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Questions and Answers
Questions and Answers
In rigor mortis, which of the following statements is true?
In rigor mortis, which of the following statements is true?
- The myosin heads are attached to actin.
- Cross-bridge cycling is absent.
- Muscles are inextensible (unable to be stretched out).
- ATP is depleted.
- All of the above. (correct)
Active sites on the actin become available for binding after what event?
Active sites on the actin become available for binding after what event?
- Actin binds to troponin.
- Troponin binds to tropomyosin.
- Calcium binds to tropomyosin.
- Calcium binds to troponin. (correct)
- Myosin binds to troponin.
Which of the following would cause your muscle to make an isometric contraction?
Which of the following would cause your muscle to make an isometric contraction?
- Bicep curls
- Squats
- A 1 mile run
- Wall sit (correct)
- Both B and D.
Interactions between actin and myosin filaments of the sarcomere are responsible for what?
Interactions between actin and myosin filaments of the sarcomere are responsible for what?
Which of the following become connected by myosin cross-bridges during muscle contraction?
Which of the following become connected by myosin cross-bridges during muscle contraction?
The bundle of collagen fibers at the end of a skeletal muscle that attaches the muscle to bone is called a(n):
The bundle of collagen fibers at the end of a skeletal muscle that attaches the muscle to bone is called a(n):
At rest, active sites on the actin are blocked by:
At rest, active sites on the actin are blocked by:
The repeating unit of a skeletal muscle fiber is the:
The repeating unit of a skeletal muscle fiber is the:
The cytoplasm of muscle fibers is called the:
The cytoplasm of muscle fibers is called the:
Which of the following is greater?
Which of the following is greater?
Which of the following best describes the term sarcomere?
Which of the following best describes the term sarcomere?
When calcium ion binds to the thin filament in a sarcomere, what occurs?
When calcium ion binds to the thin filament in a sarcomere, what occurs?
The contraction of a muscle exerts a pull on a bone because:
The contraction of a muscle exerts a pull on a bone because:
Since each myofibril is attached at either end of the muscle fiber, when sarcomeres shorten, the muscle fiber:
Since each myofibril is attached at either end of the muscle fiber, when sarcomeres shorten, the muscle fiber:
When a skeletal muscle fiber contracts, what happens to the Z lines?
When a skeletal muscle fiber contracts, what happens to the Z lines?
After death, muscle fibers run out of ATP. This results in a condition known as:
After death, muscle fibers run out of ATP. This results in a condition known as:
The process of cross-bridging, which occurs at an active site, involves a series of sequential-cyclic reactions that include:
The process of cross-bridging, which occurs at an active site, involves a series of sequential-cyclic reactions that include:
The detachment of the myosin heads from actin is directly triggered by:
The detachment of the myosin heads from actin is directly triggered by:
Muscles are organized in a precise way. Which of the following describes muscle organization from largest to smallest?
Muscles are organized in a precise way. Which of the following describes muscle organization from largest to smallest?
Muscles are categorized as:
Muscles are categorized as:
Which of the following are found in the structure labeled '3'?
Which of the following are found in the structure labeled '3'?
Where is the sarcolemma located in Figure 10-1?
Where is the sarcolemma located in Figure 10-1?
Where are the myosin molecules located?
Where are the myosin molecules located?
In response to action potentials (nerve signals) arriving along the muscle fiber, the sarcoplasmic reticulum releases:
In response to action potentials (nerve signals) arriving along the muscle fiber, the sarcoplasmic reticulum releases:
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Study Notes
Study Notes
Muscle Physiology Concepts
- Rigor mortis occurs post-mortem, resulting in muscle stiffness due to myosin heads being attached to actin and depletion of ATP; cross-bridge cycling ceases.
- Active sites on actin are made available for myosin binding when calcium binds to troponin, facilitating muscle contraction.
- Isometric contraction, characterized by no change in muscle length while maintaining tension, is exemplified by wall sits.
Muscle Structure and Function
- Muscle contraction's fundamental mechanism is the interaction between actin and myosin filaments, contributing to the striped appearance of skeletal muscle.
- Myosin cross-bridges connect thin (actin) and thick (myosin) filaments during contraction, enabling force generation.
- Tendons are collagen fiber bundles that attach skeletal muscles to bones, playing a crucial role in muscle movement.
Regulatory Mechanisms
- At rest, tropomyosin molecules block the active sites on actin, preventing muscle contraction until calcium ions signal for movement.
- Myofibrils, composed of repeating units called sarcomeres, are the contractile structures within skeletal muscle fibers.
- Sarcoplasm refers to the cytoplasm of muscle fibers, containing essential components for muscle function.
Calcium's Role in Muscle Contraction
- Muscle contraction leads to an increase in calcium ion concentration in the sarcoplasm, particularly during active contractions.
- The sarcomere is a crucial entity where thin filaments are anchored, enabling structural integrity and contraction mechanics.
- When calcium binds to tropomyosin during contraction, it shifts to expose active sites on actin, allowing myosin to interact.
Contraction Mechanics
- Contraction results in Z lines moving closer together, representing a shortening of the muscle fiber as sarcomeres contract.
- Rigor mortis is a direct consequence of ATP depletion in muscle fibers causing stiffness post-mortem.
- The cross-bridging cycle in muscle contraction consists of four sequential steps: attach, pivot, detach, and return.
Muscle Fiber Organization
- Muscle fibers (largest), myofibrils, and sarcomeres (smallest) represent a hierarchical organization critical for muscle structure and function.
- Muscles are categorized into three types: skeletal, smooth, and cardiac, each with distinct functions and characteristics.
Additional Muscle Structure Knowledge
- Muscle structure contains actin and myosin, along with tropomyosin and titin, forming complex interactions necessary for contraction.
- The sarcolemma, located at a specific structural position, is vital for maintaining the integrity and function of muscle fibers.
- Myosin molecules are present at designated locations within the muscle structure, contributing to the contraction dynamics.
Neuro-muscular Interaction
- Action potentials in muscle fibers prompt the sarcoplasmic reticulum to release calcium ions, triggering contraction and muscle movement.
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