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M2M > Muscle > Flashcards

Muscle Flashcards

1
Q

What are the boundaries of a sarcomere?

A

from one Z line to another Z line

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2
Q

What are myofibrils?

A
  • bundles of contractile filaments
  • make up a muscle fiber
  • covered with its own network of sarcoplasmic reticulum
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3
Q

What are the regulatory proteins of myofibrils?

A

tropomyosin and troponin

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4
Q

What are the thin filaments in a muscle fiber?

A
  • what myosin binds to
  • made of actin
  • tropomyosin and troponin (regulatory proteins) bind to the actin filaments
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5
Q

What are the thick filaments in a muscle fiber?

A
  • made of myosin
  • myosin heads interact with actin
  • actin-myosin work together for contraction with ATPase
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6
Q

What prevents the binding of myosin to actin in the relaxed state?

A

tropomyosin

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7
Q

How is the binding site for myosin uncovered?

A

troponin binds to Ca2+ and undergoes a conformational change -> induces conformational change in tropomyosin

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8
Q

Why does myosin exert force as soon as it binds?

A

the energy is released upon binding because it does not need ATP in order to exert force

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9
Q

What causes myosin to release from actin?

A

ATP binding and hydrolysis puts myosin into a high energy state

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10
Q

How do we get so much muscle shortening?

A
  • lots of sarcomeres in series will summate linearly

- many myosin-actin cycles occur during a single contraction

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11
Q

Is regulation of cardiac muscle like skeletal muscle?

A

yes

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12
Q

How is smooth muscle regulated?

A
  • no troponin
  • increased Ca2+ binds to calmodulin
  • Ca-calmodulin binds to CaM kinase and phosphorylates the myosin head
  • phosphorylated myosin binds to actin and generates force
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13
Q

Is the process of smooth muscle activation faster or slower than skeletal and cardiac muscle?

A

much slower

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14
Q

How is calcium removed in smooth muscle?

A

Ca pumps and Na-Ca exchangers in the sarcolemma

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15
Q

Each skeletal muscle cell of a mammal is innervated at _____ spot.

A

one

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16
Q

An action potential in the motor axon causes release of ___________.

A

acetylcholine

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17
Q

What do large muscle cells use for action potentials (re. Ca2+)?

A

the T-system and sarcoplasmic reticulum

18
Q

What would happen if skeletal or cardiac muscle cells did not contract uniformly?

A

the shear forces would destroy the cells

19
Q

What is diffusion r^2 (mean distance) proportional to?

A

time

20
Q

What is the transverse tubule system?

A
  • membrane structure that allows the action potential to propagate through the cross section of the cell
  • the action potential propagates rapidly along the length and depth of the cells
21
Q

Why is the sarcoplasmic reticulum important for skeletal and cardiac muscle contraction?

A
  • each myofibril has a SR around the bundle

- Ca2+ is stored in the SR (small distance for Ca2+ to diffuse)

22
Q

Myofilaments are bundled to form ________.

A

myofibrils

23
Q

What protein can bind to approx 50 Ca2+ and is in muscle cells?

A

calsequestrin

24
Q

At muscle relaxation, ______________ pumps Ca2+ back into the _______.

A

Ca2+ ATPase pump; sarcoplasmic reticulum

25
Q

What is a motor unit?

A

the muscle fibers innervated by a motor neuron

26
Q

Are cardiac and smooth muscle innervated?Can they function without nerve innervation?

A

they are innervated but can function without nervous innervation

27
Q

How can skeletal muscle tension be gradated?

A
  • increase the frequency of action potentials

- recruit additional motor units

28
Q

What are satellite cells regarding skeletal muscle?

A

stem cells

- source of new myoblasts to repair injured muscle

29
Q

What regulates the proliferation of satellite cells?

A

fibroblasts in the connective tissue

30
Q

Can cardiac muscle repair itself?

A

no

31
Q

Can smooth muscle repairs itself?

A

yes

- cells can dedifferentiate and regenerate new muscle cells

32
Q

What happens to your muscles when you lift weights?

A
  • no new skeletal muscle fibers

- new myofibrils are formed (cross sectional area of each cell is increased)

33
Q

What is the key difference between E-C coupling of skeletal and cardiac muscle?

A
  • Ca2+ binding is needed via DHPR entry to trigger Ca2+ release from SR in the heart (via RyR)
  • DHPRs in skeletal muscle make direct physical contact with the RyR after binding to Ca2+ and produce Ca2+ release
34
Q

What occurs in hypertrophic cardiomyopathy?

A
  • cardiac murmur
  • cardiac pump failure
  • sudden death
  • cardiomyocyte and cardiac hypertrophy
  • myocyte disarray
  • interstitial and replacement fibrosis
  • dysplastic intramyocardial arterioles
35
Q

What is the disorder that results in hypertrophic cardiomyopathy?

A
  • autosomal dominant (most)
  • missense mutation
  • incomplete penetrance
  • disease of the sarcomere (mostly)
36
Q

What does myostatin do?

A

normally negative feedback for muscle growth

37
Q

What does myostatin deficiency look like?

A
  • very muscular and strength
38
Q

What causes malignant hyperthermia?

A
  • RyR 1 mutation

- exposure to halothane and/or succinylcholine

39
Q

What is the phenotype of malignant hyperthermia?

A
  • hypermetabolism
  • skeletal muscle damage
  • hyperthermia
  • death if untreated
40
Q

What are the clinical signs of malignant hyperthermia?

A
  • muscle rigidity (masseter spasm)
  • increased CO2 production
  • rhabdomyolysis
  • hyperthermia
41
Q

What is the treatment for malignant hyperthermia?

A

dantrolene 2.5 mg/kg

M2M (41 decks)

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