Skeletal Muscle Physiology DSA

Question 1

voltage gated sodium channel

Answer 1

closed but capable of opening RMP -70

open - activated -50 to +30

closed and not capable of opening +30 to -70

Question 2

h gate

Answer 2

inactivation gate

Question 3

m gate

Answer 3

activation gate

Question 4

voltage gated potassium gate

Answer 4

closed but capable of opening at RMP

• delayed opening triggered at threshold**
• remains closed to peak potential
• 70 to +30

open from peak polarization to after hyperpolarization
+3- to -80

Question 5

resting membrane potential depends on

Answer 5

extracellular K concentrations**

increased K uptake by cell - insulin, epinephrine, aldosterone - hyperkalemia

Question 6

increased K conductance

Answer 6

hyperpolarization

Question 7

hypokalemia

Answer 7

hyperpolarization

Question 8

hyperkalemia

Answer 8

depolarization

Question 9

changes in Na and K conductance

Answer 9

Na - rapid rise and fall

K - slow rise and fall

Question 10

neurotransmitter release

Answer 10

AP at axon terminal - trigger voltage gated Ca channel opening

influx of Ca - release of synaptic vesicles

Question 11

AP at NMJ vs. synapse

Answer 11

synapse - summation of EPSPs brings to threshold
-excitatory or inhibitory

NMJ - one to one transmission of APs
-always excitatory

Question 12

postjunctional fold

Answer 12

at NMJ

-increase surface area

Question 13

receptors for ACh at NMJ

Answer 13

nicotinic AChR

Question 14

acetylcholinesterase

Answer 14

terminates synaptic transmission at NMJ

breaks down to choline + acetate

Question 15

synthesis of ACh

Answer 15

choline acetyltransferase

-choline + acetyl CoA

Question 16

ACh-H exchanger

Answer 16

uptake of ACh into vesicles
-driven by proton gradient

positive voltage and low pH inside vesicle

Question 17

vesicle fusion at NMJ

Answer 17

synaptbrevin - v-SNARE

complex with snap-25 and syntaxin (t-SNAREs)

Question 18

detects rise in Ca at NMJ and trigger exocytosis of bound ACh vesicles

Answer 18

synaptomagmin

Ca receptor**

Question 19

syntaxin and SNAM-25

Answer 19

t-SNAREs

presynaptic membrane of nerve terminal

bind with synaptobrevin**

bring vesicles closer to presynaptic membrane

Question 20

tetanus

Answer 20

synaptobrevin

Question 21

botulinum A and E

Answer 21

cleave SNAP-25

Question 22

botulinum C1

Answer 22

cleave syntaxin

Question 23

botulinum B, D, F, G

Answer 23

act on synaptobrevin

Question 24

ACh receptor

Answer 24

permeable to cations

weak ionic selectivity - functions to raise Vm above threshold

AP at -50

Question 25

opening of AChR at NMJ

Answer 25

Na and K equally permeable

• increases normally low resting permeability
• large movement of Na into cell
• small movement of K out of cell
• results in graded end plate potential

Vm shifts to between E-K and E-Na

Question 26

sarcomere

Answer 26

Z line to Z line

Question 27

A band

Answer 27

myosin thick filaments

partial overlap with actin thin filaments

Question 28

H zone

Answer 28

middle of A band

part of myosin where actin does not overlap

Question 29

I band

Answer 29

part of actin not overlapping myosin

Question 30

H zone

Answer 30

middle of A band

-part of myosin where actin does not overlap

Question 31

Z line

Answer 31

thin filament attachment

Question 32

thick filament

Answer 32

bipolar assembly of multiple myosin molecules

2 myosin heavy chains
-rod, hinge, head

4 light chains - 2 alkali, 2 regulatory

Question 33

binding sites on heavy chains

Answer 33

actin binding - for cross bridging

ATPase site - for binding ATP

Question 34

thin filaments

Answer 34

actin - F-actin

alpha helical polymer of actin is backbone

13 actin monomers makes 1 helical turn - F-actin

Question 35

tropomyosin

Answer 35

blocks actin binding to myosin at rest

interacts with 7 actin monomers

Question 36

troponin

Answer 36

interacts with 1 tropomyosin and 1 actin

Question 37

troponin T

Answer 37

TnT, TNNT

binds single tropomyosin molecule

Question 38

troponin C

Answer 38

TnC, TNNC

binds Ca

Question 39

troponin I

Answer 39

TnI, TNNI

binds actin and inhibits contraction

Question 40

Ca combines with troponin

Answer 40

tropomyosin slips away from blocking position between actin and myosin

myosin binding site on actin forms cross bridge - contraction can occur

Question 41

excitation contraction coupling

Answer 41

AP of sarcolemma (excitation)

increased Ca allows actin and myosin binding (coupling)

Question 42

increased Ca

Answer 42

intracellular signal to trigger and sustain contraction**

AP propagate fro sarcolemma to interior of muscle fibers via transverse tubules

Ca released from SR
Ca binds troponin - allows cross bridging

Question 43

triad

Answer 43

t tubule and 2 associated cisternae

propagate AP into t tubule - depolarizes triad

Ca release from lateral sacs of SR

DHPR and RyR important

Question 44

DHPR

Answer 44

dihydropyridine receptor
-L type Ca channel

voltage sensor**

associated with T tubule

tetrads - groups of 4

Question 45

RyR

Answer 45

ryanodine receptor
-Ca release

release stored Ca from SR**

cluster at portion of SR opposite the T tubule

Question 46

continued force through cross bridge cycling

Answer 46

depends on Ca supply

Question 47

relaxation

Answer 47

reuptake of Ca fro sarcoplasm back to SR

requires ATP

• Ca pumps
• ATPase binding site on myosin head

Question 48

pumps removing Ca for relaxation

Answer 48

Na-Ca exchanger
Ca pump

MAJOR - SERCA pump
-most important mechanism for returning resting Ca levels in skeletal m

Question 49

high Ca

Answer 49

inhibits activity of SERCA

Question 50

Ca binding proteins in SR

Answer 50

delay inhibition of SERCA pump

buffer increased Ca during Ca reuptake and can increase Ca storage capacity of SR

Question 51

calsequestrin

Answer 51

major Ca binding protein in skeletal m

localized in SR at triad
-form complex with Ca RyR

facilitate muscle relaxation by buffering Ca and unbinds Ca near Ca release channel

Question 52

calreticulin

Answer 52

Ca binding protein in smooth m