Muscle Physiology Lecture: Lecture 4 Excitation coupling/walk along

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the overall process that transforms the nerve impulse into muscle contraction?

Muscle contraction
Neuromuscular transmission
Action potential on muscle cell
Excitation-contraction coupling (correct)

What is the function of the sarcoplasmic reticulum in muscle contraction?

To release calcium ions
To regulate muscle relaxation
To store calcium ions (correct)
To inhibit muscle contraction

What triggers the opening of the calcium channels on the sarcoplasmic reticulum membrane?

Decrease in muscle length
Action potentials in T-tubules Conformational change in voltage-sensing proteins, known as the RYR’s
Action potentials in T-tubules cause conformational change in voltage-sensing proteins, known as the DHPR’s (correct)
Increase in calcium ion concentration

What is the function of the ryanodine receptors (RyRs) in muscle contraction?

To regulate calcium ion release (C) Signup and view all the answers

What is the role of the T tubules in muscle contraction?

To transmit action potentials to the interior of the cell (A) Signup and view all the answers

What is the function of SERCA 1a in muscle contraction?

To remove calcium ions from the myofibrillar fluid (C) Signup and view all the answers

What is the 'Walk Along Theory' of muscle contraction?

A theory that explains the mechanism of muscle contraction (D) Signup and view all the answers

What is the result of the action potential on the sarcolemma?

Fast depolarization of the membrane (A) Signup and view all the answers

What is the condition necessary for muscle contraction to continue?

High calcium ion concentration (C) Signup and view all the answers

What is the energy state of myosin heads when they bind with ATP?

Low energy configuration (C) Signup and view all the answers

What is the immediate result of ATPase activity in the myosin head?

ADP and phosphate ion are kept bound to the head (C) Signup and view all the answers

What is the role of calcium in muscle contraction?

It binds to troponin, exposing myosin-binding sites (B) Signup and view all the answers

What is the result of the power stroke in muscle contraction?

The myosin head moves from a high-energy to a low-energy state (C) Signup and view all the answers

What is the function of the troponin-tropomyosin complex in muscle contraction?

It inhibits myosin-binding sites on the actin filament (B) Signup and view all the answers

What is formed when myosin heads bind to actin filaments?

Cross-bridge (C) Signup and view all the answers

What is the result of the cleavage of ATP by the myosin head?

ADP and phosphate ion are kept bound to the head (A) Signup and view all the answers

What is the source of calcium that binds to troponin?

Sarcoplasmic reticulum (B) Signup and view all the answers

What triggers the power stroke in muscle contraction?

The release of phosphate (C) Signup and view all the answers

Which of the following is NOT true regarding the SERCA 1a (calcium pump)?

More than one above (D) Signup and view all the answers

Part 1 of steps: The AP propogates down the (1). The (2) senses membrane depolarization, opening (3) on the Sarcoplasmic Reticulum. This (4) opens briefly and releases a pulse of (5)_ ions.

T-tubules, DHPR, RYR channels, RYR's, Calcium Signup and view all the answers

Part 2: Calcium diffuses into the myofilaments and binds to (1)__, Calcium causes (2) to move away from myosin binding sites.

Troponin, tropomyosin Signup and view all the answers

Part 3: Before muscle contraction begins, myosin heads bind with _. This is the energy configuration. The ATPase activity cleaves ATP to _ and causing the head to become _ and in a ____ position.

ATP, low, ADP, inorganic Phosphate, energized, cocked Signup and view all the answers

Part 4: Myosin heads bind to the binding sites creating a ____. The release of the triggers the . This goes from a energy state to a _ energy state. The myosin head bends towards the center of the ___, causing the actin to slide toward the _ line.

Cross bridge, Inorganic phosphate, power stroke, high, low, sarcomere, M Signup and view all the answers

Part 5: As the power stroke occurs, the ____ is released from the myosin head. The myosin head remains tightly bound to actin, known as the _ state. The binding of a new causes detachment of the myosin head from the ____ filament.

ADP, rigor, ATP, actin Signup and view all the answers

Match the following terms to their description

Z-disc = Ends of sarcomere Middle of the sarcomere = M-line I band = Only thin filament; light band A band = Thick and thin filament; dark band Signup and view all the answers

What are the three energy sources for muscle contraction?

Phosphocreatine (creatine phosphate), Glycolysis and Oxidative metabolism Signup and view all the answers

A muscle fiber either contracts completely or not at all, describes:

All or None Response (B) Signup and view all the answers

Study Notes

Muscle Contraction

Excitation-contraction coupling is the process that transforms a nerve impulse into muscle contraction
Action potentials on the sarcolemma spread from the motor end plate along the length of the fiber and into the cell along the transverse tubules (T tubules)

Excitation-Contraction Coupling

T tubules are associated with the sarcoplasmic reticulum (SR)
SR is composed of large chambers called terminal cisternae and long longitudinal tubules that surround the myofibrils
The action potential causes a conformational change in voltage-sensing proteins (dihydropyridine receptors – DHPRs) on the T tubule
DHPRs are mechanically coupled to the ryanodine receptors (RyRs) calcium channels on the SR membrane
Calcium channels open, allowing calcium to rapidly diffuse out of the SR and initiate muscle contraction

Calcium Regulation

A calcium pump (SERCA 1a) removes calcium ions from the myofibrillar fluid after contraction occurs
SERCA1a is a continually active calcium pump located in the walls of the SR that pumps Ca back into the SR
Muscle contraction continues as long as Ca ion concentration remains high

Walk-Along Theory of Muscle Contraction

Before muscle contraction begins, myosin heads bind with ATP (low energy configuration)
ATPase activity of the myosin head cleaves the ATP into ADP and phosphate ion
Cleavage products are kept bound to the head, which becomes energized in a “cocked position”
Forces are generated by the interaction of the cross-bridges from myosin and actin filaments
Calcium release from the SR exposes myosin-binding sites on the actin filament, allowing myosin heads to bind and form a cross-bridge
The release of phosphate triggers the POWER STROKE – a conformational change in the myosin head, which moves from a high-energy to a low-energy state

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This lecture covers the muscle contraction process, including excitation-contraction coupling, the role of T tubules, sarcoplasmic reticulum, and calcium, and the 'Walk Along Theory' of muscle contraction.