<s>
Bathmotropic	B-Algorithm
often	O
refers	O
to	O
modifying	O
the	O
degree	O
of	O
excitability	O
specifically	O
of	O
the	O
heart	O
;	O
in	O
general	O
,	O
it	O
refers	O
to	O
modification	O
of	O
the	O
degree	O
of	O
excitability	O
(	O
threshold	O
of	O
excitation	O
)	O
of	O
musculature	O
in	O
general	O
,	O
including	O
the	O
heart	O
.	O
</s>
<s>
Positive	O
bathmotropic	B-Algorithm
effects	O
increase	O
the	O
response	O
of	O
muscle	O
to	O
stimulation	O
,	O
whereas	O
negative	O
bathmotropic	B-Algorithm
effects	O
decrease	O
the	O
response	O
of	O
muscle	O
to	O
stimulation	O
.	O
</s>
<s>
Conditions	O
that	O
decrease	O
bathmotropy	B-Algorithm
(	O
i.e.	O
</s>
<s>
A	O
substance	O
that	O
has	O
a	O
bathmotropic	B-Algorithm
effect	O
is	O
known	O
as	O
a	O
bathmotrope	B-Algorithm
.	O
</s>
<s>
While	O
bathmotropic	B-Algorithm
,	O
as	O
used	O
herein	O
,	O
has	O
been	O
defined	O
as	O
pertaining	O
to	O
modification	O
of	O
the	O
excitability	O
of	O
the	O
heart	O
,	O
it	O
can	O
also	O
refer	O
to	O
modification	O
of	O
the	O
irritability	O
of	O
heart	O
muscle	O
,	O
and	O
the	O
two	O
terms	O
are	O
frequently	O
used	O
interchangeably	O
.	O
</s>
<s>
The	O
term	O
"	O
bathmotropic	B-Algorithm
"	O
is	O
derived	O
from	O
the	O
Ancient	O
Greek	O
word	O
βαθμός	O
(	O
bathmós	O
)	O
,	O
meaning	O
"	O
step	O
"	O
or	O
"	O
threshold	O
"	O
.	O
</s>
<s>
In	O
1897	O
Engelmann	O
introduced	O
four	O
Greek	O
terms	O
to	O
describe	O
key	O
physiological	O
properties	O
of	O
the	O
heart	O
:	O
inotropy	O
,	O
the	O
ability	O
to	O
contract	O
;	O
chronotropy	O
,	O
the	O
ability	O
to	O
initiate	O
an	O
electrical	O
impulse	O
;	O
dromotropy	O
,	O
the	O
ability	O
to	O
conduct	O
an	O
electrical	O
impulse	O
;	O
and	O
bathmotropy	B-Algorithm
,	O
the	O
ability	O
to	O
respond	O
to	O
direct	O
mechanical	O
stimulation	O
.	O
</s>
<s>
The	O
bathmotropic	B-Algorithm
effect	O
modifies	O
the	O
heart	O
muscle	O
membrane	O
excitability	O
,	O
and	O
thus	O
the	O
ease	O
of	O
generating	O
an	O
action	B-Algorithm
potential	I-Algorithm
.	O
</s>
<s>
The	O
ease	O
of	O
generating	O
an	O
action	B-Algorithm
potential	I-Algorithm
is	O
related	O
both	O
to	O
the	O
magnitude	O
of	O
the	O
resting	O
potential	O
and	O
to	O
the	O
activation	O
state	O
of	O
membrane	O
sodium	O
channels	O
.	O
</s>
<s>
During	O
stage	O
4	O
of	O
an	O
action	B-Algorithm
potential	I-Algorithm
,	O
the	O
inside	O
of	O
a	O
cardiac	O
muscle	O
cell	O
rests	O
at	O
−90mV	O
.	O
</s>
<s>
When	O
enough	O
sodium	O
channels	O
are	O
opened	O
,	O
so	O
that	O
the	O
rapid	O
influx	O
of	O
sodium	O
ions	O
is	O
greater	O
than	O
the	O
tonic	O
efflux	O
of	O
potassium	O
ions	O
,	O
then	O
the	O
resting	O
potential	O
becomes	O
progressively	O
less	O
negative	O
,	O
more	O
and	O
more	O
sodium	O
channels	O
are	O
opened	O
,	O
and	O
an	O
action	B-Algorithm
potential	I-Algorithm
is	O
generated	O
.	O
</s>
<s>
The	O
electrical	O
potential	O
at	O
which	O
this	O
occurs	O
is	O
called	O
the	O
threshold	B-Algorithm
potential	I-Algorithm
.	O
</s>
<s>
As	O
various	O
drugs	O
and	O
other	O
factors	O
act	O
on	O
the	O
resting	O
potential	O
and	O
bring	O
it	O
closer	O
to	O
the	O
threshold	B-Algorithm
potential	I-Algorithm
,	O
an	O
action	B-Algorithm
potential	I-Algorithm
is	O
more	O
easily	O
and	O
rapidly	O
obtained	O
.	O
</s>
<s>
Likewise	O
,	O
when	O
the	O
sodium	O
channels	O
are	O
in	O
a	O
state	O
of	O
greater	O
activation	O
,	O
then	O
the	O
influx	O
of	O
sodium	O
ions	O
that	O
allows	O
the	O
membrane	O
to	O
reach	O
threshold	B-Algorithm
potential	I-Algorithm
occurs	O
more	O
readily	O
.	O
</s>
