Exam 1 Flashcards
1
Q
Bone is connected to muscle by?
A
Tendon
2
Q
What is the order of the muscle structure organization from smallest to largest?
A
1) Actin + myosin
2) Myofilaments
3) Muscle fiber cell (myofiber)
4) Fascicle
5) Muscle
3
Q
What contains the sarcolemma, t-tubule, and sarcoplasmic reticulum?
A
Muscle fibers
4
Q
What is the function of the t-tubule?
A
Carries out action potentials to the sarcoplasmic reticulum
5
Q
What is the function of the sarcoplasmic reticulum?
A
Stores the calcium
6
Q
Myofiber cytology
A
1) elongated cells with hundred of nuclei (termed myonuclei)
2) 70% of myofiber volume is occupied by myofibrils
3) 80% of its dry weight is preotein
4) 50% of that is myofibrillar protein
7
Q
epimysium
A
above
8
Q
Perimysium
A
around
9
Q
Endomysium
A
within
10
Q
what is the Effect of crossed extensor reflex on opposite limb?
A
During the crossed extensor reflex, the opposite limb extends, potentially pushing the entire body away from the painful stimulus
11
Q
How does skeletal muscle hypertrophy affect individual muscle fibers?
A
It results from an increase in the number of actin and myosin filaments in each myofiber, causing enlargement of the individual muscles fibers
12
Q
Acute responses and long-term adaptation are usually averages, but response are not uniform, but rather highly ______________ (inter-individual responses)
A
heterogeneous
13
Q
Are myonuclei and myofibers capable of undergoing mitosis?
A
Myonuclei (and myofibers) are post-mitotic, meaning they are terminally differentiated nuclei and not able to proliferate
14
Q
Are responses to resistance training uniform?
A
No, muscle strength and size responses to resistance training are highly individual with significant variation among different people
15
Q
Atrophy in catabolic states: key examples?
A
1) Intensive care
2) Major trauma
3) Burns
4) sepsis
5) HIV and AIDS
6) uremia
7) cancer
8) cachexia
16
Q
what is the basic components of muscle structure?
A
Actin+Myosin—-> Myofilaments—–> Muscle fiber cell —-> fascicle ——-> muscle
17
Q
Briefly describe muscular dystrophies?
A
Muscular dystrophies are a group of genetic disorders characterized by progressive weakness and degeneration of the skeletal muscles responsible for movement
18
Q
What is a metabolic syndrome related to underlying illness, characterized by muscle mass loss with or without fat mass loss, often associated with anorexia, inflammatory process, insulin resistance, and increased protein turnover
A
Cachexia
19
Q
Can a myofiber change its number of myonuclei?
A
A myofiber can increase (or decrease) in myonuclei number, a process termed myonuclear accretion via satellite cells
20
Q
can touch receptors also elicit the Flexor reflex?
A
Yes, stimulation of touch receptors can elicit a weaker and less prolonged flexor reflex
21
Q
Loss of skeletal muscle, often exacerbated by chemotherapy, which induces muscle atrophy at a molecular level through proteasomal degradation of myofibrillar proteins this is called?
A
cancer cachexia
22
Q
changes in protein Dynamics in aging are?
A
minimal increase in protein breakdown with double the decrease in protein synthesis, leading to muscle atrophy
23
Q
what are the Characteristics of atrophy in catabolic states?
A
nonuse, massive inflammation, hypercytokinemia, marked catabolic state
24
Q
connection of proprioception with the nervous system
A
aiding in the functioning of various nervous system parts to regulate muscle activity
25
What causes rapid atrophy. It is when a muscle loses its nerve supply, it no longer recieves contractile signals, leading to immediate atrophy
Denervation (initial impact)
26
Describe the basic circuit of the muscle spindle stretch?
It involves a type 1a proprioceptor nerve fiber from a muscle spindle entering the spinal cord, synapsing in the anterior horn with motor neurons, and sending signals back to the same muscle, forming a monosynaptic pathway
27
describe the final stage of denervation atrophy
in the final stage of denervation atrophy, most of the muscle fibers are destroyed and replaced by fibrous and fatty tissue, leading to a significant loss of muscle function
28
Describe the neuronal mechanism of the flexor reflex
Upon a painful stimulus to the hand, the flexor muscles of the upper arm become excited, withdrawing the hand from the stimulus. The pathway involves signal transmission first to the spinal cord interneuron pool and then to the motor neuron
29
Describe the pathway from the golgi tendon to the muscle spindle.
Golgi tendon----> sensory (dorsal root) -------> interneurons --------> Gamma motor --------> ventral horn ---------------> muscle spindle
30
Describe the relationship between transverse tubules and the sarcoplasmic reticulum
the t- tubules communicate outside of the cell membrane and, deep in the muscle fiber, each t-tubule lies adjacent to the ends of longitudinal sarcoplasmic reticulum tubules that surround all sides fo the actual myofibrils that contract
31
Describe the role of Gamma motor neurons
Gamma motor neurons innervates muscle spindles, specifically the intrafusal fibers. They transmit impulses through smaller type A gamma (Ay) motor nerve fibers and innervate special myofibers called intrafusal fibers
32
Describe the sensory innervation of muscle spindles
Primary ending: In the center of the receptor area, a large sensory nerve fiber (type 1 fiber) encircles the central portion of each intrafusal fiber, forming the primary afferent ending. it transmits sensory signals to the spinal cord
Secondary ending: usually one, sometimes two smaller sensory nerve fibers innervate the receptor region on one or both sides of the primary ending, forming the secondary afferent ending. This ending can spread like branches on a bush or encircle intrafusal fibers similar to the type 1 fiber
33
Describe the structure of the actin filament
Actin filament is composed of two helical strands of F-actin molecules and two strands of tropomyosin molecules that fit in the grooves between the actin strands. attached to the troponin complex that initiates contraction
34
Describe the two pathways of sensory signals entering the spinal cord
Sensory signals enter through the sensory roots (posterior or dorsal root) one branch terminates in the gray matter of the cord for reflexes and local effects. another branch transmits signals to higher levels like the brain stem or cerebral cortex
35
Disuse and injuries
Voluntary inactivity- induced decrease in physical activity, reduced mechanical load, and anabolic resistance, leading to decreased protein synthesis and muscle atrophy
36
Function of t-tubule in muscle cells
T-tubule carry action potentials to the sarcoplasmic reticulum
37
How do calcium ions contribute to muscle contraction?
Calcium ions initiate attractive forces between actin and myosin filaments, causing them to slide, which is the contractile process
38
How do muscle nuclei (myonuclei) contribute to muscle fiber functioning?
Myonuclei contribute either by affecting only the surrounding area or the entire muscle fiber
39
How do physiological systems adapt to demands?
Physiological systems are demand-based and respond and adapt to stimuli
40
How does single motor axon function in muscle innervation?
A single motor axon may branch to innervate several muscle fibers that function together as a group
41
How does acetylcholine function in the NMJ?
Acetylcholine is released from the lower motor neuron into the synapse, binding to skeletal muscle to initiate muscle contraction
42
How does each nerve fiber interact with myofibers?
Each nerve fiber, upon reaching the muscle, branches to cover 3 to hundreds of myofibers
43
How does exercise affect muscle aging?
Regular aerobic exercise helps aging muscles retain more youthful characteristics, like healtheir mitochondria and neuromuscular connections
44
How does exercise affect muscle protein synthesis?
Mechanical tension/ loading from exercise increases protein synthesis acutely (translational efficiency), and chronically (translational capacity)
45
How does myonuclear accretion relate to hypertrophy?
1) Hypertrophy < Myonuclear accretion: myonuclear domain decreases
2) Hypertrophy = Myonuclear accretion: Muonuclear domain remains the constant
3) Hypertrophy > Myonuclear accretion: myonuclear domain increases
46
How does myonuclear loss relate to atrophy?
1) Atrophy < Myonuclear loss: domain increases
2) Atrophy = Myonuclear loss: myonuclear domain remains constant
3) Atrophy > Myonuclear loss: myonuclear domain decreases
47
How does skeletal muscle increase in size?
1) Hyperplasia: increase in the number of cells
2) Hypertrophy: increase in the size of the individual cells
48
How does acetylcholine-gated channel function?
The channel, in a closed state, opens upon binding with acetylcholine through a conformational changes, allowing sodium ions to enter the muscle fiber and initiate contraction
49
how does the golgi tendon organ function?
It reacts to muscle TENSION changes, with a dynamic response to sudden increases and a static respone that maintains steady-state firing proportional to muscle tension
50
How does the golgi tendon reflex equalize contractile force among muscle fibers?
It inhibits fibers exerting excess tension, while fibers exerting too little tension become more excited due to the absence of reflex inhibition
51
How does action potential travel along the muscle fiber?
The action potential travels along the muscle fiber membrane similarly to how it travels along nerve fiber membranes
52
How is Ca2+ transported from the sarcoplasm back into the sarcoplasmic reticulum?
Ca2+ is transported from the sarcoplasm into the sarcoplasmic reticulum by an adenosine triphosphate-dependent calcium pump, called SERCA (sarcoplasmic reticulum Ca2+ ATPase)
53
How is forceful contraction linked to muscle hypertrophy?
Its known that the rate of synthesis of muscle contractile proteins increases significantly during hypertrophy, leading to more actin and myosin filaments in the myofibrils
54
How is muscle connected to bone?
Tendon
55
How is skeletal muscle hypertrophy achieved?
Skeletal muscle hypertrophy is accompanied by myonuclear accretion via satellite cells, but it can also occur without myonuclear accretion
56
How long does it take for muscle contraction to return to baseline after the stimulus ends?
1) It takes many milliseconds due to after discharge, with the duration depending on the intensity of the sensory stimulus
2) A weak tactile stimulus causes almost no after discharge, but after a strong pain stimulus, the after discharge may last for a second or more
57
How many myofibrils are in each myofiber?
each myofiber contains 100-1000 myofibrils
58
how many myosin and actin filaments are in each myofibril?
ach myofibril contains 1500 myosin filaments and 3000 actin filaments (polymerized protein molecules)
59
How many nerve endings usually innervate each muscle fiber, and where are they located?
Each fiber is usually innervated by only one nerve ending, located in the middle of the fiber
60
How many nuclei does a single myofiber contain, and what are they called
a single myofiber contains hundreds of nuclei, termed myonucleus (plural myonuclei)
61
Chronic inflammation associated with aging, leading to failure of resolution of inflammation
inflammageing
62
Is each muscle fiber innervated by multiple motor neurons?
No, each muscle fiber is innervated by a single motor neuron. However, an entire muscle may receive input from hundreds of different motor neurons
63
is there variability in muscle response to training within age groups?
Yes, there is a relatively high standard deviation in all cases, indicating a wide range of responses within each age group
64
Loss of motor neurons and reinnervation of denervated muscle fibers via
collateral sprouting (fiber-type grouping)
65
Motor neuron changes in aging
Loss of motor neurons and reinnervation of denervated muscle fibers via collateral sprouting, leading to fiber type grouping and loss of largest motor neurons (fast-twitch motor unit)
66
Multifactorial causes of muscle atrophy in aging
1) High low-grade inflammatory state
2) decrease motor units/ innervation
3) hormonal changes
4) lower physical activity
67
Negative charges at the channel mouth that prevent passage of _____________ such as chloride ions
Negative
68
Neuronal mechanism of crossed extensor reflex
The reflex involves signals from sensory nerves crossing to the opposite side of the spinal cord to excite extensor muscles
69
Outline the pathway from the golgi tendon to the motor end plate
1) golgi tendon
2) Sensory (dorsal root)
3) Internerons
4) alpha motor unit
5) ventral horn
5) motor end plate
70
protein metabolism in catabolic states
Maximum increase in protein breakdown and massive decrease in protein synthesis
71
purpose of proprioception
Proprioception is essential for intrinsic muscle control at a subconscious level, enabling smooth muscle and coordinated physical movement
72
Role of interneurons in crossed extensor reflex
Due to the delayed onset of the crossed extensor reflex (200 to 500 milliseconds after the initial pain stimulus), it is evident that many interneurons are involved in the process
73
Role of proprioception in muscle control
Proprioception helps control muscle contraction by providing feedback to the nervous system, including the spinal cord, cerebellum, and cerebral cortex
74
role of the sarcoplasmic reticulum in muscle cells
the sarcoplasmic reticulum stores calcium and releases it as needed
75
Age related, involuntary loss of skeletal muscle mass and strength. Factors include aging-induced anabolic resistance, decreased physical activity, and low-grade chronic inflammation
sarcopenia
76
Timing of crossed extensor reflex
the crossed extensor reflex occurs about 0.2 to 0.5 seconds (200 to 500 milliseconds) after a stimulus elicits a flexor reflex in one limb
77
what are golgi tendon organs and their role in muscle function?
Golgi tendon organs are part of the feedback mechanism of muscle function and send information to the spinal cord about muscle contraction
1) distributed in the tendons, in the interface between the myofibers and tendons
2) provides feedback information about tension/load or rate of change of tension
3) help control muscle tension in whole muscle level by its inhibitory effect
-this is important to prevent excessive tension
4) Encapsulated sensory receptor through which muscle tendon fibers pass
5) proprioception
78
What are fundamental myonuclei and their role?
Fundamental myonuclei are specialized nuclei neighboring the NMJ, which express Acetylcholinesterase (AChE) Nuclei located below the post-synapse which express neuromuscular junctions-specific genes
79
What are muscle spindles and what is their role in muscle function?
Part of the feedback mechanism of muscle function, sends to spinal cord information on MUSCLE LENGTH
1) Distributed throughout the belly of the muscle
2) Provides feedback on muscle length or rate of change of length
3) proprioception
80
What are satellite cells, and what role do they play in muscle fibers?
Satellite cells are myogenic stem cells responsible for muscle regeneration throughout the lifespan. they play a crucial role in muscle fiber maintenance, repair, and remodeling
81
What are the average muscle strength and size gains in different age groups?
The mean increase in muscle strength is around 20% for those under 60 and slightly higher for over 60. Muscle size gains are about 4.8% to 5.1% for under 60 and 4.5% for over 60
82
What are the basic types of circuits involved in the flexor reflex?
1) Diverging circuits for spreading the reflex
2) Circuits for reciprocal inhibition of antagonist muscles
3) Circuits causing afterdischarge lasting after the stimulus ends
83
What are the characteristics of skeletal muscle cells?
Skeletal muscle cells are elongated cells with hundreds of nuclei (termed myonuclei)
84
What are the characteristics and metabolism of Type 1 fibers?
1) Slow fibers (red fibers/red muscle)
2) Smaller CSA
3) Innervated by smaller nerve fibers
4) more extensive blood vessel system and more capillaries to supply oxygen compared with fast fibers
5) Greater numbers of mitochondria, high levels of oxidative metabolism
6) Slow fibers contain large amounts of myoglobin
-myoglobin: an iron-containing protein similar to hemoglobin in red blood cells
85
What are the characteristics and metabolism of type 2 fibers?
1) Fast fibers (white fibers/white muscles)
2) type 2a
3) Type 2b (in rodents, not present in humans)
4) Type 2x
5) Larger CSA
6) Extensive sarcoplasmic reticulum for rapid release of calcium ions to initiate contraction
7) Larger amount of glycolytic enzymes and fewer mitochondria than slow fibers
8) Less extensive blood supply than slow fibers (oxidative metabolism is of secondary importance)
9) less myoglobin
86
What are the two key processes involved in muscle mass maintance?
Anabolism and catabolism
87
What are translational efficiencies and translational capacity?
1) Translational efficiency is the rate of protein synthesis per unit of ribosome
2) translational capacity is the total cellular quantity of ribosomes
88
What causes muscle hypertrophy at the cellular level?
Muscle hypertrophy primarily results from an increase in the number of actin and myosin filaments in each myofiber, leading to the enlargement of individual muscle fibers (myofiber hypertrophy)
89
What causes prolonged afterdischarge after strong pain stimuli?
It results from recurrent pathways initiating oscillation in reverberating interneuron circuits, which continue transmitting impulses to anterior motor neurons even after the sensory signal ends
90
what defines the limits of a sarcomere?
The limits of a sarcomere, the basic structure in muscle contraction, are defined by two z-lines
91
What do muscle fiber cells contain?
Muscle fiber cells contain the sarcolemma, t-tubule, and the sarcoplasmic reticulum
92
What does "protein synthesis < protein degradation" indicate?
Skeletal muscle atrophy
93
What does "protein synthesis = protein degradation" indicate?
Maintenance of muscle size
94
What does "protein synthesis > protein degradation" indicates?
Skeletal muscle hypertrophy
95
What does "innervation" refer to?
Innervation refers to the nerve supply or the process of supplying nerves to an area
96
What does the connective tissue term "Epimysium" mean?
above or upon
97
What does the connective tissue term "perimysium" mean?
Around or about
98
What does the connective tissue term "Endomysium" mean?
internal or within
99
What happens a few milliseconds after a pain sensory nerve is stimulated?
The flexor response appears, and the reflex begins to fatigue over the next few seconds, a characteristic of complex integrative reflexes of the spinal cord
100
What happens to calcium ions after muscle contraction?
Calcium ions are pumped back into the sarcoplasmic reticulum by a Ca2+ membrane pump and are stored until a new muscle action potential occurs, ceasing muscle contraction
101
What happens to the synthesis of muscle contractile proteins during hypertrophy?
The rate of synthesis is far greater, leading to progressively greater numbers of both actin and myosin filaments in the myofibrils
102
What happens to the golgi tendon organs in a muscle tendon are stimulated by increase tension?
Signals are transmitted to the spinal cord, ceasing an inhibitory reflex in the respective muscle. this reflex is entirely inhibitory
103
What happens when acetylcholine acts on the muscle fiber membrane?
Acetylcholine opens acetylcholine-gated cation channels, allowing for sodium ions to enter the muscle fiber membrane
104
What initiates the muscle contraction process?
An action potential travels along a motor nerve to its ending son muscle fibers
105
What is proprioception?
Proprioception is the sense of self-movement, force, and body position. it is crucial for movement coordination and balance
106
What is a neuromuscular junction (NMJ)?
The NMJ is the connection between nerve endings and myofibers, where the nerve and muscle communicate. A synapse between a motor neuron and a myofiber
107
What is a myofiber?
A myofiber is an elongated, mutlinucleated, and post-mitotic cell
108
what is a myonucleus?
Myonucleus is the nucleus from muscle cells (myofibers)
109
What is an Alpha motor neuron and what does it innervate?
1) Alpha motor neuron innervate the usual myofibers (extrafusal fibers).
2) It gives rise to large type A (Aa) motor nerve fibers, innervating large skeletal muscle fibers
3) Stimulation of a single alpha nerve fiber can excite 3 to 100 myofibers (a motor unit)
110
What is anabolism and its role in muscle mass?
Anabolic processes require energy to build complex molecules from simple ones, helping to build and maintain muscle mass
111
What is contracture, and how is it related to denervation atrophy?
The fibrous tissue that replaces the muscle fibers during denervation atrophy also has a tendency to continue shortening for many months
112
What is included in the neuromuscular junction?
The NMJ includes skeletal muscle, lower motor neurons, and the synapsis
113
What is muscle or myofibrillar protein synthesis?
The specific synthesis of new myofibrillar proteins in muscle cells, contrasting with mitochondrial protein synthesis and sarcoplasmic protein synthesis
114
What is muscle remodeling?
Muscle remodeling is the adaptation of muscles to match function and is based on the principle of "use or lose it"
115
What is myonuclear accretion?
Myonuclear accretion is the process of acquiring new myonuclei in myofibers
116
What is responsible for muscle growth in adult organisms?
Skeletal muscle hypertrophy
117
What is ribosome biogenesis?
The de novo synthesis of ribosomes
118
What is skeletal muscle hypertrophy?
Increase in the size of individual muscle cells (myofibers), leading to an overall increase in muscle mass
119
What is the Golgi tendons reflex and its purpose?
The Golgi tendon reflex helps equalize tension among myofibers in a skeletal muscle, acting as a protective mechanism to prevent excessive tension and potential damage
120
What is the basic function of the muscle stretch reflex?
The simplest manifestation of muscle spindle function, whenever a muscle is stretched suddenly, excitation of the spindles causes reflex contraction of the large myofibers of the stretched muscle and of closely allied synergistic muscles
121
What is the difference between hyperplasia and hypertrophy?
Hypertrophy is responsible for muscle growth in adult organisms, involving the enlargement of existing cells, whereas hyperplasia refers to an increase in the number of cells
122
What is the effect of the Golgi tendon reflex on muscle load distribution?
It spreads the muscle load over all fibers, preventing damage in areas where a small number of fibers might be overloaded
123
What is the effect of the action potential on the muscle membrane?
The action potential depolarizes the muscle membrane, causing the sarcoplasmic reticulum to release calcium
124
What is the extent of each muscle fiber (myofiber) in a muscle?
Each fiber extends the entire length of the muscle
125
What is the function of a motor neuron in the motor neuron system?
The motor neuron is the efferent version of the motor neuron system, conveying signals from the central nervous system to muscles
126
What is the general response of the flexor reflex to a cutaneous sensory stimulus from a limb?
The flexor muscles of the limb contract, withdrawing the limb from the stimulating object
127
What is the hierarchical structure of muscle from the micro to macro level?
1) Myofibrillar proteins
2) Sarcomere
3) Myofibril
4) Myofiber (muscle cell)
5) whole tissue (specific skeletal muscle)
128
What is the impact of muscle hypertrophy on protein degradation?
The rate of protein degradation of the contractile proteins is increased during muscle hypertrophy, resulting in the remodeling of myofibrils. This process may involve the formation of newer sarcomeres
129
What is the main mechanism of myonuclear accretion?
Satellite cell fusion is the main (but not sole) mechanism of myonuclear accretion
130
What is the major difference between muscle spindles and Golgi tendon organs?
The major difference is in what they sense. Muscle spindles sense changes in length, While Golgi tendons organs sense changes in tension
131
What is the major mechanism of skeletal msucle hypertrophy in mature organisms?
Hypertrophy of existing myofibers
132
What is the myonuclear domain hypothesis?
The hypothesis is that a myonucleus governs a specific sarcoplasm region within the myofiber
133
What is the origin and innervation of skeletal muscle fibers?
Skeletal muscle fibers are innervated by larger myelinated nerve fibers originating from large motor neurons in the anterior horns of the spinal cord
134
What is the pathway of signals from the Golgi tendon organ?
Signals are transmitted through type 1b nerve fibers to the spinal cord, synapse in the dorsal horn, and excite an inhibitory interneuron that inhibits the anterior motor neuron. Inhibits the individual muscles without affecting adjacent muscles
135
What is the purpose of the flexor reflex?
to withdraw a pained or irritated part of the body from a stimulus, ensuring protection and response to harmful stimuli
136
What is the purpose of the tendon reflex?
To prevent excessive tension on the muscle, acting as protective mechanism to prevent muscle tearing or tendon detachment from the bone
137
What is the result of sodium ions entering the muscle fiber membrane?
The influx of sodium ions cause local depolarization, leading to the opening of voltage-gated sodium channels and initiating an action potential
138
What is the role and location of interneurons in the spinal cord?
1) Interneurons are present in all areas of the cord grey matter, including dorsal and anterior horns and intermediate areas.
2) They are 30x as numerous as anterior motor neurons, small, highly excitable, have many interconnections, and synapse directly with anterior motor neurons
139
What is the role of t-tubules in muscle contraction?
T-tubules transmit action potentials, causing calcium release close to myofibrils and triggering muscle contraction
140
What is the role of myosin filaments in muscle contraction?
Myosin filaments pull the Z membranes (Z-lines) toward each other, facilitating muscle contraction
141
What is the role of the Golgi tendon reflex in muscle tension?
It provides a negative feedback mechanism that prevents the development of too much tension in the muscle
142
What is the significance of the monosynaptic pathway in muscle spindle stretch reflex?
It allows a reflex signal to return with the shortest possible time delay
143
What is the timeframe for potential functional return to a denervated muscle?
Functional return to a denervated muscle becomes increasingly less likely over time, with no further return function expected after 1 to 2 years
144
What is transcriptional reserve capacity?
The ability of myonuclei to increase transcriptional rates required to support new demands, such as growth or repair
145
What is translational capacity and what mediates it?
The quantity of ribosomes, mediated by ribosome biogenesis
146
What is translational efficiency and what mediates it?
The rate/speed of translation per ribosome, mediated by anabolic signals (growth factors, mTORC1, MAPK pathway)
147
What myofibrils and sarcomeres composed of?
They are composed of actin and myosin filaments
148
What neurotransmitter is secreted at the nerve endings on muscle fibers, and what is its effect?
The neurotransmitter acetylcholine is secreted, and it is excitatory
149
What occurs when tension on the muscle-tendon becomes extreme?
The inhibitory effect from the tendon organ can be so great that it causes instantaneous relaxation of the entire muscle through a sudden reaction in the spinal cord
150
What percentage of a myofiber's dry weight protein?
80% of a myofiber's dry weight is protein
151
What percent of a myofiber's protein content is myofibrillar protein?
50%
152
What percent of a myofiber's volume is occupied by myofibrils?
70%
153
What triggers the release of Ca2+ in skeletal muscle during excitation-contraction coupling?
An action potential in the t-tubule causes a conformational change in the voltage sensing dihydropyridine (DHP) receptors. This opens the ryanodine (RyR) Ca2+ release channels sarcoplasmic reticulum, permitting Ca2+ to diffuse into the sarcoplasm and initiate muscle contraction
154
What type of stimulation elicits the Flexor reflex most powerfully?
Stimulation of pain endings, like a pinprick, heat, or a wound (nociceptive reflex, or pain reflex)
155
When does muscle hypertrophy occur to a greater extent?
When the muscle is loaded during the contractile process (greater demand)
156
Other conditions associated with skeletal muscle atrophy?
Chronic obstructive pulmonary disease (COPD), prolonged stravation and malnutrition, sepsis, and cirrhosis
157
What is anabolic signaling?
Anabolic signaling is the signaling transduction that leads to cell hypertrophy, such as mTOR pathway, culminating with pro-growth processes like protein synthesis and ribosome biogenesis
158
What is the function of mTORC?
1) regulate protein synthesis but also involved in translational efficiency and capacity
-increase muscle mass, need a lot of protein synthesis growing up
-initiation factors + elongation factors to help RNA translation
159
What is the proposed structure of striated muscle force generation according to recent theories?
It is proposed that striated muscle force is generated by a singular, mesh-like myofibrillar network rather than many individual, parallel myofibrils
