Cardiovasculair stelsel ademhaling nier en urinewegen (D001943)
Institution
Universiteit Gent (UGent)
Dit is een volledige samenvatting van fysiologie van vak Cardiovasculair stelsel ademhaling nier en urinewegen (deel 1). Zowel lessen als de cursus is verwerkt in deze samenvatting. Mocht er iets mis zijn met de lay-out, mag je me ook gerust altijd een berichtje sturen :)
Excita3e-contrac3e koppeling in hartspiercellen ............................................................................................. 7
Elektrofysiologie van de hartspiercel .................................................................................................................. 7
Algemeen ....................................................................................................................................................... 7
Ontstaan van de ac<epoten<aal ............................................................................................................... 7
a. Fase 0 ............................................................................................................................................... 8
b. Fase 1 ............................................................................................................................................... 8
c. Fase 2 ............................................................................................................................................... 8
d. Fase 3 ............................................................................................................................................... 8
Contrac8e van de hartspiercel ............................................................................................................................ 9
Relaxa8e van de hartspiercel .............................................................................................................................. 9
Modula8e van de contrac8ekracht van de hartspiercel ..................................................................................... 9
Inotrope factoren ........................................................................................................................................... 9
Noradrenaline en adrenaline .................................................................................................................. 10
Hartglycosiden: digoxine ......................................................................................................................... 10
CAVE: inotrope medica<e ....................................................................................................................... 10
Snelle opeenvolgende AP........................................................................................................................ 10
Acidose.................................................................................................................................................... 10
Pathofysiologie ............................................................................................................................................ 11
Acute hypoxie (myocardinfarct) .............................................................................................................. 11
Chronische hartproblemen => calcium overload .................................................................................... 11
Gevolgen van Ca2+overload ..................................................................................................................... 11
Fysiologie van het neuromusculair geleidingsweefsel .................................................................................... 12
Algemeen.......................................................................................................................................................... 12
Organisa8e van het neuromusculair weefsel ................................................................................................... 12
Ac8epoten8aalmechanisme ............................................................................................................................. 12
Mechanisme van depolarisa<efase in SA- en AV-knoop .............................................................................. 13
Gevolgen: ................................................................................................................................................ 13
Mechanisme van depolarisa<efase in His bundel en Purkinje vezels .......................................................... 13
Beïnvloeding van het hartritme ........................................................................................................................ 14
Fysiologische modula<e: ............................................................................................................................. 14
Orthosympa<sche pulsen ....................................................................................................................... 14
Parasympa<sche impulsen...................................................................................................................... 14
Temperatuur ........................................................................................................................................... 15
Thyroïdhormoon ..................................................................................................................................... 15
Kalemië ................................................................................................................................................... 15
Abnormaliteiten in het hartritme ..................................................................................................................... 15
Ritmestoornissen- hartaritmieën................................................................................................................. 15
Re-entry fenomeen ................................................................................................................................. 16
Wolff-Parkinson-White syndroom ........................................................................................................... 16
Opmerking ........................................................................................................................................................ 16
Het elektrocardiogram EKG ........................................................................................................................... 17
Algemeen.......................................................................................................................................................... 17
De standaardafleidingen van het EKG .............................................................................................................. 17
De perifere afleidingen ................................................................................................................................ 17
1
, Bipolaire perifere afleidingen.................................................................................................................. 17
Augmented unipolaire perifere afleidingen ................................................................................................. 18
De precordiale afleidingen ........................................................................................................................... 18
Principe van de me8ng ..................................................................................................................................... 19
Elektroden meten verandering in poten<aalverschillen .............................................................................. 19
De algemene vorm van het EKG ....................................................................................................................... 20
Verband tussen EKG en elektrische ac8viteit van het hart ............................................................................... 21
EKG <--> hart ............................................................................................................................................... 21
Het QRS-complex in verschillende afleidingen ............................................................................................ 22
De perifere afleiding (frontaal vlak) ........................................................................................................ 22
De precordiale afleidingen (transversaal vlak) ........................................................................................ 22
Bepaling van de elektrische as van het hart ................................................................................................ 22
Opmerking ........................................................................................................................................................ 22
Klinisch belang EKG........................................................................................................................................... 23
Zicht op het hart ............................................................................................................................................... 23
De hartcyclus ................................................................................................................................................ 24
Algemeen.......................................................................................................................................................... 24
Hartcyclus in het (linker)ventrikel ..................................................................................................................... 25
Diastole ........................................................................................................................................................ 25
Snelle relaxa<efase < 100 ms .................................................................................................................. 25
Vullingsfase = 400 ms .............................................................................................................................. 25
Systole .......................................................................................................................................................... 26
Snelle aanspanningsfase < 100 ms .......................................................................................................... 26
Ejec<efase ............................................................................................................................................... 26
De druk-volume lus ...................................................................................................................................... 28
Eigenschappen druk-volume lus ............................................................................................................. 28
Harfonen en hartgeruisen .......................................................................................................................... 28
Harfonen ................................................................................................................................................ 28
Hartgeruisen ........................................................................................................................................... 29
Drukverloop in atria + golven in de centraal veneuze terugkeer ...................................................................... 29
Atriale cyclus ................................................................................................................................................ 29
S<jging van druk = golven ....................................................................................................................... 29
Daling van de druk = descent .................................................................................................................. 29
De arteriële puls................................................................................................................................................ 30
Regeling van het hartdebiet .......................................................................................................................... 31
Algemene gegevens .......................................................................................................................................... 31
Determinanten van het hartdebiet ................................................................................................................... 31
Overzicht factoren die hartdebiet beïnvloeden ........................................................................................... 31
Hargrequen<e ............................................................................................................................................. 31
Slagvolume .................................................................................................................................................. 32
Aierload = nabelas<ng ................................................................................................................................ 32
Slagarbeid .................................................................................................................................................... 32
Inotropisme ................................................................................................................................................. 33
Het intrinsieke inotropisme .................................................................................................................... 33
Het extrinsiek inotropisme...................................................................................................................... 33
Beïnvloeding van het inotropisme .......................................................................................................... 34
Preload (= voorbelas<ng)............................................................................................................................. 34
Verband tussen preload en de slagarbeid ............................................................................................... 34
Consequen<es van ventriculaire disten<e .............................................................................................. 35
2
, Determinanten van de preload ............................................................................................................... 35
Besluit bij de regeling van het hartdebiet ......................................................................................................... 36
Invloed inotropisme, preload en a\erload op druk-volume lus ........................................................................ 37
De isovolumetrische druk-volume rela<e .................................................................................................... 37
Passieve P-V curve................................................................................................................................... 37
Isovolumetrische P-V rechte ................................................................................................................... 37
Invloed van preload op de P-V lus................................................................................................................ 37
Invloed van aierload op de P-V lus ............................................................................................................. 37
Invloed van het inotropisme op de P-V lus .................................................................................................. 38
Hartarbeid en zuursto^ehoe\e van het hart ................................................................................................... 38
Fysio verschillende bloedvatsegmenten ........................................................................................................ 39
Algemeen.......................................................................................................................................................... 39
Arteriën ............................................................................................................................................................. 39
Arteriolen .......................................................................................................................................................... 39
Venen ................................................................................................................................................................ 40
Factoren die terugvloei naar hart bevorderen ............................................................................................. 40
Capillairen......................................................................................................................................................... 41
Permeabiliteit capillairen ............................................................................................................................. 41
Mechanismen van uitwisseling .................................................................................................................... 42
Uitwisseling van opgeloste stoffen.......................................................................................................... 42
Uitwisseling van water ............................................................................................................................ 42
Opmerking: ............................................................................................................................................. 42
De lymfecircula8e ............................................................................................................................................. 42
Vloeistroom in lymfevaten ........................................................................................................................... 42
Toename van lymfevocht/inters<<ële vloeistof: oedeem ........................................................................... 43
Hemodynamica ............................................................................................................................................. 44
Verhouding druk, weerstand en debiet............................................................................................................. 44
Wet van Darcy .............................................................................................................................................. 44
Toegepast op cardiovasculair systeem: ................................................................................................... 44
Wet van Poiseuille........................................................................................................................................ 44
Laminaire en turbulente stroming .................................................................................................................... 45
Viscositeit van bloed ......................................................................................................................................... 45
Wandspanning.................................................................................................................................................. 45
Complian8e van bloedvaten ............................................................................................................................. 46
De kri8sche slui8ng- en openingsdruk .............................................................................................................. 46
Regeling van de regionale doorbloeding........................................................................................................ 47
Algemeen.......................................................................................................................................................... 47
Determinanten van de regionale doorbloeding ................................................................................................ 47
Perfusiedrukgradiënt ................................................................................................................................... 47
Lokale weerstand in weefsels ...................................................................................................................... 47
Tonus van de vasculaire gladde spiercellen ...................................................................................................... 47
Mechanismen van vasoconstric<e............................................................................................................... 48
Verhoging cytosolische Ca2+-concentra<e............................................................................................... 48
Ca2+-sensi<sa<e....................................................................................................................................... 48
Mechanismen van vasodilata<e .................................................................................................................. 48
3
, Bloeddrukverlagende geneesmiddelen: ................................................................................................. 48
Determinanten van de vaatwandtonus ............................................................................................................ 49
Metabole vasodilata<e ................................................................................................................................ 49
Autoregula<e ............................................................................................................................................... 49
Myogene respons.................................................................................................................................... 49
Invloed van vasodilaterende metabolieten ............................................................................................. 49
Andere lokale mechanismen ....................................................................................................................... 50
Regeling door endotheel ............................................................................................................................. 50
Endotheliale relaxerende factoren .......................................................................................................... 50
Endotheliale vasoconstrictorische factoren ............................................................................................ 51
Het endotheel bij cardiovasculaire aandoeningen.................................................................................. 51
Besluit .......................................................................................................................................................... 51
Doorbloeding van de verschillende vaatgebieden ......................................................................................... 52
Algemeen.......................................................................................................................................................... 52
De hersendoorbloeding .................................................................................................................................... 52
Regeling van de hersendoorbloeding .......................................................................................................... 52
1. Metabole invloed .......................................................................................................................... 52
2. Myogene tonus.............................................................................................................................. 52
Opmerking: ............................................................................................................................................. 53
De myocarddoorbloeding ................................................................................................................................. 53
Kenmerken van de coronaire doorbloeding ................................................................................................ 53
De zuurstofvoorziening van het myocard .................................................................................................... 53
Regeling van de myocarddoorbloeding ....................................................................................................... 53
Myogene tonus ....................................................................................................................................... 53
Metabole invloed .................................................................................................................................... 53
Neurogene beïnvloeding ......................................................................................................................... 53
Stoornissen van de myocarddoorbloeding .................................................................................................. 54
De nierdoorbloeding ......................................................................................................................................... 55
Doorbloeding van de huid ................................................................................................................................ 55
Factoren die huiddoorbloeding beïnvloeden............................................................................................... 55
Neurogene impulsen ............................................................................................................................... 55
Temperatuur ........................................................................................................................................... 55
Doorbloeding van het splanchnisch gebied ...................................................................................................... 56
Drukverschil ................................................................................................................................................. 56
Weerstand van splanchnische arteriolen ..................................................................................................... 57
Metabole invloed .................................................................................................................................... 57
Neurogene invloed .................................................................................................................................. 57
Doorbloeding van de skeletspieren................................................................................................................... 57
Weerstand van de skeletspierarteriolen ...................................................................................................... 58
Intramusculaire druk ............................................................................................................................... 58
Tonus van gladde spiercellen .................................................................................................................. 58
Bloeddrukregeling en cardiovasculaire reflexen ............................................................................................ 59
De arteriële doorbloeding ................................................................................................................................. 59
Determinanten van de arteriële bloeddruk....................................................................................................... 59
Regeling arteriële bloeddruk ............................................................................................................................ 59
Algemeen ..................................................................................................................................................... 59
De cardiovasculaire centra (CVC) – vasomotorische zone ........................................................................... 59
Uitmonden in PS-zenuwbanen................................................................................................................ 60
Uitmonden in OS-zenuwbanen ............................................................................................................... 60
4
, Afferente impulsen ...................................................................................................................................... 60
Centrale beïnvloeding van de CVC .......................................................................................................... 60
Perifere beïnvloeding van de CVC ........................................................................................................... 61
Efferente impulsen ....................................................................................................................................... 63
Snelle neurogene impulsen..................................................................................................................... 63
Trage neuro-endocriene impulsen .......................................................................................................... 63
Het renine-angiotensine-aldosteron systeem.............................................................................................. 64
Algemeen ................................................................................................................................................ 64
Renine ..................................................................................................................................................... 64
Angiotensine ........................................................................................................................................... 64
Bloeddrukhomeostase bij daling van het vasculaire volume ....................................................................... 65
Pathofysiologie in urgen3es .......................................................................................................................... 66
Algemeen.......................................................................................................................................................... 66
Types shock .................................................................................................................................................. 66
Erns8g trauma .................................................................................................................................................. 67
Trauma casus ............................................................................................................................................... 67
Prehospitaal aanpak van een trauma...................................................................................................... 67
Aanpak in het ziekenhuis ........................................................................................................................ 71
Anafylac8sche shock ........................................................................................................................................ 73
Algemeen ..................................................................................................................................................... 73
Behandelding anafylaxie .............................................................................................................................. 73
Longembool ...................................................................................................................................................... 74
Casus vrouw in spoed: ................................................................................................................................. 74
Acute behandeling van massief longembool ............................................................................................... 74
, Inleidende begrippen
Grote en kleine bloedsomloop in serie geschakeld
- Perifere circula>e: linker ventrikel --> alle organen (-longen)
ñ Circuits naar organen parallel geschakeld
˃ Niet serie: onderste ledematen zouden minder O2 en meer metabole
afvalstoffen hebben
˃ Doorbloeding elk orgaan afzonderlijk binnen grenzen geregeld
- Pulmonale circula>e: rechter ventrikel --> longen
Arbeid hart = hartdebiet ∙ gemiddelde arteriële BD
- Arteriële drukverschillen in grote en kleine bloedsomloop met zelfde debiet
ñ 100 mm Hg vs 15 mm Hg (aan het einde ≈ 0 mm Hg)
- Arbeid linkerventrikel ≈ 6 x arbeid rechterventrikel
∆"
Hart bouwt druk (P) op en stuwt zo bloed doorheen een buizenstelsel (Flow): 𝐹 = #
- Flow recht evenredig met arteriële bloeddruk
- Flow omgekeerd evenredig met weerstand
Func>oneel onderverdeling van het hart:
- 2 harten: linker en rechter hart => ventrikel prak>sch volledige pompfunc>e
ñ Atriale pompwerking enkel belangrijk wanneer normale vulling ventrikels te
kort schiet = turbolader
˃ Zeer hoge harUrequen>es waar diastole heel kort is
˃ Pathologische gevallen: ventrikelwand s>jver
6
, Excitatie-contractie koppeling in
hartspiercellen
Pompfunc)e hart: simultaan alternerend
verlengen en verkorten van individuele
hartspiercellen
- Ca2+-concentra>e > 100 nM: Ca2+ binden op
troponine => bindingsplaats voor myosine
vrij op ac>ne => filamenten schuiven over
elkaar
- Mechanisch antwoord (contrac>e) op
elektrische ac>viteit (AP) met kleine
vertraging1
Elektrofysiologie van de hartspiercel
Algemeen
Ac>epoten>aal = langdurig met lange plateaufase
(200 – 300 ms)
5 fasen in ac>epoten>aal2
a) Fase 0: drempelpoten>aal
b) Fase 1: snelle repolarisa>efase
c) Fase 2: plateaufase
d) Fase 3: repolarisa>efase
e) Fase 4: rust
Ontstaan van de ac+epoten+aal
Rust: Em = -90 mV
- Voornamelijk a`ankelijk van [K+]: grote permeabiliteit van membraan (evenwicht)
ñ Streven naar gelijke concentra>e
˃ [Kbinnen] >>>> [Kbuiten]: K+ wil naar buiten Evenwicht tussen
ñ Streven naar zelfde spanning fysische en
˃ Uitstroom K+: in cel heel nega>ef => K+ kan niet verder elektrische krachten
naar buiten migreren
Depolarisa>e van hartspiercel als membraanpoten>aal ≈-65 mV
- Depolarisa>e verspreidt doorheen hartspiercellen via gap junc>ons
1
Zie pagina 8
2
Zie aoeelding 1
7
,a. Fase 0
Drempelpoten>aal: spanningsgevoelige Na+-kanalen open => meer depolarisa>e => meer
Na+-kanalen gaan open => verdere depolarisa>e => …
- Evenwichtspoten>aal naar ENa (+65 mV) maar bereikt het nooit
ñ Membraan permeabel K+: verlaat de cel => nega>ever
ñ Na+-kanalen inac>veren boven bepaalde membraanpoten>aal
Reac>va>e van natrium kanalen:
- Em > -65 mV: geen reac>va>e = absolute refractaire periode (ERP)
ñ Geen nieuwe ac>epoten>aal ontstaan
ñ Verhindert tetanisa>e van hartspiercellen
˃ Belangrijk pompfunc>e: moet kunnen vullen
- -65 mV > Em > -90 mV: sporadische reac>va>e = rela>eve refractaire periode (RRP)
ñ Bij voldoende sterke s>muli nieuwe ac>epoten>aal
- Em ≤ -90 mV: alle Na+-kanalen gereac>veerd
b. Fase 1
Ini>ële snelle repolarisa>efase: sluiten van Na+-kanalen
c. Fase 2
Toestand kanalen fase 2
- Natrium-kanalen gesloten
- L-type Ca2+-kanalen open bij -35 mV
ñ Ca2+-kanalen open bij -35 mV vs natrium-kanalen bij
-65 mV
˃ Calcium kanalen trager opengaan want cel
moet meer gedepolariseerd zijn dan bij
natrium-kanalen
ñ Lengte plateaufase a`ankelijk van traagheid
inac>va>e ca2+-kanalen
ñ Calcium zorgt voor contrac>e => blokkers L-type
Ca2+-kanalen
=> contrac>ekracht afname
- K+-kanalen ‘open’: trage uitwaartse stroom van kalium
ñ Trage repolarisa>e tot -20 mV
d. Fase 3
Einde plateaufase: uitwaartse stroom kalium dominant => rustmembraanpoten>aal bereiken
- Verschillende types K+-kanalen
ñ Verschillende repolarisa>esnelheden
ñ Verschillende duur in AP
8
, Contrac6e van de hartspiercel
Contrac>liteit (vermogen om samen te kunnen trekken) beïnvloed door:
- [Ca2+]cytosolisch >>>>
- Factoren die gevoeligheid van contrac>el apparaat beïnvloeden <<<
Toename cytosolisch Ca2+:
1. Opening van L-type Ca2+-kanalen: 20% totale
toename calcium
ñ Inhibitoren: verapamil, dihydropyridines
2. Vrijstelling uit sarcoplasma>sch re>culum: 80% 3
1. Calcium (hoge C) gebonden aan
calsequestrine
2. AP bereikt T-tubulen: Calcium
concentra>e verhoogt tussen sarcolemma en SR
3. Membraan SR = ryanodine-receptoren s>muleren
4. Ryanodine-receptoren = calcium induced calcium release (CICR)
5. Via calcium induced calcium release kanalen calcium naar cytoplasma via
concentra>egradiënt
Vrijstelling calcium in SR enkel door CICR => geen extracellulair calcium = geen contrac>e
hartspier
Relaxa6e van de hartspiercel
Relaxa>e van de hartspiercellen => daling van calcium-concentra>e in cytosol4
1. Ca2+- ATPasen: pompen Ca2+ terug in sarcoplasma>sch re>culum (verbruik ATP)
2. Sluiten spanningsgevoelige Ca2+ - kanalen
3. Na+/ Ca2+-uitwisselaar: verwijdert extracellulaire Ca2+-ionen van AP uit cel
ñ SR steeds rijker aan Ca2+ worden door Ca2+- ATPasen
ñ Drijfveer: elektrochemische gradiënt Na+
4. Ca2+- ATPase pompen in sarcolemma
Modula6e van de contrac6ekracht van de hartspiercel
Sleuteleigenschap hart: gegradeerde contrac>es waarbij kracht kan variëren
- Normaal = submaximale contrac>e: Ca2+-concentra>e voldoende om frac>e van
mogelijke bruggen te vormen
- Ca2+-concentra)e ~ aantal bruggen ~ sarcoplasma)sche Ca2+-concentra)e ~ kracht
ñ Verhoogde concentra>e calcium => meer bruggen => krach>gere contrac>e
hartspier
Inotrope factoren
Inotrope factoren = factoren die contrac>liteit beïnvloeden
- Invloed op cytosolische Ca2+-concentra>e
- Invloed op binding van Ca2+aan troponine C
3
Zie aoeelding 2
4
Zie aoeelding 2
9
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