L11. Muscle

Question 1

What muscle types are striated?

Answer 1

cardiac

skeletal

Question 2

What are the functions of a skeletal muscle

Answer 2

1. body movement
2. maintenance of posture
3. respiration

Question 3

What are the functions of a cardiac muscle

Answer 3

heart beat

Question 4

What are the functions of a smooth muscle

Answer 4

1. constriction of viscera

2. constriction of blood vessls

Question 5

What is the organization of the skeletal muscle ( draw the organization)

Answer 5

skeletal muscles composed of
fasicles of muscle fiber
muscle fiber contain lots of myofibrils
myofibrils contain sacromeres

Question 6

What is the epimysium?

Answer 6

dense collagenouse CT surrounding entire muscle

Question 7

What is the perimysium?

Answer 7

collagenous connective tissue that surrounds bundles of muscle fibers called fasicles

Question 8

What is the endomysium?

Answer 8

fine sheath of connective tissues composed of reticular fibers that surround individual muscle fibers

Question 9

How do muscle fibers insert themselves into tendons

Answer 9

they have finger like muscle fibers insert into the CT of tendons

Question 10

how is the skeletal myofiber bound to the basal lamina

Answer 10

dystroglycan complex

Question 11

Describe the myofibers

Answer 11

1. long, cylindrical and striated
2. multinucleated with nuclei located at the periphery
3. wrapped with endomyocyte

Question 12

Describe myofibrils

Answer 12

1. aligned in parallel
2. myofibrils are separated by sarcaplasmic reticulum and mitochondria
3. composed of filaments: myofilaments

Question 13

What forms a triad?

Answer 13

A single T-tubule and 2 terminal cisternae

Question 14

What are t-tubules?

Answer 14

1. deep invagination of the sarcolemma

2. perpendicular to the length of the myofiber

Question 15

What is the sarcoplasmic reticulum?

Answer 15

1. forms an interconnected network of tubules
2. surrounds each myofibril
3. forms terminal cisternae on either side of the t-tubule
4. stores Ca2+ when muscle is at rest
5. releases Ca2+ in the sarcoplasm when muscle is stimulated

Question 16

What are the contractile units of a myofibril?

Answer 16

sacromeres

Question 17

what is the composition of a sacromere

Answer 17

Contains actin filaments, thin filaments and myosin filaments

Question 18

Draw a sacromere (include all bands )

Answer 18

pg 9a

Question 19

What are the 2 biding sites on a mysine head?

Answer 19

actin binding site

myosin ATPase site

Question 20

What are the 3 binding sites on tropnin

Answer 20

A: actin binding site
C: Ca2+ binding site
T: tropomyosin binding site

Question 21

Identify the troponin complex, tropomyosin and actin on pg 10a

Answer 21

pg 10 a

Question 22

What happens in the myofiber at low Ca2+ concentration

Answer 22

the myosin binding site on actin are masked by tropomyosin

Question 23

How is Ca2+ released from the SR during neural stimulation?

Answer 23

1. Ca2+ is released in the lumen of the t-tubule
2. Ca2+ stimulates the dihydropyridine receptors on the terminal cisterna of the SR
3. the ryanodine receptor releases C2+ into the sarcoplasm
4. a Ca2+ pump uses ATP to pump back the Ca2+

Question 24

What happens in the myofiber at high Ca2+ concentration

Answer 24

The Ca2+ binds to troponin and causes conformation change
the position of tropomyosin is shifted and the myosin binding site is unmasked
myosin now can bind to actin

Question 25

Describe sacromere contraction

Answer 25

1. myosin which has ADP and is bound to actin, power stroke occurs as the ADP is released and mysoin bends pulling the actin filament forward
2. new ATP binds to myosin, and myosin dissociates from actin
3. when ATP is hydrolyzed , myosin head cocks up and can bind to actin again