3.5.3 - Skeletal Muscles Flashcards
Cardiac muscle definition
Muscle found exclusively in the heart
Smooth muscle definition
Muscle found in the walls of blood vessels and gut
Skeletal muscle definition
The type that makes up the bulk of body muscle, attached to the bone and acts under conscious control
I bands definition
The part where only actin is found, so appears lighter
A bands definition
The area where there is myosin, so appears darker in parts where the actin and myosin overlap
Changes to bands when the muscle contracts?
The sarcomere shortens
The A band remains the same size
The H zone and I band narrow
H zone definition?
Part of the A band where there is only myosin, no actin present
Slow twitch muscle fibres definition
Contract slower, providing less powerful contractions over long time
Used for endurance, and adapted for aerobic respiration
In calf muscles
How slow twitch muscle fibre adapted for aerobic respiration?
Larger store of myoglobin
Larger supply of glucagon
Rich supply of blood vessels
Many mitochondria
Fast twitch muscle fibres definition
Contract more rapidly and produce a more powerful contraction for short time
In biceps
How fast twitch muscle fibres are adapted?
Thicker and more numerous myosin filaments
High concentration of enzymes involved in anaerobic respiration
Store of phosphocreatine
Role of phosphocreatine
Rapidly generated ATP from ADP
Actin structure
Globular protein, whose molecules are arranged into long chains twisted around one another
Tropomyosin structure
Forms long thin threads that are wound around the actin filaments
How are muscles stimulated?
Action potential reaches neuromuscular junction, causing calcium channels to open and move into presynaptic knob
Vesicles fuse with membrane and release acetylcholine into synapse
The neurotransmitter diffuses across and binds with the receptors on the post synaptic membrane = depolarisation
