Skeletal muscles Flashcards
What are smooth muscles? Where are smooth muscles found?
Muscles that contract involuntarily and are usually found in organs.
What are cardiac muscles? Where are cardiac muscles found?
Muscles that contract involuntarily and are usually found in the heart.
What are skeletal muscles? Where are skeletal muscles found?
Muscles that contract voluntarily
What attaches muscles and bones?
tendons
What attaches bones to bones?
ligaments
What are antagonistic pairs?
Muscles that work together to move a bone. The contracting muscle is the agonist muscle and the relaxing muscle is called the antagonist muscle.
Draw the structure of a muscle fibre.
What are myofibrils made up of?
sarcomeres
Draw and label the structure of a sarcomere.
What is the structure of the myosin filaments?
They have globular heads that have an actin-binding site and an ATP-binding site.
What is the structure of the actin filaments?
They have a myosin-binding site which is blocked by proteins called tropomyosin.
Describe the sliding filament theory.
- An action potential arrives at the muscle fibres and polarises the sarcoplasm reticulum. This causes the reticulum to release calcium ions into the sarcoplasm.
- The calcium ions bind to troponin and cause it to change shape. This pulls the tropomyosin attached to it away from the myosin-binding site.
- The globular head of the myosin filaments can now bind to the binding site and form a cross bridge.
4 The calcium ions also activate ATP hydrolase. The hydrolase breaks down the AT to release energy which is used to bend the myosin head. This pulls the actin filament along in a rowing motion. - Another ATP molecule is broken down to break the cross-bridge, this means the myosin head can bind to another binding site and pull the actin filament further along.
- This causes the sarcomeres to shorten and the muscles to contract.
- When the muscle sto[s being stimulated no more calcium ions bind to the troponin meaning the tropomyosin once again blocks the myosin binding site the sarcomere lengthens and the muscle stops contracting.
How ATP is produced so it can be used to provide energy for muscle movement?
- Aerobic respiration.
- Anaerobic respiration
- ATP-phosphocreatine system
How is ATP produced in Aerobic respiration?
Produced during oxidative phosphorylation and glycolysis.
How is ATP produced in anaerobic respiration?
produced in glycolysis
Why is using anaerobic respiration to make ATP only good for short periods of hard exercise?
It produces ATP quickly through glycolysis. However, the end product of aerobic respiration is lactate which causes muscle fatigue.
How does ATP get produced in the PCr system?
ADP + PCr - ATP + Cr (creatine)
Why is using the PCr system to make ATP only good for short periods of hard exercise?
The PCr runs out after a few seconds.
What are slow-twitch fibres?
Muscle fibres that contract slowly and can work for long periods.
What adaptations do slow-twitch fibres have that aid them in their function?
- They have a lot of mitochondria where aerobic respiration happens.
- They have a high number of blood vessels which supply them with oxygen, needed for aerobic respiration.
- The mitochondria are usually found on the edge of the muscle fibres so there is a short diffusion distance for the oxygen.
- They are rich in myoglobin, which stores oxygen. This gives them their red colour.
What are fast-twitch fibres?
Muscle fibres that contract quickly and get tired quickly.
Why do fast-twitch muscle fibres have low amounts of mitochondria and blood vessels?
They make their ATP using anaerobic respiration and the PCr system meaning they don’t need oxygen or many mitochondria.
