This preview shows page 1. Sign up to view the full content.
Unformatted text preview: ladder fibers,
crossbridges are thought to be attached (33–35).
Force generation during
myofibrils make up only about 50% of the fiber volume (3).repetitivefibers, a quick stretch of a fiber in activ
white stimulation of in intact
Thus the force per cross-sectional area three fibre is 48
of myofibrils types of toadfish
produced a force change only slightly lower than
kN m2 or only about 1 5 that of the locomotory fibers.
2), signifying that in active contraction, a con Power output of the swim bladder muscle
• The swim bladder muscle
produces very low force. 244 kN/m2 • Mechanical power (P) =
Force (F) × Velocity of
shortening (V) 192 kN/m2 24 kN/m2 FIG. 1. Force generation during repetitive stimulation in intact bundles of three L.C. etof toadfish. Both the red muscle (stimulat
Rome, fiber types al. 1999 PNAS
20 Hz) and the white muscle fibers (stimulation frequency 50 Hz) produced classic tetanic responses, a smooth and steady force rec
at a stimulation frequency of 60 Hz, the swimbladder (Inset) produced nearly separate twitches, and at stimulation frequencies of 125 H
swimbladder fibers produced a smooth force record (same trace in main figure and Inset), but force fell rapidly after a peak despite contin
[the period of stimulation at 200 Hz is depicted by dotted line beneath the time axis (Inset)]. For purposes of illustration, amplitudes of
were scaled to the mean isometric force for that fiber type. Maximum forces (mean SE, n 4) are 192 13 kN m2, 244 19 kN
kN m2 for the red, white, and swimbladder muscle, respectively. All experiments were conducted at 15°C. 2. Work loops
• Work = Force x distance
• A work loop is a graph of force
versus length during
contraction and relaxation.
• Work loops can be measured in
vivo or in vitro.
• For the latter:
1.oscillating a muscle
2.stimulating it in phase
3.recording force measure
force stimulate Work loops
• Positive Work (PW) = area under a descending curve
• Negative Work (NW) = area under an ascending curve
• Net work = PW - NW muscle
View Full Document
This note was uploaded on 01/22/2014 for the course BIOL 361 taught by Professor Dougaltshuler during the Fall '13 term at University of British Columbia.
- Fall '13