Muscles and movement Flashcards
Describe skeletal muscle
Voluntary. Attatched to the skeleton and brings about movement. It fatigues quickly.
Describe cardiac muscle
Only found in heart. Contracts without the need for external stimulation and does not fatigue
Describe smooth muscle
Lines the gut and blood vessels. It contracts slowly and does not fatigue
What are the two types of myofilament
Actin and myosin
What is a sarcomere?
Basic unit of contraction in a myofibril. The distance between two Z lines.
What is myosin?
a fibrous protein which forms (together with actin) the contractile filaments of muscle cells
describe the part played by calcium ions in muscle contraction
Changes shape of tropomysoin
Allows bridges to form
Activates myosin ATP-pase
explain how the muscle cell contracts
Myosin head changes shape
moving (actin and myosin) filaments over each other
Describe how ATP is used in muscle contraction
ATP provides energy for movement of myosin
What is the role of tropomyosin in myofibril contraction?
it moves out the way when calcium ions bind allowing myosin to bind.
What is the role of myosin in myofibril contraction?
Head of myosin binds to actin and pulls actin past myosin detaches from actin and moves further along which uses ATP
What is the benefit of high glycogen content of fast muscle fibres?
glycogen broken down gives glucose for anaerobic respiration. Glycolysis only yields 2 ATP
Why is there a high number of capillaries supplying slow muscle fibres?
Gives a high concentration of oxygen
Good glucose content with little glycogen present
Allows for a high rate of aerobic respiration
When sarcomeres contract what happens to the l band ?
it decreases
When sarcomeres contract what happens to the A band?
Stays the same
After death what causes cross bridges to remain firmly bound in a phenomenon called rigor mortis?
No respiration is occurring therefore no ATP is produced. ATP is required for separation of actin and myosin bridges and therefore they remain bound.
What causes the decrease in length of the H zone and l band?
Actin filaments slide inbetween myosin which pulls z lines closer
What is the overall rate of contraction limited by?
The splitting of ATP
In a diagram how would you be able to tell if the myofibril is contracted?
The H band would not be visible
The A band would occupy almost all of the sarcomere
Describe the role of calcium ions and ATP in the contraction of a myofibril
Calcium ions diffuse into myofibrils from
(sarcoplasmic) reticulum;
2. (Calcium ions) cause movement of tropomyosin
(on actin);
3. (This movement causes) exposure of the
binding sites on the actin;
4. Myosin heads attach to binding sites on actin;
5. Hydrolysis of ATP (on myosin heads) causes
myosin heads to bend;
6. (Bending) pulling actin molecules;
7. Attachment of a new ATP molecule to each
myosin head causes myosin heads to detach
(from actin sites)
Why do mice who produce less creatine have less muscle contraction
Unable to make phosphocreatine
Less energy therefore available for muscle contraction
