Module 6 - Skeletal Muscles

Question 1

What is an antagonist pair?

Answer 1

This is when 2 muscles work together. This occurs when one muscle contracts and the other one relaxes.

Question 2

How does the skeleton facilitate muscle contraction?

Answer 2

They are incompressible and so they act as levers for something to pull against

Question 3

What is the correct order, from largest to smallest, of the structures of a skeletal muscle?

Answer 3

Muscle bundle, Muscle fibre, microfibrils, sarcomere.

Question 4

What is the sarcoplasm and the sarcoplasmic reticulum?

Answer 4

Sarcoplasmic reticulum is a network of internal membrane that runs through the sarcoplasm. The calcium ions are stored here.

Question 5

What are two types of proteins that myofibrils are made up of?

Answer 5

Myosin and Actin

Question 6

Which protein is thick and thin in the myofirbils?

Answer 6

Actin = Thin
Myosin = Thick

Question 7

What does each zone/band in the sarcomere contain?

Answer 7

A band = Actin and Myosin overlapping
I = Only Actin
H-Zone = Only Myosin
M-Line = The centre of the Myosin
Z-Line = The start and end of the sarcomere

Question 8

What is the sliding filament theory?

Answer 8

This is when myosin and actin filaments slide over one another allowing he muscle to contract when an action potential reaches the sarcomere.

Question 9

What does the protein tropomyosin do?

Answer 9

Tropomyosin is a protein that blocks the actin-myosin binding sites. These are only moved when calcium ions are present

Question 10

What is an actomyosin bridge?

Answer 10

This is the bond between the actin and myosin heads

Question 11

Explain the first stage of actinmyosin bridge formation from the movement of trophomyosin?

Answer 11

When an action potential reaches the sarcomere, an action potential causes the release of calcium ions. Calcium ions bind to tropomyosin causing it to change shape and move, exposing the binding site

Question 12

Explain the second stage of actinmyosin bridge formation when ATPase is used?

Answer 12

The calcium ions that are present active ATPase to hydrolase ATP into ADP and Pi to provide energy for muscle contraction. Another molecule of ATP is broken down to provide energy to break the actinmyosin bridge.

Question 13

Explain the third stage of actinmyosin bridge formation when the cycle repeats

Answer 13

After the myosin head detaches from the actin filament, the bond is repeated again and the actin is pulled further along

Question 14

What happens once excitation stops?

Answer 14

Calcium ions leave their binding site and are moved by active transport back into the sarcoplasmic reticulum.
Tropomyosin moves back and blocks the binding site again.

Question 15

Why is ATP important for muscle contraction?

Answer 15

In times where aerobic respiration cannot facilitate muscle contraction, anaerobic respiration will assist ATP production

Question 16

What is the ATP-phosphocreatine system?

Answer 16

When anaerobic respiration is used to provide short bursts of energy for muscle contraction, phosphocreatine , which is stored in calls, will assist the phosphorylation of ATP from ADP.

Question 17

What are 3 main differences between slow and fast twitch muscle fibres?

Answer 17

• Slow contract, Fast contract
• Slow= used for posture, fast= used for movement
• Slow=good for endurance, fast=good for short bursts
• slow= energy released slowly during aerobic respiration, fast= energy released quickly through anaerobic respiration using glycogen.