Cardiac muscles

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Cardiac muscles by Mind Map: Cardiac muscles

1. Autorhythmic cells

1.1. Do not have a resting membrane potential

1.2. They have the funny Na channels which initiates the action potential for the rest of the heart

2. Contractile cells

2.1. have a different membrane potential from other muscles due to calcium channels

2.2. Mechanism of contraction

2.2.1. Action potential arrives from another cell, causing the Ca++ channels to open (in T tubules)

2.2.2. the Ca++ signal is amplified through RyR (Ryanodine-channel receptors) making a spark

2.2.3. sparks accumulate to create a Ca++ signel

2.2.4. C++ binds to troponin to initiate contraction

2.2.4.1. cross bridging will occur

2.2.5. C++ unbinds and muscle relax

2.2.5.1. some are then "pumped" to the SR for storage (Ca++-ATPase)

2.2.5.2. some are exchanged with Na+

2.2.6. Na+ gradient maintained by Na+-K+-ATPase

2.3. Modulation of contraction through cross-bridges (crossing of actin and myosin)

2.3.1. catecholemine

2.3.1.1. Epinephrine from adrenal medulla

2.3.1.2. Norepinephrine from sympathetic neurones

2.3.1.3. Activates B1 receptor on cardiac contractile cells -> cAMP

2.3.1.3.1. Phosphorylation of

2.3.2. more cytosolic C++

2.3.2.1. Will increase the extent of cross-bridge activity

2.3.2.1.1. more force of contraction

2.3.2.1.2. longer duration of contraction with little time to rest between

2.3.3. Frank-Starling mechanisms