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MCAT Biology > Ch 11 - The Musculoskeletal System > Flashcards

Ch 11 - The Musculoskeletal System Flashcards

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1
Q

What are the skeletal muscle involved with and how are they described?

A
  • involved in support and movement, propulsion of blood in the venous system, and thermoregulation
  • appear striated, under voluntary (somatic) control, polynucleated
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2
Q

What fibers can skeletal muscles be divided into?

A
  • red (slow-twitch) fibers that carry out oxidative phosphorylation
  • white (fast-twitch) fibers that rely on anaerobic metabolism
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3
Q

What systems use smooth muscle and how do these muscles appear?

A
  • the respiratory, reproductive, cardiovascular, and digestive system
  • nonstriated, under involuntary (autonomic) control, and uninucleated
  • display myogenic activity or contraction without neural input
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4
Q

Where is cardiac muscle and how are they described?

A
  • compromise the contractile tissue of the heart
  • striated, under involuntary (autonomic) control, uninucleated (sometimes binucleated)
  • can display myogenic activity
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5
Q

How are cardiac muscle cells connected?

A

with intercalated discs that contain gap junctions

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6
Q

What is the sarcomere?

A

the basic contractile unit of striated muscle

- made of thick (myosin) and thin (actin) filaments

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7
Q

What is found in the thin filament of sarcomeres?

A

troponin and tropomyosin, they regulate actin-myosin interactions

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8
Q

How is the sarcomere divided?

A

into different lines, zones, and bands

  • Z lines: boundaries of each sarcomere (Z ends the alphabet)
  • M line: located in the middle of the sarcomere (middle)
  • H zone: consists of only thick filaments (thicker letter) - surround M line
  • A band: contain the thick filaments in their entirety (only part that maintains a constant size during contraction) surround H zone
  • I band exclusively thin filaments, between sarcomeres
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9
Q

What do sarcomeres form when they attach end to end?

A

myofibrils (each myocyte - muscle cell/fiber- contains many myofibrils)

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10
Q

What surrounds myofibrils?

A

the sarcoplasmic reticulum, a calcium containing modified endoplasmic reticulum, and the cell membrane of a myocyte (sarcolemma)

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11
Q

What are T tubules?

A

a system of T tubules is connected to the sarcolemma and oriented perpendicularly to the myofibrils, allowing the action potential to reach all parts of the muscle

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12
Q

Where does muscle contraction begin?

A

at the neuromuscular junction, where the motor neuron release acetylcholine that binds to receptors on the sarcolemma, causing depolarization, which spread down the sarcolemma to the T tubules, triggering the release of calcium ions

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13
Q

What does the release calcium from muscle contraction do?

A

calcium binds to troponin, causing a shift in tropomyosin and exposure of the myosin-binding sites on the actin thin filament

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14
Q

When does shortening of the sarcomere occur in muscle contraction (sliding filament model)?

A

as myosin heads bind to the exposed skin on actin, forming cross bridges and pulling the actin filament along the thick filament which results in contraction

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15
Q

When do the muscle relax after contracting?

A

when acetylcholine is degraded by acetylcholinesterase, terminating the signal and allowing calcium to be brought back into the SR
- ATP binds to the myosin head, allowing it to release from actin

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16
Q

What is a simple twitch?

A

the all or nothing response muscle cells exhibit

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17
Q

What is frequency summation?

A

when addition of multiple simple twitches that occur so frequently as to not let the muscle relax at all

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18
Q

What is tetanus?

A

simple twitches that occur so frequently as to not let the muscle relax at all can lead to tetanus, a more prolonged and stronger contraction

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19
Q

Why do muscle cells have an additional energy reserve?

A

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

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20
Q

What can creatine phosphate do for muscle cells?

A

can transfer a phosphate group of ADP, forming ATP

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21
Q

What is myoglobin?

A

a heme-containing protein that is muscular oxygen reserve

22
Q

What are endoskeletons v exoskeletons?

A
  • endo: internal skeletons (like in humans)

- exo: external skeletons (like in arthropods)

23
Q

What is the difference between the axial and appendicular skeletons?

A
  • axial: structures in the midline, such as the skull, vertebral column, ribcage, and hyoid bone
  • appendicular: bonds of the limbs, pectoral girdle, and pelvis
24
Q

What is the bone derived from?

A

embryonic mesoderm and includes both compact (provides strength and is dense) and spongy bone

25
Q

What is spongy bone?

A

(cancellous bone) has a lattice-like structure consisting of bony spicules (trabeculae)
- the cavities are filled with bone marrow

26
Q

What are the diaphyses, metaphyses, and epiphysis of long bones?

A
  • long bones contain shafts called diaphyses that flare to form metaphyses and terminate in epiphyses
  • the epiphysis contains an epiphyseal (growth) plate that causes linear growth of the bone
27
Q

What surrounds the bone?

A

a layer of connective tissue (periosteum)

  • serves as a site of attachment of bone to muscle
  • cells may differentiate into osteoblasts
  • a fibrous sheath that surrounds long bones
28
Q

How do muscles attach to bone and each other?

A

muscles by tendons and to each other by ligaments

29
Q

What are the organic and inorganic components of the bone matrix?

A
  • organic: collagen, glycoproteins, other peptides

- inorganic: hydroxyapatite

30
Q

What is a lamellae and an osteon?

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
31
Q

What are lacunae and canaliculi?

A
  • between lamellar rings are lacunae, where osteocytes reside, which are connected with canaliculi to allow for nutrients and waste transfer
32
Q

What do osteoblasts and osteoclasts do?

A
  • bone remodeling is carried out by osteoblasts and osteoclasts
  • osteoblasts build bone (bone cells involved in the secretion of bone matrix)
  • osteoclasts resorb bone (large, polynucleated cells involved in bone resorption)
33
Q

What does parathyroid hormone do for bones?

A

increase resorption of bone, increasing calcium and phosphate concentrations in the blood

34
Q

What does Vitamin D do for bones?

A

increases resorption of bone, leading to increased turnover and, subsequently, the production of stronger bone

35
Q

What does calcitonin do for bones?

A

increases bone formation, decreasing calcium concentrations in the blood

36
Q

What is cartilage and where is it found?

A
  • a firm, elastic material secreted by chondrocytes
  • its matrix is called chondrin
  • usually found in areas that require more flexibility or cushioning
  • avascular and not innervated
37
Q

How do bones form in fetal life?

A
  • from cartilage through endochondral ossification
  • some bones, especially those of the skull, form directly from undifferentiated tissue (mesenchyme) in intramembranous ossification
38
Q

What is the difference between immovable and movable joints?

A
  • immovable are fused together to form sutures or similar fibrous joints
  • movable are usually strengthened by ligaments and contain a synovial capsule
39
Q

What is synovial fluid?

A
  • secreted by synovium

- aids in motion by lubricating the joint

40
Q

What is articular cartilage?

A

coats every bone to aid in movement and provide cushioning

41
Q

What are antagonistic pairs?

A

muscles that serve opposite functions

- when one muscle contracts, the other lengthens

42
Q

What is myogenic activity?

A

muscles (cardiac and smooth) will respond to nervous input, but can contract without external signals from nervous system

43
Q

What is the sarcoplasmic reticulum?

A
  • fancy name for the specialized endoplasmic reticulum in muscle cells
44
Q

What is responsible for the powerstroke?

A

the dissociation of ADP and Pi from myosin, not the hydrolysis of ATP
- the binding of ATP is required for releasing the myosin head from the actin filament

45
Q

Which zone or band in the sarcome does not change its length during muscle contraction and why?

A
  • A bind does not change because it the entire length of the myosin filament
  • the filaments do not change length, but rather slide over each other
46
Q

What are the events that initiate muscle contraction, in order, starting with neurotransmitter release and trace the pathway to the point where myosin binds with actin.

A
  • release of acetylcholine from motor neuron
  • activation of acetylcholine receptors in sarcolemma
  • depolarization of sarcolemma
  • spreading of signal T tubules
  • release of calcium from sarcoplasmic reticulum (SR)
  • binding of calcium to troponin
  • conformation shift in tropomyosin
  • exposure of myosin binding sites
  • myosin binds to actin
47
Q

What role does the binding of ATP to the myosin head play in the cross bridge cycle? What about the dissociation of ADP and inorganic phosphate from the myosin head?

A
  • ATP binding allows the myosin filament to disconnect from actin
  • dissociation of ADP and inorganic phosphate from myosin causes the powerstroke
48
Q

What chemical forms most of the inorganic components of bone?

A

hydroxyapatite crystals

49
Q

What are chondrocytes?

A

form cartilage, secret chondrin

50
Q

What are red bone marrow and yellow bone marrow involved in?

A
  • red involved in erythrocyte formation

- yellow is largely inactive and contains predominantly adipose tissue

MCAT Biology (12 decks)

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