elektrofisiologi jantung
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ELEKTROFISIOLOGI JANTUNG
DENNY AGUSTININGSIH
OCT 2008 DENNY AGUSTININGSIH 2
OCT 2008 DENNY AGUSTININGSIH 3
Two Types of Cardiac Muscle Cells
Ordinary: Make up 95%- 99% of all heart muscle cells.
Also called worker cells or contractile cellsBiochemically similar to red skeletal muscleSlow to fatigue
Specialized: make up remaining 1%-5%Also called autorythmic or automatic cells Responsible for initiation and/or transportation of electrical impulses through the heart pacemaker potential
OCT 2008 DENNY AGUSTININGSIH 4
The Pacemaker Cells
MEKANISME DEPOLARISASI DAN REPOLASASI
---------------------
+++----------------- ----+++++++++++
++++++++++++++
+++++++++++++
----++++++++++ ++++----------------
-----------------------
Awal depolarisasi Awal repolarisasi
Depolarisasi sempurna
stimulasi Resting state
+/--/+
- Depolar karena masuknya ion Ca, Na - Repolarisasi karena keluarnya ion Kalium dimudahkan oleh parasimpatis
Mem
bra
ne
Pot
enti
al (
mV
) 0
-40
-60
Time (msec)DepolarizationSpontaneous
ThresholdPotential
Ca
++ in
K+ out
Ca (T-type)
Na
K
OCT 2008 DENNY AGUSTININGSIH 7
Sinoatrial Node
Atrioventricular Node
CONDUCTING SYSTEM
OCT 2008 DENNY AGUSTININGSIH 8
OCT 2008 DENNY AGUSTININGSIH 9
Extrinsic Influences
Autonomic nervous system: utk menyelaraskan denyut cor
Hormonal influences: tiroid meningkatkan denyut cor
Ionic influencesTemperature influences: tubuh demam
denyut cor meningkat mrangsang hipotalamus agar kerja cor cepat shg membuang panas
OCT 2008 DENNY AGUSTININGSIH 10
Cardiac Arrhythmias
Tachycardia: Heart rate in excess of 100bpm
Bradycardia: Heart rate less than 60 bpm
Sinus arrhythmia: Heart rate varies 5% during respiratory cycle and up to 30% during deep respiration
Premature atrial contractions: Occasional shortened intervals between one contraction and succeeding, frequently occurs in healthy people
MYOGENIC CONDUCTION
OCT 2008 DENNY AGUSTININGSIH 12
Cardiac myocyte action potential:
OCT 2008 DENNY AGUSTININGSIH 13
AP-contraction relationship:
AP in skeletal muscle is very short-lived AP is basically over before
an increase in muscle tension can be measured.
AP in cardiac muscle is very long-lived AP has an extra component,
which extends the duration. The contraction is almost
over before the action potential has finished.
OCT 2008 DENNY AGUSTININGSIH 14
Mechanism of Cardiac Muscle Excitation, Contraction & Relaxation
Figure 14-11: Excitation-contraction coupling and relaxation in cardiac muscle
OCT 2008 DENNY AGUSTININGSIH 15
mV
+20
-90
0
4
0
12
3
AbsoluteRefractoryperiod
0 400200100 300
RelativeRefractoryperiod
Period ofSupranormalexcitability
Masa refraktor absolute: saat ion Ca masuk otot, cor g bisa dirangsan tujuannya agar cor tidak ada fase tetani/ kejang
OCT 2008 DENNY AGUSTININGSIH 16
Electrocardiogram (ECG)Composite of all action potentials of
nodal and myocardial cells detected, amplified and recorded by electrodes on arms, legs and chest
OCT 2008 DENNY AGUSTININGSIH 17
EKG:
OCT 2008 DENNY AGUSTININGSIH 18
P
Q
R
S
T
OCT 2008 DENNY AGUSTININGSIH 19
P
Q
R
S
T
OCT 2008 DENNY AGUSTININGSIH 20
P
Q
R
S
T
0.5 Sec
1 sec
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