Muscle

Question 1

What do skeletal muscle differentiate from

Answer 1

Mesenchymal cells

Question 2

Skeletal muscle development

Answer 2

• Myoblasts align and fuse to make multinucleated myotubes
• Myotubes synthesize myofilaments; cross-straitions gradually begin to appear
• Myotubes continue to differentiate into myofibrils

Question 3

Endomysium

Answer 3

• Thin Reticular fibers

- Supplies fascicles with nerves and capillaries

Question 4

Perimysium

Answer 4

CT (collagen) layer surrounding fascicles

Question 5

Septa

Answer 5

• Between fascicles

- Carry nerves, blood vessels and lymphatics

Question 6

Epimysium

Answer 6

-Dense irregular CT

Question 7

Myotendinous Junction

Answer 7

• Between muscle and tendon

- Tendon is dense collagen

Question 8

Myofilaments

Answer 8

Actin and myosin

-Arraged into sarcomeres

Question 9

A-bands

Answer 9

Ansiotropic/birefringent in polarized LM

-Myosin

Question 10

I bands

Answer 10

Isotropic

-Actin

Question 11

Thin filaments contain

Answer 11

F-Actin and G-actin, tropomyosin, and troponin

Question 12

Sarcoplasmic reticulum has high amount of which organelle

Answer 12

Mitochondria

Question 13

Muscle Contraction

Answer 13

• Nerve impulse triggers Ach release
• Ach binds nicotinic receptors in motor end plate
• Impulse travels down sarcolemma and t-tubule
• Ca release from SR
• Ca binds troponin, moves trypomysin out the way

Question 14

Muscle contraction at myosin head

Answer 14

-Attach, powerstroke, detatch, return

Question 15

Myasthenia Gravis

Answer 15

• Autoimmune disorder
• circulating antibodies bind to Ach receptors, interfering with EPP
• Leads to skeletal muscle weakness
• Extraocular eye muscles are easily affected, causing diplopia (double vision) early sign

Question 16

How does body attempt to combat myasthenia gravis

Answer 16

• Junctional folds with affected receptors are internalized, digested by lysosomes, and replaced
• However, this doesn’t last long, bc antibodies attack again

Question 17

Early sign of myesthenia gravis

Answer 17

Diplopia (double vision) bc extrinsic eye muscles affected

Question 18

Muscular dystrophy types and similarities

Answer 18

Duchenne muscular dystrophy and Becker muscular dystrophy

• Both X-linked mutations of the dystrophin gene, more common in boys
• Childhood onset: weakness begins after a delayed onset, develops after achieving motor milestones

Question 19

Dystrophin

Answer 19

-Connects the Z-line to both the sarcolemma and ECM, giving stability to myofibrils

Question 20

Duchenne Muscular Dystrophy

Answer 20

• Weakness occurs at 3-5 y/o
• Disease progresses rapidly
• Loss of fxn by 12
• May become dependent on assisted breathing

Question 21

Becker Muscular Dystrophy

Answer 21

Later onset (12 y/o)

• Slow progression
• Loss of fxn before 30

Question 22

LM appearance of Muscular Dystrophy

Answer 22

• Fat replaces muscle
• Hypertrophy and atrophy of some fibers
• Dystrophin disruption

Question 23

Muscle spindles

Answer 23

• Encapsulated by modified perimysium
• Contain intrafusal fibers
• Intrafusal fibers are modified muscle fivers

Question 24

Golgi Tendon

Answer 24

• Provide sensation of body position and maintain muscle tone
• Responsible for proprioception, reflexive inhibition, and activation of opposing muscles

Question 25

Cardiac muscle

Answer 25

- Branched | - Consists of tight bundles of cells INTERWOVEN in spiraling layers

Question 26

Syncytium

Answer 26

-Myocardial fibers plus intercalated disc

Question 27

How is an MI detected in blood

Answer 27

Elevated troponin

Question 28

Smooth muscle

Answer 28

- Under control of autonomic nervous - Parasym activate contraction - Cells are separated by ECM - Linked by Gap Junctions - No striations

Question 29

Where do thin actin filaments attach in smooth muscle

Answer 29

-Dense bodies located throughout sarcoplasm

Question 30

How does smooth muscle contract

Answer 30

- No T-Tubules, No troponin - Use myosin light-chain kinase process and Ca2+ dependent calmodulin - Parasympathetic inn activates Ca release, utilizing calmodulin and kinase cascade that encourages the formation of actin-myosin cross bridges

Question 31

Myoepithelial cells

Answer 31

- Some tissues have these, with smooth muscle contraction mechanisms - Sweat glands, mammary glands, and salivary glands, iris, seminiferous tubules of testis

Question 32

Infectious disease that impact musculoskeletal system

Answer 32

-Necrotizing fasciitis, trichonosis, and botulism

Question 33

Trichonosis

Answer 33

- Parasitic disease - Nemotode larval form in encystem within skeletal muscle - Muscle weakness as cyst impinge on nerve - Caused by consumption of undercooked pork or bear - Surgical cure

Question 34

Botulism

Answer 34

- Caused by binding of a toxin from food with microbial contamination by Clostridium botulinum - Toxin blocks release of ACH at nerve cell, causing flaccid paralysis in the muscles served by that nerve

Question 35

Necrotizing fasciitis

Answer 35

- Clostridium prefringens release enzymes that attack muscle tissue - Bacterial protease attack at demosomes - H2S gas is released causing gas bubbles