Electrical and Biochemical aspects of cardiac physiology

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Electrical and Biochemical aspects of cardiac
physiology
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Overview

• Electrical aspects of cardiac physiology
• Biochemical aspects of cardiac physiology
• Other Bio-electrical aspects of cardiac
  physiology
• Tightly integrated

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Electrical aspects of cardiac physiology

• Anatomy
• Action potential
• Travel in conduction system
• Ion channels
• Receptors

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Biochemical aspects of cardiac physiology

• Structural
• Metabolic
• Contractile
• Endothelial

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Other Bio-electrical aspects of cardiac physiology

• ANP
• Cardioplegia
• Hibernating myocardium
• Stunned myocardium
• Digoxin
• GIK
• Rigor mortis

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Electrical aspects of cardiac physiology
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Electrical Anatomy
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Travel in the conduction system
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Action potential of pacemaker tissue
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Action Potential Of Myocyte
O Depolarisation 1 Rapid
repolarisation 2 Plateau
3 Late repolarisation 4 baseline
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Effect of sympathetic or parasympathetic
stimulation
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Nerve endings on the heart
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Electrical Mechanical Association ARP vs RRP Vu
lnerable Point or R on T
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(No Transcript)
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Receptors

• Sympathetic
• Beta 1
• alpha
• Para sympathetic
• Muscurinic
• Atria and ventricles
• Dopamine
• Adenosine
• Ischaemic conditioning

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Beta receptor 7 trans membrane family of receptors
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STIM
Enoximone
Catalytic regulatory aspects of cAMP
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cAMP pathway
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IP3 pathway
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Noradrenergic neuron
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Ion channels

• Na
• K
• Ca2 at least 2 types
• T transient - depolarisation
• L long acting less voltage dependent
• H
• Exchange channels Na -K
• Exchange channels Na -Ca2

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Cardiac ion channels
1 2 3 4
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Ca2 antagonists

• Calcium entry blockers NOT direct calcium
  antagonists

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Biochemical aspects of cardiac physiology

• Structural
• Metabolic
• Contractile
• Endothelial

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Heart structure
Discs Nucleus Cytoplasm Membrane Connective tissue
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Metabolic

• Glycolysis
• Pyruvate
• TCA
• Fat - the main source of cardiac energy
• Lactate or Cori cycle
• ATP
• Adrenaline
• Q10

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Carbohydrate metabolism
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Glycolysis
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Glucose transport

• GLUT 1 to 4
• 1 and 4 on heart
• 4 on heart - insulin sensitive
• ?GIK mechanism

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Fate Of Pyruvate
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TCA
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Fat metabolism
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Lactate metabolism Cori cycle
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Sources of ATP
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Hormonal milieu

• Glucose metabolism affected by
• Catecholamines
• Insulin
• Glucagon
• Thyroid hormones
• Acetylcholine
• Bradykinin
• TNF

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Adrenaline
Inotropic Chronotropic Metabolic
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Glycogen phosphorylase and adrenaline
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Glycogen synthetase and adrenaline
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Regulation of glycogen
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Glycogen importance

• Conflicting views
• Glycogen depletion
• Increased deposition
• Increased utilisation
• Decreased utilisation
• May be important in preconditioning and ischaemia
  reperfusion
• Poullis point
• ? Importance of pre operative starvation

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Q10
100
Metabolic Rate
50
10oC
Temp
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Metabolic cardiac disease

• McArdles

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Contraction
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Muscle structure
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Contractile assembly 1 light chains
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Contractile assembly 2 heavy chains
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Actin myosin ATP
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Contraction movement
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Sarcoplasmic reticulum
Sarcoplasmic reticulum
Troponin C
Ca 2 Mobilisation for contraction
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Frank Starling
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Frank Starling
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Contractile cardiac disease

• HOCM
• Duchenne
• Beckers

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Endothelium

• Blood flow
• Cholesterol
• Diabetes
• NO

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Acetylcholine metabolism
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Endothelium And NO
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Other aspects of cardiac physiology
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ANP

• ANP atria
• BNP atria, pig brain
• CNP human brain
• In general opposite effects of angiotensin II
• ANP receptors
• A, B C
• Short half life
• Metabolised by NEP
• Released secondary to atrial stretch

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Cardioplegia

• Extracellular
• Rely on K
• St Thomass
• Intracellular
• No Ca, little/no Na, low osmolarity Mannitol
• Transplant solutions LKD

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Stunned myocardium

• Ischaemia
• Reperfusion
• Support
• Recovery
• ? 2nd protein denaturisation

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Hibernating myocardium

• Viable myocardium with no contraction
• 2nd ischaemia
• Protective mechanism
• Reversible
• Diagnosis
• Thallium
• Dobutamine
• PET
• Hope ?

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Digoxin
Na
Na
Plasma Membrane
K
-Ve
Ca
Inc Na
Digoxin
Na-K-ATPase
Na-Ca exchange pump
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GIK

• Increases cardiac glucose via GLUT 4
• Increases cellular ATP
• Increases intra cellular K
• Increases efflux of Ca
• Poullis point 1
• 50mL of 50 dextrose (Km of GLUT-4 normal plasma
  range) and BP
• Poullis point 2
• Do you need insulin with a normal pancreas ?

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Rigor mortis
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ANYONEAWAKE ?