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MSK Final Exam > Muscle Tissue > Flashcards

Muscle Tissue Flashcards

1
Q

What is muscle tissue specialized for?

A

Contraction

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2
Q

When does contraction occur in muscle tissue?

A

When thin/actin filaments and thick/myosin filaments within cytoplasm slide past one another

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3
Q

List characteristics of skeletal muscle tissue

A

Contribute to the MSK system
Pull on bones to cause body movement and maintain posture
Striated
Controlled voluntary by the NS

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4
Q

List characteristics of cardiac muscle tissue

A

Found in the wall of the heart
Striated
Involuntary
Pumps blood through the CV system

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5
Q

List characteristics of smooth muscle

A

Non-striated
Involuntary
Functions to maintain visceral organ tone and movement
Control blood vessel vasodilation and vasoconstriction
Found lining walls of hollow viscera and blood vessels

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6
Q

List functions of all muscle tissue

A

Movement of body and body fluids
Maintain posture and body position
Support soft tissues (blood vessels, intestines, urogenital tract, etc)
Sphincters at entrances and exits of certain organ systems
Maintain body temp

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7
Q

Skeletal muscle cells can be referred to as what?

A

Myocytes, myofibers or muscle fibers

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8
Q

What forms fascicles in skeletal muscle?

A

Groups of myofibers

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9
Q

What is the endomysium?

A

CT separating myofibers (skeletal)

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10
Q

What is the perimysium?

A

CT separating fascicles of skeletal muscle

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11
Q

What is epimysium?

A

CT layer surrounding the entire skeletal muscle

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12
Q

What are myofibers?

A

Cylindrical skeletal muscle cells

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13
Q

Describe skeletal muscle nuclei

A

Multinucleated and located in the periphery of the cell

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14
Q

What is skeletal muscle cell cytoplasm primarily occupied by?

A

Myofibrils which are composed of thin and thick filaments

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15
Q

What are transverse (t) tubules?

A

Invaginations of the sarcolemma

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16
Q

What structure stores Ca in skeletal muscle?

A

Sarcoplasmic reticulum

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17
Q

What are terminal cisternae?

A

Dilated ends of the SR that release Ca2+ and trigger muscle contraction

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18
Q

What is the skeletal muscle triad?

A

1 t-tubule and 2 terminal cisternae

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19
Q

When a muscle contracts what happens to the sarcomeres?

A

Every sarcomere shortens

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20
Q

What is the Z line in a sarcomere?

A

Anchor site for actin microfilaments

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21
Q

What is the M line in a sarcomere?

A

Anchor site for thick myosin filaments

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22
Q

What is the I band of a sarcomere?

A

Only contains actin thin filaments

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23
Q

What is the H zone of a sarcomere?

A

Contains only thick myosin filaments

24
Q

What is the A band of a sarcomere?

A

Overlap of thick and thin filaments plus the H zone

25
What occurs when a skeletal muscle contracts?
The thin filaments slide past the thick filaments toward the center of the sarcomere brining the Z lines closer together
26
True or false: every myofibril in a skeletal muscle cell shortens at the same time thus the entire muscle cell contracts
True
27
During contraction, do thick and thin filaments change lengths?
No - the only thing that changes is their degree of overlap which increases Muscle shortens, not the filaments
28
What is the signal to contract driven by in a skeletal muscle cell?
The release of Ca from the SR
29
Describe the steps of the sliding filament mechanisms
1. Ca influx exposes sites on actin allowing the myosin head to bind to actin 2. When myosin binds actin the power stroke is invoked 3. ATP then binds the myosin and is hydrolyzed generating energy used to release myosin head from actin and re-cock the myosin for another power stroke 4. This repeats until the Ca is removed and is transported back into the SR
30
What is rigor mortis?
Loss of a source of ATP prevents the myosin head from detaching from the actin thereby locking the muscle in place
31
What is tropomyosin?
Runs in groove formed by F-actin strands and binds to troponin
32
What are the three types of troponin?
T, I and C
33
What is troponin T?
Binds to tropomyosin
34
What is troponin I?
Inhibits the binding of myosin to actin
35
What is troponin C?
Binds Ca2+
36
What are the 4 different parts to a chemical synapse between a skeletal muscle and a motor neuron?
Pre-synaptic knob (axon terminal) Synaptic cleft Pre- and post synaptic membrane
37
What are axon terminals?
Ends of nerve fibers that store and release chemical messengers (NTs) at neuromuscular junctions
38
What is the synaptic cleft?
A space between the axon terminal and skeletal muscle plasma membrane
39
Describe the steps of the neuromuscular junction/innervation of a skeletal muscle
1. Nerve impulses stimulate release of ACh into the synaptic cleft 2. ACh binds to receptors on the sarcolemma of muscle cell 3. ACh stimulates changes in the membrane that excite the muscle fiber 4. Stimulus is carried down the T tubules to stimulate release of Ca from the SR which then initiate muscle fiber contraction
40
How is ACh removed from the synaptic cleft?
By enzymes such as acetylcholinesterase in the synaptic cleft break down ACh or any leftover ACh is taken up into the axon terminal by receptor mediated endocytosis
41
Describe cardiac muscle nuclei
Usually cardiac muscle cells have one nucleus but may have two Centrally located in the cytoplasm
42
What is unique about cardiac muscle cell contraction?
Can spontaneously contract | Do not need innervation to contract
43
What is the diad of cardiac muscle cells?
1 t-tubule and 1 SR cisternae found at Z lines and permits uniform contraction of myofibrils within a single cardiomyocyte
44
What are intercalated discs?
Specialized interdigitating junctions between cardio myocytes that are sites of cell-cell adhesion and low electrical resistance (combination of gap junctions and desmosomes)
45
What is the function of intercalated discs of cardiac muscle?
Bind cells and transmit forces of contraction to allow for the spread of excitation within the muscle
46
What are the three types of membrane to membrane contacts of an intercalated disc junction?
Transverse region includes fascia adherens and desmosomes | Longitudinal region includes gap (nexus) junctions
47
What are fascia adherens of intercalated discs?
Actin filaments at the ends of terminal sarcomeres that insert into the intercalated junction Transmit contractile forces between cells Most predominant
48
What is the purpose of the desmosomes within the intercalated disc junction?
Provide anchorage for the intermediate filaments of the cytoskeleton
49
What are the gap (nexus) junctions of the intercalated disc junction?
Sites of low electrical resistance that allows for excitation to pass between cardiac muscle cells
50
Describe smooth muscle cell nuclei
Single elliptical nucleus in center of cytoplasm
51
Describe smooth muscle cell cytoplasm
No visible striations in cytoplasm but they still use actin/myosin for contraction
52
What connects smooth muscle cells?
Gap junctions
53
What innervates smooth muscle cells?
ANS
54
What controls smooth muscle cell contraction?
Hormones
55
Describe the smooth muscle contraction apparatus
Contractile apparatus is made up of thin and thick filaments which are anchored to cytoplasmic densities/dense bodies
56
What are dense bodies comprised of and what is their function?
Desmin and vimentin intermediate filaments | Transmit tension to the cell membrane
57
True or false: smooth muscle cells contract as one unit
True and they assume a globular shape

MSK Final Exam (26 decks)

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