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Origin of Heart Beat and Its Conduction - Coggle Diagram
Origin of Heart Beat and Its Conduction
Action Potential
Fast Response AP
in most myocardial tissue (atria, ventricle and Purkinje fiber of conducting system
Slow response AP
in specialized cell responsible for pacemaker activity of heart (SA and NA node)
Differences
1) Resting membrane potential
2) rate of depolarisation
3) Propagation of AP through heart
Ionic basis
Ventricular potential
Pacemaker potential
Cardiac Conducting System
AV node
Bundle of His
Internodal node
Right and left bundle branches
Interatrial tract (Bachmann's bundle)
Purkinje fibers
SA node
Mechanism of sinus nodal rhythmicity
RMP of sinus node: -55 to -66 mV
Na+ channel mainly inactivated, Na+-Ca2+ channel open, atrial node AP start develop, then the AP will return to negative state
Properties
of cardiac muscle
Rhythmicity
it's
myogenic
in origin
initiated
by SA node
the
ability of cardiac muscle to contract
in a
regular constant manner without nerve supply
Conductivity
the
ability
of cardiac muscle fiber to conduct the
cardiac impulses
that are initiated in SA node.
fastest
conduction of velocity-
Purkinje fibre
importance: allow the
2 ventricle to contract at the same time simultaneously
The
slowest
conduction of velocity-
AV node
importance- allow
sufficient time
for ventricle to be
filled with blood before they contract
because it has few number of intercalated disc
Cardiac innervation
Sympathetic
stimuli
Tachycardia
, increase depolarization of SA node
1)
decrease
SA node
permeability to K+
>>>
less K+ efflux
2)
increase
membrane potential to
Ca2+
>>>
more Ca2+ influx
3) As result, the slope of
depolarisation increase
, cause
increase of SA node firing
and
increase HR
Parasympathetic
Stimuli
Bradycardia
, decrease depolarization of SA node
2)
decrease
membrane permeability to Ca2+ >>>
less Ca2+ influx
3) As result, the
prepotential slope decrease
, cause
decrease rate of SA node firing
and
decrease HR
1)
increase SA node
permeability to
K+
>>>> more
K+ efflux