p.18
Muscle Fiber Types and Metabolism
What changes in muscle fibers are possible with exercise?
Metabolic capacity, amount of mitochondria, number of capillaries, and size of muscle fibers.
p.17
Motor Units and Muscle Force Generation
What is the recruitment order of small motor units and why?
Small motor units are recruited first because they have the lowest threshold for firing.
p.23
Reflexes Involving Skeletal Muscle
What happens to the affected limb during the withdrawal reflex?
It undergoes flexion (withdrawal).
p.18
Muscle Fatigue and Recovery
What are the characteristics of fatigued muscles?
Decreased tension, longer contraction time, slower relaxation, and incomplete relaxation.
p.6
Types of Muscle Contractions
Why do sarcomeres shorten during isotonic concentric contractions?
Sarcomeres shorten to facilitate muscle shortening and generate force.
p.18
Muscle Fiber Types and Metabolism
What cannot be changed in muscle fibers with exercise?
Myosin ATPase type and creation of new muscle fibers in adults.
p.13
Types of Muscle Contractions
What happens to the speed of contraction as the load increases?
The speed of contraction becomes slower.
p.6
Myofibrils and Sarcomeres
Which part of the sarcomere does not change in size during muscle contraction?
The A-band does not change in size.
p.10
Muscle Fiber Types and Metabolism
What does the American Academy of Pediatrics report state about the performance benefits of creatine monohydrate supplements?
The performance benefit is small and primarily seen in short-duration, maximum-intensity resistance training, with no general benefit in aerobic activities or 'on-field' athletic performance.
p.10
Motor Units and Muscle Force Generation
What is a motor unit composed of?
A motor unit is composed of an alpha motor neuron and all of the muscle fibers it innervates.
p.10
Motor Units and Muscle Force Generation
How does the size of a motor unit affect muscle force generation?
Activation of larger or more motor units generates a greater force of contraction.
p.8
Sliding Filament Theory
How does ATP hydrolysis affect the myosin head?
Energy released from ATP hydrolysis by the myosin head provides energy for the conformational change that puts the myosin head in the high-energy form.
p.2
Neuromuscular Junction and Nerve Stimulation
What is the result of acetylcholine binding to nicotinic receptors at the motor end plate?
Depolarization of the muscle fiber.
p.16
Motor Units and Muscle Force Generation
What happens as the frequency of action potentials increases in neuron W?
Larger motor units will be recruited, starting with Y and then Z.
p.23
Reflexes Involving Skeletal Muscle
What initiates the withdrawal and crossed-extensor reflex?
Activation of nociceptors.
p.10
Muscle Fiber Types and Metabolism
What are the safety concerns regarding the use of creatine monohydrate supplements in the pediatric population?
Short-term use at usual doses appears safe in normal adults, but has not been evaluated specifically in the pediatric population. There is potential concern with the impact on kidneys due to nephrotic metabolites, and it is specifically recommended against use for those with kidney dysfunction.
p.7
Role of Calcium in Muscle Contraction
What activates the Ryanodine Ca2+ receptor/channel in the sarcoplasmic reticulum (SR)?
The activation of the Dihydropyridine (DHP) Receptor.
p.14
Motor Units and Muscle Force Generation
How does the frequency of stimuli affect tension production in muscle fibers?
The closer together the stimuli, the more fused the contractions will be, leading to greater tension production.
p.7
Role of Calcium in Muscle Contraction
What happens when calcium binds to troponin?
It facilitates muscle contraction.
p.15
Myofibrils and Sarcomeres
What happens to muscle tension if the muscle is not stretched enough or stretched too much?
Tension is reduced if the muscle is not stretched enough or if it is stretched too much.
p.22
Reflexes Involving Skeletal Muscle
What type of reflex is the Golgi Tendon Organ (GTO) Reflex?
It is a protective reflex.
p.21
Reflexes Involving Skeletal Muscle
What are the dynamic and static components of the muscle spindle reflex?
Dynamic component is immediate reflex action, and static component maintains muscle tone through constant contraction.
p.16
Motor Units and Muscle Force Generation
What characteristics does neuron Z have compared to other neurons?
Neuron Z has a larger neuron cell body and communicates with larger diameter muscle fibers, requiring more excitatory input to depolarize.
p.16
Muscle Fiber Types and Metabolism
What are the two types of skeletal muscle fibers based on speed of tension production?
Slow-twitch and fast-twitch.
p.22
Reflexes Involving Skeletal Muscle
What is the effect of the Golgi Tendon Organ Reflex on skeletal muscle contraction?
Skeletal muscle contraction is decreased (relaxation).
p.22
Reflexes Involving Skeletal Muscle
What are the components of the Golgi Tendon Organ Reflex?
The reflex has dynamic and static components.
p.12
Types of Muscle Contractions
Why is it called the 'Series' Elastic Component?
Because it is in series (in line) with the skeletal muscle cell sarcomeres.
p.12
Types of Muscle Contractions
What happens to the force of contraction until the isometric contraction becomes an isotonic contraction?
The force of contraction increases.
p.3
Structure of Skeletal Muscle Tissue
What role do T-tubules play in muscle cells?
The sarcolemma of the muscle cell penetrates the cell’s interior in structures called Transverse Tubules (T-tubules).
p.13
Types of Muscle Contractions
Why is an IM contraction occurring in this scenario?
Because the muscle is not strong enough to move the load and shorten.
p.6
Neuromuscular Junction and Nerve Stimulation
What events occur at the neuromuscular junction (NMJ)?
Events at the NMJ include the release of neurotransmitters that bind to nicotinic receptors, initiating a muscle fiber action potential.
p.17
Muscle Fiber Types and Metabolism
What type of fibers are small motor units composed of?
Small motor units are composed of slow-twitch oxidative fibers.
p.8
Sliding Filament Theory
What conformational change does myosin undergo in the sliding filament theory?
Myosin undergoes a conformational change that brings the thin filaments towards the center of the sarcomere.
p.17
Motor Units and Muscle Force Generation
What is the recruitment order of larger motor units and why?
Larger motor units are recruited last because they have the highest threshold for firing.
p.21
Reflexes Involving Skeletal Muscle
What is the stimulus for the muscle spindle reflex?
Stretch (change in muscle length).
p.21
Reflexes Involving Skeletal Muscle
What happens to the sensory fibers of the muscle spindle when the muscle stretches?
They are squeezed and their action potential frequency changes.
p.8
Sliding Filament Theory
What happens during the power stroke in the sliding filament theory?
The myosin head pulls actin towards the center of the sarcomere, shortening the sarcomere.
p.14
Motor Units and Muscle Force Generation
Why does complete tetanus produce a force 3-5 times greater than a single twitch?
Because twitches are close enough together that calcium from the first twitch is still present in the sarcoplasm when the second twitch is activated, preventing complete relaxation between stimuli.
p.16
Motor Units and Muscle Force Generation
Which motor units are activated only at lower frequencies of action potentials?
Smaller motor units, such as X.
p.15
Motor Units and Muscle Force Generation
Do muscles have varying numbers of motor units?
Yes, muscles have varying numbers of motor units.
p.4
Sliding Filament Theory
What occurs during muscle contraction at the molecular level?
Contraction occurs when the myosin head of the thick filament binds to actin on the thin filament.
p.2
Structure of Skeletal Muscle Tissue
What does the endomysium surround?
Individual muscle fibers.
p.21
Reflexes Involving Skeletal Muscle
What ensures that the muscle spindle maintains sensitivity to changes in muscle length?
The simultaneous activation of both alpha and gamma motor neurons.
p.19
Motor Units and Muscle Force Generation
What regulates Lower Motor Neuron (LMN) activity?
Excitatory and inhibitory interneurons in the spinal cord.
p.4
Myofibrils and Sarcomeres
How do myosin tails contribute to the structure of thick filaments?
The myosin tails associate with one another to produce the filament.
p.4
Myofibrils and Sarcomeres
Where are thick filaments located within the sarcomere?
Thick filaments are in the middle of the sarcomere, with myosin heads oriented in opposite directions at each end.
p.20
Reflexes Involving Skeletal Muscle
What type of sensory fiber is associated with the Golgi tendon organ?
The 1b fiber is associated with the Golgi tendon organ.
p.5
Myofibrils and Sarcomeres
Where are thin filaments anchored in a sarcomere?
Thin filaments are anchored into the Z-lines.
p.6
Myofibrils and Sarcomeres
What changes occur in the sarcomere during muscle contraction?
The Zone of Overlap increases, the I-Band decreases, and the H-Zone decreases.
p.17
Muscle Fiber Types and Metabolism
What types of muscle fibers are each motor unit within a muscle composed of?
Each motor unit within a muscle is composed of the same types of muscle fibers.
p.14
Motor Units and Muscle Force Generation
What occurs when a second stimulus is given before the contraction from the first twitch is completed?
The twitches fuse and produce more force collectively, a phenomenon called summation.
p.10
Motor Units and Muscle Force Generation
How many motor neurons innervate each muscle fiber?
Each muscle fiber is innervated by only one motor neuron.
p.14
Motor Units and Muscle Force Generation
What is the difference between incomplete tetanus and complete tetanus?
Incomplete tetanus has relaxation periods between contractions, while complete tetanus does not and results in force production 3-5 times greater than a single twitch.
p.15
Myofibrils and Sarcomeres
What is the relationship between the length of a muscle and the tension it can develop?
Muscle tension is maximized at the optimal length where actin and myosin filaments have the best overlap.
p.12
Types of Muscle Contractions
Provide an example of an isotonic concentric contraction.
Bicep curl when lifting the weight.
p.3
Myofibrils and Sarcomeres
What do myofibrils contain and how are they arranged?
Myofibrils contain myofilaments (thick and thin) that are arranged into sarcomeres.
p.3
Myofibrils and Sarcomeres
What is the functional unit of a myofibril and how is it defined?
The functional unit is the sarcomere, which runs from Z-line to Z-line.
p.12
Types of Muscle Contractions
What is the Series Elastic Component?
It does not actively generate force but transmits force passively to the ends of the muscle.
p.16
Muscle Fiber Types and Metabolism
What are the characteristics of Fast Oxidative/Glycolytic (Type IIa) muscle fibers?
They are fast-twitch and can use both oxidative and glycolytic metabolism.
p.3
Structure of Skeletal Muscle Tissue
What is the Triad in muscle cells?
The Triad is a structure formed by T-tubules close to the lateral sacs (terminal cisternae) of the Sarcoplasmic Reticulum.
p.4
Sliding Filament Theory
What enzyme activity does the myosin head contain and what is its function?
The myosin head contains an ATPase to break down ATP and release energy.
p.9
Muscle Fiber Types and Metabolism
What factors determine the contribution of aerobic and anaerobic metabolism in muscle fibers?
The metabolic enzymes present in the cell and the intensity of the exercise.
p.9
Muscle Fiber Types and Metabolism
What is the role of creatine kinase (CK) in muscle tissue?
CK levels in the blood are measured to determine if damage to muscle tissue has occurred.
p.9
Muscle Fiber Types and Metabolism
Name other protein biomarkers used to detect muscle tissue damage.
TnT, TnI, Myoglobin, and Myosin Light Chain.
p.5
Structure of Skeletal Muscle Tissue
What creates the striated appearance in skeletal and cardiac muscle?
Alternating A-bands (dark) and I-bands (light).
p.18
Muscle Fatigue and Recovery
What are some theories for muscle fatigue?
Change in membrane potential, decreased ACH, blockage of blood flow, central fatigue, increased metabolic byproducts, and depleted glycogen.
p.8
Sliding Filament Theory
What is the role of ATP in the cross-bridge cycle?
ATP binding to the myosin head breaks the cross-bridge connection between actin and myosin.
p.17
Muscle Fiber Types and Metabolism
What are the three types of muscle fibers mentioned in the text?
Type I, Type IIa, and Type IIb.
p.8
Sliding Filament Theory
What event provides energy for the power stroke in the cross-bridge cycle?
The release of inorganic phosphate from the myosin head provides energy for the power stroke.
p.12
Types of Muscle Contractions
What is the definition of an Isometric Contraction?
An isometric contraction is when the muscle generates force without changing its length.
p.12
Types of Muscle Contractions
Can you provide an example of an isometric contraction?
Holding a plank position.
p.8
Sliding Filament Theory
How many twitches can muscle cells perform with their initial ATP supply?
Muscle cells only have enough ATP for approximately 8 twitches.
p.8
Sliding Filament Theory
Why is ATP important in muscle contraction?
ATP is necessary to break the cross-bridge between actin and myosin and to provide energy for conformational changes and the power stroke.
p.21
Reflexes Involving Skeletal Muscle
What role does the gamma motor neuron play in the muscle spindle reflex?
It stimulates intrafusal fiber contraction to maintain sensitivity to changes in muscle length.
p.21
Reflexes Involving Skeletal Muscle
Why is it necessary for intrafusal fibers to contract during muscle spindle activation?
To prevent the sensory fibers from becoming slack and losing the ability to sense further changes in muscle length.
p.16
Muscle Fiber Types and Metabolism
What are the two types of skeletal muscle fibers based on metabolism?
Glycolytic and oxidative.
p.16
Muscle Fiber Types and Metabolism
What are the characteristics of Slow Oxidative (Type I) muscle fibers?
They are slow-twitch and oxidative.
p.20
Motor Units and Muscle Force Generation
What type of neuron is an Alpha Motor Neuron?
Aα (Alpha Motor Neuron) is a lower motor neuron that releases ACh and causes contraction of the extrafusal fibers.
p.20
Motor Units and Muscle Force Generation
What is the function of a Gamma Motor Neuron?
Aγ (Gamma Motor Neuron) is an efferent neuron that causes contraction of intrafusal fibers.
p.1
Neuromuscular Junction and Nerve Stimulation
What nervous system is required for skeletal muscle stimulation?
The Somatic Nervous System.
p.11
Neuromuscular Junction and Nerve Stimulation
What is the latent period in muscle contraction?
The latent period is the time between the muscle AP (action potential) and the production of muscle tension.
p.17
Muscle Fiber Types and Metabolism
What type of fibers are larger motor units composed of?
Larger motor units are composed of fast-twitch glycolytic fibers.
p.7
Neuromuscular Junction and Nerve Stimulation
What is the function of the Dihydropyridine (DHP) Receptor during excitation-contraction coupling?
DHP functions as a voltage sensor.
p.15
Myofibrils and Sarcomeres
Why is the optimal length of a muscle important for tension production?
At the optimal length, the greatest number of actin/myosin cross-bridges can form, resulting in maximal tension production.
p.2
Structure of Skeletal Muscle Tissue
What are the hierarchical structures of skeletal muscle from largest to smallest?
Whole Muscle, Muscle Fascicles, Muscle Cells (Fibers), Myofibrils, Myofilaments.
p.12
Types of Muscle Contractions
What is the definition of an Isotonic Contraction?
An isotonic contraction is when the muscle changes its length while generating force.
p.22
Reflexes Involving Skeletal Muscle
What happens when tendons stretch in response to contraction?
The GTO and afferent neurons send information to the spinal cord.
p.15
Motor Units and Muscle Force Generation
What variability exists within motor units?
Motor units vary in the number of muscle cells they communicate with, and in the diameter and strength of the muscle fibers in different motor units.
p.15
Motor Units and Muscle Force Generation
How is the recruitment of specific motor units determined?
The specific motor units recruited are based on the force needed.
p.3
Structure of Skeletal Muscle Tissue
What surrounds each myofibril?
Each myofibril is surrounded by the Sarcoplasmic Reticulum (SR).
p.16
Muscle Fiber Types and Metabolism
What are the characteristics of Fast Glycolytic (Type IIb) muscle fibers?
They are fast-twitch and glycolytic.
p.5
Role of Calcium in Muscle Contraction
What is the role of troponin in muscle contraction?
Troponin is a Ca2+ binding protein that helps retain tropomyosin’s position on actin. For a contraction to occur, Ca2+ must bind to troponin, which allows tropomyosin to move and expose the myosin binding sites on actin.
p.9
Muscle Fiber Types and Metabolism
What are the different isoforms of creatine kinase found in skeletal and cardiac muscle?
CK-MM is found in skeletal muscle, and CK-MB is found in cardiac muscle.
p.20
Reflexes Involving Skeletal Muscle
What is the function of sensory receptors in the muscle spindle?
Sensory receptors in the muscle spindle are mechano-sensitive receptors that monitor changes in muscle length.
p.11
Sliding Filament Theory
What happens during the contraction phase of muscle activity?
During the contraction phase, the muscle generates tension due to the cross-bridge cycle.
p.11
Types of Muscle Contractions
What is a twitch in muscle physiology?
A twitch is the mechanical response of a muscle fiber to a single action potential.
p.11
Neuromuscular Junction and Nerve Stimulation
When does the skeletal muscle action potential occur in relation to the mechanical response?
The skeletal muscle action potential occurs in the latent period of the mechanical response.
p.22
Reflexes Involving Skeletal Muscle
What are Golgi Tendon Organs (GTOs) sensitive to?
They are sensitive to changes in force.
p.22
Reflexes Involving Skeletal Muscle
Where are Golgi Tendon Organs located?
At the junction of tendons and muscle.
p.15
Myofibrils and Sarcomeres
What is the optimal length of a muscle?
The optimal length is where there is the best degree of overlap between the thick and thin filaments.
p.7
Neuromuscular Junction and Nerve Stimulation
What role does the arrival of an action potential (AP) play at the triad (T-tubule/SR)?
It activates the Dihydropyridine (DHP) Receptor.
p.3
Structure of Skeletal Muscle Tissue
What are the main structural components of a skeletal muscle?
Whole muscle, muscle fascicles, muscle cells (fibers), myofibrils, and myofilaments.
p.22
Reflexes Involving Skeletal Muscle
What does the stimulation of an inhibitory interneuron in the GTO Reflex lead to?
It decreases the activity of the alpha motor neuron.
p.3
Sliding Filament Theory
What happens to sarcomeres during muscle contraction?
Sarcomeres shorten because the thick filaments pull the thin filaments towards the center of the sarcomere.
p.4
Myofibrils and Sarcomeres
What are the three regions of a myosin protein?
Myosin has a head region, a hinge region, and a tail.
p.1
Structure of Skeletal Muscle Tissue
What are the characteristics of skeletal muscle cells?
Skeletal muscle cells are multinucleate, long, striated, and under voluntary control.
p.20
Reflexes Involving Skeletal Muscle
What type of sensory fiber is associated with the muscle spindle?
The 1a fiber is associated with the muscle spindle.
p.1
Neuromuscular Junction and Nerve Stimulation
What is the name of the neuron that stimulates skeletal muscles?
Alpha, Somatic, or Lower Motor Neuron (LMN).
p.5
Role of Calcium in Muscle Contraction
What are the three proteins that make up the troponin complex?
Troponin C (binds Ca2+), Troponin I (binds Actin), Troponin T (binds Tropomyosin).
p.20
Reflexes Involving Skeletal Muscle
What is the muscle spindle reflex also known as?
The muscle spindle reflex is also known as the stretch reflex or myotactic reflex.
p.5
Structure of Skeletal Muscle Tissue
What does the A-band (dark band) consist of?
The entire length of thick filaments, including the zone of overlap.
p.5
Myofibrils and Sarcomeres
What is the function of the M-line in a sarcomere?
The M-line links the central regions of thick filaments.
p.11
Role of Calcium in Muscle Contraction
What is required for skeletal muscle relaxation?
Skeletal muscle relaxation requires the removal of calcium from the cytoplasm.
p.21
Reflexes Involving Skeletal Muscle
What happens to the alpha motor neuron when afferent information enters the spinal cord?
It is activated, stimulating muscle contraction and inhibiting the alpha motor neuron of antagonistic muscles.
p.2
Structure of Skeletal Muscle Tissue
What is the function of the perimysium?
Divides the muscle into compartments called fascicles.
p.12
Types of Muscle Contractions
Provide an example of an isotonic eccentric contraction.
Lowering the weight slowly during a bicep curl.
p.4
Sliding Filament Theory
How does myosin contribute to muscle contraction?
Myosin undergoes a conformational change that brings the thin filaments towards the center of the sarcomere.
p.4
Myofibrils and Sarcomeres
How many myosin proteins make up each thick filament?
Each thick filament is made from approximately 500 individual myosin proteins.
p.19
Reflexes Involving Skeletal Muscle
How is interneuron activity regulated?
By a variety of reflex pathways and descending motor pathways.
p.19
Motor Units and Muscle Force Generation
What are the types of motor neurons mentioned?
Alpha Motor Neuron (Aα) and Gamma Motor Neuron (Aγ).
p.20
Motor Units and Muscle Force Generation
What is the role of the Alpha Motor Neuron in muscle contraction?
The Alpha Motor Neuron (Aα) is an efferent neuron that releases acetylcholine (ACh) and causes contraction of the extrafusal fibers.
p.20
Structure of Skeletal Muscle Tissue
What are extrafusal fibers?
Extrafusal fibers are skeletal muscle cells.
p.20
Structure of Skeletal Muscle Tissue
What are intrafusal fibers?
Intrafusal fibers are the muscle fibers within the muscle spindle.
p.5
Myofibrils and Sarcomeres
What is the Z-line in a sarcomere?
The Z-line is where thin filaments are anchored.
p.9
Muscle Fiber Types and Metabolism
What two types of metabolism produce ATP for muscle fibers?
Aerobic and Anaerobic metabolism.
p.1
Neuromuscular Junction and Nerve Stimulation
What is the neuromuscular junction (NMJ)?
It is the synapse where each skeletal muscle cell acts independently and synapses with one nerve terminal.
p.11
Muscle Fiber Types and Metabolism
How does the time frame for a twitch vary?
The time frame for a twitch varies based on the type of muscle fiber, such as fast-twitch versus slow-twitch fibers.
p.11
Role of Calcium in Muscle Contraction
What occurs during the relaxation phase of muscle activity?
During the relaxation phase, muscle tension decreases due to a decrease in Ca2+ and the ending of the cross-bridge cycling.
