muscular physiology Flashcards
What is a fascicle in muscle structure?
A bunch of individual fibres or cells packaged together
Fascicles are a component of the overall muscle structure.
What connective tissue surrounds the entire muscle?
Epimysium
Epimysium provides protection and support to the muscle.
What surrounds each fascicle?
Perimysium
Perimysium allows fascicles to be stimulated collectively.
What is the smallest structural unit of a muscle?
Myofibril
Myofibrils are responsible for muscle contraction.
What surrounds each individual muscle fibre?
Endomysium
Endomysium separates individual muscle cells.
What is the membrane of the muscle cell called?
Sarcolemma
Sarcolemma enables conduction of action potentials.
What are myofibrils composed of?
Cylindrical units running parallel to the cell orientation
Myofibrils are crucial for muscle contraction.
What is a sarcomere?
The basic contractile/functional unit of muscle cells
Sarcomeres contain contractile proteins that facilitate contraction.
What proteins are involved in muscle contraction within the sarcomere?
Actin (thin filament) and myosin (thick filament)
These proteins work together to enable muscle contraction.
What regulates contraction on actin filaments?
Troponin complex and tropomyosin
These regulatory proteins control the binding of myosin to actin.
What is the function of the sarcoplasmic reticulum?
Propagates action potentials and releases calcium
Calcium release is essential for muscle contraction.
What is the role of transverse tubules?
Propagate action potential to the deeper interior of the muscle cell
They ensure action potentials reach all parts of the muscle.
What connects adjacent sarcomeres?
Z discs (z lines)
Z discs play a critical role in muscle contraction.
What is the process called that underlies muscle contraction?
Cross bridge cycling
It involves the interaction between myosin heads and actin filaments.
What initiates cross bridge cycling?
Calcium binding to troponin
This exposes binding sites on tropomyosin.
What happens during the power stroke of muscle contraction?
Myosin head releases ADP & Pi and pulls actin filament
This movement causes actin and Z discs to move toward the center of the sarcomere.
What is required for the detachment of myosin from actin?
ATP
ATP is essential for resetting the myosin head.
What happens to ATP during the resetting of the myosin head?
ATP is hydrolyzed into ADP and Pi
This process releases energy that energizes the myosin head.
What is a muscle twitch?
A response of a single muscle fibre to a single action potential
It illustrates the basic functional response of a muscle fibre.
What is a motor unit?
A motor neuron and all of the fibres it innervates
Motor units are crucial for muscle contraction and control.
List the three categories of motor units.
- Type 1 – slow twitch, produce the least force, fatigue slower
- Type 2a – hybrid
- Type 2x – fast twitch, produce the most force but fatigue the fastest
Each type of motor unit has distinct characteristics and functions.
What are the two origins of muscle fatigue?
- Central fatigue
- Peripheral fatigue
Each type of fatigue has different physiological causes.
What is peripheral fatigue?
Loss of force producing capacity due to processes at or below the neuromuscular junction
Often associated with high-intensity exercises.
What is central fatigue?
Loss of force producing capacity due to processes above the neuromuscular junction
Often occurs during prolonged exercise.
