Muscle histology- keagan

Question 1

skeletal v cardiac v smooth muscle

Answer 1

skeletal- striations/ quick discontinuous voluntary
cardiac- striations/ quick continuous involuntary
smooth- no striations/ weak, slow involuntary

Question 2

Connective tissue of skeletal muscle

Answer 2

epimysium- dense CT/ surround collection of fascicles
perimysium- surround fascicle
endomysium- surround muscle fiber

Question 3

Skeletal muscle enzyme that breaks down ATP

Answer 3

Myosin ATPase

Question 4

Hierarchical structure of skeletal muscle

Answer 4

muscle
fasicle
fiber
myofibril- bundles of myofilaments- contractile elements of muscle myofilaments- actin/myosin

Question 5

Bands of sarcomere

Answer 5

A- myosin- stays constant w contraction
H- Myosin without actin- compresses
M- middle line
I- Actin- compresses
Z- holds actin- brought closer to A bands

Question 6

Titin
role and disease

Answer 6

sarcomere accessory protein
forms elastic lattice to anchor thick filaments to Z line

Dilated cardiomyopathy

Question 7

Myomesin

Answer 7

sarcomere accessory protein
myosin binding protein that holds thick filaments to M line

Question 8

Alpha- actinin

Answer 8

sarcomere accessory protein
actin binding protein that bundles and anchors thin filaments to Z line

Question 9

Nebulin

Answer 9

sarcomere accessory protein
protein that helps anchor thin filaments at Z line and regulates length of thin filaments during development

Question 10

Tropomodulin

Answer 10

sarcomere accessory protein
actin-capping protein- maintains and regulates length of actin

Question 11

Desmin*

role and disease

Answer 11

sarcomere accessory protein
intermediate filament- hold z line of sarcomere to sarcolemma (cell membrane) and hold myofibrils together

Myofibrillar myopathies

Question 12

Dystrophin

role and disease

Answer 12

large rod like protein- anchors thin filaments to ECM

Duchenne muscular disease

Question 13

Contraction cycle- 5 stages

Answer 13

1- myosin head bound to actin (RIGOR)
2- ATP binds to myosin head- conformational change in actin binding site- myosin head detaches from actin
3- ATP hydrolysis- conformational change where myosin head goes forward 5nm for next stage
4- myosin head weakly binds to new actin site- releases inorganic phosphate- binding affinity increases

5- POWER STROKE- myosin head generates force as it returns to original position (back to 1)

Question 14

Regulation of contraction involves 4 aspects

Answer 14

• Calcium- initiates/ controls contraction
  -sarcoplasmic reticulum- surrounds myofibrils (A-I jxn) (holds Terminal Cisterna- calcium reservoir)
  -transverse tubular system- holds T tubules (voltage-sensor proteins)
  -Triad- complex with T tubule and two adjacent terminal cisternae (activation of T tubules= release of calcium in cisternae)

Question 15

contractile unit of muscle fiber

Answer 15

myofibril

Question 16

sarcoplasmic reticulum importance

Answer 16

forms endoplasmic reticulum that surround myofibril and hold ions (Ca) to use in contraction

Question 17

motor unit

Answer 17

neuron + all muscle fibers it innervates

Question 18

loss of innervation results in ___

Answer 18

atrophy

Question 19

muscle spindle

Answer 19

sensory receptors that detect muscle length and movement

Question 20

Muscular dystrophy

Answer 20

disease that causes muscles to undergo destructive atropy- progressive muscle weakness and degeneration

Question 21

Duchenne muscular dystrophy

Answer 21

disorder cause by mutation of gene DMD on X chromosome position 21
estimated mutation rate is highest ever
DMD- largest human gene codes for dystrophin