slow twitch and fast twitch muscles

Smooth muscle

• involuntary- you can’t control it
• Present in digestive organs and blood

vessels

• No striations
• One nucleus per cell

Cardiac Muscle caracteristics

• Found only in the heart
• One nucleus per cell
• Striated
• involuntary

Skeletal Muscle

• Voluntary
• Makes up muscles that attach to your

bones

• Striated
• Many nuclei

How do muscles get their

energy?

•Cellular respiration!!!!

What if the cells run out of

oxygen?

• Lactic acid fermentation results
• Without enough oxygen, cells convert

glucose to lactic acid in order to make
energy (ATP)

• Lactic acids builds up and
causes muscle fatigue

Slow Twitch and Fast Twitch

Skeletal Muscle Fibers

ApproximateDistribution of Muscle Fiber
Types for Different Sports

Slow-Twitch

❖ Contract slowly

❖ More endurance

❖ Used in long distance running, biking or

swimming

Why do they have more endurance???

❖ Contain myoglobin to hold

extra oxygen

Has many mitochondria

❖ Myoglobin makes muscles dark

in appearance

Exercise increases the # of

mitochondria and the amount of myoglobin, not size of muscle

Fast-Twitch

❖ Contract fast

❖ Provide great strength for short

, rapid movements

❖ Ideal for: lifting, short sprints,

and explosive jumping

❖ Fatigue easily

Fast twitch Cont.
❖ Pale in color (lack myoglobin)

❖ Fewer mitochondria so they

rely on anaerobic respiration.
(lactic acid fermentation)

❖ Muscles increase in size