Muscle Physiology- Pt 4 Quiz

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Questions and Answers

What is the energy configuration of the myosin head when it is bound to ATP?

Low energy configuration (correct)

Variable energy configuration

High energy configuration

Neutral energy configuration

What is the result of calcium binding to troponin?

The actin binding site is closed

The myosin head is in a low energy configuration

The actin binding site is opened (correct)

The myosin head is in a high energy configuration

What is the role of SERCA1a in excitation-contraction coupling?

To transmit nerve impulses to the muscle fiber

To release calcium ions from the sarcoplasmic reticulum

To generate muscle contraction

To pump calcium ions back into the sarcoplasmic reticulum (correct)

What is the outcome of the myosin head cleaving ATP into ADP + P?

The myosin head is in a high energy configuration (A) Signup and view all the answers

Which term correctly describes the overall process which transforms a nerve impulse into a muscle contraction?

Excitation-contraction coupling (D) Signup and view all the answers

What happens to ADP after the power stroke?

ADP detaches from the myosin head (A) Signup and view all the answers

What is the term for when the myosin head moves from a high energy state to a low energy state, causing actin to be pulled closer to the M-line?

Power stroke (A) Signup and view all the answers

What is the term for when the myosin heads bend towards the center of the sarcomere?

Micro-contraction (A) Signup and view all the answers

What is the primary function of RyRs in excitation-contraction coupling?

To release calcium ions from the sarcoplasmic reticulum (B) Signup and view all the answers

What is the role of DHPR in excitation-contraction coupling?

To sense voltage changes and trigger calcium release (B) Signup and view all the answers

What is the term for when myosin is still attached to actin?

Rigor state (B) Signup and view all the answers

What is the outcome of the action potential causing a conformational change in the DHPR?

The RyRs calcium channels open (D) Signup and view all the answers

What is the name of the theory that describes actin-myosin binding for muscle contractions?

Walk along theory (C) Signup and view all the answers

Which is the correct order of events, in regards to excitation-contraction coupling?

AP scatters across sarcolemma, AP travels through T-Tubule, DHPR conformational change, RyRs calcium release, Muscle contraction (A) Signup and view all the answers

What is the primary function of the sarcoplasmic reticulum?

To store calcium ions (A) Signup and view all the answers

Which is the correct order of events, in regards to the "walk along theory"?

Cross bridge, power stroke, micro-contraction, rigor state (B) Signup and view all the answers

Study Notes

Excitation-Contraction Coupling: General Info

Excitation-contraction coupling transforms a nerve impulse into a muscle contraction.
T-Tubules are associated with the sarcoplasmic reticulum, which stores calcium.
The sarcoplasmic reticulum consists of terminal cisternae and longitudinal tubules surrounding myofibrils.
DHPR (dihydropyridine receptors) are voltage-sensing proteins mechanically coupled to RyRs (ryanodine receptors).
RyRs are calcium channels on the sarcoplasmic reticulum membrane.
Muscle contraction continues as long as calcium ion concentration remains high.
SERCA1a (sarcoplasmic reticulum calcium ATPase) is a calcium pump continuously active in the sarcoplasmic reticulum walls.

Excitation-Contraction Coupling: Steps

Action potential travels from the motor end plate to the sarcolemma.
The action potential depolarizes the T-Tubule and penetrates the cell.
DHPR conformational change triggers RyRs calcium channels to open.
Calcium rapidly diffuses out of the sarcoplasmic reticulum.
Muscle contraction is initiated.
SERCA1a removes calcium ions from the myofibrillar fluid after contraction.

Walk Along Theory (of muscle contractions): General Info

Myosin head bound to ATP is in a low energy configuration.
Myosin head cleaves ATP into ADP + P, forming a "cocked position" in a high energy configuration.

Walk Along Theory (of muscle contractions): Steps

Myosin head binds to ATP, entering a low energy configuration.
Myosin head cleaves ATP, cocking into a high energy configuration.
Calcium binds to troponin, opening the actin binding site.
Myosin head binds to actin, forming the cross bridge.
Cross bridging triggers Myosin to release the phosphate group, leaving ADP attached.
Power stroke occurs, moving myosin from high to low energy state, causing actin to pull closer to the M-line (micro-contraction).
ADP detaches from myosin, leaving it in a rigor state.
ATP binds to the myosin head group.
Myosin detaches from actin.

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Description

Learn about the process of transforming nerve impulses into muscle contractions, including the role of T-tubules and sarcoplasmic reticulum in calcium storage.