Skeletal muscle 1

Question 1

Describe each muscle fiber

Answer 1

-giant, multinucleated cell formed by fusion of many myoblast cells during development
1 cell= 1 fiber
-peripherally located nuclei

Question 2

At the end of cells, thin filaments are attached to the PM by _______ and then to the tendons via ________.

Answer 2

• Adherens junctions

- Basal lamina

Question 3

Within a muscle, a number of myofibers are clustered together in ________ which in turn can be clustered together to form a single muscle

Answer 3

-fascicles

Question 4

Endomysium

Answer 4

• CT around a single muscle fiber
• electrically insulate them from neighbors
• contains basement membrane

Question 5

Perimysium

Answer 5

-CT around muscle fascicle

Question 6

Epimysium

Answer 6

• CT around entire muscle

- aka fascia

Question 7

Muscle fiber is composed of ______ which are composed of ________.

Answer 7

Myofibrils

Sarcomeres

Question 8

Tension development is proportional to?

Answer 8

number of myosin heads overlapped by thin filaments

Question 9

Myosin polymerizes to form ______ filaments

Answer 9

bipolar

Question 10

What part of myosin is responsible for generating the powerstroke?

Answer 10

-Regulatory domain

Question 11

Monomeric vs filament actin

Answer 11

Monomeric: G-actin, ATP is hydrolyzed very slowly; this hydrolysis is not what powers contraction
Filament: F-actin; polarized filament; rapidly hydrolyzes ATP, but with slower release of Pi

Question 12

Ends of F-Actin and which connects to Z-disk

Answer 12

-Pointed end is minus end

Barbed end is plus end; anchored in Z disk

Question 13

Myosin always moves toward _______ end of actin filaments

Answer 13

Barbed

Question 14

Rigor complex

Answer 14

-Myosin catalytic/motor domains bind very tightly to actin in absence of ATP

Question 15

Actin-Myosin interaction is _______ by ATP

Answer 15

-weakened

Question 16

Myosin ATPase rate is ______ by actin

Answer 16

accelerated

Question 17

Strong and Weak binding states

Answer 17

Strong: myosin bound with ADP dissociated very slowly and therefore, binds tightly to actin

Weak: myosin with ATP or ADP.Pi dissociates rapidly from actin, so it binds much less strongly

Question 18

What is the force producing state?

Answer 18

When Pi dissociated from AM:ADP:Pi

Question 19

Tropomodulin and CapZ

Answer 19

T: capping protein that regulates actin length at pointed end

CapZ: capping protein that regulates actin length at barbed end

Question 20

Z-disks are aligned and connected to the PM by _________.

Answer 20

Intermediate filaments; ultimately connected to dystrophin complex

Question 21

Dystrophin

Answer 21

links actin filaments to protein complexes anchored in surface membrane

Question 22

How can one increase the force of contraction within a twitch?

Answer 22

-increase the force of contraction by increasing the frequency of stimuli, which increases the ca2+ as well