scholarly journals Changes in conformation of myosin heads during the development of isometric contraction and rapid shortening in single frog muscle fibres

1999 ◽  
Vol 514 (2) ◽  
pp. 305-312 ◽  
Author(s):  
Gabriella Piazzesi ◽  
Massimo Reconditi ◽  
Ian Dobbie ◽  
Marco Linari ◽  
Peter Boesecke ◽  
...  
Keyword(s):  
Isometric Contraction ◽  
Frog Muscle ◽  
Muscle Fibres

Storage and release of mechanical energy by active muscle: a non-elastic mechanism?

1985 ◽  
Vol 115 (1) ◽  
pp. 79-87 ◽  
Author(s):  
G. A. Cavagna ◽  
M. Mazzanti ◽  
N. C. Heglund ◽  
G. Citterio
Keyword(s):  
Isometric Contraction ◽  
Sarcomere Length ◽  
Mechanical Energy ◽  
Frog Muscle ◽  
Muscle Fibres ◽  
Elastic Recoil ◽  
Active Muscle ◽  
A Value ◽  
Elastic Mechanism ◽  
Isotonic Shortening

In frog muscle fibres, tetanically stimulated at a sarcomere length of about 2 micron, stretched at a velocity of 1 lengths-1 and released against a force equal to the maximum isometric, P0, a phase of rapid isotonic shortening takes place after release. As the amplitude of the stretch is increased from 1.5 to 9% of the initial length: (1) the amount of rapid isotonic shortening increases up to 9–10 nm per half sarcomere and (2) the stiffness of the fibre (an indication of the number of bridges attached) decreases to a value about equal to that measured during an isometric contraction. If a 5–10 ms delay is left between the end of stretch and release, the amount of rapid isotonic shortening increases to about 12 nm hs-1. A 300–500 ms delay, however, results in a decrease in rapid isotonic shortening to about 5 nm hs-1 and also results in a velocity transients against P0 that are similar to those described during release from a state of isometric contraction. It is concluded that the force attained after large, fast stretches is due to a greater force developed by each bridge and not to a greater number of bridges. After the elastic recoil (when the force is suddenly reduced to P0), these strained bridges are able to shorten by about 12 nm hs-1, suggesting that, during and immediately after stretching, they are charged to levels of potential energy greater than those attained in an isometric contraction.

scholarly journals Potentiometric measurement of membrane action potentials in frog muscle fibres

1966 ◽  
Vol 183 (1) ◽  
pp. 152-166 ◽  
Author(s):  
B. Frankenhaeuser ◽  
B. D. Lindley ◽  
R. S. Smith
Keyword(s):  
Action Potentials ◽  
Frog Muscle ◽  
Muscle Fibres ◽  
Membrane Action ◽  
Potentiometric Measurement

The spindle and extrafusal innervation of a frog muscle

1957 ◽  
Vol 146 (924) ◽  
pp. 416-430 ◽  
Keyword(s):  
Muscle Fibre ◽  
Short Distance ◽  
Frog Muscle ◽  
Muscle Fibres ◽  
Intrafusal Muscle ◽  
Intrafusal Fibre ◽  
Unmyelinated Axons ◽  
Intrafusal Fibres ◽  
Break Up ◽  
Tonic System

In the frog muscle, ext. long. dig. IV, there are two or three spindle systems. Each consists of a bundle of intrafusal muscle fibres with two, three or four discrete encapsulated sensory regions distributed in mechanical series along it. A sensory region is usually comprised of the coiled branches of one afferent axon. These embrace the intrafusal fibres and ultimately form long fine varicose endings on or near them. The intrafusal striations appear to be lost for a short distance within the sensory region, and in this region the intrafusal fibre nuclei crowd together. The ‘small’ extrafusal efferents break up into trusses of fine unmyelinated axons and terminate as ‘grape’ end-plates, several of which can occur on the same muscle fibre. This is the ‘tonic’ system. The ‘large’ extrafusal efferents terminate as ‘Endbiischel’ end-plates on muscle fibres not supplied by grape endings. This is the ‘twitch’ system. Both ‘grape' and ‘twitch’ end-plates occur on the intrafusal bundle (probably on separate fibres) between the sensory regions. They are supplied by branches of ‘small’ or ‘large’ axons respectively, which also innervate extrafusal fibres. Thus like the extrafusals the intrafusal bundle is composed of ‘tonic’ and ‘twitch’ muscle fibres. This situation contrasts with that of the mammal, where extrafusals are exclusively ‘twitch’ fibres and intrafusals ‘tonic’.

scholarly journals Effects of solution tonicity on crossbridge properties and myosin lever arm disposition in intact frog muscle fibres

2006 ◽  
Vol 578 (1) ◽  
pp. 337-346 ◽  
Author(s):  
Barbara Colombini ◽  
Maria Angela Bagni ◽  
Giovanni Cecchi ◽  
Peter John Griffiths
Keyword(s):  
Frog Muscle ◽  
Muscle Fibres ◽  
Lever Arm
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