MS 2 Companion Questions

Learning Objectives

Know the banding patterns
- A = Thick
- I = Not thick
- I shortens with contraction
- Z disc is connected to sheaths
Know the sheaths - connective tissues surround muscle fiber that join together
- endomysium - surrounding cells
- perimysium - surrounds fascicle (bundle of fibers) - endomysium connects to perimysium
- epimysiusm - surrounds muscle group - perimysium connects to epimysium and is continuous with tendon
Know the types of contraction
- Isometric = same lengths
- Isotonic = same force
  - (isotonic) concentric = becomes shorter
  - (isotonic) eccentric = becomes larger
Know important cells structures and what they do
- glycosomes : organelle that stores glycogen for energy
- myoglobin : protein that binds oxygen (stronger than hemoglobin)
Know the 4 factors affecting variation in tension (contraction force)
- Muscle Type
  - Type I = slow oxidative (weak but high endurance)
  - Type IIa = fast oxidation
  - Type IIb = fast glycolytic (strongest but least endurance)
    - glycolytic meaning under prolonged (over 15sec) exercise conditions
- Stretch
  - intermediate is optimal
- AP Frequency / Calcium concentration
  - twitch = 1AP
  - Incomplete Tetanus = multiple APs
  - Complete Tetanus = maximal
- Motor Unit recruitment (# of fibers used)
Know the sources of Energy
1. ATP
2. CP
3. Glucose
  - glycolysis: anaerobic produces little
    - if no O₂leads to lactic acid production
  - oxidative: aerobic (needs O₂) produces a lot
4. Glycogen
5. Blood Glucose
Know what fatigue and oxygen debt are
- caused mostly by ionic imbalance (though low ATP also involved)
- oxygen debt used to desribe fatigue and the oxygen your body needs to make ATP to:
  - restore ATP levels
  - Restore CP levels
  - Convert Lactic acid back to glucose
  - To make more ATP to pump ions back where they belong
Know that energy conversion is inefficient and loses about 60% as heat
Understand Motor units = neuron and the muscle fibers it controls
- small (ex: finger) more precise but requires more neurons
- large (ex: legts) less precise but requires fewer neurons

Smooth Muscle

Know location
- hollow organs - blood vessels, GI tract, glands
Know factors that make them never tire
- slow myosin
- more efficient
- fewer sarcomeres, so less ATP usage
know that they are individual cells rather than fused cells like skeletal muscle fibers are
Know the organization of sarcomeres is criss-crossed leading to corkscrew motion of contraction
- contraction = shorter and fatter
Know that nervous stimulation is through varicosities that activate larges sheets of cells (unlike motor units of skeletal fibers)
Know that there is less variation of contraction force (for example due to the varicosity mode of activation)
- many also have GAP junctions
Know that many tubes have 2 layers of smooth muscle: Circular & longitudinal
Know that Peristalsis (propelling of substances inside tube) is caused by the alternating contractions of the circular & longitudinal layers.

Banding Patterns, Types of Contractions, Sheaths

Notes:

- Don't worry about the Bands (A & I) or the naming of the sheaths this semester (Fall 2021). Just pay attention to it. It is useful for understanding the tissue histology in lab still
- You should know cell respiration in greater detail, this video was made in a way that could be used for another course, and so was simplified here.

Factors affecting Tension

Smooth Muscle

- Notes: Don't worry too much about the content of this video this semester (fall 2021). However, again watch it as it will give insight into the layering of smooth muscle (lab) and peristalsis (digestion if we get there).