Human Phys 2.7 Flashcards
Length tension relationship
Amount of tension developed changes according to the length of the sarcomere
Length tension relationship step by step
- Actin pulled all the way out with no cross bridge overlap (no tension)
- 2.2 micrometers long, cross bridge overlap occurs (thick filament is free providing room for sliding) (optimal length for sarcomere)
- 2 micrometers long, constant tension, ends of actin begin to touch and overlap (optimal length for sarcomere)
- 1.65 micrometers long, strength of contraction drops, Z discs abut ends of thick filament (myosin heads are not fitting well in binding sites)
Why would the end of contraction go up rather than down on a length tension relationship?
Due to passive tension
What is passive tension produced by?
Cytoskeleton and other connective tissue
When does the passive component come into play?
Only at longer lengths
Force velocity relationship
The bigger the load the slower the velocity (power)
What is the speed of the contraction determined by?
Vmax of myosin ATPase
High Vmax (fast, white)
Rapid cross bridge cycling
Rapid rate of shortening
Low Vmax (slow, red)
Slow cross bridge cycling
Slow rate of shortening
What do most muscle fibers contain?
Both fast and slow fibers but proportions will differ
What will all fibers in a particular motor unit be?
The same type of fiber
Slow twitch fiber (1)
Oxidative (resistant to fatigue)
Small diameter
High myoglobin content
High capillary density
Many mitochondria
Low glycolytic enzyme content
Fast fibers (2)
Glycolytic (fatigue quickly)
Low myoglobin content
Low capillary density
Few mitochondria
High glycolytic enzyme content
Motor unit
Anterior horn cell, nerve fiber, and all the muscle fibers it innervates
Small motor units
10 fibers
Precise control
Rapid reacting
