Muscles Flashcards
What are antagonistic pairs?
Muscles that work together against an incompressable bone. One contracts while the other one relaxes and this helps them move the bone.
Draw and label the structure of a muscle.
How does an action potential travel trough a muscle?
- The electrical impulse travels from the sarcomella and into the T-tubules.
- The T-tubules carry that electrical impulse to the sarcoplasmic reticulum.
- Thus causes the sarcoplasm reticulum to release calcium ions.
Draw and label the structure of a sarcomere.
What would you see on a microscope when looking at the sarcomere of a muscle that is contracting?
The H-zones and I-zones will decrease meaning the sacromeres will become shorter. This is what causes the muscle to contract.
What is the structure of actin?
It consists of two protein chains, troppmyosin and troponon wrapped around each other. They have a myosin binding site that is occupied by the tropomyosin when the muscle is not contracting.
What is the structure of myosinf filaments?
They have a myosimg head which has an ATP molecule attached to it.
Describe the process of muscle contraction.
- The sarcomella is depolarised when acetylcholine binds to receptors on the posynaptic membrane of a neuromuscular junction.
- The action potential travels along the T-tubules and into the sarcoplasmic reticulum.
- This depolarises the sarcoplasmic reitculum causing it to release calcium ions.
- The calcium ions bind to tropomyosin causing it to change shape and move out of the myosin binding sites.
- The myosin heads bind to the actin to form an actin myosin bridge.
- The calcium ions also activate ATP hydrolase which is hydrolises ATP to relase energy.
- The energy is used to bend the myosin heads and pull the actin filaments sideways.
- When another ATP molecule binds to the myosin head the actinmyosin bridge breaks and the myosin head attaches to the actin filament on the next binding site.
- This continues which causes the sarcomeres to shorten and the muscle to contract.
- When stimulation stops then calcium ions are removed via active transport and placed back into the sarcoplasmic reticulum. This causes tropomyosin to once again block the myosin binding sites.
What are the three methods to produce ATP? What are their benefits and downsides?
- Aerobic respiration: oxidative phosphorylation produces a higher amount of ATP but it is only possible when there is enough oxygen present. This makes it suitable for long, low-intensity exercise.
- Anaerobic respiration: ATP can be produced during glycolysis even when there is no oxygen present. However, less ATP is produced, and the product is lactate, which leads to muscle fatigue. This makes it suitable for short, high-intensity exercise.
- Using phosphocreatine: It produces ATP very quickly and does not require the presence of oxygen. It is only suitable for short bursts of movement because the phosphocreatine runs out quickly.
How is phosphocreatine used to produce ATP?
- Creatine kinase A is used to break down phosphocreatine into creatine and a phosphate ion.
- The phosphate ions are combined with ADP in a condensation reaction catalysed by ATP synthase to form ATP.
- The creatine is removed using the excretory system.
How are slow-twitch muscle fibres adapted to their function?
They contract more slowly and for longer periods. This means they have a lot of mitochondria, which produce a lot of ATP through aerobic respiration, and that releases the energy needed for muscle contraction. They undergo little anaerobic respiration, which means they don’t produce as much lactate and don’t fatigue easily. They have a lot of capillaries which makes sure they have a high oxygen and glucose supply for respiration and the release of energy. They appear dark red in colour because of the presence of myog9blin, which binds to the oxygen.
How are fast-twitch muscle fibres adapted to their function?
They contract rapidly and for shorter periods. They produce the ATP needed for the release of energy for muscle contraction using anaerobic respiration or using phosphocreatine as it is mucus quicker. Because they mostly undergo anaerobic respiration, they have little mitochondria, capillaries and myoglobin, and anaerobic respiration requires less glucose and no oxygen. It also means that they produce a lot of lactate so they are more prone to fatigue. The lack of myoglobin makes them appear lighter in colour.
