Type 1 and Type 2 muscle fibers

Muscle Fiber Type 1

endurance, last longer, slow

Muscle Fiber Type 2

strength/speed, short-lived, most tension!

Structural differences for Type 1

• small fiber diameter

• high mitochondrial density

• high capillary density

Structural differences for Type 2

• large fiber(myofibrils!) diameter

• low mitochondrial capacity

• low capillary density

Why do Type 1 muscle fiber have high mitochondrial density?

in mitochondria, ETC (oxidative phosphorylation) takes place, makes a LOT of ATP to fuel slow, endurance (the contractile) characteristic of type 1 muscle fibers

Why do Type 1 muscle fiber have high capillary density?

This is because oxygen, the last electron acceptor in the ETC(oxidative phosphorylation) travels through the capillaries.

Enzymatic characteristics for Type 1 muscle fibers

• High aerobic enzymes

• high TG(fat) content

• Low glycolyctic enzymes

• low glycogen content

Enzymatic characteristics for Type 2 muscle fibers

• low aerobic enzymes

• low TG(fat) content

• high glycolyctic enzymes

• high glycogen content

Why do Type 1 muscle fibers have high aerobic enzymes?

because aerobic = oxygen which is needed as the final e- acceptor in the ETC

Why do Type 1 muscle fibers have high TG(fat) content?

because fat enters the mitochondria, fat is highest in energy, 9kcal, provides a lot of ATP for oxidative phosphorylation to occur ?

Why do Type 2 muscle fibers have high glycolyctic enzymes and content?

because glycogen is stored glucose so a high amount is needed to undergo glycolysis to make some ATP (a little, 2)

Why do Type 2 muscle fibers fatigue fast?

because a lot of pyruvate is accumulated through glycolysis, so it becomes lactic acid(an extra H+ added). Sarcoplasmic reticulum is releasing Ca++ at the same time, leading to an accumulation of both positively charged ions, causing repulsion. SR begins releasing less Ca++, so not as much binding to troponin, tropomyosin prevents myosin binding to actin, less actin sliding over myosin heads

GTO

golgi tendon organ, monitors muscle tension

muscle spindles

monitors muscle length

What happens when you have too much tension in your muscle

GTO inhibits the contraction in order to take some of the tension off