Muscle Function

- What is the aerobic/anaerobic poise of these muscle types?

Aerobic: slow twitch - long repeated contractions without fatiguing Anaerobic: fast twitch - rapid powerful contraction; fatigues more quickly

- Sarcoplasm and T tubules in the different muscle types?

- T tubules: elaboration of plasma membrane - path of the action potential to the interior of the muscle cell - Sarcoplasm reticulum: sequesters calcium Smooth muscles have no T-tubule system or well-developed smooth ER. Slow twitch muscles have less of a sacroplasm reticulum - calcium stays out longer, so longer contractions Fast twitch muscles have more specialized sacroplasm reticulum, which allows rapid control of calcium contractions.

Slow twitch muscles

have less of a sacroplasm reticulum - calcium stays out longer, so longer contractions

Fast twitch muscles

have more specialized sacroplasm reticulum, which allows rapid control of calcium contractions

Smooth muscles

have no T-tubule system or well-developed smooth ER

What are the proteins involved in muscle contraction?

• Troponin • Tropomyosin complex • Chitin cellulose

what is the role of calcium in muscle contraction?

•Calcium exposes the site on actin (thin myofibrils) which interacts with myosin (thick myofibrils) - this is in skeletal (striated) muscle •Calcium ions and proteins bound to actin play a crucial role in both muscle cell contraction and relaxation. •When CA2+ acuumulates in the cytosol, it binds to the troponin complex, causing tropomysin bound along the actin strands to shift position and expose the myosin-binding sites on the thin filament •When the calcium concentration rises in the cytosol, the thin and thick filaments slide past each other, and the muscle fiber contracts •When calcium concentration falls, the binding sites are covered and contraction stops •Motor neurons cause muscle contraction by triggering the release of calcium ions into the cytosol of muscle cells with which they form synapses

What are fast twitch fibers?

•Muscle fibers developed 3x faster than slow •Used for brief, rapid, powerful contractions •Anaerobic poise o Anaerobic glycolysis - fermentation to lactate o Major storage fuel is glycogen o ATP o Creatine phosphate/arginine phosphate o Fatigues more quickly

What are slow twitch fibers?

•Muscle fibers developing slow tension •Often used to maintain posture; sustain long contractions •Aerobic tissue o Many mitochondria o Rich blood supply o Myoglobin (oxygen storage protein) o Major storage fuel is triglycerides •Less sarcoplasmic reticululm and pumps calcium ions at slower rate than fast-twitch

What are the types of vertebrate muscle?

•Skeletal (striated) •Cardiac (heart muscles, striated) •Smooth

What is the sarcoplasmic reticulum and what is its function?

•Specialized endoplasmic reticulum •smooth ER that releases and removes calcium -regulates calcium concentration in cytosol of muscle cells

What is the role of calcium in glycogen breakdown?

Calcium activates glycogen breakdown and inhibits glycogen synthesis