Musculoskeletal System Flashcards by Maryam Hiradfar

What is rhabdomyolysis? What is a sign?

When the products of skeletal muscle destruction, some of which are toxic, circulate in the blood until they are filtered out.
Creating kinase can be found in the blood.
A clinical sign is that an erythrocytes free urine tests positive for heme.

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How many nuclei do muscle cells have?

Multiple

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What are the different types of fibers in the muscle? What is their characteristic?

1-red fibers (slow-twitch fiber)have high myoglobin content and derive their energy aertobically.
2- White fibers (fast-twitch) contain much less myoglobin.

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What is tonus?

A constant-low level contraction of the smooth muscles.

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Which types of muscles have myogenic activity?

Smooth muscle and cardiac

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How many nuclei do cardiac muscles have?

Primarily uninucleated but can have two

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How do the cardiac muscles interact?

Intercalated discs that contain many gap junctions that connect the cytoplasm of the cells directly and enables the coordinated and rapid depolarization of muscle cells and efficient contraction of cardiac muscle.

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What pathway does the depolarization in heart travel?

SA node (sinoatrial node) 
AV node (atrioventricular node) 
His bundle (atrioventricular bundle) 
Purkinje fibers.

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What ion do all muscle types rely on for contraction?

Calcium

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What is the sarcomere and what is it made of?

The contractile unit of the skeletal muscle.

Is made of thick and thin filaments.

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What are the thick and thin filaments in the sarcomere composed of?

Thick filaments are organized bundles of myosin while the thin filaments are made of actin, trope in and tropomyosin.

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What is the role of the protein titin?

Acts as a spring and anchors the actin and myosin filaments together. Preventing excessive stretching of the muscle.

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Name the zones, bands, and lines in each sarcomere and state what each of them are.

Z-line: defines the boundaries of each sarcomere.

M-line runs down the center of the sarcomere, through the middle of the myosin filaments.
The I-band is the region containing exclusively thin filaments
H zone contains only thick filaments
A band contains the thick filaments in their entirety, including any overlap with thin filaments.

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Which zones/lines get smaller/ get closer together during muscle contraction? 
Which one(s) don’t change?

Z lines get closer together. So do M lines.
H band and I band get smaller.
A band doesn’t change.

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Sarcomeres are attached end to end to form …….(1)
(1) are surrounded by ya covering known as the ……(2)
The cell membrane of a myocyte is known as ….(3)
(3) is capable of propagating an action potential and can distribute the action potential to all sarcomeres in a muscle using a system of …..(4) that are oriented perpendicularly to the (1).
Each myocyte contains many ….. (5) arranged in parallel and can also be called a …..

(1) == myofibril
(2) ==sarcoplasmic reticulum (SR)
(3) ==sarcolemma
(4) ==transverse tubules (t-tubules)
(5) myofibrils.

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What is the sarcoplasmic reticulum and what does it contain?

Is a modified endoplasic reticulum and contains high concentrations of Ca2+ ions

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Muscle contraction contains three main steps. Name them.

1- initiation
2- contraction
3-relaxation

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What happens during the initiation phase fo the muscle contraction?

Acetylcholine is released at the neuromuscular junction, binds to the receptors on the sarcolemma, causing depolarization.
Depolarization triggers an action potential that travels down the T-tubules into the muscle tissues to the sarcoplasmic reticulum.
Action potential reaches SR and Ca2+ is released.
Ca2+ binds a regulatory subunit in troponin.
Binding of Ca2+ causes a conformational change in the tropomysoin.
The conformational change exposes the myosin-binding site on the actin thin filaments.

What happens during the contraction phase of skeletal muscle contraction?

The free globular heads of the myosin molecules move toward and bind with the exposed sites on actin. myosin pulls on actin, which draws the thin filaments toward the M-line resulting in shortening of the sarcomere.

What happens when ADP and inorganic phosphate are released from myosin?

Power stroke.

What happens when ATP binds myosin?

Myosin is released from actin.

What happens during the relaxation period of muscle contraction.

1- acetylcholinesterase degrades acetylcholine. —> termination of the signal at the neuromuscular junction —> sarcolemma repolarizes.
2- calcium release ceases and the SR takes up calcium from the sarcoplasm.
3-ATP binds to myosin head, releasing it from the actin.

What is rigor mortis?

After death, ATP production ceases.. Myosin heads cannot detach from actin, making it impossible for muscles to relax and lengthen. This condition is known as rigor mortis.

What are the three phases of the Simple twitch? describe them

1- latent period is the time between reaching threshold and the onset of contraction. It is during this time that the action potential spreads along the muscle and allows for calcium to be released form the sarcoplasmic reticulum
2-contraction
3-relaxation

What is tetanus (not the disease)?

When frequency summation occurs with such high frequency that the muscle doesn’t get to relax.

What is the pathogen for tetanus called? What does it do?

Clostridium tetani. Releases tetanospasmin. Tetanospasmin blocks the release of GABA from neurons. GABA inhibits motor neurons. tetanospasmin makes the motor neurons overexcitable.

What are the two supplemental energy reserves besides ATP that muscles use?

1-Creatine phosphate (body transfers phosphates to creatine during times of rest 2- myoglobin.

What are two definitions of oxygen debt?

1-The difference between the amount of oxygen needed by the muscle and the actual amount present is the oxygen debt 2- MAfter the cessation of strenuous exercise, the body must metabolize all of the lactic acid it has produced. Most lactic acid is converted back into pyruvate, which can enter the citric acid cycle. This process requires oxygen, and the amount of oxygen required to recover from strenuous exercise is equal to the oxygen debt.

What does the axial skeleton consist of?

Skull, vertebral column, rib cage, hyoid bone ( a small bone in the anterior neck used for swallowing).

What embryonic germ layer does bone develop from?

From the embryonic mesoderm.

What are the bony spicules in the spongy bone?

Trabeculae

What does the red bone marrow consist of?

Hematopoietic stem cells.

What does the yellow bone marrow consist of?

Adipose tissue

Just note the following

Some persisteal cells are capable of differentiating into bone forming cells.

What is the inorganic component of the bone matrix?

Calcium, phosphate and hydroxide ions: | Hydroxyapatite: (Ca10(PO4)6(OH)2)

``` In the oseteon (hasversian system) what are the names of: 1- the bony matrix? 2- small spaces between the matrix? 3- The longitudinal channels? 4- The transverse channels? ```

1- lamellae 2-lacunae 3-Haversian canals 4-Volkmann’s canals

What doe Volkmann’s and Haversian canals contain?

Blood vessels, nerve biers, Alan lymph vessels that maintain the health of the bone.

What do lacunae host?

Mature bone cells known as osteocytes.

What are the tiny channels that connect the lacunae?

Canaliculi

Just note the following:

Osteoclasts are polynucleated resident macrophages of the bone.

Note the following:

Vitamin D which is activated by parathyroid hormone promotes the resorption of the bone.

What hormone promotes osteoblast activity?

Estrogen.

What is the matrix of cartilage called and what cells release it?

Chondrin, released by chondrocytes.