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MBBCh 1- APES1001A > Histology: Muscle Tissue > Flashcards

Histology: Muscle Tissue Flashcards

1
Q

How does the muscle system work with skeletal system?

A

Muscles allow for movement of the skeleton.

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2
Q

How does the muscle system work with the circulatory system?

A
  • Carries hormones that regulate muscle activity
  • Brings nutrients to muscles and takes waste away
  • Cardiac muscle allows for blood to be pumped and circulated
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3
Q

How does the muscle system work with the nervous system?

A

Stimulus sent via motor neuron to muscle

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4
Q

How does the muscle system work with the immune system? (2)

A
  • When fighting infection —> T cells lose functionally through continuous stimulation
  • Cells migrate from muscles —> develop into functional T cells
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5
Q

How does the muscle system work with the respiratory system?

A

Diaphragm muscle allows for breathing

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6
Q

How does the muscle system work with the digestive system? (3)

A
  • Muscles of the jaw help chew food
  • Muscles lining the oesophagus move food from mouth —> stomach
  • Muscles lining intestines moves digested food and muscle controls sphincters
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7
Q

What is muscle tissue responsible?

A

Muscle tissue responsible for body movement.

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8
Q

Muscle cells consist of filaments containing proteins ____ and _____, which together enable muscle contraction .

A

actin

myosin

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9
Q

What are the features of smooth muscle? (3)

A
  1. Has spindle-shaped, non striated uninucleated fibres
  2. Occurs in walls of internal organs
  3. Is involuntary
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10
Q

What are the features of the cardiac muscle? (3)

A
  1. Has striated, branched, uninucleated fibres.
  2. Occurs in the walls of the heart
  3. Is involuntary
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11
Q

What are the features of skeletal muscle? (3)

A
  1. Has striated tubular, multinucleated fibres.
  2. Is usually attached to the skeleton
  3. Is voluntary
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12
Q

Where is smooth muscle found? (2)

A
  • Found in the walls of the digestive tract, urinary bladder, arteries, and other internal
  • Involuntary: example, churning of the stomach & constriction of arteries
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13
Q

Cardiac muscle
• _____ like skeletal
• Branched fibers that interconnect via _____ disks

A

Striated

intercalated disks

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14
Q

Cardiac muscle forms the _____ wall of the heart.

A

contractile

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15
Q

Cardiac muscle Has similar contractile properties as _____ muscle.

A

skeletal

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16
Q

What do branched fibres in cardiac muscle do? (2)

A
  • Branched fibers relay signals from cell to cell and help synchronise heart contraction
  • Involuntary control
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17
Q

What do skeletal muscle consist of?

A

Consists of bundles of long cells: muscle fibres.

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18
Q

How does skeletal muscle form?

A

• Form by the fusion of many cells- resulting in multiple nuclei in each muscle fiber

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19
Q

How does skeletal muscle have a striped appearance?

A

Arrangement of contractile units (sarcomeres) along the fibres gives the cells a striped (striated) appearance.

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20
Q

Skeletal muscle tissue is attached to _____ by tendons.

A

bones

21
Q

Skeletal muscle, or striated muscle, is responsible for ______ movements.

A

voluntary

22
Q

In adult mammals, building muscle increases the ___ but not the _____ of muscle fibres.

A

size

number

23
Q

What does muscle cell contraction rely on?

A
  • Relies on the interaction between protein structures—> thin and thick filaments.
24
Q

-The major component of thin filaments is the globular protein _____.

A

actin

25
Q

Which structures function in cell motility?

A
  • thin filaments —> two strands of polymerized actin coiled around one another —> similar to the actin structures called microfilaments function in cell motility
26
Q

What are thick filaments?

A
  • thick filaments —> staggered arrays of myosin molecules
27
Q

What is muscle contraction result of?

A
  • Muscle contraction —> result of filament movement powered by chemical energy: muscle extension
    occurs only passively
28
Q

What are the main components of skeletal muscle? (3)

A
  • Within typical skeletal muscle —> is a bundle of long fibres running along the length of the muscle
  • Each individual fibre is a single cell —> within are multiple nuclei —> derived from one of the embryonic cells that fused to form the fibre
  • Surrounding these nuclei —> longitudinal myofibrils —> consist of bundles of thin and thick filaments
29
Q

What are myofibrils?

A
  • myofibrils in muscle fibres—>made up of repeating sections called sarcomeres—> the basic
    contractile units of skeletal muscle
30
Q

Where do borders of the sarcomere line up?

A
  • borders of the sarcomere line up in adjacent myofibrils—>forming pattern of light and dark bands
    (striations) visible with a light microscope—>skeletal muscle also called striated muscle
31
Q

Where do thin filaments attach at?

A 
-Thin filaments attach at Z lines —> sarcomere ends & thick filaments—> anchored in the middle of
the sarcomere (M line)
32
Q
  • In resting/relaxed myofibril—> thick and thin filaments partially overlap: (3)
A
  • Near edge of the sarcomere —> only thin filaments
  • Zone in the centre —> only thick filaments
  • Partially overlapping arrangement is how the sarcomere and whole muscle contracts
33
Q

What must happen for a muscle to contract?

A
  • For a muscle cell to contract—> sarcomere must shorten
34
Q

How do thick and thin filaments contract?

A
  • However —> thick and thin filaments—the components of sarcomeres—do not shorten -Instead
    —> they slide by one another, causing the sarcomere to shorten while the filaments remain the same length
35
Q

Why was the sliding filament theory of muscle contraction developed? (2)

A
  • The sliding filament theory of muscle contraction was developed to fit the differences observed in the
    named bands on the sarcomere at different degrees of muscle contraction and relaxation
  • The mechanism of contraction is the binding of myosin to actin —> forming cross-bridges that
    generate filament movement
36
Q

What happens when a sarcomere shortens?

A
  • When a sarcomere shortens —> some regions shorten whereas others stay the same length
37
Q

How is a sarcomere defined as?

A
  • A sarcomere—>defined as the distance between two consecutive Z discs or Z lines; when a muscle
    contracts: the distance between the Z discs is reduced
38
Q

What does the H zone contain?

A

-The H zone—>the central region of the A zone—>contains only thick filaments and is shortened during
contraction

39
Q

-The I ___ contains only thin filaments and also shortens

A

band

40
Q

Does the A band shorten?

A
  • NO, the A band does not shorten—it remains the same length—but A bands of different sarcomeres move closer together during contraction —> eventually disappearing
41
Q

What are thin filaments pulled by?

A
  • Thin filaments are pulled by the thick filaments toward the center of the sarcomere until the Z discs approach the thick filaments
42
Q

What happens in the zone of overlap?

A
  • The zone of overlap—>in which thin filaments and thick filaments occupy the same area, increases as
    the thin filaments move inward.
43
Q

Does the actin and myosin filaments change length?

A
  • No, the actin and myosin filaments themselves do not change length —> but instead slide past each other
44
Q

What is the process of ATP and muscle contraction? (5)

A
  1. Starting here, the myosin head is bound to ATP and is in its low-energy configuration
  2. The myosin head hydrolyzes ATP to ADP and Pi (inorganic phosphate) and is in its high-energy configuration
  3. The myosin head binds to actin, forming a cross-bridge with the thin filament
  4. The cross-bridge couples the release of ADP and Pi to a power stroke that slides the thin filament along the myosin and returns the myosin head to a low-energy state
  5. Binding of a new molecule of ATP releases the myosin head from actin, and a new cycle begins
45
Q

Muscle contraction requires repeated cycles of binding and release: (5)

A

• During each cycle of each myosin head, the head is freed from a cross-bridge, cleaves the newly
bound ATP, and binds again to actin.
• Because the thin filament moves toward the centre of the sarcomere in each cycle, the myosin head
now attaches to a binding site farther along the thin filament than in the previous cycle.
• Each end of a thick filament contains approximately 300 heads, each of which forms and re-forms
about five cross-bridges per second, driving the thick and thin filaments past each other. At rest, most muscle fibres contain only enough ATP for a few contractions. Powering repetitive contractions requires two other storage compounds: creatine phosphate and glycogen.
• The transfer of a phosphate group from creatine phosphate to ADP in an enzyme-catalysed reaction synthesizes additional ATP. In this way, the resting supply of creatine phosphate can sustain contractions for about 15 seconds.
• ATP stores are also replenished when glycogen is broken down to glucose. During light or moderate muscle activity, this glucose is metabolized by aerobic respiration. This highly efficient metabolic
process yields enough power to sustain contractions for nearly an hour.
- intense muscle activity—> oxygen becomes limiting and ATP is instead generated by lactic acid
fermentation—>anaerobic pathway very rapid—>generates much less ATP per glucose molecule and
can sustain contraction for only about 1 minute

46
Q

What is the function of the regulatory protein tropomyosin? (2)

A
  • The regulatory protein tropomyosin and the troponin complex, a set of additional proteins,
    bind to actin strands on thin filaments when a muscle fibre is at rest.
  • This prevents actin and myosin from interacting.
47
Q

What is the stimulus leading to the contraction of a muscle fibre?

A

The stimulus leading to contraction of a muscle fiber is an action potential in a motor neuron that makes a synapse with the muscle fiber.

48
Q

The synaptic terminal of the motor neuron releases the neurotransmitter acetylcholine. What is the function of this?

A

Acetylcholine depolarizes the muscle, causing it to produce an action potential.

MBBCh 1- APES1001A (38 decks)

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