9/24 Excitation-Contraction Coupling

Question 1

what is the Excitation-Contraction Coupling?

Answer 1

the process by which an electrical stimulus triggers the release of Ca by the sarcoplasmic reticulum, initiating the mechanism of muscle contraction by sarcomere shortening

Question 2

Axon

Question 3

Acetylcholine and genetic expression

Answer 3

Acetylcholinesterase breaks down Ach into choline and acetyl

Question 4

Neuromuscular Junction

-subneural clefts

Question 5

Calcium and Exocytosis

• Voltage-gated Ca channels open
• 300,000 vesicles stored per end plate
• 125 vesicles released per AP

Question 6

Synaptic Cleft

ACh is what kind of gated channel?

Answer 6

ligand gated channel

Question 7

Action Potential Transmission

Question 8

Calcium Release from SR

• Dihydropyridine (DHP) Receptors = along T-tubule
• Ryanodine (RyR) Receptors = on sarcoplasmic reticulum

Answer 8

Calcium Sequestration in SR

• ATP-dependent Ca pump moves Ca into SR
• Calsequestrin binds Ca allowing 40x more Ca to be stored

Question 9

Sarcomere

Question 10

Cross-Bridge

2 light chains and 2 heavy chains

Answer 10

Question 11

Tropomyosin and Troponin Complex

• Troponin I • Strong affinity for actin
• Troponin C • Strong affinity for Ca
• Troponin T • Strong affinity for tropomyosin

Answer 11

Calcium and Contraction

Question 12

Walk-Along/Ratchet Theory

• ATPase enzyme on myosin head cleaves ATP to ADP + P

Answer 12

Myosin Head Cocking

Question 13

Power Stroke

Question 14

Length-Tension Curve

1.8-2.2um sarcomere length produces the strongest tension

Answer 14

Force Generation

• Motor unit = all muscles innervated by a single nerve fiber
• Small, more precise muscles have more nerve fibers than larger muscles
• ~ 80-100 muscle fibers per motor unit

Question 15

Tetany = Tetany is a disorder of increased neuronal excitability usually associated with hypocalcemia.

• Summation = adding together of individual twitch contractions to increase the intensity of overall muscle contraction

• Increase number of motor units contracting simultaneously

• Increase frequency of contraction

Question 16

Rigor Mortis

• State of constant contracture
• Lasts 15-25 hours

Question 17

ATP Regeneration

Answer 17

phosphocreatine

8-10 seconds

Question 18

Glycolysis

1.3-1.6 minutes

Answer 18

Oxidative Metabolism, which is Nutrient Dependent

Question 19

Fiber Types

Question 20

Time to Fatigue

Answer 20

Training

• Strength determined by muscle size
• Endurance depends on glycogen stored prior to exercise (high-carb diet)
• Hypertrophy increases diameter, not number of fibers

1. Increased myofibrils
2. 120% increased mito enzymes
3. 60-80% more components of phosphagen systems
4. 50% increased glycogen