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Questions and Answers
Questions and Answers
What triggers the release of Ca2+ from the sarcoplasmic reticulum (SR) during muscle contraction?
What triggers the release of Ca2+ from the sarcoplasmic reticulum (SR) during muscle contraction?
- Movement of the troponin-tropomyosin complex
- Acetylcholine (ACh) binding to receptors on the muscle motor end plate
- Opening of voltage-gated calcium channels
- Na+ influx into the muscle cell (correct)
During relaxation, which of the following is responsible for breaking down acetylcholine (ACh) in the synaptic cleft?
During relaxation, which of the following is responsible for breaking down acetylcholine (ACh) in the synaptic cleft?
- Ca2+ release channels closing
- Opening of Na+ channels
- Active transport pumps for Ca2+ back into SR (correct)
- Acetylcholinesterase (AChE)
What is the main cause of rigor mortis that occurs after death in skeletal muscles?
What is the main cause of rigor mortis that occurs after death in skeletal muscles?
- Cross bridges detaching from actin
- Leakage of Ca2+ ions from the sarcoplasmic reticulum (SR)
- Enzymes digesting decomposing cells
- Continued ATP synthesis (correct)
What is the role of troponin during muscle contraction?
What is the role of troponin during muscle contraction?
What process triggers muscle action potential that spreads over sarcolemma and down into the transverse tubules?
What process triggers muscle action potential that spreads over sarcolemma and down into the transverse tubules?
What leads to the shortening and generation of force in a muscle cell during contraction?
What leads to the shortening and generation of force in a muscle cell during contraction?
What is the initial event that triggers the release of acetylcholine (ACh) into the synaptic cleft?
What is the initial event that triggers the release of acetylcholine (ACh) into the synaptic cleft?
What causes the inside of the muscle cell to become positive, leading to the triggering of a muscle action potential?
What causes the inside of the muscle cell to become positive, leading to the triggering of a muscle action potential?
What is the role of troponin when calcium binds to it in muscle contraction?
What is the role of troponin when calcium binds to it in muscle contraction?
What leads to the reorientation of myosin heads during muscle contraction?
What leads to the reorientation of myosin heads during muscle contraction?
What event marks the end of a muscle action potential and the beginning of muscle relaxation?
What event marks the end of a muscle action potential and the beginning of muscle relaxation?
What is responsible for moving tropomyosin to cover actin's binding sites during muscle relaxation?
What is responsible for moving tropomyosin to cover actin's binding sites during muscle relaxation?
What is the correct definition of 'Extension' in terms of joint motions?
What is the correct definition of 'Extension' in terms of joint motions?
Which movement involves the action of 'Circumduction'?
Which movement involves the action of 'Circumduction'?
What characterizes 'Smooth Muscle' tissue?
What characterizes 'Smooth Muscle' tissue?
Which muscle action involves 'Upward Rotation'?
Which muscle action involves 'Upward Rotation'?
In relation to joint movements, what does 'Adduction' involve?
In relation to joint movements, what does 'Adduction' involve?
What does 'Endomysium' refer to in muscle composition and structure?
What does 'Endomysium' refer to in muscle composition and structure?
'Hyperplasia' is best described as:
'Hyperplasia' is best described as:
'Excitability' in muscle tissue refers to:
'Excitability' in muscle tissue refers to:
'Radial Flexion or Deviation (ABD)' involves:
'Radial Flexion or Deviation (ABD)' involves:
'Negative Feedback' mechanism serves to:
'Negative Feedback' mechanism serves to:
Which type of skeletal muscle fiber is characterized by being red in color and having lots of mitochondria, myoglobin, and blood vessels?
Which type of skeletal muscle fiber is characterized by being red in color and having lots of mitochondria, myoglobin, and blood vessels?
Which type of skeletal muscle fiber is designed for anaerobic movements for short durations and is characterized by being white in color with few mitochondria and blood vessels?
Which type of skeletal muscle fiber is designed for anaerobic movements for short durations and is characterized by being white in color with few mitochondria and blood vessels?
How is a motor unit defined in relation to skeletal muscles?
How is a motor unit defined in relation to skeletal muscles?
Which type of skeletal muscle fiber splits ATP at a very fast rate and is used for walking and intermediate intensity activities?
Which type of skeletal muscle fiber splits ATP at a very fast rate and is used for walking and intermediate intensity activities?
What characterizes Type IIb skeletal muscle fibers in terms of energy production?
What characterizes Type IIb skeletal muscle fibers in terms of energy production?
What is the main function of motor unit recruitment in muscle contractions?
What is the main function of motor unit recruitment in muscle contractions?
In muscle physiology, what does the term 'all-or-none response' refer to?
In muscle physiology, what does the term 'all-or-none response' refer to?
Why do precise movements require smaller motor units with fewer fibers?
Why do precise movements require smaller motor units with fewer fibers?
What is the purpose of muscle tone involving the involuntary contraction of a small number of motor units?
What is the purpose of muscle tone involving the involuntary contraction of a small number of motor units?
Which group of muscles provides stability and movement for the shoulder joint?
Which group of muscles provides stability and movement for the shoulder joint?
Why are forearm muscles typically categorized into anterior and posterior groups?
Why are forearm muscles typically categorized into anterior and posterior groups?
What is the primary function of bones surface markings such as processes?
What is the primary function of bones surface markings such as processes?
How do bone depressions differ from processes in terms of function?
How do bone depressions differ from processes in terms of function?
Which feature characterizes the upper extremity anatomy in terms of bones?
Which feature characterizes the upper extremity anatomy in terms of bones?
What is the primary role of the hand muscles responsible for thumb movements?
What is the primary role of the hand muscles responsible for thumb movements?
Questions and Answers
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Study Notes
Study Notes
Muscle Contraction Mechanisms
- Ca2+ release from the sarcoplasmic reticulum (SR) is triggered by an action potential reaching the T-tubules.
- Troponin's role involves binding calcium ions, leading to a conformational change that allows actin-myosin interaction during contraction.
- The movement of tropomyosin over actin sites is responsible for muscle relaxation.
Acetylcholine Dynamics
- Acetylcholine (ACh) is broken down by acetylcholinesterase in the synaptic cleft during relaxation.
- The release of ACh into the synaptic cleft is initiated by the influx of calcium ions from the presynaptic terminal.
Rigor Mortis
- Rigor mortis occurs postmortem due to the depletion of ATP, which prevents myosin release from actin filaments.
Muscle Action Potential
- A muscle action potential spreads across the sarcolemma and into T-tubules via depolarization caused by sodium ion influx.
- When the inside of the muscle cell becomes positive due to sodium influx, this triggers the muscle action potential.
Muscle Contraction and Force Generation
- Shortening and force generation in muscle cells occur through the sliding filament mechanism where myosin heads pull actin filaments toward the center of the sarcomere.
- Myosin head reorientation during contraction is facilitated by ATP hydrolysis.
Joint Movement Terminology
- 'Extension' refers to the straightening motion at a joint, increasing the angle between body parts.
- 'Circumduction' involves a circular movement at a joint, combining flexion, extension, adduction, and abduction.
- 'Adduction' involves moving a body part toward the midline of the body.
Muscle Tissue Characteristics
- Smooth muscle tissue is characterized by being involuntary, non-striated, and capable of sustained contractions.
- Skeletal muscle fibers with red color and high myoglobin content are classified as slow-twitch type I fibers, suited for endurance.
- Fast-twitch type IIb fibers, white in color, are optimized for anaerobic activities and short-duration power.
Muscle Structure and Recruitment
- Endomysium refers to the connective tissue surrounding individual muscle fibers.
- A motor unit consists of a motor neuron and all the muscle fibers it innervates, coordinating muscle contraction.
- Motor unit recruitment enhances the strength of contractions by activating a greater number of muscle fibers.
Muscle Responses and Precision
- The 'all-or-none response' means that a muscle fiber contracts fully or not at all when stimulated.
- Precise movements are achieved with smaller motor units containing fewer muscle fibers, allowing for finer control.
Additional Muscle Functions
- Muscle tone maintains posture through the involuntary contraction of some motor units at all times.
- The shoulder joint stability and movement is provided by rotator cuff muscles.
Anatomic Considerations
- Forearm muscles are categorized into anterior and posterior groups depending on their respective actions.
- Bones have surface markings like processes that serve as attachment points for muscles and ligaments.
Upper Extremity Anatomy
- The upper extremity is characterized by a complex arrangement of bones, optimizing mobility and stability.
- Hand muscles responsible for thumb movements primarily facilitate opposition, enhancing grip and dexterity.
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