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Kaplan MCAT > BIO Ch. 11 Musculoskeletal System > Flashcards

BIO Ch. 11 Musculoskeletal System Flashcards

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MCAT flashcards
1
Q

What is the purpose of calcium?

A

muscle contraction

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2
Q

Describe skeletal muscle.

A

innervated by somatic NS, striated due to sarcomeres, multinucleated, under voluntary control

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3
Q

What are red fibers made of?

A

slow-twitch fibers, have high myoglobin to drive energy aerobically, and many mitochondria to carry out oxidative phosphorylation

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4
Q

What are white fibers made of?

A

fast-twitch fibers contain less myoglobin and thus less heme and hence less color, and fatigue quickly, use anaerobic respiration

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5
Q

Describe smooth muscle.

A

involuntary movement controlled by autonomic NS, a single nucleus in the center of the cell

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6
Q

What is myogenic activity?

A

the contraction of muscle without NS input, but directly in response to stretch or other stimuli

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7
Q

Describe cardiac muscle.

A

1-2 nucleus per cell, involuntary movement innervated by the ANS, appears striated

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8
Q

What is the role of gap junctions in cardiac myocytes?

A

myocytes are connected by an intercalated disc which contains many gap junctions that connect b/w the cytoplasmic of adjacent cells, allowing for the flow of ions directly b/w cells which allows for coordinated muscle cell depolarization and efficient contraction of cardiac muscle

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9
Q

How does myogenic activity allow for myocytes to maintain their rhythm?

A

starting at the SA node, depolarization spreads using conduction pathways at the AV node spreading down into the bundle of His and its branches, and then to the Purkinje fibers

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10
Q

How does epinephrine increase heart rate?

A

epinephrine from the adrenal medulla increased intracellular calcium levels within the myocytes

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11
Q

What is a sarcomere?

A

the contractile unit of skeletal muscle

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12
Q

What are the proteins that make up the sarcomere?

A

myosin - thick filaments
actin - thin filaments
troponin and tropomyosin - help regulate interaction b/w actin and myosin filaments
titin - acts as a spring and anchors the actin and myosin filaments together, preventing excess stretching of the muscle

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13
Q

What are the parts of the sarcomere?

A

Z-line - defines the boundaries of the sarcomere
M-line - runs down the center of the myosin filaments
I-band - contains exclusively thin filaments
H-Zone - contains only thick filaments
A-band - contains thick filaments

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14
Q

Which part of the sarcomere is constant during contraction?

A

the A-band

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15
Q

What covers myofibrils?

A

sarcoplasmic reticulum - a modified endoplasmic reticulum that contains high [Ca2+] ions

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16
Q

What is the sarcolemma?

A

the cell membrane of the myocytes that is capable of propagating an action potential

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17
Q

What is a myofibril, muscle fiber, and muscle?

A

a myofibril is an arrangement of many sarcomeres in series. a muscle fiber contains myofibrils arranged in parallel. a muscle is made up of parallel muscle fibers

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18
Q

Describe the physiology of muscle contraction.

A

Starting at the NMJ, acetylcholine is released and causes a depolarization at the sarcolemma, triggering an AP which then travels down the T-tubules toward the SR and releases calcium into the cell

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19
Q

Describe thesliding filament model

A
  1. Motor (efferent) neurons at the NMJ release acetylcholine that binds its receptors on the sarcolemma, causing depolarization
  2. this depolarization travels down the sarcolemma to the T-tubules, triggering the release of calcium in the sarcoplasmic reticulum
  3. Then calcium ions are released and bind to troponin which causes a conformational change in the tropomyosin protein that opens up myosin binding sites on the actin thin filaments.
  4. Then myosin can bind to actin forming an actin-myosin bridge
  5. The disassociation of ADP from the myosin-cocked head creates a power stroke, and it causes the myosin filament to slide down the actin filament, shortening the sarcomere and drawing the thin actin filaments towards the M-line.
  6. Then an ATP binds to the myosin head, releasing it from the actin filament, causing muscle relaxation.
  7. ATP is hydrolyzed to ADP, and the energy released is used to recock the myosin head to allow the process of muscle contraction to begin all over again.
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20
Q

What proteins makeup actin and myosin?

A

Thick filaments have myosin and ADP, whereas the thick filament has actin, tropomyosin, and troponin

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21
Q

What causes tetanus?

A

when muscle cells are unable to relax between contractions, they are in prolonged and constant contraction

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22
Q

When does muscle relax?

A

when acetylcholine is removed from the NMJ by the enzyme acetyl esterase which breaks down acetylcholine. the sarcolemma becomes repolarized and calcium is taken up from the sarcoplasmic reticulum

23
Q

What is frequency summation?

A

the addition of multiple simple twitches before the muscle has an opportunity to fully relax

24
Q

What are the additional energy reserves muscles have to reduce oxygen debt?

A
  1. creatin phosphate can transfer a phosphate group to ADP during times of rest, forming ATP
  2. Myoglobin is a heme-containing protein that is a muscular oxygen reserve
  3. lactic acid under anaerobic conditions such as exercise
25
Q

What is the diff b/w an axial and appendicular skeleton?

A

axial - skull, vertebrae column, ribcage, and hyoid bone in the neck
appendicular - bone of the upper and lower limbs, pectoral girdle (scapula and clavicle0, and pelvis

26
Q

Which embryonic structure are bones derived from?

A

from the embryonic mesoderm

27
Q

What is the diff b/w compact and spongy/cancellous bone?

A

compact - provides strength and is dense
spongy - a lattice-like structure consisting of bony spicules/trabeculae. cavities are filled with bone marrow

28
Q

Describe the structure of long bones

A

long bones contain shafts called diaphyses that flare to form metaphyses and terminate in the epiphysis, filled with bone marrow.
the epiphysis contains an epiphyseal growth plate
the outermost portion is composed of compact bone, whereas the internal core is made of spongy bone
a fibrous sheath/layer of connective tissue called the peritoneum

29
Q

What is the diff b/wred and yellow bone marrow?

A

red bone marrow is filled with hematopoietic stems which are responsible for the regeneration of the cells in our body, and yellow bone marrow is composed primarily of fat and is relatively inactive

30
Q

What is the diff b/w tendons, joints, and ligaments?

A

ligaments attach bones to stabilize joints. tendons attach muscle to bone

31
Q

What are the structural units of the bone matrix?

A

osteons or haversian systems

32
Q

What are longitudinal channels whose axes are parallel to the bone called?

A

Haversian canals

33
Q

What are transverse channels whose axes are perpendicular to the bone called?

A

Volkmann’s canals

34
Q

What is the role of Volkmann’s and Haversian canals?

A

they contain BV, nerve fibers, and lymph vessels that maintain the health of the bone

35
Q

What is the role of Lucunae?

A

they house mature bone cells known as osteocytes

36
Q

What is the purpose of canaliculi?

A

they interconnect lacunae and allow for the exchange of nutrients and waste b/w osteocytes and the Haversian and Volkmann’s canals

37
Q

What is the diff b/w osteoblast, osteocytes, and osteoclast?

A

osteoblasts build bones by secreting bone matrix.
osteocytes are mature bone cells that eventually become surrounded by their matrix.
osteoclast are large polynucleated macrophages that break down bones for reabsorption.

38
Q

What is the role of parathyroid hormone in the bones?

A

parathyroid hormone, a peptide released by the parathyroid gland in response to low blood calcium, promotes the resorption of bone, increasing the concentration of calcium and phosphate in the blood

39
Q

What is the role of vitamin D in the bones?

A

activated by parathyroid hormone, also promotes resorption of bone, encouraging the growth of new, stronger bones

40
Q

What is the role of calcium in the bones?

A

a peptide hormone released by the parafollicular cells of the parathyroid in response to high blood calcium promotes bone formation, lowering blood calcium levels

41
Q

What is the diff b/w cartilage and bone?

A

cartilage is softer and more flexible than bone, it is avascular (without blood or lymphatic vessels) and is not innervated (without nerves)

42
Q

What is the role of chondrocytes?

A

they secrete chondrin with an elastic matrix that comprises cartilage

43
Q

What are the 2 ways cartilage is hardened into bones?

A
  1. endochondral ossification is responsible for the formation of long bones in the body
  2. intramembranous ossification in which undifferentiated embryonic connective tissue (mesenchymal tissue) is transformed into and replaced by bone as seen in bones of the skull
44
Q

What is the diff b/w movable and immovable joints?

A

immovable joints consist of bones fused to form structures of similar fibrous joints such as bones in the skull
movable joints like the hinge and ball-in-socket joints permit bones to shift relative to one another

45
Q

What are joints made up of?

A

connective tissue

46
Q

What do movable joints consist of?

A

synovial capsule that encloses the articular joint cavity, and a layer of soft tissue called synovium

47
Q

What is the role of synovium?

A

it secretes synovial fluid in the joint which lubricates the movement of joints

48
Q

What is the role of the articular cartilage?

A

coats the articular surface of each bone to aid in movement and provide cushioning so the bones do not rub against each other

49
Q

What is the origin and insertion of bone?

A

the end of the muscle with a larger attachment to bone is called the origin
the end of the muscle with a larger attachment to bone is called insertion

50
Q

What is the diff b/w the abductor and the adductor?

A

abductor muscles move the part of the body away from the midline, whereas the adductor muscles move the part of the body toward the midline

51
Q

What are the events that initiate muscle contraction?

A

release of acetylcholine from the motor neurons –> activation of acetylcholine receptors in sarcolemma
–> depolarization of sarcolemma –> spreading of signal binding of calcium to troponin –> conformational shift of tropomyosin –> exposure of myosin-binding sites –> myosin binds to actin

52
Q

What comprised bone matrix?

A

organic compounds like collagen, glycoproteins, and other peptide, and inorganic compounds like hydroxyapatite crystals

53
Q

What is the periosteum?

A

a fibrous sheath of cartilage that surrounds long bones to protect them and serve as a site for muscle attachment. some of its cells can differentiate into bone-forming cells called osteoblast

54
Q

What is the role of the epiphyseal plate?

A

site of longitudinal and linear growth of bone (height).

Kaplan MCAT (52 decks)

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