Muscles Physio Flashcards
(135 cards)
1
Q
made up of several hundred to several thousand of parallely arranged myofibrils having the special function of contraction
A
Muscle fibers
2
Q
posses the contractile proteins myosin (thick) and actin (thin) myofilaments results in regular repetition of dark and light bands in the skeletal and cardiac muscles
A
Myofibril
3
Q
large protein molecule composed of 6 polypeptide chains 2 of which are 100% α – helically exist
A
Myosin
4
Q
have Hinges to alter the position of the head.
A
Myosin
5
Q
has enzymatic ability to split ATP and release energy.
A
Myosin
6
Q
Enzyme for myosin
A
Myosin ATPase
7
Q
Required for activating myosin enzymes
A
Actin and Mg2+
8
Q
much smaller molecule than myosin and contains only one polypeptide chain per molecule
A
Actin
9
Q
- molecules are rod shaped they lie in the 2 grooves of the double stranded actin filament and aggregate end to end to produce two strands of tropomyosin running enter length of this filament.
A
Tropomyosin
10
Q
- More ellipsoidal or globular molecule, binds to a particular site on the tropomyosin molecule.
A
Troponin
11
Q
- This chain has site for attachment with tropomyosin
A
Troponin - T
12
Q
- Inhibits the actin activated myosin ATP ase. attach not only with troponin C and T and but also with actin in the absence of Ca2
A
Troponin - I
13
Q
- binding sites (4 numbers) for Ca2+
A
Troponin - C
14
Q
Dark bands of myosin representation
A
A - Band
15
Q
Light bands of actin
A
I band
16
Q
Partial overlapping of the myosin filaments with actin filament
A
H zone
17
Q
Small projections of myosin filaments that protrude out of the myosin filaments along the entire length except the very center
A
Cross bridges
18
Q
Centre of I band
A
Z line or Z disc
19
Q
Portion of myofibril between two successive z discs
A
Sarcomere
20
Q
physiological contractile unit of muscle.
A
Sarcomere
21
Q
Dark line seen at center of A band
A
H band
22
Q
Cross striated and attached to skeleton, 40% of the total body weight, Voluntary neural control.
A
Skeletal Muscles
23
Q
Cross striated in structure, Involuntary in function, Under autonomic nervous system control.
Myofibril
A
Cardiac Muscle
24
Q
are simple due to ill developed sarco plasmic reticulum. cardiac muscles have rich mitochondrial supply and many Ca-Na exchangers.
A
Triads
25
No cross striations found, poorly organized Actin and Myosin filaments.Ratio of Actin and Myosin is 15:1, Absence of Troponin complex.
Smooth muscle
26
present at the level of Z line and not at the level of A and I bands.
T Tubular System
27
like neurons can be excited chemically, electrically and mechanically to produce an action potential that is transmitted along their cell membrane
Muscle Cells
28
Cell membrane in muscles
Sarcolemma
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Site for fat deposition
Epimysium
30
smaller sheets of connective tissue arise and divide muscle into several small bundles.
Perimysium
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Each muscle fiber is enclosed by ? which is a fine sheet of connective tissue arising from perimysium.
Endomysium
32
the muscle fibers are arranged as number of muscle bundles known as
Fasciculus
33
Absent in canines
Type 3b White or fast twitch glycolytic cells
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FOG Cells
Fast twitch oxidative glycolytic cells
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Type I or red
Slow twitch oxidative cells
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Mitochondria counterpart in muscles
Sarcosomes
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Because skeletal muscle cell in a mature muscle originates form fusion of 100 – 200 different embryonic muscle cells called
Myoblasts
38
Fluid present inside each muscle fiber
Sarcoplasm
39
Cytoplasm of the muscle cell is called sarcoplasm which contains
Myoglobin
40
present which is a transverse structure connecting thick filaments at their centre is made up of M protein and creatine kinase.
M line
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HMM meaning
Heavy meromyosin
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At one end of these chains get folded into a globular structure called
Myosin head
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The elongated coiled portion of the myosin molecule is called
Tail
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extends outward from the body of the myosin filament.
Arm
45
Flexible points of the arm
hinges
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Protruding arms and heads together are called
cross bridges
47
possess ATPase enzyme, which helps to cleave the ATP to release energy for the contraction process.
Myosin head
48
It is composed of three proteins; actin, tropomyosin and troponin
Actin filament
49
provides the active binding site to myosin head.
G-actin
50
The presence of troponin and (?) in actin filament inhibits the binding reaction of actin with myosin. In a relaxed muscle fibre, the tt – complex physically covers the “G” actin for binding with myosin.
tropomyosin and troponin complex or tt-complex
51
In smooth muscle instead of troponin another regulatory protein that reacts with four Calcium ions
Calmodulin
52
Muscle cells contain a special structure which has two sets of tubules
Sarcotubular system
53
Present parallel to myofibrils. At both the ends of the tubule, bulbous structures known as terminal cisternae function as a storage place for the Ca++ ions and play a key role in muscle contraction.
L tubule system
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The T system consist of set of tubules formed by the invaginations of the
plasmalemma
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are located at the junction of “A” and “I” bands which pass through the fibres, open into the inter-fibre space, permits the flow of extracellular fluid.
T tubules
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It is a paired cisternae and a “T” tubule in between the cisternae.
Triad
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counterpart of calmodulin in resting muscle
Calsequestrin
58
As action potential passes, Ca2+ are pumped again to sarcoplasmic reticulum and relaxation happens. This cycle is known as
excitation contraction coupling
59
ability of any living cell or tissue to exhibit an electrochemical change
Excitability
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caused by a sequence of changes or events occurring in the membrane permeability to Na+ and K+ ions.
Action potential
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rapid changes in the membrane potential from its normal negativity to positive potential inside the cell membrane which last for few milliseconds, and then returns back to its original resting negative potential level.
Action potential
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resting cell membrane with a normal negative resting membrane potential.
Polarised Membrane
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first event of action potential is characterised by rapid increase in the permeability to Na+ ions (5000 folds) to interior of the cell generating more positive electrical potential inside of the cell.
Depolarization stage
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It is associated with gradual opening to allow K+ ions outflow to the exterior of the cell membrane. The potential inside cell is re-established to its normal resting level (- 75mV)
Voltage gated K+ channel
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The potential inside cell is re-established to its normal resting level (- 75mV). This stage is called as the
repolarisation stage
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Higher concentration of K+ ions in the exterior of the cell towards the end of the action potential continues for a short period creates more negativity inside referred to as
Hyper-polarised state
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The final event is characterised by ? which aids in the transport of three Na+ ions to the exterior for every two K+ ions to interior of the cell and create the normal resting potential (- 75 mV) on the inside of the cell membrane.
electrogenic pump mechanism
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have two gates, the external gate or activation gate which opens to outside of the cell.
voltage gated Na channel
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This channel has only one gate at the interior of the membrane. It may either close or open to the interior of the cell.
Voltage gated potassium channel
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Electro-chemical changes during action potential Spike potential
Over shoot
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This electrical potential difference across the cell membrane is called as
Membrane potential
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The components such as sarcolemma sheath at the end of the muscle fibers, the tendon and the hinged arms of the cross bridges of the myosin filaments are known as
Series elastic components of the muscle
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This causes the tension to rise just to exceed the force of contraction due to the effect of the weight. Thereafter the tension in the muscle remains constant.
Isotonic contraction
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these series elastic components develop greater tension that opposes the contraction of the myofibrils. Hence the contraction becomes zero, but the tension is very high.
Isometric Contraction
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All the muscle fibres in a muscle that are innervated by a single motor neuron (all the muscle fibres supplied by a single motor neuron) are called as
Motor Unit
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Muscle contraction without shortening in length that occurs during the manifestation of the process of muscle contraction.
Isometric Contraction
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On stimulation, the muscle contracts between one fixed and one moveable points (eg. Lifting the weight) shows shortening in length, but the tension on the muscle remains constant.
Isotonic contraction
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innervate each muscle cell.
Axon terminals
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sends finger like processes into these infoldings but they remain separated by a space of 40 – 60 nm.
Axon terminal
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The nerve impulse propagated along the motorneuron and its axon collaterals reaches the
Neuromuscular junction
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The motor neuron branches at its end and each branch comes into a close opposition with the skeletal muscle at a specialized area called
Neuromuscular junction
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a narrow space between the nerve and muscle,
Synaptic cleftT
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Terminal portion of the axon of the motor neuron
Presynaptic knob
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contains a large number of vesicles called synaptic vesicles
Axoplasm
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excitatory neurotransmitter
Acetylcholine
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Enzyme for acetylcholine
Acetylcholinesterase
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narrow space of 20 to 30nm wide separates the presynaptic membrane and postsynaptic sarcolemma membranes.
Synaptic cleft
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filled with extracellular fluid and spongy reticular filaments called basal lamina.
Synaptic cleft
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The postsynaptic cell membrane has a series of invaginations called
Junctional folds
90
Depolarization in the end plate potential opens voltage-gated Na+ channels at the ? ,leads to the generation of an action potential on the muscle cell membrane.
postsynaptic membrane
91
neuromuscular disorder in which autoantibodies are produced against acetylcholine receptors. Hence, neuromuscular transmission is impaired and leads to paralysis.
Myasthenia gravis
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accomplished by a sliding together or telescoping of the interdigitating thick and thin filaments and as a result narrowing and eventual disappearance of the H zone and shortening of I band happen.
Muscle contraction
93
rotating of the cross bridge cause actin filament to move towards the center of the sacromere.
Swiveling
94
Summary of Muscle contraction
Before contraction and without calcium ions, Troponin T strongly binds with tropomyosin and troponin I and C. Troponin I is firmly attached to actin, hence it blocks the binding sites of myosin with actin. But through stimulation, when an action potential travels along a motor nerve to the muscle fiber, it reaches the neuromuscular junction and will secrete acetylcholine that acts on the muscle's sarcolemma, this will open the acetylcholine gated ion channel. Inflow of sodium ions to the interior of the muscle fiber initiates an action potential throughout the membrane as it travels deeply into the sarcoplasmic reticulum into the triad, during this time it releases Ca++ ions from the cistern into the myofibrils. As it reached the triad, Ca2+ ions binds with troponin C, leading to conformation change in the tt-complex, exposing the G actin in the actin to the myosin head, as troponin I loses affinity towards actin. Due to lost linkage, troponin T cannot hold tropomyosin strand out of the groove, then myosin binding site is marked. Here, myosin heads bind with actin and swivel simultaneously for muscle contraction. Once over, ATP is hydrolyzed and energy is liberated then CA2+ is rebounded to the sarcoplasmic reticulum then the muscle relaxes.
95
Theory of contraction
Walk-along theory or Sliding mechanism of contraction
96
Other term for Walk along theory
Ratchet theory
97
External agent, applied to an excitable tissue to provoke a visible response
Stimulus
98
Sub minimal, unable to produce a response
Sub threshold
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Minimum intensity, strong enough to initiate an action potential
Threshold
100
Higher strength than threshold
Sub maximal
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Highest threshold strength
Maximal
102
Destructive to tissues
Supramaximal
103
Pain, Pressure, and Touch
Mechanical stimulus
104
Acid, Alkali; Thermal: Warmth, Cold
Chemical Stimulus
105
Hypertonic solution, Hypotonic solution
Osmotic stimulus
106
occurs because a nerve contains many different motor neurons having different threshold levels for initiating an action potential.
Recruitment
107
It is the period between the application of stimulus and beginning of contraction (about 10m.second).
Latent Period
108
This period indicates the actual shortening (about 40m.second).
Period of contraction
109
It is the period between the point of maximum contraction and the period of complete relaxation (about 50m.second).
Period of relaxtion
110
It is a brief period during which a muscle undergoing contraction for a first stimulus is unable to respond to a second stimulus.
Refractory Period
111
It is the time interval between the twin impulses (less than 3millisecond) during which the muscle can not be stimulated even by stronger stimuli.
Absolute refractory period
112
It is the period of reduced excitability, which requires increased intensity of second stimulation to generate another action potential
Relative refractory period
113
When a stimulus of constant strength and duration is repeated once or twice per second (below tetanizing frequency)causes increased contractions during the first few stimulations
Trappe or Staircase phenomenon
114
added effect of individual muscle twitches to get strong and powerful muscle contraction.
Summation
115
The strength or the force of contraction of a muscle increases progressively with respect to increasing number of contracting motor units by increasing the strength of stimulation.
Spatial Summation
116
The frequency of stimulation is increased to a motor unit or units in such a way that the successive stimuli stimulate additional motor units during its contraction phase.
Temporal Summation
117
Applying stimuli in rapid succession to a muscle increases the excitatory potential of the postsynaptic nerve ending. This increased excitatory potential is often referred to as
Excitatory postsynaptic potential
118
The first factor is governed by the strength of stimulus. The second is mostly by the rate of effective stimuli. The last is by the initial length of the muscle fiber.
Starlings Law
119
fusion of successive twitches when the frequency of stimuli is given at a rapid rate.
Tetanization
120
defined as fusion of individual contractions caused by repeated experimental stimulation of a viable muscle, by which two kinds of tetanus can be produced by using gastrocnemius muscle of the frog.
Experimental tetanus
121
If the frequency of the successive stimulation to a muscle is so adjusted that the subsequent effective stimuli fall during the preceding contraction phase
Complete Tetanus
122
How to obtain complete tetanus
Tonic contraction
123
lowest frequency required to produce a complete tetanus.
Critical frequency
124
When the subsequent effective stimuli are applied to fall during the relaxation phase of the preceding contraction
Incomplete tetanus
125
how to obtain incomplete tetanus
clonic contraction
126
provide a resistance to change in the length immediately after contraction.
Viscose inertia of sarcoplasm, sarcolemma etc
127
decrease in the working capacity of a muscle or tiredness of the muscle when it is continuously stimulated.
Muscle fatigue
128
3 sites which are easily fatigued
Synapses of CNS
Neuromuscular junction
The muscle
129
When a work is performed by the muscle and energy is required. Heat generation by a muscle is directly proportional to its work performance due to increase hydrolysis of ATP.
Fenn effect
130
Used for biochemical reactions during resting state
Resting heat
131
produced both at initiation and during the course of muscle contraction. It is dependent on aerobic change in the muscle due to breakdown of ATP and creatine PO4 and formation of lactic acid.
Initial heat
132
produced due to Ca transport associated with initiation of contraction
Activation heat
133
Liberated by sliding reaction, muscle lifts load and does external work.
Shortening heat
134
Heat liberated in a muscle that is stimulated but does not lead to physical work (isometric contraction); it is proportional to duration of contraction and tension developed during contraction.
Maintenance heat
135
Heat liberated after contraction of muscle fiber. It is due to pumping of Ca++ back into the tubules and re-synthesis of ATP for next cycle.
Recovery Heat
