Muscles Flashcards
What is an antagonistic pair of muscles?
For each part of the skeleton there are two muscles attached and work oppositely (as one contracts, the other relaxes)
What is a myofibril?
Fused cells that are made up of nuclei and cytoplasm (called sarcoplasm).
What are the adaptations of myofibrils?
Many mitochondria to provide ATP for respiration
Have a large surface area for faster contraction
What proteins make up myofibrils?
Myosin and actin (these form the sarcomere)
Myosin
Thick filament
Actin
Thin filament
Sliding filament theory
- Action potential reaches a muscle and stimulates a response
- Calcium ions released from sarcoplasmic reticulum
- Calcium ions cause tropomyosin’s structure to change and reveal the actin binding sites
- ADP attaches to the myosin heads, allowing them to bind to actin and form cross bridges
- Cross bridge forms tension, so myosin pulls along actin and releases ADP and Pi
- ATP can them bind to myosin head, causing it to change shape and release from actin
- ATPase from sarcoplasm (activated by calcium ions) hydrolyses ATP causing ADP and Pi to be released
- Myosin head returns to original position
What is phosphocreatine?
Used in anaerobic respiration as it provides phosphates for ADP to regenerate ATP
A band
Total width of myosin and ends of actin. Remains same width in muscle contraction
H zone
Myosin only (centre part). Becomes smaller in muscle contraction
I band
Actin only. Becomes smaller in muscle contraction
M line
Middle point of myosin
Z lines
Mark the end / beginning of each sarcomere. Z lines move closer together in muscle contraction (sarcomere shortens)
What is the structure of slow twitch fibres?
- Large store of myoglobin
- Rich blood supply
- Many mitochondria
Where can slow twitch fibres be found?
Calf muscles
What are the properties of slow twitch fibres?
- Contract slower
- Respire aerobically
- Adapted for endurance e.g. marathons
What is the structure of fast twitch fibres?
- Thicker
- More myosin filaments
- Large store of glycogen
- Stores phosphocreatine
- High conc. of enzymes used in anaerobic respiration
Where can fast twitch fibres be found?
Biceps
What are the properties of fast twitch fibres?
- Contract faster
- Short bursts of powerful contractions
- Adapted for intense exercise e.g. sprinting or weightlifting
