Muscles

Question 1

What are the names of the two groups of muscle tissue? Which types do they contain?

Answer 1

Striated - Skeletal and cardiac

Smooth - smooth muscle

Question 2

What is the smallest section of skeletal muscle called? What filaments are they made up of? Which is thick and which is thin?

Answer 2

Sarcomeres
Made up of actin and myosin
Myosin is thick, actin is thin

Question 3

Where is the calcium binding site located on an actin filament?

Answer 3

Troponin

Question 4

List the steps of muscle contraction

Answer 4

• Rigor state - myosin and actin bound
• ATP binds to myosin to break bond to actin
• ATP hydrolysis - myosin-actin crossbridge formed
• Calcium presented, phosphate is released, power stroke happens
• ADP is released

Question 5

What is excitation-contraction coupling?

Answer 5

The release of calcium from an action potential to cause a muscle contraction

Question 6

Define tension and twitch

Answer 6

Tension - amount of force a muscle fibre generates during contraction
Twitch - single contraction of a muscle fibre in response to a single action potential

Question 7

Define isometric contraction. What happens?

Answer 7

Tension without movement

Actin-myosin cross bridges are formed, but no power stroke

Question 8

What are intercalated discs made of?

Answer 8

Gap junctions and desmosomes

Question 9

How does cardiac muscle ensure prolonged beats?

Answer 9

They are auto-rhythmic and have very long action potentials

Question 10

Describe the morphology of smooth muscle cells

Answer 10

Minimal SR, no T-tubules

Actin-myosin filaments are criss-crossed

Question 11

What regulates excitation-contraction coupling in smooth muscle?

Answer 11

Calcium
Calmodulin
Myosin light-chain kinase

Question 12

What are the three ATP production pathways in muscles?

Answer 12

Creatine phosphate
Anaerobic glycolysis
Aerobic oxidative phosphorylation

Question 13

What are the two classifications of muscle fibres? What controls them?

Answer 13

Tonic muscle fibres (Smooth) - autonomic nervous system

Twitch muscle fibre - voluntary nervous control (motor neurons)

Question 14

Name the three types of twitch muscle fibres, the method of ATP production they use, and their function

Answer 14

• Slow oxidative (SO) - Aerobic catabolism - isometric, small/slow movements
• Fast glycolytic (FG) - Anaerobic glycolysis - burst exercise
• Fast oxidative glycolytic (FOG) - aerobic catabolism OR anaerobic glycolysis - long, sustained movements

Question 15

What are the two types of muscle in fish, and what are their functions

Answer 15

Red muscle - slow twitch - aerobic

White muscle - fast twitch - anaerobic

Question 16

Define: multi-terminal, mono-neuronal and motor units

Answer 16

multi-terminal - motor neurons innervate more than one muscle fibre

Mono-neuronal - each muscle fibre is only innervated by a single neuron

Moto units - motor neuron and all the fibres it innervates