Muscles and homeostasis Flashcards
What’s the difference between slow twitch and fast twitch muscle fibres?
-Slow twitch: adapted for endurance activities e.g. marathons -Fast twitch: adapted for intense exercise e.g. sprinting
Compare slow twitch fibres in calf muscles to fats twitch muscles found in biceps, in terms of structure and general properties:
-ST muscles found in calf muscles, have a high concentration of myoglobin, lots of mitochondria and a rich supply of blood. WHEREAS, FT are thicker, have more myosin and a high storage of glycogen and phosphocreatine. -ST contract slowly and respire aerobically for long periods of time WHEREAS FT contract faster in short bursts.
Describe the sliding filament theory
1) Action potentials travels to muscle fibres and depolarises the sarcolemma via T tubules, causing the release of calcium ions from the sarcoplasmic reticulum.
2) Calcium ions bind to tropomyosin molecules and cause them to move, exposing the mysosin binding site on the actin filament.
3) Actin-myosin cross bridge formed upon attachment
4) ATP is hydrolysed by ATPase to detach the myosin head, allowing reattachment at a further site. The sarcomere shortens, causing the muscle contraction.
5) When the impulse stops, calcium ions are actively transported back into the sarcoplasmic reticulum.
6) This allows tropomyosin to block the actin filament from binding to myosin, so muscle contraction stops.
What is the role of phosphocreatine in muscle contraction?
- Phosphocreatine regenerates ATP by adding phosphate (Pi) to ADP, which is released upon muscle contraction
- Important because muscles require a high concentration of ATP and sometimes, aerobic respiration can’t produce enough ATP to meet this demand.
How would you describe muscle tissue in 4 characteristics?
-It is excitable, contractile, extensible & elastic. • -This means it reacts to a stimulus, contracts and applies force, stretches and returns to its original length!
Where is CARDIAC, SMOOTH AND SKELETAL muscle found? Function?
• Cardiac muscle is found in the heart • Smooth muscle is usually involuntary and is found in tube like structures (eg bronchioles , SI) lining the bladder etc • Skeletal muscle is voluntary and creates movement about a joint
How do skeletal muscles act to create movement?
-Skeletal muscles act in antagonistic pairs against an incompressible skeleton to create movement
. -Antagonistic muscles are a pair muscles called antagonists and agonists, where as one contracts the other relaxes
-Tendons attach to skeletal muscles and these muscles work in a pair to move the bones.
What are agonists BS antagonists?
-Antagonists are the muscles that relax and which muscle is the antagionist varies depending on the movement. -For example, when you bend your arm, your tricep muscle relaxes so that’s the antagonist and when you straighten your arm, these tricep muscles contract and so are now agonist. -Vice versa for agonists
Describe the role of ATP in muscle contraction? (4 marks)
- ATP binds to myosin - Causes head to detach from actin -ATP hydrolysed to ATP + Pi -Energy released is used to reposition the mysoin head - Cross bridge cycle can then be repeated.
Using your knowledge of ATP, explain why rigor mortis causes the muscles to stiffen? (2 marks)
– no ATP is produced - ATP is required to break down the actin-myosin bridges
How is the structure of actin and myosin adapted for their functions? (2 marks)
Myosin –globular heads/binding sites for actin and ATP Actin – binding sites for myosin heads
i) What is the role of tropomyosin in muscle contraction? (3 marks)
– tropomyosin blocks the actin-myosin binding sites - prevents muscle contraction during rest period - Displaced in presence of calcium ions.
Calcium ions trigger muscle contraction. Explain the role of calcium ions in this process. (6 marks)
) – The action potential depolarises the sarcolemma - depolarisation spreads down the T-tubules to the sarcoplasmic reticulum -Calcium ions are released - Calcium ions cause tropomyosin to move out of the actin-myosin binding site -Myosin head binds to actin filament to form an actin- myosin cross bridge - ATPase activated by Ca2+
Why do muscle cells contain a large quantity of mitochondria? (2 mark)
Mitochondria produce ATP which is required for muscle contraction
A – T-tubules B - Sarcolemma C – Myofibril
