Msk: Muscle 1

Front 1

Skeletal muscle histo

Back 1

Striated, multinucleate, longitudinal fibers;
endomysium around individual fibers, perimysium around bundles of fibers, epimysium around entire muscle.

Front 2

tendons

Back 2

Heavy, parallel collagenous fibers that are site of muscle attachment, Musculotendinous junction = common injury site

Front 3

skeletal muscle blood supply

Back 3

Rich circulation pierces the epimysium and run parallel to perimysium. Capillary system can increase 45% during strenuous exercise.

Front 4

skeletal muscle nerve supply

Back 4

Afferent and efferent fibers; each nerve fiber is distributed to a group of muscle fibers (1 to 200)
-precision = small motor unit
-gross = large motor unit

Front 5

Parts of a sarcomere

Back 5

Sarcomere runs from Z line to Z line
-I band: thin filaments only
-A band: length of thick filaments
-M line: middle of sarcomere
-H zone: thick filaments only

Front 6

sarcomere during contraction and stretching

Back 6

contraction: shortens up to 50%; H zone and I band get shorter; A band always stays the same

stretching: lengthens up to 120%; limited by collagenous tissue

Front 7

what tells a skeletal muscle to contract

Back 7

-voluntary impulse from cortex or a reflex impulse arising in upper/lower MN
-all-or-nothing response

Front 8

RMP and depolarization

Back 8

Nerve cell has RMP of -85. When a nerve cell fires, Na permeability increases and then K efflux restores RMP.

Front 9

4 insoluble proteins that make up myofibrils

Back 9

myosin + actin + tropomyosin + troponin

Front 10

thick filament

Back 10

Myosin chain has 2 globular heads that bind Actin have ATPase activity in the presence of Ca

Front 11

Thin filament

Back 11

Actin + Troponin + Tropomyosin
-G actin binds ATP and polymerizes to form F actin, which binds Ca tightly

Front 12

tropomyosin and troponin

Back 12

Tropomyosin complexes w/ F actin and prevents myosin crossbridges from binding. Ca binds troponin and induces tropomyosin shift that allows actin/myosin to interact

Front 13

role of ATP

Back 13

attaches to myosin heads and produce cross-bridge w/ actin. Very sensitive to Ca

Front 14

Steps in contraction

Back 14

Action potential >> Ca released from Sarcoplasm >> crossbridge are made/broken under Ca regulation >>

Front 15

Type I skeletal muscle

Back 15

Slow twitch, red fibers are rich in mitochondria and myoglobin, do lots of oxidative phos. Good for endurance exercise.

Front 16

Type IIa skeletal muscle

Back 16

mixture of glycolytic and oxidativ enzymes; intermediate twitch time, fatigue resistant

Front 17

Type IIb skeletal muscle

Back 17

White fibers, glycolytic pathway, fast-twitch, fatiguable
-weight training causes hypertrophy of type II

Front 18

muscle fiber recruitment

Back 18

more motor units recruited as physical effort increases. Type I provide first 20% of strength, then type II are recruited as effort increases. Type II still fatigue first.

Front 19

fiber type ratio

Back 19

Ratio is set, have some ability to convert btw type II's, but effort must be severe/sustained.
Fiber type depends on MN supplying it, and if a nerve is changed, the muscle fiber may change type.

Front 20

fatigue

Back 20

MN unable to maintain firing rate; muscle contractile mechanism becomes less efficient.

Front 21

skeletal muscle hypertrophy

Back 21

number of fibers stays constant but size of myofibrils increases. Isometric exercises are best.

Front 22

atrophy

Back 22

occurs due to disuse. Type II fibers are particularly prone.

Front 23

myositis ossificans

Back 23

non-neoplastic proliferation of bone and cartilage w/in skeletal muscle at the site of previous injury. if it remains symptomatic, can excise it once it is mature (1-2yrs)

Front 24

CO

Back 24

HR x SV
-early increase in CO w/ exercise is due to increase in SV, then mainly due to increased HR.

Front 25

training and lactic acid

Back 25

training increases lactic acid threshold and increases oxidative capacity (by increasing SV and decreasing resting HR)

Front 26

isometric exercise

Back 26

joint doesn't move during contraction; good for arthritic joints. Ex: straight leg raise. Don't build as much strength but are more tolerable.

Front 27

isotonic exercise

Back 27

fixed resistance; mainstay of weight-lifting regimen.
-concentric: force applied as muscle shortens
-eccentric: force applied as muscle lengthens

Front 28

isokinetic exercise

Back 28

joint moves at same speed throughout motion; better at improving muscle strength but machines are $$$
**only positive (concentric), so decrease soreness
-most efficient way to train

Front 29

DOMS

Back 29

exacerbated by eccentric muscle contractions; collagen/CT injury

Front 30

anabolic steroids

Back 30

androgenic effect produces muscle hypertrophy but linked to renal and hepatic malfunction.

Front 31

creatine

Back 31

helps build muscle and reduces recovery time. side effects related to water loss. Purity is a concern.

Front 32

maximum HR

Back 32

220-age; train btw 55% and 90% max HR for 30 min

Front 33

recommendations for sedentary patients

Back 33

poor CV reserve that can't tolerate rapid increase in HR. start w/ 55-65% of max HR