H a ra k a t p o te n s ia li y u z a g a c h iq is h i u c h u n m e m b r a n a n i 30 m v g a c h a
depolyarizatsiyalash kifoya. K ardiom itsitlar XP da quyidagi davrlari tafovut qilinadi:
1 d a v r - te z b o s h la n g ‘ich depolyarizatsiya, 2 d a v r - y a s s ilik y o k i plato, 3 d a v r - t e z
repolyarizatsiya, 4 d a v r - tin c h lik davri.
Y u r a k n in g
0
‘ tk a z u v c h i m i o t s i t l a r i , b o ‘ I m a c h a l a r v a q o r in c h a la r
m io k a rd i X P b irin c h i d a v r i k e l ib c h iq is h s a b a b i, n e r v v a s k e le t m u sk u lla ri
X P b i l a n b i r x il, y a ’n i h u j a y r a m e m b r a n a s i n i n a t r i y io n l a r i u c h u n
o ‘tk a z u v c h a n lig i o r tis h i, n a t r i y k a n a l i a r i n i f a o l l a s h i s h i h is o b ig a y u z a g a
c h iq a d i. X P c h o ‘q q is ig a y e tg a n d a , h u ja y r a m e m b r a n a s in i q u tb i o ‘z g a ra d i
( - 9 0 d a n + 3 0 m v g a c h a ) . M e m b r a n a n in g d e p o l y a r i z a t s i y a s i n a tr iy -k a liy
n a s o s l a r i n i a s t a - s e k i n a k t i v l a s h i s h i g a o l i b k e l a d i . K a ls iy io n la r in i
s a r k o p l a z m a t i k r e t i k u l a d a n c h i q i b , h u j a y r a i c h i g a k i r i s h i h a r a k a t
p o te n s ia lin i y a s s i ( p la t o ) d a v r in i k e l t i r i b c h i q a r a d i ( 2 - d a v r ) .
Bu davrda k inaktivatsiyaga uchraydi va h u ja y ra m u tla q refrakter holatida
b o ‘ lad i. B ir vaq tn i o ‘z id a k a liy k a n a lla ri fa o lla s h a b o s h la y d i. H ujayradan
chiqayotgan K+ionlari m em branani te z rep o ly arizatsiy asin i ta ’m inlaydi (3-davr).
K alsiy kanallari yopilib, repolyarizatsiya ja ra y o n in i tezlash tirad i.
H u ja y r a m e m b ra n a s in in g r e p o ly a r i z a ts iy a s i n a t r i y k a n a lia rin i q a y ta
faollashishiga olib keladi. N atijad a k ardiom iotsitlam i q o ‘z g ‘aIuvchanligi qayta
tiklanadi. Bu davr nisbiy refrakteriik davri deyiladi.
Y u ra k n in g ish ch i m io k a rd id a (boM m acha v a q o r in c h a ) tin c h lik p o te n sia li
n is b a ta n b ir x ild a u s h la b t u r i l a d i . Y u ra k r i tm i n i y e t a k c h is i v a z ifa s in i
b a j a r u v c h i s i n o a t r i a l t u g u n s o h a s i d a , s e k i n s p o n t a n d i a s t o l i k
d e p o ly a r iz a ts iy a k u z a tila d i. D e p o ly a r iz a ts iy a k r i t i k d a r a ja s i g a y e tg a c h
( ta x m in a n - 5 0 m d ) y a n g i X P y u z a g a c h iq a d i. S h u m e h a n iz m h is o b ig a y u ra k
m u s k u lla ri a v to m a tik q is q a ris h x o s s a s ig a e g a . B u X P h u ja y ra la r b o sh q a
x u s u s i y a t l a r i g a h a m e g a : 1 - X P u n c h a l i k y u q o r i e m a s 2 - s e k in
re p o ly a riz a ts iy a d a v ri (2 d a v r ) a s ta - s e k in te z r e p o ly a r i z a ts iy a d a v rig a (3 -
d a v r) o ‘ta d i; 3 m e m b ra n a p o te n s ia li 6 0 m v g a y e ta d i.
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