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MCAT - Bio/Biochem > Muscle, skin, tissue, etc > Flashcards

Muscle, skin, tissue, etc Flashcards

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1
Q

What are the principle descriptors of skeletal muscle?

A
  1. Voluntary
  2. On bones
  3. Multinucleate
  4. Striated
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2
Q

What is the hierarchy of muscle components/cells

A

Actin + Myosin -> sarcomere -> myofibril -> myofiber (now considered the muscle CELL–contains organelles and cytoplasm) -> fascicle -> whole muscle

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3
Q

The sarcoplasmic reticulum stores what?

A

Calcium

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4
Q

The sarcoplasmic reticulum acts like a net that surrounds bundles of what?

A

myofibrils

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5
Q

How does the calcium stored in the sarcoplasmic reticulum reach into the innermost part of the myofibril bundle?

A

T tubules! Go crosswise across muscle cell, allowing AP to travel to the interior of the cell.

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6
Q

What level of muscle complexity is the initial unit of contraction?

A

Sarcomere

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7
Q

What kind of filament(s) make(s) up the I band?

A

Actin only

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8
Q

What kind of filament(s) make(s) up the A band?

A

Actin and myosin

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9
Q

What kind of filament(s) make(s) up the H zone?

A

myosin only

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10
Q

What part of the sarcomere “disappears” during contraction?

A

H zone disappears and I band shrinks greatly

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11
Q

What step(s) in actin-myosin binding require ATP?

A
  1. The PRESENCE (but not hydrolysis) of ATP is required for myosin to release actin after the power stroke.
  2. ATP hydrolysis is used to reset the myosin head to a “high energy conformation”
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12
Q

Does the power stroke of actin-myosin binding require ATP?

A

NO!

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13
Q

When you run out of ATP, your muscles can’t _________.

A

Relax! This is why rigor mortis occurs.

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14
Q

Do myosin head groups act synchronously or asynchronously?

A

Asynchronously

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15
Q

What does tropomyosin do?

A

Covers up the myosin binding sites so that actin and myosin cant interact

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16
Q

What does troponin do?

A

When calcium is released, it binds to troponin, tugging tropomyosin out of the way so that it no longer blocks the myosin binding sites -> myosin can bind to actin -> filaments slide (contraction)

17
Q

What causes release of calcium from the sarcoplasmic reticulum?

A

Depolarization of the cell (SR) -> opens voltage-gated calcium channels and calcium floods the cytosol, binds to troponin

18
Q

What is a motor unit? How would you describe contraction at this level?

A

A motor neuron and all the muscle cells it controls.

Contraction at this level is all or none.

19
Q

In what is the first energy used by muscle cells?

A

Phosphocreatine

20
Q

What molecule stores oxygen in the muscles?

A

Myoglobin

21
Q

What things cause the oxyhemoglobin saturation curve to shift to the right?

A
  1. Increased CO2
  2. Increased temp
  3. Decreased pH
22
Q

What are the characteristics of Type II muscle fibers? Which is the fastest?

A 
White
Contract fast
Contract strongly
Fatigues easily
Low myoglobin
Low mito
Low blood supply

Type IIB = the fastest of all

23
Q

What are the characteristics of Type I muscle fibers?

A 
Red
Contract slowly but for longer
Not as strong
High myoglobin
High mito
Highly vascular
24
Q

What are the regions of a long bone and what are they made of?

A

long shaft called diaphysis made of compact bone and yellow marrow (fat). The innermost region that contains the marrow is called the medullary cavity.

+ 2 collagenous growth plates at each end

The knobs at the ends are made of spongy bone and are called epiphysis

25
Q

What is an osteocyte?

A

Mature bone cell, dormant

26
Q

Compact bone is made of many __________.

A

Osteons

27
Q

What is at the center of each osteon?

A

A central canal to bring blood and exchange nutrients and waste with the osteocytes via canaliculi

28
Q

What type of cell builds new bone?

A

Osteoblast

29
Q

What is the larynx made out of?

A

Cartilage

30
Q

What prevents food from entering the trachea while swallowing?

A

The epiglottis

31
Q

What is the purpose of surfactant?

A

Reduce surface tension in the lungs

32
Q

Describe cardiac muscle

A
  1. Striated
  2. Branched
  3. Mononucleate
  4. Connected via gap junctions
33
Q

Where is red marrow found?

A

Spongy part of flat and long bones (epiphyses/knobs of long bones)

34
Q

Which of protein binds calcium in smooth muscle cells?

A

Calmodulin

MCAT - Bio/Biochem (9 decks)

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