Skeletal Muscle

Question 1

What 4 things are muscles composed of?

Answer 1

• Muscle fibres (cells)
• Vascular cells
• Fibroblasts
• Satellite cells

Question 2

What is the process of a cross bridge mechanism?

Answer 2

1) Ca2+ causes tropomyosin/troponin to move away from the binding site.
2) Energized myosin cross bridge on the the thick filaments to bind to actin
3) Cross bridge binding triggers the release of ATP hydrolysis, products from myosin, producing angular movement
4) ATP bound to myosin breaking link between actin and myosin - dissociate cross bridge
5) ATP binds again - repeat

Question 3

What are the 3 muscle fibre types?

Answer 3

Type IIx
Type IIa
Type I

Question 4

What are the 3 energy systems? And how do they arise?

Answer 4

Creative Phosphate - Provides energy fast forming ATP from ADP + P, only lasts 1-2 secs
Glycolysis - Energy from glucose in the absence of o2
Oxidative Phosphorylation - Energy from glucose or fat with o2 preset

Question 5

What is Excitation-Contraction Coupling for relaxed muscle?

Answer 5

There is low calcium ions, therefore cross bridges cannot form as tropomyosin is covering the binding site

Question 6

Sliding filament process?

Answer 6

1. Energized myosin cross bridges on the thick
   filaments bind to actin
2. Cross bridge binding triggers release of ATP
   hydrolysis products from myosin, producing
   angular movement
3. ATP bound to myosin, breaking link between
   actin and myosin → cross bridge dissociate
4. ATP bound to myosin, is split, energizing the
   myosin cross bridge

Question 7

Neuromuscular junction process?

Answer 7

1. Motor neuron’s action potential arrives at
   the axon terminal which depolarizes plasma membrane
2. This opens Ca2+ channels so Ca2+ions diffuse into axon terminal and binds to proteins
3. Synaptic vesicles release acetylcholine (Ach)
4. Ach diffuses from axon terminal to motor end plate, binding to nicotinic receptors
   5.Binding of Ach opens an ion channel Na+ and K+ can pass through these channels (electrochemical gradient across plasma membrane means more Na+ moves in than K+ out)
5. local depolarization of the motor end plate
6. Muscle fibre action potential initiated
7. Propagation (end plate potential)

Question 8

Define Tension?

Answer 8

The force that a muscle exerts on the joint when it is contracting

Question 9

Define load?

Answer 9

The force exerted on a muscle by an object

Question 10

What are the different types of contractions?

Answer 10

Concentric - Shortening
Eccentric - Lengthening
Isometric - Constant length

Question 11

What are the 5 mechanisms involved in muscle fatigue?

Answer 11

1. Conduction failure
2. Lactic acid build up
3. Inhibition of Cross-bridge cycling
4. Fuel substrates
5. Central command fatigue

Question 12

What is Hypertrophy?

Answer 12

Increase in muscle fibre size due to addition of contractile proteins

Question 13

What is hyperplasia?

Answer 13

Increase number of muscle fibres

Question 14

Excitation-Contraction Coupling for a active muscle?

Answer 14

High Calcium, Calcium binds to troponin causing tropomyosin to move away from the binding site allowing actin to bind