Muscle Physiology

Question 1

where do action potentials in muscles propagate?

Answer 1

sarcolemma

Question 2

Triad Junction

Answer 2

• T tubule w/ 2 terminal cisternae, which are specialized regions of sarcoplasmic reticulum

Question 3

what is happening when the muscle shortens?

Answer 3

it means it’s contracting and producing tension

Question 4

where can we find ryanidine receptors?

Answer 4

skeletal and cardiac muscles

Question 5

sarcomere

Answer 5

repeating unit b/w adjacent Z disks/lines

smallest functional unit of skeletal muscle

Question 6

proteins tethered to z disk of skeletal muscles

Answer 6

actin
nebulin
titin
alpha actinin

Question 7

alpha actinin

Answer 7

crosslinks antiparallel thin filaments at z disk

helps to anchor myofibrillar actin filaments

Question 8

titin

Answer 8

connects myosin to z disk

Question 9

stretch sensing and signal communication to nucleus of skeletal muscle

Answer 9

titin, nebulin

Question 10

a filament that forms internal support and attachment for actin

Answer 10

nebulin

Question 11

what is the back bone of thin filament?

Answer 11

F-actin

Question 12

structure of F-actin

Answer 12

right-handed, two-stranded helix of non-covalently polymerized actin molecules

Question 13

what is another calcium-binding protein that is closely related to troponin C?

Answer 13

calmodulin

Question 14

Troponin T binds to…

Answer 14

a single molecule of tropomyosin

Question 15

Troponin I

Answer 15

binds to actin and inhibits contraction

Question 16

what enhances myosin cross-bridge interactions?

Answer 16

phosphorylation of RLC (myosin regulatory light chain) by myosin light chain kinases

Question 17

myosin light chain phosphatase function

Answer 17

dephosphorylates regulatory light chain of the motor protein myosin II

Question 18

how do calcium ions exert their effect in muscle contraction?

Answer 18

they bind to regulatory proteins rather than directly interacting w/ contractile proteins

Question 19

myosin II

Answer 19

responsible for ATP-dependent force generation in all types of myocytes

Question 20

location of the 2 high affinity sites on skeletal muscles

Answer 20

c lobe of TNNC2 (troponin C subtype)

Question 21

location of 2 low affinity sites on skeletal muscle

Answer 21

n lobe of TNNC2

Question 22

how many molecules of ATP are consumed after one round of cross-bridge cycle?

Answer 22

only one ATP molecule

Question 23

what is the most important mechanism for the termination of muscle contraction?

Answer 23

calcium ion reuptake by SR via the SARCOPLASMIC ENDOPLASMIC RETICULUM Ca-ATPase.

Question 24

calreticulin

Answer 24

• a calcium binding protein that is found in smooth muscles in high concentration

Question 25

calsequestrin

Answer 25

calcium-binding protein in SKELETAL MUSCLES buy may also be present in cardiac and smooth muscle

Question 26

minor mechanism in termination of muscle contraction

Answer 26

NCX or PMCA na-ca exchanger or plasma membrane ca-atpase

Question 27

what determines the amount of tension developed?

Answer 27

degree of overlap between actin and myosin filaments

Question 28

how is the shortening velocity affected with higher loads?

Answer 28

velocity is slower because more cross-bridges are simultaneously active.

Question 29

relationship b/w load and velocity

Answer 29

they're INVERSELY PROPORTIONAL

Question 30

what structures interconnect cardiac myocytes from end to end?

Answer 30

intercalated disks

Question 31

what is an absolute requirement for cardiac muscle contraction?

Answer 31

influx of Ca++ through the L-type calcium channels

Question 32

what type of junction is made b/w single terminal cisterna of SR and t-tubule?

Answer 32

dyad junction

Question 33

what is needed IOT pump calcium back into SR?

Answer 33

ATP

Question 34

what maintains Na+ gradient during EC coupling in cardiac muscle?

Answer 34

Na-K ATPase

Question 35

In skeletal muscle, how many calcium ions bind to TNNC2 subtype?

Answer 35

4 calcium ions

Question 36

In cardiac muscle, how many calcium ions bind to TNNC2 subtype?

Answer 36

3 calcium ions

Question 37

what inhibits SR calcium pump?

Answer 37

PHOSPHOLAMBAN

Question 38

nerve bundles that release NTs in smooth muscles

Answer 38

varicosities (close to postsynaptic membrane of smooth muscle cell) smooth muscles don't have synaptic clefts

Question 39

multiunit smooth muscle

Answer 39

each SM cell receives its own synaptic input iris, walls of blood vessels

Question 40

unitary smooth muscle

Answer 40

only a few cells receive direct synaptic input hollow organs

Question 41

function of gap junctions in smooth muscles

Answer 41

permit coordinated contraction

Question 42

why is the rate of rising of action potential lower in smooth muscles?

Answer 42

calcium channels open much slower than Na+ channels in cardiac and skeletal muscles.

Question 43

purpose of fast, voltage Na+ channels in smooth muscles

Answer 43

hasten activation of voltage-gated Ca++ channels, which contribute to faster rate of depolarization

Question 44

what causes spontaneous electrical activity in smooth muscles?

Answer 44

regular, repetitive oscillations in Vm and contractions (SLOW WAVE POTENTIAL)

Question 45

what can activate contract in smooth muscles?

Answer 45

both extracellular and intracellular calcium ions

Question 46

2 proteins that tonically inhibit interaction b/w actin and myosin

Answer 46

caldesmon and calponin

Question 47

tonically inhibit actin-activated ATPase activity of myosin

Answer 47

caldesmon

Question 48

tonically inhibits ATPase activity of myosin

Answer 48

calponin