Biomedical Engineering Reference
In-Depth Information
however, is that blockade of
I
Kr
prevents the generation of a sufficiently negative
membrane potential, which prevents the L-type Ca
2+
current or
I
f
to become activated
and that blockade of L-type Ca
2+
current prevents the upstroke of action potentials in
sinus node cells. Blockade of the
I
f
current, either by Cs
+
or by alinidine or comparable
agents, affects peripheral nodal cells more than the primary pacemaker area and thus
does not disturb the standard nodal activation pattern [41].
4 Autonomic Modulation of the Adult Sinus Node
The pacemaker current involved in pacemaking are all more or less sensitive to
environmental changes, amongst which autonomic modulation. Figure 5 (taken from
[6]) shows a scheme of the rabbit sinus node with the dominant, leading (or primary)
Fig. 5.
Pacemaker shifts in response to several interventions.
CT
crista terminalis,
SEP
interatrial septum,
SVC
vena cava superior,
IVC
vena cava inferior,
E-4031
blocker of rapid
component of delayed rectifier current,
4-AP
4-amino pyridine (blocker transient outward
current).
Adr
adrenaline,
Ach
acetylcholine,
Nif
nifedipine (blocker L-type Ca
2+
current)
Reproduced with permission from [6].
