Topic 1

Question 1

contractile apparatus of striated muscle is organized into –

Answer 1

sarcomere

Question 2

How does skeletal muscle perform mechanical work?

Answer 2

via the skeleton under voluntary neural control

Question 3

How does the cardiac muscle perform mechanical work?

Answer 3

has it’s own pacing control but modulated by ANS

Question 4

How does smooth muscle perform mechanical work in target organ systems?

Answer 4

modulated by NT, metabolic, local and hormonal factors

Question 5

How are myocytes organized?

Answer 5

in layers or syncytium which forms heart chambers

Question 6

Describe how neurons from ANS innervate the heart.

Answer 6

innervate regions of specialized fibers (not individual myocytes)

Question 7

How is the heart’s mechanical activity rhythmically paced?

Answer 7

from special pacemaker cells in SA node of right atrium (NT modification)

Question 8

Where does striations of cardiac and skeletal muscle come from?

Answer 8

interdigitation of thick and thin filament proteins within sarcomere

Question 9

What contributes to sarcomere organization and muscle function?

Answer 9

ECM and cytoskeleton

Question 10

How are sarcomeres in skeletal muscle organized to form the whole muscle?

Answer 10

large fibers

Question 11

How are sarcomeres in cardiac muscle organized?

Answer 11

syncytium of myocytes

Question 12

What is the basis of striated muscle force generation and shortening?

Answer 12

sliding filament hypothesis

Question 13

what is the molecular motor that generates force and movement in muscle?

Answer 13

myosin (specifically cross-bridges)

Question 14

What reaction occurs to generate force?

Answer 14

ATP hydrolysis (chemomechanical transduction)

Question 15

Explain the importance of the two S1 heads on myosin?

Answer 15

increases probability that myosin and actin bind/cycle (cooperativity)

Question 16

What protein component generates the force in the actomyosin cross-bridge?

Answer 16

S1 head conformational change

Question 17

How much force does the cross-bridge generate?

Answer 17

10 pN (10^-12 N)

Question 18

How fat does cross-bridge move per ATP?

Answer 18

10 nm/CB cycle

Question 19

with unregulated actin, crossbridges with cycle indefinitely under what circumstances?

Answer 19

enough ATP

myosin and actin in proximity

Question 20

What element regulates striated muscle contraction?

Answer 20

Ca2+

Question 21

tropomyosin and troponin lie along –

Answer 21

actin thin filament

Question 22

binds to the long tropomyosin molecule every 7 actin molecules.

Answer 22

Troponin T

Question 23

physically inhibits the binding of myosin to actin when no calcium is present.

Answer 23

Troponin I

Question 24

binds calcium

Answer 24

Troponin C

Question 25

When Ca2+ is bound, the conformation changes moving – off the myosin binding site on actin permitting crossbridge cycling

Answer 25

TnI

Question 26

Describe Ca2+ binding sites on TnC

Answer 26

two Mg2+

two Ca2+ (only one functional in cardiac)

Question 27

– regulation by troponin/tropomyosin complex

Answer 27

allosteric

Question 28

the sequence of events that link the depolarization of the surface membrane with tension development by the contractile machinery.

Answer 28

excitation contraction coupling

Question 29

Describe calcium source in humans and mammals?

Answer 29

70% from SR

30% outside

Question 30

intracellular Ca2+ resequestered from SR by –

Answer 30

SR Ca2+ pump

Question 31

rate of SR Ca2+ pump modulated by –

Answer 31

phospholamban

uses ATP

Question 32

extracellular Ca2+ resequestered from myocyte by –

Answer 32

Na/Ca2+ exchanger and T-tubule Ca pump

Question 33

describe intracellular Ca2+ levels for a relaxed cell

Answer 33

low

Question 34

How does Ca2+ enter cell from outside?

Answer 34

through L-type Ca2+ channel (after an AP)

Question 35

what does extracellular Ca2+ trigger?

Answer 35

release of more Ca2+ from SR