Muscle types 9b

darker

more blood supply

what factors increase force of skeltal muscle contraction

more myosin cross brisges w actin, greater force generated, increase size of indivisual fibers and fasicles and increase overall muscle cell

1. force= XS area of muscle

2. Power= work per unit time (force x velocity) increase in velcity of muscle contraction, it will increase power e.g fast will generate more force

Type 1 

more myglobin, more mitocondria, resistance to fatigue, aerobic capacity, numbe rof capillaries

type 2 

larger muscle fiber size , faster speed of contraction

type 1

SLOW OXIDATIVE

make more myoglobin, make type 1 myosin (thinner) smaler nerves 5um or smaller, slower contraction times 2-8 m sec slower twitch, more vascular , more mitochondria

type 2a

fast fibers fast oxidative glycolytic

lwaa myoglobin, make type 2 myosin thicker, have lg nerves associated w them (10-20um) conduction velocity of fast twitch (8-40) fast twitch has 3-5 times force of slow twitch, uses atp faster than type 1

type 2xb

FASTEST FIBERS FAST GLYOLYTIC

have thickest myosin isoform, fastest speed of contraction (20-80m/sec) 10x then slow, have lgest diameters nerves, containes fewest mitochondria, fatigue easily

force generated depends of muscle cell type speed of muscle contraction

varies w cell muscle type, in order for muscles to keep contracting they need ATP, supplies the energy they need for muscle fiber too:

1. move and deattach cross bridges

2. pump calcium back into SR

3. pump na out and k back into cell after excitation-contraction coupling

ATP gets used up quickly due to limited supply-atp is regenrated quickly by 3 mech

direct phosphorylation of ADP by creatine phosphate 

anaerobic pathway: glycolysis and latic acid formation

aerobic respiration

creatine phosphate

unique molecules located in muscle fibers that donates a phosphate to ADP to instanoty form ATP

creatine phosphate plus ADP = creatine + atp

muscle fibers have enough atp and cp reserves to power cell for 15 secs

anaerobic pathways

atp can also be genrated by breaking down and using energy store in gluclose- w/o o2 gluclose can be broken down into 2 pyruvic acids molecules and 2 atp are generated for each gluclose broken down

low o2 levels

pervent pyruvic acid from entering aerobic respiration phase so this pathway is limiting in supplying atp-pathway is also in absense of 02 reffered to as anaerobic glyclosis)

pryorvic acid converted into latic acid lead to muscle fatigue by increase acidity of cell

anerobic pathway 

lactic acid, diffuses into bloodstream uses as feul by liver, kidneys, heart, converted back into pyruic acid or gluclose by liver, anaerboc respiration yeilds only 5% as much ATP as aerobic respiration, but produces ATP 2 ½ times faster (bulding muscle pinch off o2 supply)

once atp is used up skeltal muscle will switch to aerobic (ceelur resp) to produce more of it:

produces 95% of ATP during ret and light to moderate exersis slower than anaerobic pathway, consists of senes of chemical reactions that occur in mitochondria and require o2 breaks gluclose into co2 h20 and lg amts of atp (32 produces)

aerobic respiration

feuls used include gluclose from glycogen stored in muscle fiber, then bloodborn gluclose and free fatty acids main fuel after 30 mn of exersise

energy systems used during sports: 

aerobic endurance: length of time muscle contract using aerobic pathways light to moderate activity, which can continue for hours 

anaerobic threshold: point at which muscle metabolism converts to anaerobic pathway- heavy strenous exersise aka lifting

muscle fatigue:

physiological inability to contract despite continued stimulis

usally occurs when theres ionic imbalances 1. levels of k, ca, p can interfere e-c coupling 2. prolong exersise may damage SR and interfere with ca regulation and relaspe 

lack of atp is

rarley primarly the reason the reason for fatigue instead its oxygen ( if muscle is being pushed hard, o2 delivery cant keep up and cell will switch to anerobic respiration. complication switching, called reaching the anerobic threshold (latic acid threshold)

oxygen debt

during rest/mod. exersise, respitory and cardiovascular systems supply enough o2 to support aerobic resp

anaerobic latic acid threshold

shift in metabolism from aerobic to anaerobic, during strenous muscle activity, when the above systems cant supply the necessary o2- latic acid is provided 

oxygen debt 2

most o2 in strenous exersise is used to produce ATP for muscle contraction, not for converting lactic acid to gluclose

end of strenous exersise, muscles may be left w o2 debt

This is amount of oxygen needed by liver cells to convert the accumulated lactic acid to glucose, and to restore muscle ATP and creatine phosphate concentrations

muscle fatigue 2

inability to contract muscle, common causes: decrease blood flow, ion imbalences across sacrolemma, loss of desire to continue exercises, accumulation of latic acid (controversial)

liver cells can synthesize

gluclose from latic acid produced anaerobically

in the body latic acid— lactate H= ion

during strenous exersise o2 is used to make ATP for muscle contraction rather than using it to react w latic acid to make gluclose (as a consequence latic acid accumulates and H+ enters bloodstrem

for a muscle to return to pre-exersise state

o2 resenes are replunished 2 latic acid needs to be reconverted ti pyrovic acud in liver cells/use o2) 3 glycloen stores are replaaces 4) atp and creatine phosphate reserves are resynthesises (all replenshing steps require extra o2 excess post exersise o2 consumption or o2 debt

typical person muscle fibers in calf

type 1: 50

Type 2a: 40%

Type 2b 10%

all muscle fibers

got larger hypertrophy (commn adaptation to workload) 5-10% muscle fibers change thru exersise

adaptation to workload

The more aerobic workouts you do the better your cells get at adapting to that type of stress, anaerobic exersises make more right ezyme for boody to adapt to stress

person gets larger

volume increases (ratio of cross sectional area of muscle to volume gets larger as you get bigger

reason why smaller people can lift a higher proportion of their weight

ratio of volume of person/muscle mass, since volume increases much faster relative ti criss sectional area of muscles

muscle cramps

Involuntary muscle contraction (quite painful)
Myosin heads remain in contracted position,
muscle bulges, fires nerves, pain receptors