SILVER SULFADIAZINE
S
LOCATION AND FUNCTION OF THE SINOATRIAL NODE
The sinoatrial (SA) node is a small mass of specialized muscle cells in the
right atrium of the heart. It sends out impulses at an inherent rate of about 100
impulses per minute. External control by the vagus nerve reduces the rate to
about 70 per minute. Other mechanisms also affect the rate.
Sinoatrial
node
Rightatrium
Rightventricle
Left
ventricle
Heart
m uscle
Spread of the impulse
From the SA node, the waves
ofcontraction spread over
both atria and then to the
atrioventricular node serving
the ventricles.
Leftatrium
Atrioventricular
node
Wave of
excitation
spreading
overatria
Excitation
spreading
over
ventricles
The electrocardiogram
The spread ofexcitation over
the two atria is fairly slow;
the spread over the
ventricles is rapid.
s ilv e r s u lfa d ia z in e
A n
a n tib a c te ria l d ru g
a p p l i e d a s a c r e a m
t o p r e v e n t i n f e c t i o n a f t e r s k i n g r a f t s o r
i n b u r n s , l e g u l c e r s , a n d p r e s s u r e s o r e s .
S i d e e f f e c t s m a y i n c l u d e p e r m a n e n t g r e y
s k i n d i s c o l o r a t i o n , r a s h e s , o r i t c h i n g .
s im ia n c re a s e
A s i n g l e d e e p , h o r i z o n t a l c r e a s e o n t h e
p a l m o f t h e h a n d . T h i s f e a t u r e i s a s s o c i -
a t e d w i t h c h r o m o s o m a l d i s o r d e r s s u c h
a s
D o w n ’s s y n d ro m e .
s im p le lin c t u s
S e e
lin c t u s
.
s im v a s ta tin
A
lip id - lo w e r in g d ru g
t h a t
a c t s
o n
t h e
l i v e r e n z y m e s t h a t p r o d u c e
c h o le s t e ro l.
S i m v a s t a t i n
m a y
c a u s e
b o w e l
u p s e t s ,
h e a d a c h e s ,
a n d
m u s c l e
p a i n s .
I t
m a y
a l s o
r a i s e
l i v e r
e n z y m e
l e v e l s ,
w h i c h
m u s t b e m o n i t o r e d .
S in e m e t
T h e
b r a n d
n a m e
f o r
c o - c a r e l d o p a ,
a
p r e p a r a t i o n o f
le v o d o p a
a n d c a r b i d o p a ,
d r u g s f o r
P a rk in s o n ’s d is e a s e .
s in e w
A n o n m e d i c a l t e r m f o r a
t e n d o n
.
s in g e r ’s n o d e s
S m a l l , g r e y i s h - w h i t e n o d u l e s t h a t d e v e -
l o p
o n t h e v o c a l c o r d s . S i n g e r ’s n o d e s
a r e t h e r e s u l t o f c o n s t a n t v o i c e s t r a i n ,
c a u s i n g h o a r s e n e s s o r l o s s o f v o i c e .
A
b io p s y
( r e m o v a l o f a s a m p l e o f t i s -
s u e f o r m
i c r o s c o p i c e x a m i n a t i o n )
m a y
b e c a r r i e d o u t t o e x c l u d e t h e p o s s i b i l i t y
o f a m a l i g n a n t t u m o u r ( s e e
la ryn x, c a n c e r
o f)
b e i n g
p r e s e n t . T r e a t m e n t
o f a c u t e
c a s e s o f s i n g e r ’s n o d e s c o n s i s t s o f r e s t -
i n g t h e v o i c e . I n c h r o n i c c a s e s , s u r g i c a l
r e m o v a l o f t h e n o d e s m a y b e n e c e s s a r y .
s in o a t ria l n o d e
T h e n a t u r a l p a c e m a k e r o f t h e
h e a rt.
T h e
s i n o a t r i a l n o d e c o n s i s t s o f a c l u s t e r o f
s p e c i a l i z e d m u s c l e c e l l s i n t h e r i g h t a t r i -
a l w a l l . T h e s e c e l l s e m i t r a p i d e l e c t r i c a l
i m p u l s e s
t h a t
i n i t i a t e
t h e
h e a r t ’s
c o n -
t r a c t i o n s ( b e a t s ) . V a r i o u s h o r m o n e s a n d
n e r v o u s s y s t e m a c t i v i t i e s m a y a l t e r t h e
r a t e a t w h i c h t h e n o d e e m i t s i m p u l s e s .
( S e e a l s o
h e a rt ra te .)
s in u s
A c a v i t y i n a b o n e ; i n p a r t i c u l a r , o n e o f
t h e a i r - f i l l e d s p a c e s
i n t h e b o n e s s u r -
r o u n d i n g t h e n o s e ( s e e
s in u s , f a c ia l) .
T h e t e r m
“ s i n u s ” a l s o r e f e r s t o a n y
w i d e c h a n n e l t h a t c o n t a i n s b l o o d , o r t o
a n a b n o r m a l , o f t e n i n f e c t e d , t r a c t .
s in u s a rrh y th m ia
A n o r m a l v a r i a t i o n i n t h e h e a r t r a t e t h a t
o c c u r s w i t h b r e a t h i n g a n d i s p a r t i c u l a r -
l y f o u n d i n c h i l d r e n a n d y o u n g a d u l t s .
D u r i n g i n s p i r a t i o n
( b r e a t h i n g i n ) , t h e
h e a r t r a t e i s i n c r e a s e d ;
d u r i n g
e x p i r a -
t i o n ( b r e a t h i n g o u t ) i t d e c r e a s e s .
s in u s b ra d y c a rd ia
A
s l o w ,
b u t
r e g u l a r ,
h e a r t
r a t e
( f e w e r
t h a n
6 0 b e a t s p e r m i n u t e )
t h a t i s t h e
r e s u l t
o f r e d u c e d
e l e c t r i c a l
a c t i v i t y
i n
t h e
s in o a t ria l n o d e .
T h e
s y m p t o m
o f
s i n u s b r a d y c a r d i a i s n o r m a l i n a t h l e t e s
a n d p e o p l e w h o a r e f i t , b u t i n o t h e r s i t
m a y b e c a u s e d b y
h y p o t h y ro id is m ,
a
m y o -
c a rd ia l in fa rc tio n ,
o r d r u g s s u c h a s
b e ta -
b lo c k e rs
o r
d ig o x in .
690
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