Muscle Contraction Cycle Flashcards

Questions and Answers

Once the muscle cell has been excited it will ______________.

contract

A muscle action potential will trigger a release of __________ into the sarcoplasm.

ca2+

What do the calcium ions bond?

The calcium ions bond to regulatory proteins and trigger a contraction.

A single nervous signal releases calcium ions in the ____________ to initiate the contraction cycle.

sarcoplasm Signup and view all the answers

List the 4 steps of the contraction cycle.

<ol> <li>ATP Hydrolysis, 2. Cross bridge attachment, 3. Power stroke, 4. Cross bridge detachment.</li> </ol> Signup and view all the answers

What happens during Step 1: ATP Hydrolysis?

ATP provides the energy to myosin molecules back into the energized configuration necessary to perform the power stroke. Signup and view all the answers

What occurs during Step 2: Cross Bridge Attachment?

Myosin temporarily binds to Actin. Signup and view all the answers

Describe Step 3: Power Stroke.

When the phosphate is released, the myosin filament moves the centre of the sarcomere and ADP is released. Signup and view all the answers

What happens during Step 4: Cross Bridge Detachment?

Binding of ATP to myosin cross bridge detaches myosin from actin. Signup and view all the answers

The contraction cycle will repeat so long as ______________.

the myosin ATPase hydrolyzes the newly bound molecule of ATP. Signup and view all the answers

The contraction will continue so long as ______________.

ATP is available and the calcium ions level near the thin filament is sufficiently high. Signup and view all the answers

What happens during maximum muscle contraction?

During maximum muscle contraction, the distance between the 2 Z discs can decrease to half of the resting length. Signup and view all the answers

Study Notes

Muscle Contraction Cycle Overview

Muscle contraction initiates once the muscle cell is excited and ready to contract.
A muscle action potential triggers the release of calcium ions (Ca2+) into the sarcoplasm, essential for contraction.

Role of Calcium Ions

Calcium ions bind to regulatory proteins in muscle fibers, initiating the contraction process.
Calcium release occurs in the sarcoplasm as a response to a single nervous signal, acting as a trigger for the contraction cycle.

Contraction Cycle Steps

The contraction cycle consists of four key steps:
- ATP Hydrolysis
- Cross Bridge Attachment
- Power Stroke
- Cross Bridge Detachment

Step 1: ATP Hydrolysis

ATP (adenosine triphosphate) energizes myosin molecules, enabling them to perform power strokes necessary for contraction.

Step 2: Cross Bridge Attachment

Myosin heads temporarily attach to actin filaments, forming cross bridges essential for muscle contraction.

Step 3: Power Stroke

Myosin filaments pull the actin filaments during the power stroke after phosphate is released, sliding the filaments and causing contraction. ADP is also released during this phase.

Step 4: Cross Bridge Detachment

The binding of a new ATP molecule to the myosin cross bridge results in detachment from actin, allowing the cycle to repeat.

Contraction Cycle Continuity

The contraction cycle continues as long as myosin ATPase can hydrolyze newly attached ATP molecules.

Conditions for Continued Contraction

Sustained contraction is dependent on the availability of ATP and high calcium ion levels near thin filaments.

Maximum Contraction

During maximum muscle contraction, the distance between Z discs can reduce to half their resting length, indicating a fully contracted state.

Description

Test your knowledge on the muscle contraction cycle with these flashcards. Each card covers key concepts such as muscle cell excitation, calcium ion release, and regulatory proteins that trigger contractions. Perfect for students studying muscle physiology!