NICOTINE
HOW NEUROTRANSMITTERS WORK
When an electrical impulse travels
down a nerve cell axon, it causes the
release of a chemical neurotransmitter
at the axon terminals. The chemical
released is not the same in every
case; acetylcholine, noradrenaline
(norepinephrine), dopamine, and
serotonin are all important examples.
N e r v e c e l l a x o n
E le c t r ic a l i m p u l s e
A x o n t e r m in a l
I
The impulse travels down the
neuronal axon (above), from the
cell body towards the axon terminals;
the neurotransmitter is released from
tiny swellings, called synaptic knobs,
atthe axon terminals.
2
The neurotransmitter crosses the gap,
or synapse, to the surface membrane
ofthe target cell (right), where it binds to
a protein called a receptor.
3
Ifsufficient target cell receptors are
activated byneurotransmitter binding,
an impulse is initiated and passes in turn
down the target cell’s axon (below right).
Example of neurotransmitter activity
Neurotransmitters enable the pupil to change
size in different light conditions.
C ell b o d y
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V - X
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D e n d r it e s
- A x o n
t e r m in a l
- S y n a p s e
R e c e p t o r s
P r e s y n a p t ic
P o s t s y n a p t i c
N e u r o t r a n s m it t e r
m e m b r a n e
m e m b r a n e
c h e m i c a l
( a x o n t e r m in a l )
( d e n d r i t e o f
t a r g e t c e l l )
E le c t r ic a l i m p u l s e
t o t a r g e t
t e s t s a r e p e r f o r m e d t o c h e c k f o r
p h e n y l -
k e t o n u r i a
( a n i n h e r i t e d e n z y m e d e f e c t )
a n d
h y p o t h y r o i d i s m
( u n d e r a c t i v i t y o f t h e
t h y r o i d g l a n d ) . O t h e r t e s t s m a y a l s o b e
p e r f o r m e d , d e p e n d i n g o n f a m i l y h i s t o r y
a n d t h e b a b y ’s h e a l t h .
CONDITIONS IN THE NEWBORN
S o m e b a b i e s s u f f e r i n j u r y d u r i n g b i r t h
( s e e
b i r t h i n j u r y
) ,
s u c h a s
c e p h a l h a e m a -
t o m a
( a
s w e l l i n g
o f p a r t
o f t h e
h e a d
c a u s e d b y b l e e d i n g b e t w e e n t h e s c a l p
a n d t h e s k u l l ) .
J a u n d i c e ( a y e l l o w i n g o f t h e s k i n a n d
t h e
w h i t e s
o f t h e
e y e s ;
s e e
j a u n d i c e ,
n e o n a t a l
)
i s a n e x t r e m e l y c o m
m o n c o n -
d i t i o n t h a t o c c u r s i n n e w b o r n b a b i e s ,
e s p e c i a l l y i f t h e b a b y i s b r e a s t - f e d . U s u -
a l l y a p p e a r i n g
o n t h e s e c o n d o r t h i r d
d a y o f l i f e , t h e j a u n d i c e u s u a l l y d i s a p -
p e a r s o v e r t h e n e x t f e w d a y s . I n m o s t
c a s e s ,
n e o n a t a l
j a u n d i c e
i s
h a r m l e s s ;
h o w e v e r , t h e c o n d i t i o n m a y b e s e r i o u s
i f i t o c c u r s d u r i n g t h e f i r s t 2 4 h o u r s , i f
i t
i s
s e v e r e
( s e e
k e r n i c t e r u s
) ,
o r
i f i t
a f f e c t s a p r e m a t u r e i n f a n t .
S o m e n e w b o r n b a b y g i r l s h a v e s l i g h t
v a g i n a l
b l e e d i n g
o r
d i s c h a r g e ,
a n d
b a b i e s o f e i t h e r s e x m a y h a v e e n l a r g e d
b r e a s t s . T h e s e
c o n d i t i o n s a r e h a r m l e s s
a n d a r e t h e r e s u l t o f t h e m
o t h e r ’s c i r c u -
l a t i n g
s e x
h o r m o n e s
t h a t
r e a c h
t h e
f e t u s
t h r o u g h
t h e
p l a c e n t a . A n y
e x t r a
h o r m
o n e s l e a v e t h e b a b y ’s b l o o d s t r e a m
a n d t h e i r e f f e c t s s o o n d i s a p p e a r .
I n f e c t i o n s
o f
t h e
u m b i l i c a l
c o r d
s t u m p
s o m e t i m e s
o c c u r ,
a n d
a n t i s e p t i c
s o l u t i o n
i s
u s u a l l y
a p p l i e d
t o
p r e v e n t
t h i s . A b l o t c h y ,
r e d r a s h
( s e e
u r t i c a r i a ,
n e o n a t a l
) a f f e c t i n g t h e f a c e , c h e s t , a r m s ,
a n d
t h i g h s
o f
t h e
b a b y
m a y
o c c u r
a r o u n d t h e s e c o n d d a y a f t e r b i r t h ; t h i s
c o n d i t i o n
i s
h a r m l e s s ,
o f
n o
k n o w n
c a u s e ,
a n d
d i s a p p e a r s
w i t h o u t
t r e a t -
m e n t . ( S e e a l s o
p r e m a t u r i t y ; p o s t m a t u r i t y .
)
n e w v a ria n t CJD
O n e f o r m o f
C r e u t z f e l d t - J a k o b d i s e a s e
.
NGU
A n
a b b r e v i a t i o n
f o r
t h e
c o n d i t i o n
n o n g o n o c o c c a l u r e t h r i t i s .
n ia c in
S e e
v i t a m i n B c o m p l e x
.
n ic k e l
A m e t a l l i c e l e m e n t t h a t i s p r e s e n t i n t h e
b o d y
i n
m i n u t e
a m o u n t s .
N i c k e l
i s
t h o u g h t
t o
a c t i v a t e
c e r t a i n
e n z y m e s
( s u b s t a n c e s
t h a t
p r o m o t e
b i o c h e m i c a l
r e a c t i o n s ) a n d i t m a y a l s o p l a y a p a r t i n
s t a b i l i z i n g c h r o m o s o m a l m a t e r i a l i n t h e
n u c l e i o f c e l l s .
D i s e a s e d u e t o a d e f i c i e n c y o f n i c k e l
i s
u n k n o w n .
E x p o s u r e
t o
n i c k e l
m a y
c a u s e
d e r m a t i t i s
( i n f l a m m a t i o n
o f t h e
s k i n ) .
L u n g c a n c e r
h a s b e e n r e p o r t e d i n
w o r k e r s i n n i c k e l r e f i n e r i e s .
n ic lo s a m id e
A n
a n t h e l m i n t i c d r u g
u s e d t o t r e a t
t a p e -
w o r m i n f e s t a t i o n
.
N i c l o s a m i d e c a u s e s t h e
t a p e w o r m t o l o o s e n i t s g r i p o n t h e i n n e r
w a l l o f t h e i n t e s t i n e . T h e w o r m i s t h e n
p a s s e d o u t o f t h e b o d y i n t h e f a e c e s . S i d e
e f f e c t s o f n i c l o s a m i d e i n c l u d e a b d o m i -
n a l p a i n , l i g h t h e a d e d n e s s , a n d i t c h i n g .
n ic o ra n d il
A
p o t a s s i u m c h a n n e l a c t i v a t o r
d r u g u s e d i n
t h e p r e v e n t i o n a n d l o n g - t e r m t r e a t m e n t
o f
a n g i n a p e c t o r i s
( c h e s t p a i n d u e t o i n a d -
e q u a t e b l o o d s u p p l y t o t h e h e a r t ) . S i d e
e f f e c t s , w h i c h
i n c l u d e f l u s h i n g ,
n a u s e a ,
v o m i t i n g , a n d d i z z i n e s s , a r e m a i n l y d u e
t o n i c o r a n d i l ’s
v a s o d i l a t i o n
( w i d e n i n g o f
t h e b l o o d v e s s e l s ) e f f e c t s a n d u s u a l l y w e a r
o f f
w i t h
c o n t i n u e d
t r e a t m e n t .
R a r e l y ,
m o u t h u l c e r s a n d m u s c l e p a i n c a n o c c u r .
n ic o tin a m id e
S e e
v i t a m i n B c o m p l e x
.
n ic o tin a m id e a d e n in e
d in u c le o tid e
S e e
N A D
.
n ic o tin e
A s t i m u l a n t d r u g f o u n d i n t o b a c c o t h a t
i s r e s p o n s i b l e f o r t o b a c c o
d e p e n d e n c e .
A f t e r
i n h a l a t i o n ,
n i c o t i n e
i n
t o b a c c o
s m o k e
p a s s e s
r a p i d l y
i n t o
t h e
b l o o d -
s t r e a m . N i c o t i n e i n c h e w i n g t o b a c c o i s
a b s o r b e d m o r e s l o w l y v i a t h e l i n i n g o f
t h e m o u t h . T h e d r u g s t i m u l a t e s t h e n e r -
v o u s s y s t e m u n t i l i t i s b r o k e n d o w n b y
t h e l i v e r a n d e x c r e t e d i n t h e u r i n e .
N
545
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