Muscles and movement

Question 1

Describe skeletal muscle

Answer 1

Voluntary. Attatched to the skeleton and brings about movement. It fatigues quickly.

Question 2

Describe cardiac muscle

Answer 2

Only found in heart. Contracts without the need for external stimulation and does not fatigue

Question 3

Describe smooth muscle

Answer 3

Lines the gut and blood vessels. It contracts slowly and does not fatigue

Question 4

What are the two types of myofilament

Answer 4

Actin and myosin

Question 5

What is a sarcomere?

Answer 5

Basic unit of contraction in a myofibril. The distance between two Z lines.

Question 6

What is myosin?

Answer 6

a fibrous protein which forms (together with actin) the contractile filaments of muscle cells

Question 7

describe the part played by calcium ions in muscle contraction

Answer 7

Changes shape of tropomysoin
Allows bridges to form
Activates myosin ATP-pase

Question 8

explain how the muscle cell contracts

Answer 8

Myosin head changes shape

moving (actin and myosin) filaments over each other

Question 9

Describe how ATP is used in muscle contraction

Answer 9

ATP provides energy for movement of myosin

Question 10

What is the role of tropomyosin in myofibril contraction?

Answer 10

it moves out the way when calcium ions bind allowing myosin to bind.

Question 11

What is the role of myosin in myofibril contraction?

Answer 11

Head of myosin binds to actin and pulls actin past myosin detaches from actin and moves further along which uses ATP

Question 12

What is the benefit of high glycogen content of fast muscle fibres?

Answer 12

glycogen broken down gives glucose for anaerobic respiration. Glycolysis only yields 2 ATP

Question 13

Why is there a high number of capillaries supplying slow muscle fibres?

Answer 13

Gives a high concentration of oxygen
Good glucose content with little glycogen present
Allows for a high rate of aerobic respiration

Question 14

When sarcomeres contract what happens to the l band ?

Answer 14

it decreases

Question 15

When sarcomeres contract what happens to the A band?

Answer 15

Stays the same

Question 16

After death what causes cross bridges to remain firmly bound in a phenomenon called rigor mortis?

Answer 16

No respiration is occurring therefore no ATP is produced. ATP is required for separation of actin and myosin bridges and therefore they remain bound.

Question 17

What causes the decrease in length of the H zone and l band?

Answer 17

Actin filaments slide inbetween myosin which pulls z lines closer

Question 18

What is the overall rate of contraction limited by?

Answer 18

The splitting of ATP

Question 19

In a diagram how would you be able to tell if the myofibril is contracted?

Answer 19

The H band would not be visible

The A band would occupy almost all of the sarcomere

Question 20

Describe the role of calcium ions and ATP in the contraction of a myofibril

Answer 20

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)

Question 21

Why do mice who produce less creatine have less muscle contraction

Answer 21

Unable to make phosphocreatine

Less energy therefore available for muscle contraction