Regulation of muscle

Question 1

describe the relationship between force of contraction and calcium concentration

Answer 1

increased calcium, increased contraction

Question 2

what type of neurons regulate skeletal mm contraction?

Answer 2

motor neurons

Question 3

what is a motor unit?

Answer 3

all of the individual myofibers innervated by the same motor unit

Question 4

what synthesized Ach is motor neurons?

Answer 4

choline + acteylCoA by choline acetyltransferase

Question 5

what packages Ach into vesicles?

Answer 5

vesicular ACh transporter (vACht)

Question 6

what types of transporters are on the Ach vesicle membrane?

Answer 6

proton pump, ACh-H+ exchanger

Question 7

what provides the energy for ACh to be pumped into vesicles?

Answer 7

H+ gradient

Question 8

what are “active zones”?

Answer 8

active zones are the linearly arranged ACh vesicles on the pre-synaptic neuron

Question 9

describe post-juctional folds

Answer 9

on the post- synaptic membrane of skeletal mm, clustered Ach receptors with voltage gated Na channels in the fold below

Question 10

what is the function of post-junctional folds

Answer 10

increase the surface area on the post-synaptic membrane

Question 11

how do post junctional folds help to differentiate skeletal mm from other mm types?

Answer 11

because of the arrangement at the active zones and the post junctional fold, every releases of ACh will result in the generation of an AP

Question 12

what lines the synaptic cleft in skeletal mm?

Answer 12

basal lamina

Question 13

what is contained in the basal lamina that lines the synaptic cleft in skeletal mm?

Answer 13

acetylcholinesterase

Question 14

what is the post-synaptic receptor on skeletal mm cells?N

Answer 14

nicotinic ACh receptor

Question 15

what ions can flow in the nicotinic ACh receptor?

Answer 15

Na+ in and K+ out

Question 16

what is the net depol caused by ACh release in response to one AP in the motor neuron?

Answer 16

about 40 mV, which triggers action potential

Question 17

what will the action potential activate in the T-tubules of skeletal mm?

Answer 17

DHP receptors

Question 18

what happens once DHP receptors are activated?

Answer 18

DHP receptors have a physical interaction with RyR-1 receptors that triggers the release of Ca from sarcoplasmic reticulum

Question 19

what removes Ca from cytosol in skeletal mm?

Answer 19

SERCA pumps and calsequestrin

Question 20

what is calsequestrin?

Answer 20

Ca binding protein in skeletal mm to reduce cytosolic Ca

Question 21

describe myasthenia gravis

Answer 21

myasthenia gravis is an autoimmune disease in which antibodies to the ACh receptors are made which causes mm weakness by decreasing transmission of the stimulus for contraction

Question 22

what are the MOA of botulinum toxin and tetanus toxin?

Answer 22

decrease ACh release

Question 23

what is the MOA od tubocaranine (poison dart)?

Answer 23

blocks ACh receptor channel

Question 24

differentiate between multi-unit and single unit smooth muscles

Answer 24

multi-unit allows for the control of individual mm cells and single unit allows for coordinated contraction of groups of smooth mm cells

Question 25

which type of smooth mm unit allows for fine mm movements?

Answer 25

multi-unit

Question 26

what is the source of Ca for skeletal mm contraction?

Answer 26

sarcoplasmic reticulum via RyR-1 receptors ONLY

Question 27

what is the sources of Ca for smooth mm contraction?

Answer 27

extracellular via voltage gated Ca channels and sarcoplasmic reticulum via IP3 receptors

Question 28

what is the neurotransmitter and receptor used for parasympathetic nerves in smooth mm?

Answer 28

Ach and muscarinic receptors

Question 29

what is the neurotransmitter and receptor used for sympathetic nerves in smooth mm?

Answer 29

norepinephrine and b-adrengergic receptors

Question 30

describe smooth mm stimulation by parasympathetic nerves

Answer 30

parasympathetic- generally promotes contraction of smooth mm (think rest and digest), release ACh that binds to muscarinic receptors, this stimulated Gaq, Gaq will stimulate phospholipase C that increases IP3 and DAG, IP3 will stimulate IP3 receptor on SER that triggers Ca release leading to contraction (through activation of MLCK)

Question 31

describe smooth mm stimulation by sympathetic nerves

Answer 31

norepinephrine binds to b-adrengeric receptor, activates GaS, this activates adenylyl cyclase resulting in increased cAMP, cAMP will inhibit MLCK, causing relaxation

Question 32

what synthesizes NO in endothelial cells?

Answer 32

eNOs

Question 33

what activated eNOs?

Answer 33

increased Ca concetration

Question 34

what is the action of NO in smooth mm?

Answer 34

synthesized by eNOs in endothelial cell via paracrine signaling, travels into vascular smooth mm NO activates guanylyl cyclase inside vascular smooth mm cell guanylyl cyclase increases cGMP levels cGMP stimulates MLCP which promotes relaxation

Question 35

describe the MOA of viagra

Answer 35

viagra is a phosphodiesterase inhibitor that increased cGMP levels, this activates MLCP and causes relaxation and erection

Question 36

do all smooth mm cells require external input to generate AP?

Answer 36

No!

Question 37

discuss Ca independent regulation of smooth mm contraction

Answer 37

via Rho-A kinase, when Rho-A kinase receptor is bound, it activates rho-A kinase, which phosphorylates serene/threonine on MLCP which inactivates it and promotes contraction

Question 38

which ion is MOST responsible for the upstroke of depol in smooth mm cells?

Answer 38

calcium is MOST responsible for the upstroke of depol because there are far more Ca channels than Na channels

Question 39

what are the pacemaker cells of the gut?

Answer 39

interstitial cells of canal

Question 40

what accounts for the "plateau" seen on membrane pot graphs of cardiac mm?

Answer 40

opening of Ca channels will balance K efflux, resulting in plateau

Question 41

what is the function of DHP receptors in cardiac mm?

Answer 41

voltage gated Ca channels

Question 42

describe the action of RYR-2 receptors

Answer 42

in cardiac mm, they are ca gated ca channels that allow for the release of Ca from SER

Question 43

what is phospholamban?

Answer 43

modulator of SERCA activity in cardiac mm

Question 44

what is the role of unphosphorylated-PLB?

Answer 44

inhibits SERCA pump to promote contraction

Question 45

what is the role of phosphorylated-PLB?

Answer 45

no inhibition of SERCA, allows SERCA to remove Ca from cytosol and promotes relaxation