2. Musculoskeletal system

Question 1

What are the Skeletal muscle diseases gone over in this lecture?

Answer 1

Rhabdomyolysis

and Duchenne Muscular dystrophy

Question 2

What are the bone diseases gone over in this lecture?

Answer 2

• Paget’s disease

- Gout

Question 3

What is the patient case gone over in this lecture?

Answer 3

• osteoporosis

Question 4

What is a sarcomere?

Answer 4

• most basic functional cell unit of a muscle cell

Question 5

thick filaments aka?

Answer 5

myosin

Question 6

thin filaments aka?

Answer 6

actin filaments

Question 7

which zones in the saromere get shorter during contraction?

and which one stays the same length?

Answer 7

• H zone (from actin filament to actin filament)
• I band ( end of actin- Z line to other end of actin)
• A band ( just the myosin)

Question 8

3 components of actin filaments?

Answer 8

1. actin molecules
2. troponin - Ca+ binds to troponin inducing conformational change
3. tropomyosin –> covers myosin binding site

Question 9

2 components of the myosin filaments ?

Answer 9

1. myosin molecules

2. myosin heads

Question 10

2 binding sites on myosin head?

Answer 10

• Actin AtPase

- Myosin ATPase –> induce relaxation after contraction and stops binding of myosin head to actin binding site

Question 11

what is the point of the globular heads?

Answer 11

• build cross bridges to actin

Question 12

Role of Ca+ in muscular contractions?

Answer 12

• Ca+ comes from sarcoplasmic reticulum
• T tubules transmit Action Potential signal to lateral sacs
• Ca+ released and induces vesicle exocytosis for Ach at the NMJ synaptic cleft

Question 13

Ca+ role at the sarcomere?

Answer 13

• Ca+ attaches and binds to troponin, pulls off tropomyosin from actin , myosin head binds to and forms cross bridges to actin -> power stroke etc….

Question 14

what did we learn about eccentric muscle contractions?

Answer 14

• actin and myosin are far apart
• TITIN pulls them together to allow eccentric contractions –> LOTS OF CROSS BRIDGING –> MORE CONTRACTION –> PASSIVE TENSION

Question 15

Aging on the musculoskeletal system?

Answer 15

• sarcopenia –> involuntary loss of muscle mass
• Muscle loss: decrease in contractile proteins, and circulating hormones, MU changes
• fiber type distribution: 2 is faster, 1 is slower
• MU firing rates decrease

Question 16

Rhabdomyolysis ?

And what is the population most affected?

Answer 16

• rapid breakdown of muscles –> relase of intracellular contents ( myoglobin) in to the bloodstream
• Detrained athletes that are asked to do something strenuous or difficult (ie hell week)

Question 17

Rhabdo pathophysiology?

Answer 17

• Excessive muscular contraction over a long period of time, direct trauma, toxins, drug, hereditary enzyme disorders

Question 18

clinical manisfestations?

Answer 18

• DARK URINE
• muscle pain, weakness
• also can happen via direct trauma (ie car crash)

Question 19

DMD? what is this?

Answer 19

• Duchenne muscular dystrophy

- progressive muscle fiber loss due to weakness of mostly voluntary muscles (diaphragm)

Question 20

DMD pathophys?

Answer 20

• mutations in dystrophin gene

Question 21

DMD clinical manisfestations ?

Answer 21

• sway back thick lower leg muscles (due to fat deposition), foot drop, poor balance, frequent falls

Question 22

Most important protein we talked about for DMD?

Answer 22

• Dystrophin gene getting fucked –> helps anchor sarcolemma with cytoskeletal proteins better and helps with force transmission.

Question 23

Bone overview: what is an osteoid?

Answer 23

• unmineralized, organic portion of bone matrix: bone’s tensile strength, precipitation of Ca phosphate
• Forms prior to maturation of bone tissue