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Musculoskeletal System Flashcards

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1
Q

Skeletal muscles cannot move on their own so they are attached to bones by

A

Tendons

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2
Q

Tendons

A

Strong connective tissue made of collagen

Connect muscle to bone

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3
Q

By contracting, skeletal muscle draws

A

The points of attachment on the two bones closer together

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4
Q

Skeletal muscle is not only composed of muscle tissue, but also contains contractile tissue held together in bundles called

A

Fascicles

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5
Q

Muscle fibers (Myofibers)

A

Within each fascicles of connective tissue in the muscles

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6
Q

Each myofiber is a

A

Single skeletal muscle cell

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7
Q

Skeletal muscle cells are multinucleate syncytia formed by

A

The fusion of individual cells during development

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8
Q

Skeletal muscle cells (myofibers) are innervated by a

A

Single nerve ending

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9
Q

Skeletal muscle cells (myofibers) stretch the

A

Entire length of a muscle

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10
Q

The myofiber has a cell membrane called the

A

Sarcolemma

Made of plasma membrane and an additional layer of polysaccharide and collagen to help muscles fuse with tendons

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11
Q

Within each myofiber are several

A

Myofibrils

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12
Q

Myofibril is responsible for

A

Striated appliance of skeletal muscle and generates the contractile force of skeletal muscle

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13
Q

Proteins in the myofibril that generate contraction are polymerized ___ and ____

A

Actin and Myosin

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14
Q

Actin polymers form ___ while myosin forms ____

A

Actin: Thin filaments
Myosin: Thick filaments

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15
Q

Striated appearance of the skeletal muscle is due to

A

Overlapping arrangement of bands of thick and thin filament in sarcomeres

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16
Q

Myofibril has many sarcomeres aligned end-to-end bout by two

A

Z-lines

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17
Q

Z line

A

Actin attach to each Z line and overlap with Myosin in the middle of the sarcomere

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18
Q

I bands

A

Regions of sarcomere with only Actin

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19
Q

A band

A

Full length of the myosin filament

Includes the overlap regions of myosin and actin and the region with only myosin

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20
Q

H zone

A

Myosin only (only seen in resting sarcomeres)

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21
Q

Contraction occurs when

A

Myosin and actin slide over one another, shortening the length of the muscle cell

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22
Q

Filament sliding is powered by

A

ATP hydrolysis

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23
Q

Myosin is an

A

Enzyme that uses the energy of ATP to create movement (Myosin ATPase)

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24
Q

Each myosin monomer contains a

A

Head: attaches to the actin at the myosin binding site
Tail

Contraction occurs when head and tail angle between decreases

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25
Q

Cross bridge

A

When the myosin is blinded to the actin at the myosin binding site

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26
Q

Steps of the filament sliding during contraction

  1. Myosin binds to actin forming _______ (Myosin has___ and ___ bound)
  2. _______ occurs and myosin head moves to low-energy conformation and pulls actin towards _____ of sarcomere (_______)
  3. ________ needed to release actin from myosin head
  4. ATP hydrolysis occurs immediately and myosin head is _____ (high energy conformation)
A
  1. Myosin binds to actin forming the cross bridge (Myosin has ADP and Pi bound)
  2. Power stroke occurs and myosin head moves to low-energy conformation and pulls actin towards center of sarcomere (ADP is released)
  3. Binding new ATP needed to release actin from myosin head
  4. ATP hydrolysis occurs immediately and myosin head is cocked (high energy conformation)
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27
Q

Myosin actin contraction cycle is spontaneous, but in the body, contraction only occurs when the cytoplasmic Ca2+ increases

Why?

A

Troponin-tropomyosin complex prevents contraction when Ca2+ is not present

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28
Q

Tropomyosin:

A

Long fibrous protein winding around the actin polymer, blocking myosin binding sites

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29
Q

Troponin

A

Globular protein bound to tropomyosin that can bind Ca2+

When Ca2+ is bound, troponin undergoes conformational change that moves tropomyosin out of the way so that myosin heads can attach to actin and filament sliding can occur

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30
Q

What protein is responsible for ATP hydrolysis during muscle contraction

A

Myosin is responsible for al ATPase activity

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31
Q

Neuromuscular junction

A

Synapse between myofiber and axon terminus (ACh)

Infolding of the cell membrane
Axon terminus elongated to fill the synaptic cleft

Purpose is to depolarize a large region of the postsynaptic membrane all at once

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32
Q

Motor end plate

A

Postsynaptic myofiber cell membrane

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33
Q

End plate potential (EPP) vs Miniature EPP (MEPP)

A

EPP: ACh reaches receptor and invokes a postsynaptic sodium influx which depolarizes the postsynaptic membrane

MEPP: Smallest measurable EPP caused by excitation of a single ACh vesicle

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34
Q

Acetylcholinesterase

A

Destroy ACh to stop the NMJ firing

Hydrolysis of ACh to choline + acetyl

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35
Q

The AP bus depolarize ___ if the contraction is going to occur

A

The entire myofiber

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36
Q

Transverse tubules (T-tubules)

A

Indentations in the cell membrane to allow the AP to reach past the cell membrane and get to the interior of the cell

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37
Q

Sarcoplasmic reticulum

A

Specialized smooth endoplasmic reticulum which enfolds each myofibril in the cell specialized to sequester and release Ca2+

Active transports in the SR rapidly remove calcium from the sarcoplasm

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38
Q

Upon action potential firing, the sarcoplasmic reticulum releases:

When the cell depolarizes, calcium is

A

Ca2+ via its VG calcium channels

Actively sequestered by the SR and contraction is ended

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39
Q

Smallest measurable contraction

A

Twitch

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40
Q

NS can increase the force of contraction via:

A

Motor unit recruitment: Larger contraction by activating more motor neurons and thus more myofibers

Frequency summation: Rapid firing AP does not allow Ca2+ to leave the cleft and therefore builds on the previous contraction, growing in size

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41
Q

Creatine phosphate role in the cell

A

Intermediate-term energy storage molecule: Needed because the cells typical measures cannot keep up to provide enough ATP for continuous contraction

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42
Q

Myoglobin

A

Globular protien similar to one of the four subunits in hemoglobin

Provides oxygen reserve taking O2 from hemoglobin and then releasing as needed during prolonged contraction

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43
Q

During prolonged contraction, the supply of oxygen nevertheless runs low and the cell

A

Releases lactic acid which moves into the bloodstream and drops pH

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44
Q

When the cell produces lactic acid, the liver

A

picks up the lactate and converts it to pyruvate which can be used in other pathways

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45
Q

Cramps result from

A

Exhaustion of energy supplies (temp lack of ATP in cells)

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46
Q

Rigor mortis

A

Rigidity of skeletal muscles which occurs soon after death

Results from complete ATP exhaustion
Without ATP, myosin heads cannot release actin and the muscle can neither contract nor relax

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47
Q

Skeletal Muscle Type I Slow Twitch Fibers

A

Red slow twitch/red oxidative fibers

High myoglobin content
Better blood supply due to extensive capillary network

Hence: maintain contraction for extended periods of time without fatigue

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48
Q

Skeletal Muscle Type IIA Fast Twitch Fibers

A

Fast twitch oxidative, somewhat resistant to fatigue

Intermediate contraction, medium force generation, some mitochondria, medium capillaries, medium fatigue resistance (30 minutes of use)

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49
Q

Skeletal Muscle Type IIB Fast Twitch Fibers

A

White fast twitch

Lack mitochondria and capillaries
Contract quickly with a lot of force
Fatigue just as quickly, Max out after about 1 minute

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50
Q

Cardiac and skeletal muscle are similar in three ways:

A
  1. Actin and myosin organized into sarcomeres (striation)
  2. T-tubules (transmit AP into the interior of large, thick cell)
  3. Troponin-tropomyosin (regulates contraction)
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51
Q

Structure of the cardiac muscle compared to skeletal

A

Cardiac muscle has one nucleus, not broken down like skeletal muscle into smaller components

Muscles of the heart are interconnected by gap junctions known as intercalated disks (allow AP to propagate without sharing cytoplasmic contents)

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52
Q

Heart muscle is called a ____ because it acts like a syncytium but isn’t really one

A

Functional syncytium

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53
Q

Ca2+ source for skeletal muscle vs cardiac muscle

A

C: some comes from extracellular environment
S: all comes from SR

54
Q

Stimulation and contraction differences for skeletal muscle vs cardiac muscle

A

Cardiac muscle contraction doesn’t depend on motor neurons, but the vagus nerve which is inhibitory to the SA node using ACh to slow the heart rate and prevent continuous contraction

vs. NMJ releasing excitatory ACh

55
Q

AP depend on which ions? Skeletal vs cardiac muscle

A

S: depend on Na+ (figure similar to Neuro AP)

C: depend on Na+ and Ca2+ through slow leak channels (caused plateau)

56
Q

Plateau in the AP of cardiac muscle is important for two reasons:

A

Longer duration of contraction, better ventricular emptying

Longer refractory period helps prevent disorganized transmission of impulses thought the heart making summation impossible

57
Q

Smooth muscle length / width vs skeletal muscle

A

Smooth is much narrower and shorter

58
Q

T-tubules and smooth muscle

A

No T-tubules in smooth muscle

Depolarization on surface can depolarize whole cell because the smooth muscle is so small

59
Q

Smooth muscle cell and structure compared to skeletal

A

Smooth has only one nucleus and is connected to neighbors by gap junctions like cardiac muscle allowing impulse to speed

Smooth and cardiac are functional syncytia

60
Q

Smooth muscle vs skeletal:

Sarcomeres

A

Smooth not organized into sarcomeres

Instead, actin and myosin are dispersed in the cytoplasm giving a smooth appearance

61
Q

Smooth muscle vs skeletal:

Troponin-tropomyosin

A

T-T not present in smooth

Contraction is instead regulated by calmodulin and myosin light chain kinase (MLCK)

62
Q

Contraction is regulated by calmodulin and myosin light chain kinase (MLCK) in smooth muscle which functions:

A

Calmodium binds Ca2+ and then activates MLCK which phosphorylates a portion of the myosin molecules thus activating its activity

63
Q

Smooth muscle vs skeletal:

Sarcoplasmic Reticulum

A

Smooth does not have a well developed SR and instead relies on stored Ca2+ and extracellular stores of Ca2+ for contraction

64
Q

Smooth muscle vs skeletal:

Action potentials

A

Smooth AP varies depending on location

Spike potentials are determined by slow channels only, since no Na+ fast channels are present so it takes 10-20x as long to initiate

65
Q

Some smooth muscle that must maintain prolonged contractions has action potentials similar to cardiac muscle with a less sharp spike

Smooth muscles have a ____ resting potential because

A

Constantly fluctuating “slow waves”

Ions pass through gap junctions

66
Q

Slow waves

A

Changes in RMP of smooth muscle, do not initiate contraction

Help coordinate AP
NT binds to help push RMP closer to threshold in response to stimulus
Slow waves pass through primed cells and reach threshold, undergo spike potential

67
Q

Amplitude of slow waves is inc by: ___ and dec by: ____

A

Inc: ACh
Dec: Norepi

68
Q

Smooth muscle vs skeletal:

Motor neurons

A

Smooth: autonomic motor neurons instead of somatic meaning no control over them

Individual motor neuron does activate cell but the AP spreads from cell to cell

69
Q

Skeletal system’s five roles

A 
Support the body
Framework for movement
Protect vital organs
Store calcium 
Hematopoiesis = synthesize the formed elements of blood (in marrow)
70
Q

Axial and appendicular components of the endoskeletal system

A

Axial: skull, vertebral column and rib cage

Appendicular: all other parts

71
Q

Fibroblast

A

Makes up all connective tissue (cells and materials they secrete)

72
Q

Fibroblast excretes fibrous material such as (20

A

Collagen (strong fibrous protein)

Elastin (ability to stretch tissue and regain shape)

73
Q

Fibroblast derived cells include (3)

A

Adipocytes (fat cells)
Chrondocytes (cartilage cells)
Osteocytes (bone cells)

74
Q

Bone is different in that it is mostly extracellular components with a few cells scattered

The extracellular material is called:

A

Matrix

75
Q

Matrix consists of collagen and elastin as well as

A

Ground substance

76
Q

Grouns substance

A

In matrix
Thick, visceral material with protein core and carbohydrate chains (hydrophilic // always surrounded by water giving thickness and firmness)

77
Q

Loose connective tissue

A

Areolar tissue (soft material between most cells in body) and adipose tissue (fat)

78
Q

Dense connective tissue

A

Large amounts of fibers (specifically collagen) such as tendons, ligaments, cartilage and bone

79
Q

Two primary bone shapes: flat and long

A

Flat: Location of hematopoeises (synthesis of blood elements in marrow) and protect organs
-scapula, ribs, skull, etc.

Long: support and movement
-limbs

80
Q

Diaphysis and ephiphysis

A

Dia: long shaft
Epi: flared end

81
Q

Compact or spongy bone

A

Compact: hard and dense
Spongy: porous, surrounded by compact always

82
Q

Diaphysis portion of bone is composed only of

A

Compact bone

83
Q

Bone marrow

A

Non-Bony material found in shafts of long bones and pores of spongy bones

84
Q

Red marrow

A

Found in spongy bone within flat bones, site of hemapoeitisis

85
Q

Red marrow activity

A

increases in response to erythropoietin, kidney hormone

86
Q

Yellow marrow

A

Found in shafts of long bone
Filled with fat
Inactive

87
Q

Bone two principle ingredients

A

Collagen and hydroxyapatite

88
Q

During bone synthesis,

A

collagen is laid down in a highly ordered structure and then hydroxyapatite crystals form around the collagen framework, giving bone its strength and flexibility

89
Q

Spikes of bone surrounding marrow containing cavities in spongy bone are called

A

Spicules or trabeculae

90
Q

Osteon

A

basic unit of compact bone

91
Q

Center of the osteon there is a hole called the ___ which contains

A

Central Canal

Blood, lymph vessels and nerves

92
Q

Surrounding the osteon’s central canal are the

A

Concentric rings of bone “lamellae”

93
Q

____ are tiny channels branching out from the central canal to spaces called lacunae

A

Canaliculi

94
Q

In each lacunae is an osteocyte which functions as a

A

Mature bone cell extending down the canaliculi to contact other osteocytes through gap junctions to exchange nutrients and waste through impermeable membrane

95
Q

Perforating canals

A

Channels that run perpendicular to central canals to connect osteons

96
Q

Cartilage is strong but flexible extracellular tissues secreted by cells called

A

Chondrocytes

97
Q

Three types of cartilage:

A

Hyaline, elastic and fibrous

98
Q

Hyaline cartilage

A

Strong and somewhat flexible

Lines joints (articular cartilage) and forms larynx and trachea

99
Q

Articular cartilage

A

Lines joints

Type of hyaline cartilage

100
Q

Elastic cartilage

A

Found in structures requiring support and more flexibility than hyaline cartilage can provide (outer ear, epiglottis)

101
Q

Fibrous cartilage

A

Rigid and found in places where very strong support is needed

(anterior connection of pelvis and spine)

102
Q

Cartilage is avascular meaning

A

Does not contain blood vessels and is not innervated

103
Q

How does cartilage receive nutrients and immune protection?

A

Surrounding fluid

104
Q

Ligaments

A

Connect bones to bones

105
Q

Synarthoses

A

Immovable joints

Two bones are fused together (skull)

106
Q

Amphiarthroses

A

Slightly movable and much supportive (amphi means both moving and supporting)

Vertebrae

107
Q

Diarthroses

A

Freely moving joints

ball and socket, hinge

108
Q

All movable joints are supported by ___ and lubricated by ____

A

Ligaments

Synovial fluid

109
Q

Synovial capsule

A

Holds synovial fluid

110
Q

Two surfaces of the bone that are in contact with each other are perfectly smooth because they are

A

Lined with articular cartilage which lacks blood vessels

Easily damaged by overuse and infection

111
Q

Inflammation of joints

A

Arthritis leads to the destruction of articular cartilage causing pain and stiffness

112
Q

Endochondral ossification

A

Bone growth (hyaline cartilage Is produced and then replaced by bone)

113
Q

Epiphyseal plate function

A

formed in childhood between diaphysis and epiphysis

Actively being produced and forcing the two sections of bone apart

Then the cartilage is replaced by bone

114
Q

Process of endochondral ossification is stimulated by

A

Growth hormone and rate of ossification is faster than rate of cell division (cartilage growth) so around age 18 the two halves of bone fuse together and the lengthening can no longer occur

115
Q

Epiphyseal line

A

Epiphyseal plate in adults once the bones have fused

116
Q

Remodling

A

In adults bone is constantly degraded and remade

117
Q

Osteoblasts

A

Cells that make bone

118
Q

How does the osteoblast shut off

A

Osteoblast keeps making bone until it is surrounded by bone, space left is called a lacuna and the osteoblast is not called an osteocyte

119
Q

OsteoClasts

A

Continually destroy bone by dissolving the crystals to be replaced with osteoblasts

120
Q

Ratio of osteoclast:osteoblast is important for

A

Releasing the right amount of calcium and phosphate into the blood stream

Maintains proper blood levels

121
Q

Parathyroid Hormone (PTH), Calcitonin and Calcitriol role in the cell

A

Regulate the osteoblast and osteoclast activity and thus blood calcium levels

122
Q

PTH and Calcitriol: ___ while calcitonin _____

A

PTH and calcitriol increase blood calcium and calcitonin reduces it

123
Q

PTH effect on bones

A

Stimulates osteoclast activity

124
Q

PTH effect on kidneys

A

Increases reabsorption of calcium, stimulates conversion of vitamin D into cacitriol

125
Q

PTH effect on intestines

A

Indirectly increases intestinal calcium absorption

126
Q

Calcitriol effect on bones

A

Stimulates osteoclast activity, minor effect

127
Q

Calcitriol effect on kidneys

A

INC reabsorption of phosphorus

128
Q

Calcitriol effect on intestines

A

Indirectly increases intestinal absorption of calcium

129
Q

Calcitronin effect on bones

A

Inhibits osteoclast activity

130
Q

Calcitronin effect on kidneys

A

DEC reabsorption of calcium

My MCAT Biology (13 decks)

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