DD - Skeletal Muscle

Question 1

What are the 3 muscle types?

Answer 1

Skeletal muscle- voluntary muscles we control for movement, posture and to regulate body temperature

Smooth muscle- involuntary and lines organs such as the stomach, bladder and blood vessels

Cardiac muscle- involuntary and found in the heart

Question 2

What is a sarcomere?

Answer 2

The basic unit of striated muscle tissue

• Repeats between two Z-lines

Question 3

What is the plama mebrane of the sarcolemma called?

Answer 3

Sarcoplasmic reticulum

Question 4

What happens in the sliding filament theory?

Answer 4

Thick and thin filaments slide over each other

• H-zone becomes narrower

Question 5

What is shown in the structure of Myosin?

Answer 5

• Contains an actin-binding site
• Contains a myosin ATPase site

Question 6

How are Actin filaments structured and function?

Answer 6

Contain Tropomyosin

• A protein that binds to and stabilises actin filaments in cells

1) Calcium ions bind to troponin
2) Troponin changes shape and moves tropomyosin away from the myosin binding sites
3) Myosin binds and muscle contracts

Question 7

How is Ca2+ released from the Sarcoplasmic Reticulum?

Answer 7

1. Impulse is transferred from a neuron to the sarcolemma of a muscle cell
2. The impulse travels along the sarcolemma and down the t-tubules (to the sarcoplasmic reticulum)
3. Calcium gates in the membrane open, and Ca2+ ions diffuse out of the SR
4. Ca2+ fills the binding sites in troponin molecules, tropomyosin moves away
5. Myosin head contacts actin

Question 8

What are the 4 stages of the Cross bridge cycle?

Answer 8

1. Cross bridge formation (activated head binds to actin)
2. Power Stroke (ADP released)
3. Cross bridge detachment (ATP binds and weakens link)
4. Reactivation of myosin head (ATP is hydrolysed, and the energy released reactivates the myosin head)

Question 9

What are the 3 types of skeletal muscle contraction?

Answer 9

Twitch- A single contraction and relaxation cycle produced by an action potential within the fibre

Summation- If another action potential is applied before complete relaxation of the twitch, then the next twitch will sum onto the previous

Tetanus- When the frequency of muscle action potentials increases such that the muscle contraction reaches its peak force and plateaus

Question 10

What does a motor unit consist of?

Answer 10

Consists of a neuron and all the muscle fibres connected to it

Question 11

What is the size principle in muscles?

Answer 11

Motor units will be recruited in order of size from smallest to largest depending upon the intensity