6.3 Skeletal Muscle Contraction Flashcards
What is the gross structure of skeletal muscles?
Whole muscle
Bundle of muscle fibres
Single muscle fibres
Myofibril
Multinucleate
How are the long giant cells in muscle fibres formed?
They form from the fusion of smaller cells The sarcoplasm (cytoplasm) are full of myofibril - which are bundles of protein filaments that cause contraction
What initiates the muscle contraction - due to what?
The sarcolemma (cell surface membrane) allows an action potential to pass along
What are the prefixes for muscle?
Sarco and Myo
How do muscles work?
In antagonistic pairs against an incompressible skeleton
Using flexion and extension
What are slow twitch fibres used for?
Aerobic respiration
They contract more slowly and provide less powerful contractions but over a long period
Adapted for endurance
How are slow twitch adapted?
Large store of myoglobin
Rich supply of blood vessels
A lot of mitochondria
What are fast twitch fibres used for?
Anaerobic respiration
They contract more rapidly and provide more powerful contractions but over a shorter period
Adapted for intense exercise
How are fast twitch adapted?
Thicker and more myosin filaments
Higher concentration of enzymes (for anaerobic respiration)
Higher concentration of phosphocreatine - to generate ATP from ADP
Supply of glycogen
What is involved in the structure of myofibril?
Actin and myosin
They are darker where they overlap
Sarcomere A band H zone I band M line Z line
What do all the sections of myofibril represent?
A band - length of the myosin filament H zone - myosin only I band - actin only M line - middle of the sarcomere Z line - ends of the sarcomere
How do you remember which band for the colours on a myofibril diagram?
LIght - I band - just actin
dArk - A band - length of myosin filament
What is the sliding filament theory?
When the muscle contracts the sarcomere becomes smaller
The filaments don’t change length they just slide past an overlap
What is a neuromuscular junction?
Like a synapse
Allows the muscle to contract when threshold is exceeded as sufficient acetylcholine is released
What is different about a neuromuscular junction to a cholinergic synapse?
The post synaptic membrane is muscular
The sarcolemma can transmit an action potential along it
The sarcolemma have T-tubials (a large indent in the cell surface membrane which brings the action potential directly to the sarcoplasmic reticulum