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Cell Biology Block 1 > Muscle > Flashcards

Muscle Flashcards

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1
Q

What type of PNS innervation are the 3 types of muscle cells?

A 
Skeletal= somatic motor
Cardiac= involuntary automatic nervous system control
Smooth= involuntary automatic nervous system control
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2
Q
  1. What does skeletal muscle look like on a slide?

2. Difference between cardiac and smooth muscle on a slide?

A
  1. Many muscle cells are fused together
  2. Cardiac cells are separated by intercalated discs; smooth cells are separated by ECM (on slide, cardiac looks like there is more white spots - glycogen)
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3
Q

Hierarchical levels of organization of skeletal muscle? (From big to small)

A

Muscle fascicles, muscle fiber, myofibril, sarcomere

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4
Q

3 connective tissue layers that surround and subdivide skeletal muscle?

What do these connective layers contain?

A

Epimysium, perimysium,
Endomysium

Blood vessels and nerves supplying muscle cells

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5
Q

When staining a skeletal muscle slide, which type of fiber looks darker?

A

Dark staining = slow twitch fibers

Light staining = fast twitch fibers

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6
Q

Function of the sarcoplasmic reticulum?

A

Ca2+ storage site; releases Ca2+ into cytoplasm when muscle is activated

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7
Q

What is a triad?

A

Cell membrane of muscle cell forms T tubules arranged in parallel with sarcoplasmic reticulum (terminal cisterna) — triads can cause the SR to release its Ca2+

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8
Q

muscle contraction: Inside a myofibril, two major types of proteins are anchored at the ___

A

Z line

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9
Q

Thick filaments = ?
Thin filaments are combination of 3 things = ?

Which ones are anchored to the Z line?

A 
Thick = myosin
Thin= actin, tropomyosin and troponin

Thin

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10
Q

What causes skeletal muscle to appear striped (striated)?

A

Sarcomere

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11
Q

Sarcomere extends from the ___ (location)

What is dystrophin?

A

Z line which is linked to the sarcolemma

A protein that links the Z line to the cell membrane

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12
Q

What is happening in muscle contraction?

A

Thick and thin filaments pull on each other to shorten the sarcomere and entire muscle

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13
Q

Myosin has a head and tail, significance?

A

Myosin heads have binding sites for actin, ATP, and ATPase

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14
Q

What does the enzyme ATPase do?

A

Releases energy by converting ATP to ADP + Pi

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15
Q

Function of troponin?

A

Can bind tropomyosin and Ca2+

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16
Q

Steps of the cross bridge cycle (sliding filament model)

A

~Before cycle starts, troponin blocks myosin head~
Activation of muscle cell leads SR to release Ca2+
Ca2+ binds to troponin, leading it to expose the myosin head for actin to bind to
ATP binds to myosin head, causing actin to detach
ATP gets broken down and energy is released causing conformational change in myosin head
POWER STROKE= unbinding of Pi leads to strengthened binding of actin, which pulls on the thin filament thus shortening the sarcomere

17
Q

After power stroke step, how does another contraction start or cycle stop?

A

When no ATP is present, the myosin will remain attached to then actin (so unable to start another contraction) (rigor mortis)

18
Q

So what two things are necessary for muscle contraction?

A

ATP and Ca2+ release

19
Q

Neural input steps in order to get to the start of the cross bridge cycle?

A

Nerve impulse triggers release of acetylcholine into synaptic cleft
Acetylcholine binds to ionotropic receptors (Na+ channels) allowing Na+ to enter the cell thus increasing voltage
The voltage change causes Ca2+ release from SR into cytoplasm

20
Q

What is another name for an axon terminal?

A

Bouton

21
Q

So overall, release of ___ leads to Ca2+ release

A

Acetylcholine

22
Q

Clinical correlation: Myasthenia Gravis

  1. Pathophysiology?
  2. How does it present?
  3. Diagnostic tests? Will see improvement upon administering?
A
  1. Antibodies are generated against nicotinic acetylcholine receptor
  2. Muscle weakness (at first muscle strength will seem the same, but muscle will fatigue much quicker than it should)
  3. Detection of nAchR antibodies; administration of acetycholinesterase inhibitor (edrophonium)
23
Q
  1. Muscular Dystrophy (Duchenne and Becker Types) is caused by what?
  2. More common in boys or girls? How does it present?
  3. Difference in onset and progression of Duchenne vs Becker
A
  1. Mutations of dystrophin gene
  2. More common in boys (X linked); presents as weakness after achieving motor milestones (crawling, standing, walking, etc.)
  3. Duchenne- 3-5 years old, much more rapid progression (inability to walk by 12)
    Becker- 12 year old onset, slower progression (unable to walk by 25)
24
Q

Two sensory structures of skeletal muscle and what they sense?

A

Muscle spindles- sense muscle stretch

Golgi tendon organs-sense contraction

25
Q

What type of muscle spindle senses the muscle length and speed of stretch?

These provide what information to the CNS?

A

Intrafusal muscle fibers (purely sensory)

Proprioception and reflexive contraction of muscle (“muscle tone”)

26
Q

How do golgi tendon organs sense muscle contraction?

What information do they send to CNS?

A

By detecting tension on tendon during muscle contraction (innervate the tendons, not muscle)

Proprioception and they mediate 2 reflexes (reflexive inhibition of the same muscle and activates reflexive contraction of opposing muscle)

27
Q

How does one cardiac cell commuicate with another cardiac cell?

A

Gap junctions

28
Q

Cardiac muscle release hormone like peptides (ANF, atriopeptin, and auriculin) what do they do?

A

Act at the kidney to promote Na+ and water excretion

29
Q

What are purkinje fibers?

A

Processes coming off of cardiac conducting cells

30
Q

Energy sources for cardiac muscle?

A

Primarily metabolize fatty acids but can also use glycogen

31
Q

Autonomic NS control of smooth muscle?

A

Generally, parasympathetics activate contraction; sympathetics inhibit or do not innervate the muscle

32
Q

Smooth muscle also follows the cross bridge cycle but their filaments are anchored at various points in the cell at ____ that intersect with what?

A

“Dense bodies” that intersect with intermediate filaments of the cytoskeleton

33
Q
  1. What kind of innervation activates Ca2+ release in smooth muscle?
  2. What complex does this calcium release activate?
  3. This complex activates?
A
  1. Parasympathetic
  2. Calcium-calmodulin complex
  3. Kinases (which allow formation of the actin-myosin cross bridges)
34
Q

Which muscle type has the slowest contraction?

Length of contraction of smooth muscle?
Explain?

A

Smooth (its also graded, not all or none- similar to skeletal)

Smooth can also stay in contracted state for extended time
ATPase can be inhibited by phosphorylation, blocking cleavage of ATP and release of energy needed to detach myosin head from actin

35
Q
  1. What is a myoepithelial cell?

2. Name 5 instances of these in the body

A
  1. Tissues composed of epithelial cells that contain contractile mechanisms similar to smooth muscle cells
  2. Sweat glands, salivary glands, mammary glands, seminiferous tubules of testis and iris

Cell Biology Block 1 (13 decks)

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