Muscle Performance Flashcards
What are passive (local) potentials?
Graded potentials that decay with distance and time, including EPSP and IPSP.
EPSP: Excitatory Post-Synaptic Potential; IPSP: Inhibitory Post-Synaptic Potential.
What is the action potential characterized by?
VGNaC and K channels, threshold, absolute and relative refractory periods.
What components make up a neuron?
Dendrites, soma, axons, and synapses.
What is the ‘resting’ membrane potential determined by?
The ratio of [Ion]out/[Ion]in and the permeability/conductance of the membrane.
What types of gated membrane ion channels exist?
- Voltage-gated Na+ channels
- K+ channels
- Mechanical variants
- Ligand-gated variants
- Na+, K+ - ATPase
What is saltatory conduction?
The process by which action potentials jump from one node of Ranvier to another.
What occurs at the chemical synapse?
- Presynaptic events: [Ca2+]i, vesicle fusion, NT release
- Postsynaptic events: ionotropic and metabotropic receptors
What is the function of acetylcholine (Ach) at the neuromuscular junction?
It facilitates the one-for-one action potentials in skeletal muscle.
What is excitation/contraction coupling?
- Actin and myosin interaction
- [Ca2+] driven
- ATP dependent
What defines Type I muscle fibers?
- Slow oxidative fibers
- Fatigue resistant
- High oxidative enzyme content
- Rich blood supply
- Slow contraction speed
What defines Type II muscle fibers?
- Fast glycolytic fibers
- Fatigue-prone
- Fast contraction speed
- Limited oxidative capacity
What are the features of Type IIA muscle fibers?
- Fast form of myosin ATPase
- Mix of oxidative and glycolytic enzymes
- Intermediate speed and fatigue resistance
What factors limit muscle performance?
- Fibre types
- Length-tension relationship
What is the role of a motor unit?
A single motor neuron and all the muscle fibers it innervates.
How does motor unit size affect force output?
Max force from a motor unit depends on its size; larger units can generate more force.
What are the two mechanisms for controlling muscle force?
- Frequency modulation
- Recruitment
Define frequency modulation in muscle control.
Changing the rate of action potential activity in each motor unit increases force.
What is the size principle in motor unit recruitment?
Smaller motor units are recruited first, followed by larger units as needed.
What occurs during tetanic contraction?
At high frequencies of stimulation, twitches merge to produce continuous force.
What adaptations occur from strength training?
- Increased actin and myosin
- Increased fiber diameter (hypertrophy)
- More cross-bridges for more force
What adaptations occur from endurance training?
- Increased oxidative capacity
- More mitochondria and capillaries
- Increased muscle lipid stores
- Enhanced lipid utilization from blood
What is the significance of the force-length relationship?
The velocity and tension achieved depend on the load and length of the muscle.
What do muscle spindles provide information about?
Current muscle length and velocity for optimal control.
What happens when [Ca2+]i rises during high-frequency stimulation?
It increases actin/myosin interaction, enhancing force production.
