Muscle IV (WS 18)

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created 3 years ago by sh7606
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updated 3 years ago by sh7606
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1

Skeletal Muscle Fiber types

1. Slow- twitch red fibers, for aerobic respiration, resists fatigue
Type 1: dark red
oxidative
small diameter
2. Fast- twitch white fibers- anaerobic (no O2) respiration
fatigues quickly
Glycolytic
red (pink)
3. Intermediate fibers are fast-twitch but adapted for aerobic respiration
medium sized
Type 2X white
Large fibers
color varies with blood supply and myoglobin content

2

Myoglobin

Oxygen carrying pigments of muscle
O2 reservoir in hypoxia
Transfers O2 from muscle surface to mitochondria
Provides red color to muscle
Has a high affinity for O2

3

Smooth muscle characteristics

Major homeostatic role
Controls fluid flow
Sphincters- Control emptying of bladders, tubes
Tonic contractions with little fatigue
Low O2 use, slow contraction
Has single tapered cells- small curved cells
Longer/more actin and myosin- ratio is 10-15:1, skeletal is 2-4:1
no sarcomere arrangement
Less EPR than skeletal
Has tropomyosin, no troponin

4

Single Unit Smooth muscle

Synchronous activity- whole muscle acts as one unit (works together)
Locations- intestinal tract, uterus, small diameter blood vessels
Each fiber is electrically linked to adjacent fibers
Action potentials spread via gap junctions
Pacemaker cells may initiate activity- initiated by stretching or anxiousness