cardiac physiology & excitation contraction coupling in cardiac muscle
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Course
Cardiology (BM3501)
Institution
The University Of Aberdeen (Aberd)
The mechanisms which regulate the contractile function of cardiac muscle will be examined at the cellular level. These mechanisms will be related to structure of the cardiac cell. Revision of the cardiac action potential and conduction.
📌 Sodium and calcium excite
things
Potassium and chloride
calm things down
phase 0
Depolarisation - Na+ channels
open to let Na+ into cell
phase 1
Repolarisation - Na+ channels
close (K+ open to let K+ out)
phase 2
plateau phase - L-type Ca2+
channels open to let Ca2+ in →
contraction
phase 3
Repolarisation - K+ channels
open to let K+ leave the cell
phase 4
Cardiac Physiology & Excitation Contraction Coupling in Cardiac Muscle 1
, spontaneous depolarisation to
threshold
Pacemaker Action Potential
initiated in the pacemaker cells → SA node
no resting membrane potential
depolarise spontaneously
atrioventricular (AV) node
slows down spread of
depolarisation wave from atria to
ventricle
ie AV node delay
Why would you want to
slow down the spread of
depolarisation?
to allow atria to complete
contraction before
ventricles
directs the electrical signal via
specialised fast conducting cells
Bundle of His
Purkinje fibre cells
Heart beat
1. SA node initiate action potential
2. atrium contracts, forcing blood
into ventricles
3. wave of depolarisation travels
down to the AV node
4. small delay occurs (0.1s) →
allows atria to contract fully and
ventricles to fill before contracting
Cardiac Physiology & Excitation Contraction Coupling in Cardiac Muscle 2
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