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Muscle Lecture Exam Flashcards

1
Q

Name three types of muscle tissue

A

skeletal, cardiac and smooth

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2
Q

Is skeletal, cardiac and smooth muscle tissue all the same

A

no, they differ in structure, location, function and means of activation

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3
Q

What are the five functional characteristics of muscle tissue

A

responsiveness (excitability), conductivity, contractility, extensibility & elasticity

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4
Q

Responsiveness (excitability) is

A

when muscle is stimulated by chemical signals, stretch, and other stimuli, muscle cells respond with electrical changes across the plasma membrane - ion gates open Na+ rushes into cell and K+ rushes our of cell

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5
Q

conductivity is

A

when local electrical charge triggers a wave of excitation that travels along the muscle fiber

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6
Q

contractility is

A

muscle shortens when stimulated enables them to pull on bones and other organs to create movement

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7
Q

extensibility

A

capable of being stretched

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8
Q

elasticity

A

capable of returning to original resting length after being stretched

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9
Q

Which muscle tissue is voluntary

A

skeletal

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10
Q

which muscle tissue is involuntary

A

cardiac and smooth

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11
Q

Which muscle tissue is responsible for locomotion

A

skeletal

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12
Q

Which muscle tissue is responsible for coursing blood through the body

A

cardiac

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13
Q

Which muscle tissue helps maintain blood pressure & squeezes or propels substances (food, feces) through organs

A

smooth

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14
Q

What are the five recognized functions of skeletal muscle

A

produce movement, maintain posture, maintain body temperature and guard body entrances & exits

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15
Q

Skeletal and smooth muscle cells are elongated and are called muscle fibers
True or False

A

True

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16
Q

Muscle contraction in all types depends on two kinds of myofilaments, name them

A

actin and myosin

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17
Q

Describe cardiac muscle

A

occurs only in the heart is striated, involuntary, has intercalated discs and contracts at a fairly steady rate, neural controls allow the heart to respond to changes in bodily needs

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18
Q

Describe smooth muscle

A

found in the walls of hollow “visceral” organs, such as the stomach, urinary bladder & respiratory passages, forces food and other substances through internal body channels; non striated and is involuntary, contractions tend to be slow and sustained

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19
Q

Which muscle is usually in sheets, short and fusiform in shape

A

smooth (visceral) muscle

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20
Q

Describe skeletal muscle

A

voluntary striated attached to bones, muscle fibers (myofibers) as long as 30 cm; exhibits alternating light and dark transverse bands or striations; has multiple nuclei

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21
Q

List the organization level of muscle structure

A

tendon/aponeurosis (sheetlike muscle) to bone - muscle - fascicle - muscle fiber - myofibril - sarcomere - myofilaments (actin & myosin)

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22
Q

Muscles can attach

A

directly or indirectly

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23
Q

muscles that attach directly is when

A

the epimysium of the muscle is fused to the periosteum of the bone

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24
Q

muscles that attach in directly is when

A

connective tissue wrappings extend beyond the muscle as a tendon or aponeurosis

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25
Most are attached in at least two places called the
insertion and origin
26
The site that usually has no movement is the site of
origin
27
The site that usually has movement is the site of
insertion
28
growth of muscle tissue through cellular enlargement is called
hypertrophy
29
growth of muscle tissue through cellular multiplication is called
hyperplasia
30
shrinkage/loss of muscle tissue due to age, disuse or disease is called
atrophy
31
Describe thick filaments
made of 200 to 500 myosin molecules - is a long protein - 2 entwined polypeptides (looks like golf clubs) - arranged in a bundle with heads directed outward in a spiral array around the bundled tails - central area is a bare zone with no heads - myosin heads contain actin binding sites & ATPases
32
ATPases
enzyme that split ATP and generate energy for contraction
33
Describe thin filaments
composed of actin - subunits, tropomyosin & troponin, contain the active sites to which myosin heads attach during contraction - there is one small, calcium-binding troponin molecule on each tropomyosin molecule
34
What are tropomyosin and troponin
Subunits on the thin filaments of actin
35
Why do muscles shorten
because their individual sarcomeres shorten - pulls the Z dis closer together - no change in length of the thick or this filaments during shortening - they overlap as the sarcomeres shorten
36
What is resting membrane potential
the membrane "sarcomeres" is polarized (charged), this means the outside surface of the membrane is slightly positive and the inside surface is slightly negative
37
Muscle cells are electrically excitable | True or False
True
38
Why must muscle cells be polarized?
because this creates the resting membrane potential which muscles need in order to respond to stimulation from nerve cells
39
Membrane potential is defined as
voltage across a membrane
40
Membranes are more permeable to K+ than to Na+ | True or False
True
41
What is peristalsis
a wave of constriction traveling along a tubular organ such a the esophagus or ureter, serving to propel it contents
42
What is hyperplasia
the growth of a tissue through cellular multiplication, not cellular enlargement
43
What is stress relaxation response or receptive-relaxation response
smooth muscle exhibits this, when stretched, it briefly contracts and resists, but then relaxes - this is apparent in the bladder
44
What is muscular dystrophy?
a collective term for several hereditary diseases in which the muscles degenerate, weaken and are gradually replaced by fat and fibrous scar tissue.
45
What is the most common type of muscular dystrophy?
DMD, Duchenne Muscular Dystrophy
46
Is DMD a sex linked recessive trait the affect about 1 out of every 3,500 live-born boys
Yes
47
Describe how DMD progresses
Not evident at birth - first noticed when child has difficulty keeping up with other children, falls frequently, and has hard time to stand up - typically diagnosed between the ages of 2 and 10 - order of muscles affected first in the hips, then legs, abdominal, spinal, respiratory and cardiac - muscles shorten like with atrophy, causing postural abnormalities such as scoliosis - usually wheel chair bound by age 10 or 12 and seldom live past 20 - also decline in mental ability - death usually result of respiratory insufficiency, pulmonary infection, or heart failure. DMD is in curable. cause of DMD is a mutation in the gene for the muscle protein dystropin - which causes no coupling between the thin myofilaments and the sarcolemma - sarcomeres move independantly of the sarcolemma creating tears in the membrane - torn membrane admits excess Ca+ into the cell which activates intracellular proteases - these degrade the contractile proteins of the muscle leading to weakness with cellular necrosis - dying muscle fibers replaced with scar tissue - block blood circulation in the muscle - muscle degeneration accelerates in a fatal spiral of positive feedback
48
What is muscle fatigue
is the physiological inability of muscles to contract - progressive weakness from use - ATP synthesis declines as glycogen is consumed - sodium potassium pumps fail to maintain membrane potential and excitability - lactic acid inhibits enzyme function - accumulation of extrecellular K+ hyper polarizes the cell - motor nerve fibers use p their acetylcholine
49
What is oxygen debt
heavy breathing after strenuous exercise - known as excess post exercise oxygen consumption
50
What is the purpose for the extra oxygen that is part of oxygen debt
-replace oxygen reserves - replenish the phosphagen system, reconverting lactic acid to glucose in kidneys and liver - serves the elevated metabolic rate that occurs as long as the body temperature remains elevated by exercise
51
What is depolarization
when the Na+ cations override the negative charge inside the membrane, so the inside of the membrane briefly becomes positive - occurs when Na+ channels open and Na+ enters the cell's sarcoplasm
52
What are the three steps involved in an action potential
depolarization, propagation & repolarization
53
What is propagation
the local depolarization wave spreads to the adjacent areas of the sarcolemma and opens voltage-regulated Na+ channels
54
What is repolarization
sarcolemma is restored to its initial polarized state (resting membrane potential)
55
What is threshold stimulus
weakest stimulus capable of producing a response in an irritable tissue
56
What is the all or none phenomenon
action potentials are "all-or-none" they either happen completely or they don't happen at all
57
What is a motor unit
one nerve fiber and all the muscle fibers innervated by it
58
Where are small motor units found
where fine control is needed such in eye movement
59
Where are large motor units found
where strength is more important then fine control is needed such in the gastrocnemius muscle of the calf
60
The point where a nerve fiber meets any target is called a
synapse
61
when the target cell is a muscle fiber, the synapse is also called a
neuromuscular junction (NMJ) or motor end plate
62
at each synapse the nerve fiber ends in a bulbous swelling called a
synaptic knob
63
What is the synaptic cleft
the synaptic knob does not directly touch the muscle fiber but is separated from it by a narrow space
64
what organelle is the synaptic knob filled with
acetylcholine (ACh)
65
What does ACh function as
a chemical messenger from the nerve cell to the muscle cell - stimulates a skeletal muscle fiber
66
ACh receptor
located in the sarcolemma
67
Where is acetylcholinesterase (AChE)
in the sarcolemma breaks down ACh after the ACh has stimulated the muscle cell - it turns off muscle contraction and allows the muscle to relax
68
What is a myogram
a chart that shows the timing and strength of a muscles contraction
69
A minimum voltage necessary to generate an action potential in the muscle fiber is called the
threshold
70
Twitch is defined as
a single stimulus that cause a quick cycle of contraction and relaxation
71
What is muscle tone
a state of continual, partial contraction of resting skeletal or smooth muscle - does not produce active movements - keeps the muscles firm, healthy and ready to respond to stimulus - helps to stabilize joints and maintain posture
72
What is wave summation
when new twitch arrives before the previous twitch is over - each new twitch "rides piggyback" on the previous one and generates higher tension - one new wave of contraction added to another
73
the effect produces by wave summation is called
incomplete tetanus because it is a state of sustained fluttering
74
What is complete (fused) tetanus
the twitches fuse into a single, non-fluctuating contraction
75
What is hypotonia
decreased or lost muscle tone - usually an injury to spinal cord causes hypotonic muscles
76
What is hypertonia
increased muscle tone - twitches - characterized by muscle stiffness and sometimes associated with a change in normal reflexes
77
What type of contraction is one in which there is a change in muscle length (muscle shortens or lengthens during contraction) - like in doing curls
Isotonic contraction - iso means same - tonic means tension
78
What is an Isometric contraction?
metric means length - is increasing muscle tension (muscle does not shorten during contraction) - like in holding an object for a while
79
the force exerted on an object by a contracting muscle is called
muscle tension
80
the opposing force exerted on the muscle by the weight of the object to be moved is called
load
81
concentric isotonic contraction
the muscle shortens while maintaining a constant degree of tension - muscle moves a load
82
eccentric isotonic contractions
the muscle maintains tension while it lengthens, allowing a muscle to relax without going suddenly limp
83
The three metabolic pathways of ATP generation are
direct phosphorylation, glycolysis and aerobic respiration
84
This ATP pathway using creatine phosphate (CP) molecule by CP donating P to ADP to make ATP is called
direct phosphorylation - phosphagen system - makes one ATP per CP molecules - think of as sprinter - can provide energy for about 15 seconds
85
Glycolysis or the glycogen-lactid system is
ATP production through the energy source of glucose - produces 2 ATP per glucose molecule - can provide enough energy for about 30-60 seconds - also produces to pyretic acid that can be used in anaerobic pathway - muscles obtain glucose from blood and stored glycogen
86
This ATP pathway uses oxygen during the process
Aerobic respiration
87
Does glycolysis and direct phosphorylation use oxygen
no
88
95% if ATP used in muscle activity comes from
aerobic respiration which uses oxygen
89
Glucose + O2 =
CO2 + H2O + 36 ATP - aerobic respiration
90
Where is the oxygen found for aerobic respiration
from lungs by hemoglobin in red blood cells - in skeletal muscle it is myoglobin
91
what must be present in for skeletal muscle contraction
be at resting membrane potential be stimulated by a nerve ending propagate an electrical current, or action potential, along its sarcolemma have a rise in intracellular Ca2+ levels, the final trigger for contraction can only occur if there is sufficient Ca2+ and ATP energy
92
what neurons stimulate skeletal muscle
somatic (voluntary) motor neurons
93
Name a few neuromuscular toxins
pesticides, tetanus or lockjaw and flaccid paralysis
94
What happens with the neuromuscular toxin - pesticides
bind to acetylcholinesterase and prevent it from degrading ACh - spastic paralysis and possible suffocation
95
What is tetanus or lockjaw?
spastic paralysis - the continually contracting muscles caused by toxin Clostridium bacteria - blocks glycine release in the spinal cord an causes overstimulation of the muscles
96
called limp muscles, respiratory arrest
flaccid paralysis

Muscular Systems (4 decks)

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