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Muscle Physiology Flashcards

(84 cards)

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1
Q

Types of Muscle

A

skeletal, smooth, and cardiac
Skeletal- movement
Smooth- autonomic functions
Cardiac- pumping blood

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2
Q

Flexion

A

decrease angle of a joint

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3
Q

Extension

A

increase angle of a joint

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4
Q

Size of muscle cells

A

several inches.

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5
Q

Another name for muscle cells

A

muscle fibers

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6
Q

Contents of muscle fibers

A

multiple nuclei and mitochondria

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7
Q

Sarcolemma

A

outer membrane of the muscle fiber. Equivalent to the plasma membrane of a regular cell

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8
Q

Sarcomere

A

contractile units that make up the myofibrils. Have discs at each end called Z disks

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9
Q

Troponin

A

protein that binds tropomyosin and actin. Has an affinity for calcium ions

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10
Q

Actin

A

thin protein filaments that attach to the z discs and extend toward the center. Intertwines with tropomyosin. Troponin bound intermittently

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11
Q

Myosin

A

thick filaments suspended among the actin. Resembles a golf club with globular heads that can bind ATP and actin

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12
Q

Sarcoplasmic Reticulum

A

surrounds the myofibrils in a reticulated network. Stores calcium during contraction

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13
Q

T tubules

A

invaginations of the sarcolemma that transverse the network of myofibrils similar to poking straws into a bowl of spaghetti noodles. Filled with extracellular fluid and aid with action potential depolarization

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14
Q

Sarcomere Organization

A
  1. Z-line
  2. I-band
  3. A-band
  4. H-zone
  5. M-line
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15
Q

Z line

A

forms periphery of sarcomere where thin actin filaments attach.

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16
Q

I band

A

light area, only actin

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17
Q

A band

A

dark area with actin and myosin overlapping

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18
Q

H zone

A

center light zone, only myosin

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19
Q

M line

A

middle of the myosin

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20
Q

Action Potential

A
  1. acetylcholine is released at the NMJ
  2. activates nicotinic acetylcholine receptors on sarcolemma
  3. Voltage gated Na ion channels open
  4. action potential spreads
  5. calcium released from sarcoplasmic reticulum
  6. contraction initiated
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21
Q

Other name for milk fever

A

parturient paresis

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22
Q

Milk Fever

A

state of semi-paralysis seen in dairy cows after calving. Fewer calcium ions are available at the NMJ and less acetylcholine is released from the axon end. Less acetylcholine means less depolarization of the sarcolemma

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23
Q

Excitation-Contraction Coupling

A
  1. increased calcium in sarcoplasm
  2. additional calcium binds troponin
  3. tropomysin moves deeper in groove- exposes myosin binding site on actin
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24
Q

Rigor Mortis

A

shortening of muscle fibers without an action potential. Actin and myosin remain contracted because there is not enough ATP to release the myosin head

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25
Puerperal Tetany
hypocalcemia following whelping. Dogs differ from cows at the NMJ in that calcium deficiency causes voltage-gated Ca and Na to become more permeable to sodium. The influx of sodium make the membrane less polarized (less negative) and this means less stimulus is needed for depolarization. The nerve fibers become more excitable and discharge repetitively. This results in tetanic muscle contractions.
26
Skeletal Muscle Fiber Types
1. Type I slow twitch 2. Type II fast twitch 3. intermediate fibers with characteristics of I and II
27
Type I Muscle Fibers
slow twitch. Darker color due to myoglobin. Rich blood supply. More mitochondria. More aerobic
28
Type II Muscle Fibers
Fast twitch. Larger fibers with expansive sarcoplasmic reticulum. Fewer mitochondria, less extensive blood supply, fatigue quickly.
29
Type IIA Muscle Fibers
intermediate between fast and slow twitch
30
Type IIB Muscle FIbers
traditional fast twitch fibers
31
Muscle Fibers in Dogs
Endurance athletes have more Type I muscle fibers, so a high capacity for aerobic metabolism. Dogs use fatty acids and glucose for fuel.
32
Motor Unit
one alpha motor neuron and all the striated muscle fibers it innervates. The muscle fibers are the same type and will contract at the same time.
33
How to increase contraction?
Spatial summation and temporal summation
34
Spatial Summation
increase the number of motor units firing at the same time
35
Temporal Summation
increase the frequency of motor unit activation
36
Myocardial Cells
striated involuntary muscle cells. Have a single nucleus per cell and are connected to each other by junctions called intercalated discs
37
How many nuclei does a skeletal muscle cell have?
multiple
38
Where are the nuclei in a skeletal muscle cell
at periphery
39
Characteristics of skeletal muscle cell
long and tubular. T tubules, sarcoplasmic reticulum. Voluntary control
40
How many nuclei are in a cardiac muscle cell?
1
41
Where are the nuclei in cardiac muscle cells?
central
42
Characteristics of cardiac muscle cell
branching networks, T tubules. Less abundant sarcoplasmic reticulum. autonomic control. Intercalated discs
43
Smooth Muscle Cells Size
smaller and shorter than skeletal muscle cells
44
Smooth Muscle Cells
no visible striations, no T tubules, less developed sarcoplasmic reticulum. Can receive input from more than one neuron, autonomic
45
Types of Smooth Muscle Cell
multiunit, single-unit
46
Multiunit Smooth Muscle Cell
contract independently. Each fiber innervated separately. Allows for fine movement. Found in the iris
47
Single-Unit Smooth Muscle Cell
communicate and contract in a coordinated manner. Important for intestinal, uterine, and urethral contractions
48
Smooth Muscle Stimuli
mechanical pressure, blood pH, oxygen status, and extracellular ion concentration
49
Variscocities
found along the nerve fiber of smooth muscle. Releases acetylcholine (parasympathetic) or norepinephrine (sympathetic) diffusely along a muscle fiber sheet
50
Smooth Muscle Contraction
1. Intracellular concentrations of calcium increase when calcium enters the cell and is released from the sarcoplasmic reticulum 2. Calcium binds to calmodulin 3. Activates myosin light chain kinase 4. MLCK phosphorylates light chains in myosin heads and increases myosin ATPase activity
51
What shape are smooth muscle cells
spindle-shaped with single nuclei packed closely
52
Which muscles have striations?
skeletal and cardiac
53
Which muscle does not have striations?
smooth muscle
54
Where are the nuclei in smooth muscle cells?
in the center of the cell
55
Description of T tubules in skeletal muscle
part of triads at A-I junction
56
Description of T tubules in cardiac muscle
part of dyads at Z disc
57
Skeletal muscle sarcoplasmic reticulum
abundant with two terminal cisterns in the triads
58
Cardiac muscle sarcoplasmic reticulum
less abundant with one terminal cistern per sarcomere in dyads
59
Smooth muscle sarcoplasmic reticulum
no distinctive organization
60
Distinctive structural feature of skeletal muscle
highly organized sarcomeres and triads
61
Distinctive structural feature of cardiac muscle
intercalated discs with adhesion and gap junctions
62
Distinctive structural feature of smooth muscle
gap junctions, caveolae, and dense bodies
63
Contraction Mechanism of Skeletal Muscle
Ca binding to troponin C exposes myosin binding site on actin
64
Contraction Mechanism of Cardiac Muscle
similar to skeletal muscle
65
Contraction Mechanism of Smooth Muscle
Ca binds calmodulin, triggers MLCK mediated phosphorylation of myosin and actin binding
66
Skeletal Muscle Connective Tissue
endomysium, perimysium, and epimysium
67
Cardiac Muscle Connective Tissue
endomysium, subendocardial, and subpericardial
68
Smooth Muscle Connective Tissue
endomysium and less organized CT sheaths
69
Locations of Skeletal Muscle
muscle, tongue, upper esophagus, eyes
70
Locations of Cardiac Muscle
heart
71
Locations of Smooth Muscle
blood vessels and walls of most organs
72
Innervation of Skeletal Muscle
motor for voluntary movement
73
Innervation of Cardiac Muscle
autonomic for involuntary pumping of blood
74
Innervation of Smooth Muscle
autonomic for involuntary movement
75
Growth of Skeletal Muscle
hypertrophy, limited renewal involving satellite cells
76
Growth of Cardiac Muscle
hypertrophy, little/no renewal
77
Growth of Smooth Muscle
hypertrophy and hyperplasia/mitosis
78
What makes up muscle fibers?
myofibrils
79
What are cardiac muscle cells called?
myocytes. Shorter and connected through intercalated discs
80
What anchors actin thin filaments in smooth muscle?
dense bodies
81
What are the sarcoplasmic invaginations of smooth muscle?
calveoli
82
What regulates actin/myosin binding in smooth muscle contraction?
calmodulin
83
Electromyogram
measure the strength of muscle contraction. Used to determine if paresis or paralysis is from issues with the CNS, NMJ, motor neuron, or skeletal muscle
84
Cross-bridging
when myosin is bound to actin

Physiology (16 decks)

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