1. Chapter 7 Excitation of Skeletal Muscle
Dr. Marko Ljubković
Department of Physiology

2. Neuromuscular Junction
Synaptic gutter
Synaptic cleft (space)
Subneural clefts

3. Secretion of Ach from Nerve Terminals
Nicotinic receptor

4. Effect of Ach on Postsynaptic Membrane
End plate potential
Binding to nicotinic receptor
End plate potential
Acetylcholine esterase
Reuptake of choline
Drugs that interact with neuromuscular transmission:
Nicotine, carbachol
Curariform drugs
Botulinum toxin
Neostigmine, diisopropyl fluorophosphate
A – effect of curare
B – normal state
C – effect of botulinum toxin
Myasthenia gravis

5. Spread of the Action Potential and Excitation-Contraction Coupling
Voltage-gated Na+ channels
T-tubules (extracellular space)
L-type Ca2+ channels
SR cysternae
Ryanodine receptors (RYR)
Voltage-induced Ca2+ release

6. Chapter 9 Physiology of Cardiac Muscle
Types of cardiac muscle:
Contractile
Excitatory and conductive
Properties of contractile cardiac muscle:
Composed of individual cardiomyocytes
Intercalated discs (gap junctions)
Syncytium

7. Action Potential in Cardiac Muscle
AP in ventricular myocytes:
0 – fast Na+ channels
1 – Transient outward K+ current
2 – L-type Ca2+ channels + K+ channels (reduced conductance)
3 – Outward K+ current dominate
4 – Excess Na+ and Ca2+ removed, resting state
Refractory period

8. Differences between Skeletal and Cardiac Muscle
Ventricular muscle:
AP lasts longer (250 ms)
Spreads through gap junctions (syncytium)
Ca2+-induced Ca2+ release from SR
Extracellular Ca2+ important for contraction
Skeletal muscle:
AP shorter (up to 10 ms)
Each muscle fiber has nerve ending
Voltage-induced Ca2+ release from SR
Extracellular Ca2+ not required for contraction