What Happens to the Amount of Total Force the Muscle Generates During the Stimulated Twitch
Background:
The passive rubberband properties of muscles can exist modelled as nonlinear springs. Their force-tension bend becomes exponentially steeper at longer lengths of stretch.
In addition to the passive force when the musculus is stimulated information technology contracts to produce an agile force. This active strength is derived from interactions of the actin and myosin filaments. The active strength length tension curve is described by Sliding Filament model and has its maximum at the muscle'southward normal resting length in the body. At this length there is the most interaction between the actin and myosin filaments bookkeeping for the largest active force production. At longer lengths the filaments take less opportunity for forming cross-bridges and therefore produce less force. A the muscle deceases in length past its resting length the filaments become more closely packed and are able to form fewer cross-bridges.
relates to Hooke's Police, but nonlinear.
assume muscle can be modelled as a nonlinear spring.
gastrocnemius or sartorius musculus
Requirements:
(1) Dissection for sartorius muscle and sciatic nerve.
We'll apply Rana Pipiens, the leopard frog. Pithing, exposure of sciatic nerve
TA or JD will exercise dissection (unless a premed would like to try...)
Pithing is used to euthanize the frogs past scrambling the CNS. A sharp, pointed probe is inserted through the skin into the foramen magnum between the base of the skull and the tiptop of the vertebrae. (midline at the level of the caudal typanic oval).
Once the CNS has been scrambled, the spinal cord should be destroyed to suppress any reflexes that might disturb the experiment. The technique should be attempted only after acquiring knowledge of beefcake using skeletons, and later a period of training including practice on expressionless animals. This method could activate pain receptors if the proper regions of the cord are not completely destroyed.
Incisions, surgery to betrayal sciatic nerve, and relate to stimulator.
frog, dissection tray, gloves, instruments to utilize: foreceps, tweezers, pins, drinking glass probe, scissors, Ringer'south solution, 2-0 silk thread.
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link to Dissection
use of Ringer's solution for exposed tissue.
Description:
Likewise known as Ringer'due south irrigation: A solution of recently boiled distilled water containing 8.6 gm sodium chloride, 0.iii gm potassium chloride, and 0,33 gram calcium chloride per litre – the aforementioned concentrations as their occurrence in body fluids. Ingredients are: NaCL six g, KCL 0,075 g, CaCl2 0,ane g, NaHCO3 0,i k.
specifically for amphibians:
6.5 g NaCl
0.42 g KCl
0.25 grand CaCl2
1 liter dH2O
Ringer experimented with various solutions containing the chlorides of sodium, potassium, calcium and magnesium, in order to obtain a suitable physiological saline solution which would continue the centre beating exterior of the body. Several different formulas are at present used. Variants are called Locke'south or Tyrode'due south solution. Locke's, or Ringer-Locke solution, containins more glucose and sodium, and is specially used for mammals.
Gear up-Up:
Securely pin downwardly the frog merely above the articulatio genus, no part of the preperation should motility including the dissection pan. Attach the thread tied to the Achilles tendon to the forcefulness transducer using an S claw. Adjust the length between the strength transducer and the frog muscle prepartation in the tray then that information technology is just naught as the thread is just less than taut (your first active tension reading should be 0). Attach the stimulating electrodes to a Narishige micromanipulator stand up and adjust them and so that the sciatic nervus is elevated out of trunk and resting on the end of the electrode.
Make all the connections betwixt the muscle training and the stimulator, oscilloscope and computer. The stimulating electrodes should be connected the stimulator. Ready the stimulator to a frequency of 0.2 Hz, start with manual stimulation by setting the output mode switch to the unmarried position and utilize the current choice, (not the voltage). To find the excitation threshold set the current to 0 and trigger the stimulator and wait for a twitch, if you have it hooked up you lot should be able to see information technology on the oscilloscope, slowly increment the electric current until you accept reached the maximum twitch tension, then increment the electric current past well-nigh 10% to ensure a supra-maximal stimulus. Yous can start with the oscilloscope at a time base of 1 msec/div and vertically 0.i-0.01 Volts/div. Trigger ready on the external input and the triggering level control to suit to trigger the oscilloscope sweep when the stimulator is activated. Yous may also want an electrode to record the action potentials in the nerve and/or muscle (to run across wrinkle freq/tetanus) these should exist fastened to the oscilloscope and estimator through a pre-amp. The pre-amp should have the input in differential way with a gain of either 100 or 1000; if possible include ring pass filters (ten Hz low pass and 3 kHz high pass). The force transducer should also be hooked upwardly to the computer and then that y'all tin can record the forces at the various lengths.
exposure of sciatic nerve, testing
(2) Measure length tension of frog gastrocnemius (calf) or sartorius (thigh)musculus
Use of Force transducer: specs, springs.
Create LabVIEW six to capture triggered waveforms and inspect for maximum and steady steady state (passive) data.
to come across data and generate curves.
measuring length: Narishige micromanipulator to stretch muscle.
attachment to muscle by silk thread.
mechanical deviation of force transducer?
Explore utilise of the stimulator (unmarried pulse) to cause maximal twitch; record twitch on 'scope and selection off maximum and steady state (passive) data points.
Show the passive and active L-T curves from a curt muscle length when tension is zero to a "maximum" length when tension is about 80-100 grams. How reproducible is the curve?
Frog Physiology Respiration, regulate temperature, muscle fiber types. fast, slow
The short fibers gastrocnemius and a greater corporeality of connective tissue do not prove a local maximum in the full length tension curve. In comparing, the longer, parallel muscle fibers of the sartorius contribute less to the passive tension and therefore bear witness a local maximum in the total length tension bend.
Background on thermocouples.
References pages 8-11 from McMahon
Links
Source: https://www.brown.edu/Departments/Engineering/Courses/En123/MuscleExp/Length_Tension.htm
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