Muscly physiology part b Flashcards
What is rate limiting step for cycle
ATP hydrolysis
Fast fibers=
Myosin with fast ATPase activity
Slow fibers=
Myosin with slow ATPase activity
Slow fiber contractions last how much longer then fast
10 times
How to classify as oxidative or glycolitic
based on primary source of energy
Oxidative fibers primary energy source is
oxidative phosphorylation
Properties of oxidative fibers
Many mitochondria
Myoglobin (red)
Small diameter
Resistant to fatigue
Glycolytic fibers properties
Fewer mitochondria Many glycolytic enzymes High glycogen stores Use little oxygen - anaerobic Large diameter Rapid to fatigue
What are the three types of muscle fiber types
Slow oxidative
Fast oxidative
Fast glycolytic
Properties of slow oxidative fibers
Low myosin ATPase High oxidative capacity- aerobic Mitochondria Rich blood supply Myoglobin (red) Small diameter Little tension Small diffusion barrier) Fatigue slowly
Properties of fast glycolytic fibers
High myosin ATPase activity High glycolytic capacity High glycogen stores Many glycolytic enzymes No myoglobin (white) Large diameter Greater tension Fatigue rapidly
Properties of Fast oxidative fibers
High myosin ATPase activity High oxidative capacity - Aerobic Myoglobin Slow to fatigue, but more rapid than slow oxidative Intermediate diameter
Proportions of fibers in a muscle depends on what
Function of muscle, postural muscle more slow oxidative
What is the recruitment order of fibers?
Slow oxidative, fast oxidative, fast glycolytic
Causes of muscle fatigue in high intensity exercise
Build up of lactic acid
Compression of blood vessels
Depletion of acetylcholine (neuromuscular fatigue)
Causes of fatigue in low intensity exercise
Depletion of energy reserves
What are other possibilities of fatigue
Build up of inorganic phosphates
Changes in ion distribution
What is central fatiue
psychological fatigue
What is change is muscle size due to?
Change in size of individual cells
What is disuse atrophy
Decrease in size( lose myofibrils)
What is denervation atrophy
Motor neuron destroyed so no excitation, atrophy due to lack of use
What is hypertrophy
Increase in size (increase myofibrils)
Increase production of actin & myosin
Aerobic exercise adapts muscle how
Increases oxidative capacity of muscle
More mitochondria
Increase blood supply (capillaries)
Decrease in diameter
how does anaerobic ex adapt muscle
Increases ability of muscle to generate more tension (strength) Increases amount actin & myosin Increases number of myofibrils Increases diameter of muscle fiber Increases glycolytic enzymes Decreases oxidative capacity
Does smooth muscle contain actin and myosin
yes
Some properties of smooth muscle
No sarcomeres higher actin:myosin ratio actin and myosin much longer myosin heads over entire length arranged diagonally One nucleus Tropomyosin No troponin Dense bodies analogous to Z line Slow myosin ATPase Myosin has light chains Little sarcoplasmic reticulum
Steps of excitation-contraction coupling for smooth muscle
Opening of calcium channels in plasma membrane
- Voltage
- Receptor
- Mechanically-gated
2. Calcium triggers release of calcium from sarcoplasmic reticulum
3. Calcium binds to calmodulin
4. Ca-Calmodulin activates MLCK
5. MLCK phosphorylates myosin
6. Crossbridge cycling
how does relaxation of smooth muscle occur
Phosphatase removes phosphate from myosin
Calcium removed from cytoplasm
Ca-ATPase
Ca-Na counter transport
Is myosin ATPase slower or faster in smooth or skeletal muscle
SLower
Action potential in smooth muscle are mediated by what
Calcium
What determines tension
Intracellular Ca
Intracellular Ca influenced by what
Neural control - Autonomic NS
Hormonal control
Paracrines (local controls)
What is the most common type of smooth muscle. Where are these found?
Single unit.
Intestinal tract
Blood vessels
Respiratory tract
Where are multi-unit smooth muscle found
Large airways and arteries, eye
Similarities of cardiac muscle with skeletal muscle
Striated - sarcomeres Troponin & Tropomyosin regulation T tubules Sarcoplasmic reticulum, but not as well developed Similar to slow oxidative fibers myoglobin mitochondria slow to fatigue
What is lacking in cardiac muscle?
Summation, action potential lasts almost as long as tension
