Musculoskeletal System Flashcards
(130 cards)
1
Q
Skeletal muscles cannot move on their own so they are attached to bones by
A
Tendons
2
Q
Tendons
A
Strong connective tissue made of collagen
Connect muscle to bone
3
Q
By contracting, skeletal muscle draws
A
The points of attachment on the two bones closer together
4
Q
Skeletal muscle is not only composed of muscle tissue, but also contains contractile tissue held together in bundles called
A
Fascicles
5
Q
Muscle fibers (Myofibers)
A
Within each fascicles of connective tissue in the muscles
6
Q
Each myofiber is a
A
Single skeletal muscle cell
7
Q
Skeletal muscle cells are multinucleate syncytia formed by
A
The fusion of individual cells during development
8
Q
Skeletal muscle cells (myofibers) are innervated by a
A
Single nerve ending
9
Q
Skeletal muscle cells (myofibers) stretch the
A
Entire length of a muscle
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
11
Q
Within each myofiber are several
A
Myofibrils
12
Q
Myofibril is responsible for
A
Striated appliance of skeletal muscle and generates the contractile force of skeletal muscle
13
Q
Proteins in the myofibril that generate contraction are polymerized ___ and ____
A
Actin and Myosin
14
Q
Actin polymers form ___ while myosin forms ____
A
Actin: Thin filaments
Myosin: Thick filaments
15
Q
Striated appearance of the skeletal muscle is due to
A
Overlapping arrangement of bands of thick and thin filament in sarcomeres
16
Q
Myofibril has many sarcomeres aligned end-to-end bout by two
A
Z-lines
17
Q
Z line
A
Actin attach to each Z line and overlap with Myosin in the middle of the sarcomere
18
Q
I bands
A
Regions of sarcomere with only Actin
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
20
Q
H zone
A
Myosin only (only seen in resting sarcomeres)
21
Q
Contraction occurs when
A
Myosin and actin slide over one another, shortening the length of the muscle cell
22
Q
Filament sliding is powered by
A
ATP hydrolysis
23
Q
Myosin is an
A
Enzyme that uses the energy of ATP to create movement (Myosin ATPase)
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
25
Cross bridge
When the myosin is blinded to the actin at the myosin binding site
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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)
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)
27
Myosin actin contraction cycle is spontaneous, but in the body, contraction only occurs when the cytoplasmic Ca2+ increases
Why?
Troponin-tropomyosin complex prevents contraction when Ca2+ is not present
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Tropomyosin:
Long fibrous protein winding around the actin polymer, blocking myosin binding sites
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Troponin
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
30
What protein is responsible for ATP hydrolysis during muscle contraction
Myosin is responsible for al ATPase activity
31
Neuromuscular junction
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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Motor end plate
Postsynaptic myofiber cell membrane
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End plate potential (EPP) vs Miniature EPP (MEPP)
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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Acetylcholinesterase
Destroy ACh to stop the NMJ firing
Hydrolysis of ACh to choline + acetyl
35
The AP bus depolarize ___ if the contraction is going to occur
The entire myofiber
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Transverse tubules (T-tubules)
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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Sarcoplasmic reticulum
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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Upon action potential firing, the sarcoplasmic reticulum releases:
When the cell depolarizes, calcium is
Ca2+ via its VG calcium channels
Actively sequestered by the SR and contraction is ended
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Smallest measurable contraction
Twitch
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NS can increase the force of contraction via:
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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Creatine phosphate role in the cell
Intermediate-term energy storage molecule: Needed because the cells typical measures cannot keep up to provide enough ATP for continuous contraction
42
Myoglobin
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
43
During prolonged contraction, the supply of oxygen nevertheless runs low and the cell
Releases lactic acid which moves into the bloodstream and drops pH
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When the cell produces lactic acid, the liver
picks up the lactate and converts it to pyruvate which can be used in other pathways
45
Cramps result from
Exhaustion of energy supplies (temp lack of ATP in cells)
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Rigor mortis
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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Skeletal Muscle Type I Slow Twitch Fibers
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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Skeletal Muscle Type IIA Fast Twitch Fibers
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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Skeletal Muscle Type IIB Fast Twitch Fibers
White fast twitch
Lack mitochondria and capillaries
Contract quickly with a lot of force
Fatigue just as quickly, Max out after about 1 minute
50
Cardiac and skeletal muscle are similar in three ways:
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)
51
Structure of the cardiac muscle compared to skeletal
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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Heart muscle is called a ____ because it acts like a syncytium but isn't really one
Functional syncytium
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Ca2+ source for skeletal muscle vs cardiac muscle
C: some comes from extracellular environment
S: all comes from SR
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Stimulation and contraction differences for skeletal muscle vs cardiac muscle
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
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AP depend on which ions? Skeletal vs cardiac muscle
S: depend on Na+ (figure similar to Neuro AP)
C: depend on Na+ and Ca2+ through slow leak channels (caused plateau)
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Plateau in the AP of cardiac muscle is important for two reasons:
Longer duration of contraction, better ventricular emptying
Longer refractory period helps prevent disorganized transmission of impulses thought the heart making summation impossible
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Smooth muscle length / width vs skeletal muscle
Smooth is much narrower and shorter
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T-tubules and smooth muscle
No T-tubules in smooth muscle
Depolarization on surface can depolarize whole cell because the smooth muscle is so small
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Smooth muscle cell and structure compared to skeletal
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
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Smooth muscle vs skeletal:
Sarcomeres
Smooth not organized into sarcomeres
Instead, actin and myosin are dispersed in the cytoplasm giving a smooth appearance
61
Smooth muscle vs skeletal:
Troponin-tropomyosin
T-T not present in smooth
Contraction is instead regulated by calmodulin and myosin light chain kinase (MLCK)
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Contraction is regulated by calmodulin and myosin light chain kinase (MLCK) in smooth muscle which functions:
Calmodium binds Ca2+ and then activates MLCK which phosphorylates a portion of the myosin molecules thus activating its activity
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Smooth muscle vs skeletal:
Sarcoplasmic Reticulum
Smooth does not have a well developed SR and instead relies on stored Ca2+ and extracellular stores of Ca2+ for contraction
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Smooth muscle vs skeletal:
Action potentials
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
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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
Constantly fluctuating "slow waves"
| Ions pass through gap junctions
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Slow waves
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
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Amplitude of slow waves is inc by: ___ and dec by: ____
Inc: ACh
Dec: Norepi
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Smooth muscle vs skeletal:
Motor neurons
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
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Skeletal system's five roles
```
Support the body
Framework for movement
Protect vital organs
Store calcium
Hematopoiesis = synthesize the formed elements of blood (in marrow)
```
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Axial and appendicular components of the endoskeletal system
Axial: skull, vertebral column and rib cage
Appendicular: all other parts
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Fibroblast
Makes up all connective tissue (cells and materials they secrete)
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Fibroblast excretes fibrous material such as (20
Collagen (strong fibrous protein)
| Elastin (ability to stretch tissue and regain shape)
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Fibroblast derived cells include (3)
Adipocytes (fat cells)
Chrondocytes (cartilage cells)
Osteocytes (bone cells)
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Bone is different in that it is mostly extracellular components with a few cells scattered
The extracellular material is called:
Matrix
75
Matrix consists of collagen and elastin as well as
Ground substance
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Grouns substance
In matrix
Thick, visceral material with protein core and carbohydrate chains (hydrophilic // always surrounded by water giving thickness and firmness)
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Loose connective tissue
Areolar tissue (soft material between most cells in body) and adipose tissue (fat)
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Dense connective tissue
Large amounts of fibers (specifically collagen) such as tendons, ligaments, cartilage and bone
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Two primary bone shapes: flat and long
Flat: Location of hematopoeises (synthesis of blood elements in marrow) and protect organs
-scapula, ribs, skull, etc.
Long: support and movement
-limbs
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Diaphysis and ephiphysis
Dia: long shaft
Epi: flared end
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Compact or spongy bone
Compact: hard and dense
Spongy: porous, surrounded by compact always
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Diaphysis portion of bone is composed only of
Compact bone
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Bone marrow
Non-Bony material found in shafts of long bones and pores of spongy bones
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Red marrow
Found in spongy bone within flat bones, site of hemapoeitisis
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Red marrow activity
increases in response to erythropoietin, kidney hormone
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Yellow marrow
Found in shafts of long bone
Filled with fat
Inactive
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Bone two principle ingredients
Collagen and hydroxyapatite
88
During bone synthesis,
collagen is laid down in a highly ordered structure and then hydroxyapatite crystals form around the collagen framework, giving bone its strength and flexibility
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Spikes of bone surrounding marrow containing cavities in spongy bone are called
Spicules or trabeculae
90
Osteon
basic unit of compact bone
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Center of the osteon there is a hole called the ___ which contains
Central Canal
| Blood, lymph vessels and nerves
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Surrounding the osteon's central canal are the
Concentric rings of bone "lamellae"
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____ are tiny channels branching out from the central canal to spaces called lacunae
Canaliculi
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In each lacunae is an osteocyte which functions as a
Mature bone cell extending down the canaliculi to contact other osteocytes through gap junctions to exchange nutrients and waste through impermeable membrane
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Perforating canals
Channels that run perpendicular to central canals to connect osteons
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Cartilage is strong but flexible extracellular tissues secreted by cells called
Chondrocytes
97
Three types of cartilage:
Hyaline, elastic and fibrous
98
Hyaline cartilage
Strong and somewhat flexible
Lines joints (articular cartilage) and forms larynx and trachea
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Articular cartilage
Lines joints
Type of hyaline cartilage
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Elastic cartilage
Found in structures requiring support and more flexibility than hyaline cartilage can provide (outer ear, epiglottis)
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Fibrous cartilage
Rigid and found in places where very strong support is needed
(anterior connection of pelvis and spine)
102
Cartilage is avascular meaning
Does not contain blood vessels and is not innervated
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How does cartilage receive nutrients and immune protection?
Surrounding fluid
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Ligaments
Connect bones to bones
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Synarthoses
Immovable joints
Two bones are fused together (skull)
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Amphiarthroses
Slightly movable and much supportive (amphi means both moving and supporting)
Vertebrae
107
Diarthroses
Freely moving joints
| ball and socket, hinge
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All movable joints are supported by ___ and lubricated by ____
Ligaments
| Synovial fluid
109
Synovial capsule
Holds synovial fluid
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Two surfaces of the bone that are in contact with each other are perfectly smooth because they are
Lined with articular cartilage which lacks blood vessels
Easily damaged by overuse and infection
111
Inflammation of joints
Arthritis leads to the destruction of articular cartilage causing pain and stiffness
112
Endochondral ossification
Bone growth (hyaline cartilage Is produced and then replaced by bone)
113
Epiphyseal plate function
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
Process of endochondral ossification is stimulated by
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
Epiphyseal line
Epiphyseal plate in adults once the bones have fused
116
Remodling
In adults bone is constantly degraded and remade
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Osteoblasts
Cells that make bone
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How does the osteoblast shut off
Osteoblast keeps making bone until it is surrounded by bone, space left is called a lacuna and the osteoblast is not called an osteocyte
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OsteoClasts
Continually destroy bone by dissolving the crystals to be replaced with osteoblasts
120
Ratio of osteoclast:osteoblast is important for
Releasing the right amount of calcium and phosphate into the blood stream
Maintains proper blood levels
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Parathyroid Hormone (PTH), Calcitonin and Calcitriol role in the cell
Regulate the osteoblast and osteoclast activity and thus blood calcium levels
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PTH and Calcitriol: ___ while calcitonin _____
PTH and calcitriol increase blood calcium and calcitonin reduces it
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PTH effect on bones
Stimulates osteoclast activity
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PTH effect on kidneys
Increases reabsorption of calcium, stimulates conversion of vitamin D into cacitriol
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PTH effect on intestines
Indirectly increases intestinal calcium absorption
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Calcitriol effect on bones
Stimulates osteoclast activity, minor effect
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Calcitriol effect on kidneys
INC reabsorption of phosphorus
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Calcitriol effect on intestines
Indirectly increases intestinal absorption of calcium
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Calcitronin effect on bones
Inhibits osteoclast activity
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Calcitronin effect on kidneys
DEC reabsorption of calcium
