D I S T R I B U T I O N O F A F F E R E N T C O N D U C T O R S IN T H E D I V I S I O N S
OF THE HEART
by
A. J.
KHABAROVA
M o r p h o l o g y L a b o r a t o r y o f I. P . P a v l o v I n s t i t u t e o f P h y s i o l o g y ,
(Dir. Prof. Dr. N . G. Kolossow) '
Leningrad
T h e p r o b l e m o f t h e a f f e r e n t i n n e r v a t i o n o f t h e h e a r t w i t h depressor
n e r v e s is n o w
s o l v e d in p r i n c i p l e . N e v e r t h e l e s s t h e r e is a l a c k o f e x p e r i m e n t a l w o r k t h a t m a y a c c u r a t e l y
d e t e r m i n e t h e c o u r s e o f t h e a f f e r e n t f i b e r s , t h e i r d i s t r i b u t i o n as w e l l as t h e d i s t r i b u t i o n o f
t h e i r e n d i n g s in t h e d i f f e r e n t l a y e r s a n d d i v i s i o n s o f t h e h e a r t .
We tried to solve this problem by e x p e r i m e n t a t i o n with the h e a r t s of cats
and y o u n g goats. In ten cases of the investigation described the right vagus
nerve of the animals was divided. In t w e n t y one case — it was the l e f t vagus
nerve in t h e neck of the animal, 1—2 cm lower t h a n g. nodosum
t h a t was
divided.
T h e time elapsed a f t e r o p e r a t i o n varied f r o m 19 to 144 hours.
In each heart the f o l l o w i n g divisions were studied: the right a n d left
atrium (the anterior a n d posterior walls) the atrial septum and the ventricles.
The heart was studied on section a n d total preparations. T h e m a t e r i a l was
stained by the B I E L S C H O W S K Y — G R O S m e t h o d .
S t u d y i n g the e x p e r i m e n t m a t e r i a l w i t h vagus nerves division we established
that both vagus nerves p a r t i c i p a t e in the f o r m a t i o n of the a f f e r e n t cardial
plexus.
T h e a f f e r e n t cardial plexus is f o r m e d by thick myelin fibers (5—8 microns)
in which it is easy to distinguish clearly the initial m i d d l e and final divisions.
From the analysis of literature d a t a it becomes evident that the investigators which dedicated their w o r k to the study of the a f f e r e n t i n n e r v a t i o n of the
hearts of men and animals did n o t give a complete picture of a f f e r e n t plexus
structure but described only the third division of the a f f e r e n t cardial plexus
with its nerves fibers and a f f e r e n t endings. This area has d i f f e r e n t names in
their w o r k d e p e n d i n g on the completeness of their observations. T h e e n d i n g
area of the a f f e r e n t plexus t h a t has been more or less f u l l y exposed some call
the a f f e r e n t cardial plexus. O t h e r s call it receptor field, a n d others, w h o h a v e
it less fully observed describe it as separate a f f e r e n t ending. T h e initial a n d
m i d d l e areas of the cardial a f f e r e n t plexus till now were left not investigated
bv scientists.
A.
J.
KHABAROVA
W e established t h a t t h e initial a n d m i d d l e divisions of t h e a f f e r e n t plexus
are situated in the v e g e t a t i v e t r u n k s plexus a n d t h a t t h e t e r m i n a l d i v i s i o n lies
separately.
T h e a f f e r e n t fibers of t h e initial division a r e located in the big t r u n k s of
the s u b e p i c a r d i a l , m y o c a r d i a l a n d e n d o c a r d i a l h e a r t plexuses.
These are thick
(7,5—:8 ,,) myelin fibers not b r a n c h i n g a n d not a n a s t o m o s i n g w i t h the v e g e t a t i v e
fibers r u n n i n g near by.
T h e a f f e r e n t fibers of t h e m i d d l e division lie in t h e m i d d l e t r u n k s of
t h e h e a r t plexus. In c o n f o r m a n c e with t h e course of t h e n e r v e t r u n k s of this
plexus a n d in the spots of t h e i r r a m i f i c a t i o n s t h e a f f e r e n t f i b e r s a r e r e p e a t e a d l y
d i c h o t o m i c a l l y d i v i d e d w h i l e t h e i r d i a m e t e r r e m a i n s u n c h a n g e d . A p a r t of t h e
fibers f o r m e d as t h e result of division p e n e t r a t e s i n t o t h e s u r r o u n d i n g tissue
w h e r e it t e r m i n a t e s in a f f e r e n t receptors.
T h e t e r m i n a l division in the last division of t h e a f f e r e n t plexus. Its f i b e r s
lie freesly in the i n n e r v a t e d layer a n d t e r m i n a t e in s e p a r a t e a f f e r e n t e n d i n g s or
in massive receptor fields. T h e s e are c o m p o s e d of a system of b r a n c h i n g a n d
intersecting a f f e r e n t n e r v e fibers a n d of the a f f e r e n t e n d i n g s mass. M u l t i p l e
t e r m i n a l receptors of t h e a f f e r e n t plexus a r e c o m p a c t t y p e e n d i n g s t h e t e r m i n a l
twigs of which are in c o n t a c t w i t h t h e nuclei of t h e glial cells. T h e f o r m of t h e
e n d i n g s is m o r e o f t e n t r e e - l i k e a n d m o r e r a r e l y c l e w - l i k e w i t h a series of f o r m s
b e t w e e n t h e m (Fig. 1).
A f f e r e n t fields were o b s e r v e d in the epicardium,
myocardium
a n d endocardium of the atriums as well as in the epicardium
of t h e ventricles. In some
cases o n e field was b o u n d t o a n o t h e r by t h e passing of f i b e r s f r o m o n e plexus
i n t o a n o t h e r . T h e area o c c u p i e d by the receptor
fields reached in some cases
1 e n r a n d t h e n u m b e r of e n d i n g s could be c o u n t e d by h u n d r e d s .
T h e receptor fields a r e disposed in d e t e r m i n e d areas of the h e a r t i. e. t h e y
p e n e t r a t e t h r o u g h the t h i c k n e s s of t h e vena cava m o u t h walls a n d the
posterior
wall of t h e right a n d left atrium of ventricles.
R e f e r i n g t o the question of t h e a f f e r e n t fibers d i s t r i b u t i o n in the d i f f e r e n t
p a r t s of the h e a r t it is t o be n o t i c e d t h a t t h e l a t t e r r u n t h r o u g h the n e r v e s t r u n k s
of the v e g e t a t i v e plexus.
W h i l e d i v i d i n g t h e vagus nerves a n d i n v e s t i g a t i n g t h e e x p a n s i o n in the
heart of t h e d e g e n e r a t e d a f f e r e n t fibers passing t h r o u g h each n e r v e it w a s
f o u n d t h a t the a f f e r e n t f i b e r s of the right a n d left vagus nerves e n t e r the same
areas of t h e h e a r t . T h u s the right atrium posterior a n d anterior w a l l s a r e i n n e r v a t e d with a f f e r e n t fibers passing t h r o u g h t h e left vagus n e r v e . S i m u l t a n e o u s l y
a f f e r e n t fibers a r e b r o u g h t i n t o the right atrium by the right vagus n e r v e . H e r e
the a f f e r e n t fibers of b o t h n e r v e s t e r m i n a t e in a f f e r e n t endings.
A f f e r e n t fibers of both nerves f o r m massive receptor
fields in t h e right
atrium. T h e right vagus n e r v e at the expence of t h e a f f e r e n t fibers f o r m s fields
p r e d o m i n a n t l y in t h e area of t h e vena cava m o u t h s (Fig. 2) w h i l e the a f f e r e n t
fibers of t h e left vagus n e r v e f o r m fields in t h e area of the posterior wall of the
atrium (see Fig. 1).
T h e a f f e r e n t fibers a n d t h e endings of t h e right a n d left vagus n e r v e s a r e
f o u n d in the same layers of t h e right atrium.
It can be o f t e n seen h o w the
epicardium
(see Fig. 1, 2), t h e myocardium
(Fig. 3, 4) a n d endocardium
(Fig.
3, 6) of t h e right atrium a r e i n n e r v a t e d w i t h the a f f e r e n t e n d i n g s of t h e right
a n d left vagus nerves a f f e r e n t fibers.
I.
A f f e r e n t e n d i n g s a n d t h e c h a r a c t e r of their r e l a t i o n s h i p w i t h the fibers o f t h e a f f e r e n t
plexus (72 hr a f t e r d i v i s i o n o f t h e l e f t vagus
nerve). B I E L S C H O W S K Y G K O S M — 9 , o b j e c t i v e 4 0 , e y e p i e c e 10.
A.
Fig. 2.
J.
KHABAROVA
T e r m i n a l d i v i s i o n o f t h e a f f e r e n t plexus a t t h e m o u t h of t h e posterior
vena cava
of
a cat ( b o r d e r b e t w e e n che inner a n d o u t e r l a y e r s ) ( 9 6 hr a f t e r d i v i s i o n o f t h e right
vagus n e r v e ) . B I E L S C H O W S K Y — G R O S M B — 1 , o b j e c t i v e 4 0 , e v e p i e c c 1 0 .
"Hie s t r u c t u r e of the a f f e r e n t fibers of t h e right a n d left vagus nerves does
not d i f f e r . T h e v a r i a t i o n s t a k i n g place in t h e s t r u c t u r e of the a f f e r e n t a p p a r a tuses a r e d e t e r m i n e d by t h e i n n e r v a t e d tissue. T h i s is c o n f i r m e d b y t h e f a c t
t h a t the a f f e r e n t e n d i n g s of t h e same n e r v e m a y h a v e a d i f f e r e n t s t r u c t u r e
d e p e n d i n g u p o n its location (muscle, c o n n e c t i n g tissue).
T h e same r e g u l a r i t y (the p a r t p l a y e d b y b o t h nerves) was n o t i c e d by us
in the left atrium too w i t h t h e o n l y d i f f e r e n c e t h a t t h e receptor fields here were
met m o r e seldom a n d they belonged to the a f f e r e n t fibers of t h e l e f t
vagus
nerve. E x a c t l y as in t h e case of the a f f e r e n t i n n e r v a t i o n of t h e right atrium
we
observed in the same layer t h e a f f e r e n t e n d i n g s of b o t h nerves.
M e a n w h i l e it is t o be noticed t h a t t h e l e f t vagus n e r v e i n n e r v a t e s p r e d o m i n a n t l y the myocardium
of b o t h a t r i a a n d t h e right, — the b o t h a t r i a l endocardium.
AFFERENT
CONDUCTORS
OF
THE
157
HEART
I n t h e a t r i a l septum a f f e r e n t e n d i n g s were f o u n d . T h e y belonged o n l y t o
the a f f e r e n t f i b e r s passing t h r o u g h t h e right vagus nerve.
T h e e n d i n g s a n d t h e receptor fields f o u n d in the ventricles
epicardium
were f o r m e d by t h e a f f e r e n t fibers of t h e left vagus n e r v e (Fig. 7).
Fig. 3. D e g e n e r a t i o n of an a f f e r e n t e n d i n g in t h e interstitial tissue of t h e myocardium
t h e posterior
w a l l of the right atrium
of a cat ( 7 2 hr a f t e r d i v i s i o n of t h e right
nerve). B I E L S C H O W S K Y — G R O S . K R A U S E — B A U S C H , objective 9 0 , eyepiece 6
Fig. 4. D e g e n e r a t i n g a f f e r e n t e n d i n g in t h e interstitial tissue of the myocardium
posterior
w a l l of t h e right atrium
o f a cat ( 7 2 hr a f t e r d i v i s i o n of the
n e r v e ) B I E L S C H O W S K Y — G R O S . M B — 1 , o b j e c t i v e 4 0 , e y e p i e c e 6.
front
vagus
of
the
left
vagus
158
A.
J.
KHAIlAKO\ A
F i g , 5 . D e g e n e r a t i o n o f a n a f f e r e n t e n d i n g in t h e endocardium
o f t h e posterior
wall of the
r i g h t atrium
o f a c a t ( 7 2 h r a f t e r d i v i s i o n o f t h e l e f t vagus
nerve). B I E L S C H O W S K Y
GROS. M B — I , o b j e c t i v e i m m e r s i o n 9 0 , e y e p i e c e 6 .
F i g . 6. T h e f i n a l s t a g e o f d e g e n e r a t i o n o f a f f e r e n t e n d i n g s in t h e endocardium
of the
posterior
w a l l o t t h e r i g h t atrium
o f a cat ( 9 6 hr a f t e r d i v i s i o n o f t h e r i g h t vagus
nerve).
BIELSCHOWSKY—GROS.
M B I — 1 , objective i m m e r s i o n 90, e y e p i e c e
10; B a u s h & L o m b .
o b j e c t i v e 4 3 , e y e p i e c e 10 sic.
AFFERENT
CONDUCTORS
OF
THE
HEART
159
Fie. 7. T h e t e r m i n a l d i v i s i o n o f a n a f f e r e n t plexus
in the s u p e r f i c i a l l a y e r o f the
ep,card,um
o f t h e v e n t r i c l e of a y o u n g goat ( 7 2 hr a f t e r d i v i s i o n of t h e l e f t vagus
nerve).
BIELSCHOVSKY-GROS.
M B I — 1 ,
objective 4 0 . eyepiece 1 7 (total preparation).
16C
A
J.
KHABAROVA
T h e a b o v e mentioned d a t a show t h a t an intersection of a f f e r e n t fibers
takes place in the heart. A p a r t of the a f f e r e n t fibers of the right, as well as
of the left vagus nerves i n n e r v a t e the right atrium
while their o t h e r p a r t
i n n e r v a t e the left atrium. I n this relation o u r e x p e r i m e n t a l m o r p h o l o g i c a l d a t a
is in c o n f o r m a n c e with the indications given in the investigations c a r r i e d o u t by
I . F . C Y O N a n d L U D W I G ( 1 8 8 6 ) upon the course taken by the depressor
nerves
fibers in the heart.
Simultaneously the i n f o r m a t i o n s given by Nettleship
(1936) upon the
innervation of the heart a r e completed with the description of the f u l l y
discovered by the a u t h o r a f f e r e n t plexus f r o m the a f f e r e n t e x t r a c a r d i a l nerves
up to their endings.
While d i v i d i n g the vagus nerves we o b t a i n e d an evident degeneration of
the a f f e r e n t nerves and their endins. The presence of all the process stages
beginning with the initial u p to the terminal show w i t h o u t a n y d o u b t t h a t they
belong to the a f f e r e n t fibers r u n n i n g in the vagus nerve composition.
Bibliography
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C Y O N 1. T . , L U D W I G , K . : D i e R e f l e x e i n e s der s e n s i b l e n N e r v e n d e s H e r z e n s a u f d i e M o t o r i
d e r B l u t g e f ä ß e . B e r i c h t e d e r S ä c h s G e s e l l s c h a f t d e r W i s s e n s c h a f t B d . 18, S. 7 0 7 , 1 8 S 6 .
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