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Electrophysiology of the Heart, How Cardiac Muscle can increase force of…
Electrophysiology of the Heart
Cardiac Muscle Cells
Cardiac Myocytes
Excitability
Conductivity
Dromotropic state
"dromo" means running
rate of the ions movements
Contractility
Dyad: T-tube and Sarcoplasmic Reticulum
Ca2+ inside binds onto receptor in SR inducing release of more Ca2+
Ca2+ Binds to troponin
Toponin removes tropomysoin out of the way
Cross bridge forms between actin and myosin
Cross-bridge moves closer towards center
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Ca2+ induced Ca2+ release
In skeletal muscle its different, it will be voltage induced calcium release because extracellular calcium does not cause more calcium to be released. it depends all on sarcoplasmic reticulum calcium
In smooth muscle it doesn't always require an action potential to get excited, it just depends on the phosphorylation of light chain myosin channels. It also can get stimulated
Helps depolarization spread to cell faster
In skeletal muscle this is called a Triad
Myosin are thick filaments (my sins are thicc)
Actin are thin filaments
Myosin + Actin + ADP + Pi
ADP + Pi
Permeability
Conductance
Flux
Current
movement of charges
movement of ions
ability of ions to move thru channels
ability of ions to move thru membrane
Inotropic state
"Ino" means fibers
rate of contraction
Specialized Conducting Tissues
Conductivity
Nodes
Leaky Na+ Channels
T- type Calcium channels
-55mv
-40mv Threshold
L-type Calcium Channels
Depolarization (+spike)
Cations move thru Gap Junction
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+40mv
-60mv RMP
SA Node
Pace maker of heart
fastest AP generator in heart
Gives raise to
Sinus Rhythm
(normal heart rate)
Atria
AV Node
Bundle of His
Bundle Branches
Purkinje Fibers
Fastest conducting
Left BB
Right BB
only electrical link between A&V (Junctional Tissue)
separated by fibrous tissue ring
AV nodal delay (0.1s)
conduction is the slowest
Less gap junctions
smaller fiber diameter
to give time for atria to contract to allow blood to enter
Affected by beta blockers
Overdrive suppression
Automaticity (autorhythmicity)
spontaneous generation of impulses
Chronotropic state
"chrono" means time
rate of impulse generation
Extrinsic Cardiac Conduction System
Sympathetic
Makes myocardium membrane more permeable to Na+ and Ca2+ ions
Parasympathetic
Makes myocardium membrane more permeable to K+ ions
Intrinsic Cardiac Conduction System
How Cardiac Muscle can increase force of contraction
ANS activation
Released catecholamines
Increase in venous return
Energy Sources of Cardiac Muscle
Glucose, Fatty acid, lactic acid, ketone bodies (to an extent)
Always a 20mv difference between RMP and AP threshold
Cycle Restarts
