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Questions and Answers
Which fiber type is primarily associated with endurance athletes?
Which fiber type is primarily associated with endurance athletes?
What is the size principle in muscle recruitment?
What is the size principle in muscle recruitment?
Which indirect test can provide estimates of fiber type composition?
Which indirect test can provide estimates of fiber type composition?
What percentage of Type 1 fibers is generally found in the general population?
What percentage of Type 1 fibers is generally found in the general population?
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How do male and female training rep ranges typically differ at 90% of 1RM?
How do male and female training rep ranges typically differ at 90% of 1RM?
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Which characteristic of muscle enables it to shorten forcefully?
Which characteristic of muscle enables it to shorten forcefully?
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What is the smallest contractile unit of muscle called?
What is the smallest contractile unit of muscle called?
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What is the primary role of muscles in stabilizing joints?
What is the primary role of muscles in stabilizing joints?
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How do muscles produce heat?
How do muscles produce heat?
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What type of muscle fibers are considered the smallest functional units within a muscle?
What type of muscle fibers are considered the smallest functional units within a muscle?
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Which muscle characteristic allows for stretching beyond normal resting lengths?
Which muscle characteristic allows for stretching beyond normal resting lengths?
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Which muscle function is primarily responsible for maintaining posture against gravity?
Which muscle function is primarily responsible for maintaining posture against gravity?
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What is generated as a result of muscle contractions during shivering?
What is generated as a result of muscle contractions during shivering?
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What type of muscle is primarily responsible for voluntary movements in the human body?
What type of muscle is primarily responsible for voluntary movements in the human body?
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What is the role of the motor neuron in muscle contraction?
What is the role of the motor neuron in muscle contraction?
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Which type of muscle fibers have the highest levels of glycolytic enzymes?
Which type of muscle fibers have the highest levels of glycolytic enzymes?
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Which muscle fiber type is characterized by low force production and high resistance to fatigue?
Which muscle fiber type is characterized by low force production and high resistance to fatigue?
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What is the capillary density like in Type 2a (FOG) muscle fibers compared to Type 1 (SO) fibers?
What is the capillary density like in Type 2a (FOG) muscle fibers compared to Type 1 (SO) fibers?
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Which statement correctly describes the fiber diameter of the different muscle fiber types?
Which statement correctly describes the fiber diameter of the different muscle fiber types?
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What is the main characteristic of Type 2x (FG) muscle fibers?
What is the main characteristic of Type 2x (FG) muscle fibers?
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Which muscle fiber type is most likely to be found in muscles that require fine motor control?
Which muscle fiber type is most likely to be found in muscles that require fine motor control?
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Which of the following is true regarding the hypertrophic potential of muscle fibers?
Which of the following is true regarding the hypertrophic potential of muscle fibers?
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What type of muscle fiber is likely to have the highest stores of lipids?
What type of muscle fiber is likely to have the highest stores of lipids?
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What occurs when Ca2+ binds to troponin?
What occurs when Ca2+ binds to troponin?
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In which type of contraction does the external load remain constant?
In which type of contraction does the external load remain constant?
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Which contraction type occurs when the muscle is actively lengthening against an external force?
Which contraction type occurs when the muscle is actively lengthening against an external force?
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What happens to the rate of cross-bridge detachments during eccentric contractions according to Herzog's findings?
What happens to the rate of cross-bridge detachments during eccentric contractions according to Herzog's findings?
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What characterizes isometric contractions?
What characterizes isometric contractions?
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How does the titin protein affect eccentric contractions?
How does the titin protein affect eccentric contractions?
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In what instance would delayed onset muscle soreness (DOMS) typically occur?
In what instance would delayed onset muscle soreness (DOMS) typically occur?
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What do eccentric muscle contractions primarily involve?
What do eccentric muscle contractions primarily involve?
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What is the resting membrane potential (RMP) of a neuron?
What is the resting membrane potential (RMP) of a neuron?
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Which ion is primarily responsible for the initial depolarization during an action potential?
Which ion is primarily responsible for the initial depolarization during an action potential?
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During which phase does the neuron experience an absolute refractory period?
During which phase does the neuron experience an absolute refractory period?
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What is the threshold potential (TP) required to trigger an action potential?
What is the threshold potential (TP) required to trigger an action potential?
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What occurs during the relative refractory period?
What occurs during the relative refractory period?
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What is the primary function of synaptic vesicles at the neuromuscular junction?
What is the primary function of synaptic vesicles at the neuromuscular junction?
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Which ion primarily exits the neuron during the repolarization phase of an action potential?
Which ion primarily exits the neuron during the repolarization phase of an action potential?
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What does the all-or-none theory of action potentials state?
What does the all-or-none theory of action potentials state?
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What kind of neuron controls voluntary muscle contractions?
What kind of neuron controls voluntary muscle contractions?
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What is the main role of the Na/K pump during action potentials?
What is the main role of the Na/K pump during action potentials?
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Study Notes
Neuromuscular Physiology
- Neuromuscular physiology is the study of how muscles and nerves work together to produce movement.
- Muscles are important for movement, posture, and heat production.
Skeletal Muscle Structure
- Three types of muscle in the human body: skeletal, smooth, and cardiac.
- The two main types of skeletal muscle are fast and slow twitch
- The lowest contractile unit of muscle is a sarcomere.
Muscle Characteristics
- Excitable: Motor neurons use action potentials to stimulate contraction.
- Contractile: Muscles forcibly shorten due to changes in membrane potential.
- Extensible: Muscles stretch beyond their normal resting point.
- Elastic: Stretched muscle can retract back to normal/resting point.
Muscle Functions
- Producing Movement: Movement depends on certain muscles contracting together.
- Posture: Maintaining posture against gravity requires muscles to stay stable.
- Stabilize Joints: Muscles wrap around joints to create stability.
- Produce Heat: Cellular respiration produces heat, and shivering (quivering contractions) generates more heat.
Skeletal Muscle Anatomy
- Tendon: Connects muscle to bone.
- Epimysium: Dense irregular connective tissue surrounding the whole muscle.
- Perimysium: Dense irregular connective tissue surrounding fascicles (bundles of muscle fibers).
- Endomysium: Thin layer of connective tissue around individual muscle fibers (cells).
- Fascicle: Bundle of muscle fibers.
- Muscle fiber (cell): Individual muscle cell.
- Myofibril: Strand within a muscle fiber, containing sarcomeres.
- Sarcomere: Basic functional unit of muscle contraction.
- I Band: Light band, contains only thin filaments.
- A Band: Dark band, contains both thick and thin filaments.
- Z Disc: Boundary between adjacent sarcomeres.
- M Line: Middle of the sarcomere, connecting thick filaments.
- H Zone: Part of the A band, contains only thick filaments.
- Thin filament (actin): Thin protein filaments in the sarcomere.
-
Thick filament (myosin): Thick protein filaments in the sarcomere.
- Myosin head: Part of the myosin molecule involved in binding to actin.
- ATP binding site: on myosin head.
- Sarcoplasmic reticulum (SR): Stores calcium ions.
- Mitochondria: Provide energy for muscle contraction.
- Sarcolemma: Muscle cell membrane.
- T Tubules: Infoldings of the sarcolemma that allow action potentials to reach the SR.
- Triad: Structure formed by a T tubule and two terminal cisterns.
Motor Unit and Fiber Types
- Motor unit: A motor neuron and the muscle fibers it innervates. The smallest functional unit in muscle.
- Three types of motor units (and thus muscle fibers):
- Type 1 (SO): Slow oxidative, long-distance running
- Type 2a (FOG): Fast oxidative-glycolytic, middle-distance running
- Type 2x (FG): Fast glycolytic, sprinting
- Characteristics that distinguish fiber types: contraction velocity, relaxation time, force production, fatigability, and stores/enzymes.
Fiber to Motor Unit Ratio
- Low ratio in slow oxidative (SO) fibers indicates fine motor control (e.g., eye muscles).
- Higher ratio in fast glycolytic (FG) and fast oxidative-glycolytic (FOG) fibers indicates gross motor control (e.g., leg muscles).
Age of Miss America and Murders
- This example shows a spurious correlation, not a cause-and-effect relationship.
How to Determine Fiber Type
- Direct: Muscle biopsy and staining.
- Indirect: Various exercise tests (e.g., Wingate test, Fatigue Index).
Sex Differences in Fiber Types
- Females generally have a greater proportion of type 1 (slow oxidative) fibers compared to males.
Action Potential: All or None Theory
- Action potential: a rapid change in membrane potential.
- All or none principle: an action potential either occurs fully or does not happen at all.
Action Potential: Ion Flow
- Depolarization: Na+ influx
- Repolarization: K+ efflux
- Hyperpolarization: K+ continues to leave the cell
- Na+/K+ Pump: Potassium and sodium ions are actively pumped to their initial positions
Excitation-Contraction Coupling
- AP enters muscle through t-tubules
- Calcium is released from SR
- Troponin moves tropomyosin, exposes actin active sites
- Myosin binds strongly to actin
- power stroke, filaments slide.
- Calcium levels return to normal in the SR, so contraction stops
Neuromuscular Junction
- Synaptic vesicle release acetylcholine (ACh)
- ACh binds to receptors
- Triggers skeletal muscle contraction through a cascade of intracellular events
Types of Muscle Contraction
-
Isotonic: External load stays the same.
- Concentric: Muscle shortens during contraction
- Eccentric: Muscle lengthens during contraction
- Isometric: Position stays the same.
- Isokinetic: Speed of contraction stays the same.
Force-Velocity Curve
- The ability to generate force is related to the velocity of muscle contraction.
Length-Tension Relationship
- Muscle force production is influenced by muscle length.
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Test your knowledge on exercise physiology concepts including muscle fiber types, recruitment principles, and gender differences in training. Challenge yourself with questions about endurance athletes and fiber composition. Ideal for students and fitness enthusiasts alike!
