Physiology Muscle Mechanics I And Ii

Front 1

isometric vs isotonic contraction

Back 1

isometric - mnimal movement, measures foce generation

isotonic - movement, measures muscle shortening

Front 2

can you determine how active force varies with muscle length in a whole muscle

Back 2

not directly, because passive elements like CT sheaths, sarcolemma, and titin resist stretch or force when muscle is stretched beyond a critical length

so measure passive force of a muscle(force due to ct, etc) and measure total force at that length. Subtracting the two will give you the active force(just the force due to muscle contraction)

Front 3

passive force curve, linear non linear?

Back 3

non linear, CT elemtents are extended when stretched, are initially compliant then sharply resist futher extension

Front 4

elastin vs collagen content in muscle and effect on passive force curve

Back 4

the slower increase in resistive force is due to elastin which is more compliant, the sharp increase in resistance is due to collagen which is not compliant

Front 5

see page 277 of muscle weakness module for information on isometric length force relationship

Back 5

oh

Front 6

at short muscle length which contributes more, active or passive force?

Back 6

all total force is active, at long lengths, passive force contributes more and active force decreases because of decreased thin/thick filament overlap

Front 7

pre-load vs afterload

Back 7

preload = length of muscle, max F that can be developed

afterload = the resistance which the muscle must contract against

Front 8

describe picking up a cup of coffee in terms of isometric and isotonic F

Back 8

increase in isometric F to overcome the weight of the coffee

isotonic shortening(constant F) as you lift it to your mouth

isotonic relaxation as you put the cup down (contstant F)

isometric relaxation as the muscle relaxes since no load is present

Front 9

length tension relationship

Back 9

j

Front 10

force velocity relationship

Back 10

i

Front 11

relationship between length/tension and force/velocity

Back 11

m

Front 12

three types of skeletal muscle fiber

Back 12

slow twitch oxidative: brown
fast twitch A oxidative
fast twitch B fatigable: white

Front 13

fenn effect

Back 13

muscle utilizes more atp when it is shortening vs an isometric contraction

Front 14

immediate recovery reactions of skeletal muscle when E is depleted

Back 14

creatinine kinase, PCr +ADP = ATP + Cr

myokinase, 2ADP = ATP +AMP

Front 15

secondary recovery reactions

Back 15

req a finite period of time to be activated

glycolysis
ox phos

Front 16

does training increase resistance to fatigue in fast twitch glycolytic fibers?

Back 16

no, , but does increase amount of force generated

Front 17

is smooth or skeletal myosin faster

Back 17

skeletal is faster, smooth muscle myosin is sparse and slower

Front 18

caldesmon

Back 18

thin filaments of smooth muscle contain Ca,calmodulin,actin, myosin binding protein called caldesmon

it inhibits myosin ATPase activity

Front 19

what are the critical differences between smooth and striated muscle?

Back 19

smooth: NO troponin, instead thin filaments are made of actin tropomyosin, caldesmon and calponin,
classical sarcomeres as in striated muscle do not exist in smooth muscle

Front 20

Force-length relationship in smooth muscle

Back 20

force length relationship aka length-tension curve aka the preload curve thing

sliding filament explanation still holds for smooth muscle even though its sarcomeres are messed. Difference is smooth muscle can develop isometric force over a broader range of muscle lengths. Ie plateau(Lo) of the length tension curve in smooth muscle is extremely broad

Front 21

Force-Velocity relationship

Back 21

Vo = max velocity at 0 load(dep only on isoform!)
Fo = maximal force at 0 velocity

smooth muscle has a much lower velocity of shortening because of its isoform, but the maximal force that can be generated is still the same as skeletal

Front 22

explain a smooth muscle AP

Back 22

1) activation of a v-dependent inward Ca current, DHP R v-gated(not sensor)

2)activation of v-dep outward K AND inactivation of early transient inward Ca

3) plateau is a fight between sustained activation of v-dep Ca in and v-dep K out

4) repol = inactivation of Ca in and activation of Ca-dep outward K current

Front 23

is an AP required for an increase in force?

Back 23

not in smooth muscle, AP's can increase contraction, but smaller depols will cause a graded increase in Force

called electromechanical coupling

Front 24

explain in more detail smooth muscle AP and Ca

Back 24

calcium enters the cell through VOC's (DHP R, voltage operated channels) enough to initiate contraction, and can also enter through ROC's(receptor operated channels, ie IP3 DAG pathway that opens IP3R ca channel on SR!, ryanodine R are also present but we dont know what they do)

Front 25

in a cardiac AP what source of Ca is responsible for the initial spike? what is responsible for the plateau?

Back 25

spike = SR
plateau = EC Ca influx

Front 26

describe smooth muscle activation of contraction

Back 26

at resting levels smooth muscle is inactive, when AP hits Ca-Calmodulin complex binds MLC kinase, which then activates myosin allowing it to interact with actin and cross-cycle

smooth muscle is a true activation system, not disinhibition

Front 27

what turns off smooth muscle contraction

Back 27

MLC phosphatase deP's myosin light chain inactivating it

Critical concept: smooth muscle must be phosphorylated to interact with actin and produce force

Front 28

latch state

Back 28

maintenance of high levels of force during conditions of low or basal Ca levels and MLC phosphorylation, force is maintained by deP'd latchbridges

Front 29

what causes greater force per Ca in smooth muscle, stimulation by an agonist (IP3 pathway) or membrane depol (DHP Ca channel)?

Back 29

stimulation by an agonist,

Front 30

RhoA

Back 30

GTPbinding protein activates Rhokinase which can
1) p MLC and activate it
2) inhibit MLC phosphatase