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MCAT - Biology > Chapter 11 - The Muscular System > Flashcards

Chapter 11 - The Muscular System Flashcards

1
Q

What are the three main types of Muscle?

A
  1. Sekeltal
  2. Smooth
  3. Cardiac
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2
Q

What is the role of Skeletal Muscle?

A

Involved in support and movement, propulsion of blood in the venous system, and thermoregulation.

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3
Q

How does Skeletal Muscle carry out its function?

A

Skeletal Muscle appears striated, is under voluntary (somatic) control, is ploynucleated and can be divided into red (slow twitch) fibres that carry out oxidative phosphorylation and white (fast-twitch) fibres that rely on anaerobic metabolism.

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4
Q

What is the role of Smooth Muscle?

A

Smooth Muscle is relevant in the respiratory, reproductive, cardiovascular, and digestive systems.

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5
Q

How does Smooth Muscle carry out its function?

A

It appears non-striated, is under involuntary (autonomic) control and is un-nucleated. It can display myogenic activity, or contraction without neural input.

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6
Q

What is the role of Cardiac Muscle?

A

Cardiac Muscle comprises the contractile tissue of the heart.

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7
Q

How does Cardiac Muscle carry out its function?

A

It appears striated, is under involuntary (autonomic) control, and is un-nucleated (sometime bi-nucleated). It can also display myogenic activity. Cells are connected with intercalated discs that contain gap junctions.

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8
Q

What are Sarcomeres?

A

The Sarcomere is the basic contractile unit of striated muscle and is made of thick (myosin) and thin (actin) filaments.

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9
Q

Where are Troponin and Tropomyosin found?

A

They’re found on the thin filament and regulate actin-myosin interactions.

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10
Q

What boundaries, lines, zones and bands are Sarcomeres divided into?

A
  1. Z-lines
  2. M-line
  3. I-band
  4. H-zone
  5. A-band
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11
Q

What is the role of Z-lines?

A

Define the boundaries of each sarcomere.

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12
Q

Where is the M-line located?

A

Located in the middle of the sarcomere.

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13
Q

What do I-bands contain?

A

Only thin filaments

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14
Q

What do H-zones consist of?

A

Only thick filaments

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15
Q

What is the role of A-Bands?

A

The A-band contains the thick filaments in heir entirety. It is the only part of the sarcomere that maintains a constant size during contraction.

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16
Q

How do Sarcomeres attach?

A

Attach end-to-end to become myofibrils, and each myocyte (muscle cell or muscle fibre) contains many myofibrils.

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17
Q

What are Myofibrils surrounded by?

A

The Sarcoplasmic Reticulum, a calcium containing modified endoplasmic reticulum, and the cell membrane of a myocyte known as the sarcolemma.

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18
Q

What is the role of the system of T-tubules connected t the Sarcolemma?

A

Oriented perpendicular to the myofibrils, the system allows the action potential to reach all parts of the muscle.

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19
Q

How does muscle contraction occur?

A

Muscle contraction begins at the neuromuscular junction, where the motor neuron releases acetylcholine that binds to receptors on the sarcolemma, causing depolarization. This depolarization spreads down the sarcolemma to the T-tubules, triggering the release of calcium ions.

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20
Q

What occurs when Calcium binds to Troponin?

A

Causes a shift in tropomyosin and exposure of the myosin-binding sites on the actin thin filament.

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21
Q

When does shortening of the Sarcomere occur?

A

Shortening of the Sarcomere occurs as myosin heads bind to the exposed sites on actin, forming cross brides and pulling the actin filaments along the thick filament, which results in contraction. This is known as the Sliding Filament Model.

22
Q

In the Actin-Myosin Cross-Bridge cycle, what is responsible for the powerstroke?

A

The dissociation of ADP and Pi from myosin, NOT the hydrolysis of ATP. ATP is required for releasing the myosin head from the actin filament.

23
Q

What is the name of the all-or-nothing response exhibited by muscle cells?

A

Simple Twitch

24
Q

What is Frequency Summation?

A

Addition of multiple simple twitch before the muscle has an opportunity to fully relax.

25
Q

What can result when simple twitches that occur so frequently as to not let the muscle relax at all?

A

Tetanus; a more prolonged and stronger contraction.

26
Q

Why do muscle cells have additional energy reserves?

A

To reduce oxygen debt (the difference between the amount of oxygen needed and the amount present) and forestall fatigue.

27
Q

What is the role of Creatine Phosphate?

A

Can transfer a phosphate group to ADP, forming ATP.

28
Q

What is Myoglobin?

A

A heme-containing protein that is a muscular oxygen reserve.

29
Q

Why does the A-band not change length during muscle contraction?

A

Because it is the entire length of the myosin filament. The filaments do not change length, but rather slide over each other; thus, the A-band should remain a constant length during contraction.

30
Q

In order, what are the 9 events that initiate muscle contraction?

A
  1. Release of acetylcholine from motor neuron
  2. Activation of acetylcholine receptors in sarcolemma
  3. Depolarization of sarcolemma
  4. Spreading of signal using T-tubules
  5. Release of Calcium from Sarcoplasmic Reticulum
  6. Binding of Calcium to Troponin
  7. Conformational shift in tropomyosin
  8. Exposure of myosin-binding sites
  9. Myosin binds to actin.
31
Q

What is the difference between Endoskeletons and Exoskeletons?

A

Endo: internal skeletons (humans)
Exo: external skeletons (arthropods)

32
Q

What are the 2 divisions of the human skeleton?

A
  1. Axial

2. Appendicular

33
Q

What does the Axial Skeleton consist of?

A

The structures in the midline such as the skull, vertebral column, ribcage and hyoid bone.

34
Q

What does the Appendicular Skeleton consist of?

A

The bones of the limbs, the pectoral girdle, and the pelvis.

35
Q

What is bone derived from?

A

Embryonic mesoderm and includes both compact and spongey (cancellous) types.

36
Q

What is the difference between Compact Bone and Spongey or Cancellous Bone?

A

Compact provides strength and is dense; Spongey has a lattice-like structure consisting of bony spicules known as trabeculae.

37
Q

What are the shafts found in long bones called? What is their function?

A

Diaphyses; they flare to form metaphyses and terminate in epiphyses. The epiphyses contains an epiphyseal (growth) plate that causes linear growth of the bone.

38
Q

What is the layer of connective tissue surrounding bone called?

A

Periosteum

39
Q

How are bones attached to muscles and to each other ?

A

To muscles by tendons; to eachother by ligaments.

40
Q

What is Bone Matrix made up of?

A

Both organic compounds, like collagen, glycoproteins, and other peptides; and inorganic components like hydroxyapatite.

41
Q

How is Bone organized?

A

Bone is organized into concentric rings called lamellae around a central Haversian or Volkmann’s canal. This structural unit is called an osteon or Haversian System.

42
Q

What lie between Lamellar rings?

A

Lacunae, where osteocytes reside, which are connected with canaliculi to allow for nutrient and waste transfer.

43
Q

What is bone remodelling carried out by?

A

Osteoblasts: build bone
Osteoclasts: reabsorb bone

44
Q

How does Parathyroid hormone increase reabsorption of bone? What about Vitamin D?

A

By increasing calcium and phosphate concentration in the blood. Vitamin D also increases reabsorption of bone, leading to turn over and, subsequently, the production of stronger bone.

45
Q

What does Calcitonin do?

A

Increases bone formation, decreasing calcium concentrations in the blood.

46
Q

What is Cartilage?

A

A firm, elastic, material serrated by chondrocytes. Its matrix is called chondrin. It’s avascular and is not innervated.

47
Q

How does bone form from cartilage in fetal life?

A

Via endochondral ossification. Some bones, especially those of the skull, form directly from undifferentiated tissue (mesenchyme) in intramembranous ossification.

48
Q

Why are Immovable Joints fused together?

A

To form sutures or similar fibrous joints.

49
Q

How are Movable Joints strengthened?

A

By ligaments and contain a synovial capsule.

50
Q

What is the function of Synovial Fluid?

A

Secreted by synovium, it aids in motion by lubricating the joint.

51
Q

What are each bone in a joint coated with?

A

Articular Cartilage, to aid in movement and provide cushioning.

52
Q

What does it mean when muscles come in Antagonistic Pairs?

A

If two muscles serve opposite functions; when one muscle contracts the other lengthens.

MCAT - Biology (12 decks)

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