Muscles II Flashcards
Type 1 or 2: large and numerous mitochondria
Type 1
Type 1 or 2: slow rate of cross-bridge cycling
Type 1
Force generation in muscle depends on (3)
- types and number of motor units recruited
- initial muscle length
- nature of neural stimulation of motor unit
Define incomplete (unfused) tetanus
Sustained but wavering contraction
How is oxidative capacity increased?
Increased capillarization, number of mitochondria, and amount of glycolyti cenzymes
Weight training (increases/decreases) synchrony
Increases
How are muscle fibres typed? (4)
- muscle biopsy
- staining for type of myosin ATPase
- immunohistochemical staining
- gel electrophoresis
Type 1 or 2: Higher capacity for electrical transmission of APs
Type 2
Frequency of stimulation depends on… (3)
- simple twitch
- summation
- tetanus
Three characteristics in which skeletal muscle fibre types differ
- primary mechanisms to produce ATP
- type of motor neuron innervation
- type of myosin heavy chain expressed
Prolonged workouts result in _______ NMJ area
More expansive
Slow fibres have myosin with _____ ATPase activity
Slow
Two reasons that fast fibres exert more force than slow fibres
- max force per cross-sectional area
2. more cross-bridges per cross-sectional area
Fast fibres contract ____ times faster than slow fibres
2-3x
Fast fibres have myosin with ______ ATPase activity
Fast
Define isometric contraction
Muscle exerts force without changing length
Define asynchronous summation
During submaximal contraction, mu contract and summate asynchronously (some contract while other’s relax)
How does fibre composition affect fatigue?
Fuel availibility
Action potential through motor neuron causes release of ACh at _____ muscle fibres that it innervates
All
Rate limiting step of relaxation
Ca2+ ATPase
Muscle hypertrophy causes (increased/decreased) protein synthesis, statelite cell (proliferation/degredation), (less/more) and (thinner/thicker) myofibrils, (less/more) sarcomeres, and increased stores of ____, _____, ______
Increased; proliferation; more thicker; more; and ATP, CrP, glycogen
Breakdown of fibres in non-athletes (%)
50-50 fast and slow
Load changes with
Position of limb
________: increase in muscle fibre size with strength training
Hypertrophy
Central/neural causes of temporary reduction in muscular performance
Mechanisms including proximal (upstream) to the NMJ
Factors of local fatigue (3)
Fibre composition, failure at NMJ, failure of contractile mechanisms
Fast fibres relax _____ times faster than slow fibres
10x
Biochemical properties of muscle fibre characteristics (2)
- oxidative capacity (number of capillaries, mitochondria, myoglobin)
- type of myosin ATPase (speed of ATP degradation)
As strength demand increases, we want to increase (synchrony/asynchrony)
Synchrony
What is the rate limiting step of contraction cycle?
ATP hydrolysis
Define complete (fused) tetanus
When all troponin has Ca2+ bound and crossbridge cycling is maxed out, so individual contractions can’t be measured and a smooth, max force contraction occurs
Muscle fatigue begins when?
Immediately with the start of physical activity
High fibre : nerve = _____ movements
Gross movements
Type 1 or 2: well developed short-term glycolytic system
Type 2
The max velocity of shortening is greatest at (highest/lowest) force
Lowest
Which fibre type has highest maximal shortening velocity? I, IIa, IIx
IIx
How do contractile mechanisms start to fail during fatigue?
Depletion of phosphagen stores, increased acidity and temp, and degradation of contractile proteins
Two main characteristics of muscle fibre types
- biochemical properties
2. Contractile properties
Type 1 or 2: Less well-developed glycolytic capacity (ie. less lactate dehydrogenase)
Type 1
Define concentric contraction
Muscle shortens during force production
At any absolute force, the speed of movement is greater in muscles with a (higher/lower) percent of fast-twitch fibres
Higher
Muscle/peripheral causes of temporary reduction in muscular performance
Mechanisms of excitation-contraction coupling as well as metabolic accumulation
Isotonic twitches get larger in ________ as recruited in _____ loads
Larger muscle fibres; larger loads
Low fibre : nerve = ______ movements
Fine movements
A fast-to-slow shift in fibre type characteristics is seen in ________ and ______ training
Endurance and resistance
High intensity workouts result in ______ of synapses
greater dispersion
Type 1 or 2: Rapid calcium release and reuptake by efficient SR
Type 2
Contractile properties of muscle fibre contraction (3)
- maximal force production (force per unit of cross sectional area)
- speed of contraction (myosin ATPase activity)
- muscle fibre efficiency
How does staining for type of myosin ATPase tell you which fibre type a sample is?
Type 1 is darkest, type 11a is lightest, and type 11x is in between
How does immunohistochemical staining help type fibres?
Antibodies bind selectively to unique myosin proteins, and fibre types are differentiated by colour difference
How does gel electrophoresis help type muscle fibres?
Identifies myosin isoforms specific to different fibre types
Type 1 or 2: fatigue resistant
Type 1
________: increase in muscle fibre number during strength traiinng
Hyperplasia
For maximal/explosive contractions, we use (synchrony/asynchrony)
Synchrony
What fibre types are more likely to exhibit failure at NMJ?
Type II
Endurance training (increases/decreases) oxidative capacity
Increases
Isometric twitches within a given muscle cell twitch all have _____ magnitude and shape
the same
Metabolic adaptations via improved glucose transport cause…..
Enhanced activation of insulin signalling cascade, and increased [GLUT-4 protein]
Increased synchrony (increases/decreases) strength without changing fibre size
Increases
Type 1 or 2: generate energy for ATP synthesis via aerobic system
Type 1
Type 1 or 2: high myosin ATPase activity
Type 2
Define eccentric muscle contraction
Muscle produces force but length increases
Hypertrophy or hyperplasia: seen in humans during strength training
Hypertrophy
Faster rate of myosin ATP hydrolysis causes a faster rate of _______
crossbridge cycling
