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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
Q

What occurs when a skeletal muscle contracts?

A

The thin filaments slide past the thick filaments toward the center of the sarcomere brining the Z lines closer together

26
Q

True or false: every myofibril in a skeletal muscle cell shortens at the same time thus the entire muscle cell contracts

A

True

27
Q

During contraction, do thick and thin filaments change lengths?

A

No - the only thing that changes is their degree of overlap which increases
Muscle shortens, not the filaments

28
Q

What is the signal to contract driven by in a skeletal muscle cell?

A

The release of Ca from the SR

29
Q

Describe the steps of the sliding filament mechanisms

A
  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
Q

What is rigor mortis?

A

Loss of a source of ATP prevents the myosin head from detaching from the actin thereby locking the muscle in place

31
Q

What is tropomyosin?

A

Runs in groove formed by F-actin strands and binds to troponin

32
Q

What are the three types of troponin?

A

T, I and C

33
Q

What is troponin T?

A

Binds to tropomyosin

34
Q

What is troponin I?

A

Inhibits the binding of myosin to actin

35
Q

What is troponin C?

A

Binds Ca2+

36
Q

What are the 4 different parts to a chemical synapse between a skeletal muscle and a motor neuron?

A

Pre-synaptic knob (axon terminal)
Synaptic cleft
Pre- and post synaptic membrane

37
Q

What are axon terminals?

A

Ends of nerve fibers that store and release chemical messengers (NTs) at neuromuscular junctions

38
Q

What is the synaptic cleft?

A

A space between the axon terminal and skeletal muscle plasma membrane

39
Q

Describe the steps of the neuromuscular junction/innervation of a skeletal muscle

A
  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
Q

How is ACh removed from the synaptic cleft?

A

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
Q

Describe cardiac muscle nuclei

A

Usually cardiac muscle cells have one nucleus but may have two
Centrally located in the cytoplasm

42
Q

What is unique about cardiac muscle cell contraction?

A

Can spontaneously contract

Do not need innervation to contract

43
Q

What is the diad of cardiac muscle cells?

A

1 t-tubule and 1 SR cisternae found at Z lines and permits uniform contraction of myofibrils within a single cardiomyocyte

44
Q

What are intercalated discs?

A

Specialized interdigitating junctions between cardio myocytes that are sites of cell-cell adhesion and low electrical resistance (combination of gap junctions and desmosomes)

45
Q

What is the function of intercalated discs of cardiac muscle?

A

Bind cells and transmit forces of contraction to allow for the spread of excitation within the muscle

46
Q

What are the three types of membrane to membrane contacts of an intercalated disc junction?

A

Transverse region includes fascia adherens and desmosomes

Longitudinal region includes gap (nexus) junctions

47
Q

What are fascia adherens of intercalated discs?

A

Actin filaments at the ends of terminal sarcomeres that insert into the intercalated junction
Transmit contractile forces between cells
Most predominant

48
Q

What is the purpose of the desmosomes within the intercalated disc junction?

A

Provide anchorage for the intermediate filaments of the cytoskeleton

49
Q

What are the gap (nexus) junctions of the intercalated disc junction?

A

Sites of low electrical resistance that allows for excitation to pass between cardiac muscle cells

50
Q

Describe smooth muscle cell nuclei

A

Single elliptical nucleus in center of cytoplasm

51
Q

Describe smooth muscle cell cytoplasm

A

No visible striations in cytoplasm but they still use actin/myosin for contraction

52
Q

What connects smooth muscle cells?

A

Gap junctions

53
Q

What innervates smooth muscle cells?

A

ANS

54
Q

What controls smooth muscle cell contraction?

A

Hormones

55
Q

Describe the smooth muscle contraction apparatus

A

Contractile apparatus is made up of thin and thick filaments which are anchored to cytoplasmic densities/dense bodies

56
Q

What are dense bodies comprised of and what is their function?

A

Desmin and vimentin intermediate filaments

Transmit tension to the cell membrane

57
Q

True or false: smooth muscle cells contract as one unit

A

True and they assume a globular shape

MSK Final Exam (26 decks)

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