Muscle Structure And Function Pt 2- Week 4 Flashcards
What is isotonic contraction ?
Muscle tendon remains unchanged where muscle length decreases
What is isokinetic contraction ?
Muscle length decreases with constant velocity
What affects the oxidative capacity of muscle fibres ? (3)
Quantity of mitochondria, capillaries and myoglobin around fibre
More mitochondria, more energy
What are the 3 types of muscle fibres and their use/characteristics ?
Type 1 slow twitch , slow oxidative glycolic fibres
Type 2a intermediate fibres, fast oxidative glycolytic fibres
Type 2 x fast twitch, glycolytic fibres
What is the equation for maximal power output ?
Max power output = force x shortening velocity
What muscle fibre type fatigue fastest?
Type 2
Type 1 are more fatigue resistant
What does muscle contraction speed depend on ?
Rate of cross-bridge cycling
- myosin ATPase isoforms
What does shortening of a muscle fibre change in terms of cross bridge bands ?
Changes in I band but not A band
How are muscle fibres typed after biopsy ?
Immunohistochemical staining
What happens/found during Immunohistochemical staining ? (2)
Selective antibody fluids are unique to myosin proteins
Fibre types are differentiated by colour difference
What muscle type has the most mitochondria ?
Slow twitch
What are the dominant energy systems used for each muscle fibre type ?
Type 1 - aerobic
Type 2a - both
Type 2 x - anaerobic
What muscle fibre type has the highest ATPase activity ?
Type 2 x
The more motor units the ….
Greater the force produced
What is a motor unit ?
Each muscle fibre is innervated by a single axon , one alpha motor neuron supplies many fibres forming a motor to unit
What are small motor units best for ?
Fine motor control
What are large motor units used for ?
Large force production
What do motorneurons supplying larger/faster motor units have ? (5)
Large cell bodies
Large diameters
More axonal branches
Sparse afferent innervation
More complex motor end plate of neuromuscular junction
Which motor units are easily excited ?
Slow easy , fast are harder to excite
How does muscle length affect force regulation ? (3)
If sarcomere is too small - less force produced
If sarcomere longer can have more fore
If too long then cross bridges can’t fully form
What happens when a neuron is stimulated close to each impulse ?
Tetanus - muscle can’t produce any more force
What is the force-velocity relationship?
At any given force, the velocity of the movement is greater in muscles with higher% of type 2
Same applied to any given velocity, power is greater in type 2
