Energy Generation
Energy materials stored within muscle fibers
myoglobin, glycogen, creatine phosphate (mitochondria for ATP production)
The resting membrane potential of a skeletal muscle fiber
About -90 mV
Locations of smooth muscle
Blood vessels, bronchioles, intestines, ureters, uterus, and hollow organs
Resting tension created by involuntary stimulation w/out movement
Muscle tone
Three main ways skeletal muscle makes more ATP
Creatine phosphate, glycolysis, and aerobic cellular respiration
~5 seconds
short, branched, striated fibers with 1 or 2 nuclei, many mitochondria, and joined by intercalated discs with desmosomes and gap junctions
Main features of cardiac muscles
endurance training improves ATP production capacity & resistance training causes hypertrophy and increase glycogen reserves and mitochondria
Repeated stimuli arrive before muscle relaxation causing contraction collection and tension increase
Wave summation
Process that does not require oxygen, occurs in the cytosol, and yields 2 ATP per glucose
Glycolysis in muscle
When the end-plate potential reaches threshold (~65mV) causing rapid depolarization and repolarization
Muscle action potential
Fusiform, smaller than skeletal muscle fibers, lack T-tubules and sarcomeres, have sparse SR, and use caveolae and extracellular calcium
Structural features of smooth muscles
Reduced ability to produce tension
Muscle fatigue: primarily due to decreased glycogen stores during prolonged exercise or at the neuromuscular junction, in excitation-contraction coupling, or in crossbridge cycling
Isometric vs Isotonic contraction
Isometric: tension is generated without movement or shortening// Isotonic: movement occurs and muscle shortens concentrically or lengthens eccentrically
Aerobic respiration in muscle
When a muscle generates maximum force
Triggered by autorhythmic pacemaker cells (automaticity) with rate and force influenced by the autonomic nervous system
Effect of aging on skeletal muscle
Decreases muscle size, power, endurance, O2 storage, recovery capacity, fiber size, satellite cell availability, and fibrosis
ACh release stops, ACh is broken down by AChE, action potentials cease, Ca release stops, Ca is pumped back to SR, and tropomyosin blocks actin binding sites
Skeletal muscle relaxation
The extra oxygen needed after exercise to restore pre-exercise conditions, including restoring oxygen stores, glycogen, ATP, creatine phosphate, and converting lactic acid back to glucose
Oxygen debt
Partial fusion of twitches at higher stimulus frequencies
incomplete tetany (tetany: smooth contraction with no relaxation between stimuli)
Controlled by the automatic nervous system and responds to stress, hormones, pH, O2, CO2, drugs, and pacemaker cells
Smooth muscles
Ca binds to calmodulin, activates myosin light-chain kinase, phosphorylates myosin, allows crossbridge formation
Smooth muscle contraction regulation