Excitatory Contractile Coupling Flashcards
What is excitation contraction coupling?
The process by which an electrical stimulus triggers the release of calcium by the sarcoplasmic reticulum, initiating the mechanism of muscle contraction by sarcomere shortening
What is anterograde transport?
Towards the axon terminal
What is retrograde transport?
Towards the cell body
How many vesicles per release of AP?
125 vesicles
What is the purpose of the subneural clefts?
Increase the surface area at the synaptic cleft in order to receive more signals from the axon terminus
What happens once acetylecholine binds to ligand gated sodium channels?
Sodium rushes in and creates a potential difference, which will open voltage gated sodium channels, allowing more sodium to enter and create an action potential down sarcolemma
How does the DHP receptor get triggered? What does the DHP receptor do?
An action potential goes down the t-tubule and causes a conformational change in the DHP receptor
It then causes change in ryanidine receptor and opens sacroplasmic reticulum; all calcium rushes out into sarcoplasm
What does calcium ATPase do?
Pumps calcium back into the SR
What does calsequestrin do?
Binds calcium to hold more of it in the SR
What does troponin T do?
Binds tropomyosin; part of the troponin complex
What does troponin I do?
Binds actin; a part of the troponin complex
What does troponin C do?
Binds calcium; part of the troponin complex
Steps of ratchet theory
ATP binds myosin head
ATP dissociates to ADP and Pi
That potential energy creates cocking mechanism on myosin head
Myosin binds to the active site because its near and has a high affinity for it to bind
Inorganic phosphate will leave and that energy is used to create the powerstroke
The powerstroke is the pulling of actin towards the M line
To release, an ATP will come in and exchange for ADP. Releases actin to get it back into its resting position
What does length tension curve show?
The relationship between sarcomere length and relative tension
When is relative tension the highest?
When sarcomere length is between 2 and 2.5 micrometers
This is the perfect tension; all of the myosin heads are attached to actin and there is the right amount of overlap
What is a motor unit?
All the muscles innervated by a single nerve fiber
How do small muscles compare to larger muscles?
Small muscles have more nerve fibers for more precise movements
What is summation and what does it lead to?
Adding together all individual twitch contractions to increase intensity of overall muscles contraction; increase number of motor units contracting simultaneously; increases the frequency of contraction
It leads to tetanization (can’t recover from contraction and so they stay contracted)
What is rigor mortis?
A state of contracture; lasts 15-25 hours
Because the myosin heads stay in a cocked state because there is no new ATP to displace the ADP
What is phosphocreatine?
A molecule that is abundant in the muscles which gives a phosphate to ADP to make ATP. Creation of ATP will allow for muscle contraction
It only lasts for about 8-10 more seconds
When does glycolysis begin for muscle contraction?
After the phosphocreatine reserves are depleted
It will add another 1.3 -1.6 minutes
What does strength training increase?
Increases myofibrils; the diameter of muscles, not the number of fibers.
More sarcomeres per muscle fiber.
