Skeletal muscle (wk4)

Question 1

Describe the skeletal muscle structure:

Answer 1

-There are 3 types of muscle -> skeletal (has striations, multi-nuclei, voluntary control), cardiac (found in the heart, involuntary control) and smooth muscle (found in organs, involuntary control)
-Muscles are composed of many cell types;
1. Muscle fibres
2. Vascular cells
3. Fibroblasts
4. Satellite cells
-Epimysium covers the muscle fascicles

Question 2

Describe the energy systems in the body (refer to diagram 16/10)

Answer 2

-Skeletal muscle energy metabolism -> The non-overlapped areas represent specificity of metabolic function among the body’s three energy systems; the three overlapped portions represent generality
1. Creatine Phosphate (PC) – Provides energy very fast to form ATP from ADP but lasts only 1-2 seconds
2. Glycolysis – Energy from glucose in the absence of oxygen (anaerobic metabolism)
3. Oxidative phosphorylation – Energy from glucose of fat in the presence of oxygen (aerobic metabolism)
-Replenishing muscle stores of glycogen and CP, and removing lactic acid requires energy. To achieve this the muscle uses more oxygen to produce the energy needed after the exercise has finished. This is called oxygen debt.

Question 3

Describe the frequency-tension relationship:

Answer 3

-Mechanical properties of muscles -> The contraction depends on the length of the muscle. Under stretched muscles have 70% of their optimal length and have a very low % of max isometric contraction. Overstretched muscles are at 175% of their optimal length and have a moderate % of max isometric contraction. The optimal length of muscles have n 100% optimal length and have the highest % of max isometric contraction possible

Question 4

Describe the motor unity types found in the muscle and refer to the table of characteristics (16/10)

Answer 4

-Skeletal muscle energy metabolism and fibre types -> The two main types of fibres that differ in 3 characteristics;
1. Primary mechanism used to produce ATP
2. Type of motor neuron innervation
3. Type of myosin heavy chain expressed
-Type;
* IIx (2b): Fast-twitch, fast-glycolytic fibres
* IIa (2a): Intermediate fibres, fast-oxidative glycolytic fibres
* I (1): Slow-twitch, slow-oxidative fibres