available for
864:
635:
502:
301:
267:
253:
182:
156:
131:
79:
activation) as well as stimulation by sympathetic nerves (which can release
892:
623:
220:
193:
160:
887:
321:
An increase in preload results in an increased force of contraction by
235:
56:
44:
40:
39:(thin) tissue. The degree of binding depends upon the concentration of
727:
722:
258:. Drugs that positively render the effects of catecholamines such as
175:
32:
335:
An increase in heart rate will increase contractility (through the
859:
446:
328:
An increase in afterload will increase contractility (through the
36:
28:
411:
122:. When phospholamban is not phosphorylated, it inhibits the
170:
An increase in heart rate also stimulates inotropy (
923:
873:
840:
826:
806:
743:
645:
589:
541:
454:
445:
19:
represents the innate ability of the heart muscle (
325:; this does not require a change in contractility.
380:
378:
167:) by a mechanism that is not fully understood.
423:
27:. It is the maximum attainable value for the
8:
51:is driven by precisely timed releases of a
837:
451:
430:
416:
408:
107:- which has a number of effects including
71:. This is done by a number of mechanisms:
196:to use will increase the force developed.
47:intact heart, the action/response of the
439:Physiology of the cardiovascular system
349:
361:. Lippincott Williams & Wilkins.
211:If the heart is experiencing anoxia,
63:Mechanisms for altering contractility
7:
357:Richard Klabunde (3 November 2011).
103:activated, resulting in increase of
270:appears to have both inotropic and
391:Cardiovascular Physiology Concepts
387:"Cardiac Inotropy (Contractility)"
359:Cardiovascular Physiology Concepts
14:
251:altered by the administration of
226:Loss of parts of the myocardium.
126:that pump calcium back into the
278:Model as a contributing factor
159:can cause a small increase in
1:
566:Aortic valve area calculation
683:Effective refractory period
562:) / End-diastolic dimension
323:Starling's law of the heart
230:can cause a section of the
148:. This will increase their
1038:
141:to the effects of calcium.
99:of the receptor to render
49:sympathetic nervous system
1022:Cardiovascular physiology
968:Tubuloglomerular feedback
915:Critical closing pressure
735:Hexaxial reference system
658:Cardiac electrophysiology
943:Renin–angiotensin system
91:on myocytes) causes the
17:Myocardial contractility
973:Cerebral autoregulation
938:Kinin–kallikrein system
905:Jugular venous pressure
555:End-diastolic dimension
533:Pressure volume diagram
146:L-type calcium channels
43:in the cell. Within an
910:Portal venous pressure
900:Mean arterial pressure
814:Ventricular remodeling
560:End-systolic dimension
518:Cardiac function curve
155:An abrupt increase in
128:sarcoplasmic reticulum
551:Fractional shortening
491:End-diastolic volume
855:Vascular resistance
693:Electrocardiography
688:Pacemaker potential
618:Conduction velocity
523:Venous return curve
496:End-systolic volume
385:Klabunde, Richard.
292:Conduction velocity
111:phospholamban (via
963:Myogenic mechanism
581:Left atrial volume
513:Frank–Starling law
181:Drugs. Drugs like
23:or myocardium) to
1009:
1008:
1005:
1004:
822:
821:
662:Action potential
653:Conduction system
599:Cardiac pacemaker
571:Ejection fraction
101:adenylate cyclase
1029:
948:Vasoconstrictors
925:Regulation of BP
838:
771:pulmonary artery
744:Chamber pressure
452:
432:
425:
418:
409:
402:
401:
399:
397:
382:
373:
372:
354:
144:Phosphorylating
118:Phosphorylating
113:Protein kinase A
69:action potential
1037:
1036:
1032:
1031:
1030:
1028:
1027:
1026:
1012:
1011:
1010:
1001:
919:
869:
831:
828:Vascular system
818:
802:
739:
641:
626:(Contractility)
585:
537:
528:Wiggers diagram
441:
436:
406:
405:
395:
393:
384:
383:
376:
369:
356:
355:
351:
346:
337:Bowditch effect
280:
245:
218:
206:Parasympathetic
172:Bowditch effect
109:phosphorylating
96:
88:
81:norepinepherine
65:
12:
11:
5:
1035:
1033:
1025:
1024:
1014:
1013:
1007:
1006:
1003:
1002:
1000:
999:
998:
997:
992:
987:
977:
976:
975:
970:
965:
958:Autoregulation
955:
950:
945:
940:
935:
929:
927:
921:
920:
918:
917:
912:
907:
902:
897:
896:
895:
890:
883:Pulse pressure
879:
877:
875:Blood pressure
871:
870:
868:
867:
862:
857:
852:
846:
844:
835:
824:
823:
820:
819:
817:
816:
810:
808:
804:
803:
801:
800:
795:
794:
793:
788:
780:
779:
778:
768:
767:
766:
761:
753:
751:Central venous
747:
745:
741:
740:
738:
737:
732:
731:
730:
725:
720:
715:
710:
705:
700:
690:
685:
680:
679:
678:
673:
668:
660:
655:
649:
647:
643:
642:
640:
639:
633:
632:(Excitability)
627:
621:
611:
601:
595:
593:
587:
586:
584:
583:
578:
573:
568:
563:
557:
547:
545:
539:
538:
536:
535:
530:
525:
520:
515:
510:
505:
500:
499:
498:
493:
483:
482:
481:
476:
469:Cardiac output
466:
460:
458:
456:Cardiac output
449:
443:
442:
437:
435:
434:
427:
420:
412:
404:
403:
374:
368:978-1451113846
367:
348:
347:
345:
342:
341:
340:
333:
326:
319:
316:
308:
307:
304:
299:
294:
289:
279:
276:
260:norepinephrine
249:iatrogenically
244:
241:
240:
239:
224:
216:
209:
198:
197:
190:
179:
168:
153:
142:
135:
116:
94:
89:-adrenoceptors
86:
83:that binds to
64:
61:
21:cardiac muscle
13:
10:
9:
6:
4:
3:
2:
1034:
1023:
1020:
1019:
1017:
996:
993:
991:
988:
986:
983:
982:
981:
978:
974:
971:
969:
966:
964:
961:
960:
959:
956:
954:
951:
949:
946:
944:
941:
939:
936:
934:
931:
930:
928:
926:
922:
916:
913:
911:
908:
906:
903:
901:
898:
894:
891:
889:
886:
885:
884:
881:
880:
878:
876:
872:
866:
863:
861:
858:
856:
853:
851:
848:
847:
845:
843:
839:
836:
834:
829:
825:
815:
812:
811:
809:
805:
799:
796:
792:
789:
787:
784:
783:
781:
777:
774:
773:
772:
769:
765:
762:
760:
757:
756:
754:
752:
749:
748:
746:
742:
736:
733:
729:
726:
724:
721:
719:
716:
714:
711:
709:
706:
704:
701:
699:
696:
695:
694:
691:
689:
686:
684:
681:
677:
674:
672:
669:
667:
664:
663:
661:
659:
656:
654:
651:
650:
648:
644:
637:
634:
631:
628:
625:
622:
619:
615:
612:
609:
605:
602:
600:
597:
596:
594:
592:
588:
582:
579:
577:
576:Cardiac index
574:
572:
569:
567:
564:
561:
558:
556:
552:
549:
548:
546:
544:
540:
534:
531:
529:
526:
524:
521:
519:
516:
514:
511:
509:
506:
504:
501:
497:
494:
492:
489:
488:
487:
486:Stroke volume
484:
480:
479:Stroke volume
477:
475:
472:
471:
470:
467:
465:
464:Cardiac cycle
462:
461:
459:
457:
453:
450:
448:
444:
440:
433:
428:
426:
421:
419:
414:
413:
410:
392:
388:
381:
379:
375:
370:
364:
360:
353:
350:
343:
338:
334:
331:
327:
324:
320:
317:
314:
313:
312:
306:Contractility
305:
303:
300:
298:
295:
293:
290:
288:
285:
284:
283:
277:
275:
273:
269:
265:
261:
257:
255:
250:
242:
237:
233:
229:
225:
222:
215:(increased CO
214:
210:
207:
204:
203:
202:
195:
191:
188:
184:
180:
177:
173:
169:
166:
162:
158:
154:
151:
147:
143:
140:
136:
133:
129:
125:
124:calcium pumps
121:
120:phospholamban
117:
114:
110:
106:
102:
98:
90:
82:
78:
74:
73:
72:
70:
62:
60:
58:
54:
53:catecholamine
50:
46:
42:
38:
34:
30:
26:
22:
18:
990:Carotid body
953:Vasodilators
833:hemodynamics
638:(Relaxation)
630:Bathmotropic
604:Chronotropic
394:. Retrieved
390:
358:
352:
330:Anrep effect
309:
281:
272:chronotropic
252:
246:
228:Heart attack
199:
165:Anrep effect
150:permeability
137:Sensitizing
77:β-Adrenergic
66:
41:calcium ions
35:(thick) and
16:
15:
995:Glomus cell
985:Aortic body
980:Paraganglia
791:ventricular
764:ventricular
713:QT interval
708:QRS complex
703:PR interval
676:ventricular
614:Dromotropic
264:epinephrine
232:ventricular
213:hypercapnia
208:activation.
933:Baroreflex
850:Compliance
842:Blood flow
718:ST segment
646:Conduction
636:Lusitropic
608:Heart rate
591:Heart rate
543:Ultrasound
474:Heart rate
396:27 January
344:References
287:Heart rate
187:antiporter
139:troponin-C
893:Diastolic
865:Perfusion
624:Inotropic
503:Afterload
302:Afterload
268:digitalis
254:inotropic
183:digitalis
157:afterload
132:lusitropy
1016:Category
888:Systolic
666:cardiac
243:Inotropy
221:acidosis
194:Troponin
161:inotropy
25:contract
508:Preload
297:Preload
236:systole
97:subunit
57:cytosol
45:in vivo
798:Aortic
786:atrial
759:atrial
755:Right
728:U wave
723:T wave
698:P wave
671:atrial
365:
256:agents
176:ATPase
33:myosin
860:Pulse
807:Other
782:Left
776:wedge
447:Heart
219:) or
37:actin
29:force
398:2011
363:ISBN
262:and
105:cAMP
553:= (
1018::
389:.
377:^
339:).
332:).
115:).
830:/
620:)
616:(
610:)
606:(
431:e
424:t
417:v
400:.
371:.
238:.
217:2
163:(
134:.
95:s
93:G
87:1
85:β
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