Introduction to experimental physiology including the description of various appliances used and the procedure of recording a simple muscle twitch.

1. EXPERIMENTAL PHYSIOLOGY
If I have seen further than others, it is by standing upon the shoulders of giants.
Sir Issac Newton (1642-1726)
INTRODUCTION TO
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2. • Common appliances used in Experimental Physiology
• Gastrocnemius – Sciatic Preparation
• Simple Muscle Twitch
• Effect of two successive stimuli
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3. The ability of a tissue to respond to external stimuli
EXCITABLITY
STIMULUS
A change in the external environment that causes a
tissue to respond in a particular fashion
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4. Types of Stimuli
• Physical
• Mechanical
• Chemical
• Osmotic
• Electrical
Choice of Stimuli
Electrical
 Strength and Duration can
be easily controlled
 Least injurious
 Allow repeated stimuli and
proper localisation of
stimuli
 Resemble natural mode of
excitation.
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5. Type of Electric Current
Galvanic Current Long Duration Current e.g. Dry cell
Induced Current
e.g. Faraday Current
• Very short lived
• Do not cause damage
• Can be applied repeatedly
Alternating Current As it is Iethal as such, never employed without modifying it.
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8. • Constant current of low voltage (3-6 volts)
is fed to primary coil of induction coil.
• Dry Battery Cells connected in series
• Central Low Voltage Unit
• Step Down Transformer
• Rectifier
1. POWER SOURCE
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9. • It is a device for completing or
interrupting a circuit.
• This is connected in the primary
circuit in series with DC source.
• The key is pressed gently and
released, to make and break
the circuit.
2. KEY
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10. 3. DU BOIS REYMOND INDUCTORIUM
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11. Parts of an Inductorium
1. Primary Coil
2. Secondary Coil
3. Neefs Hammer Assembly
4. Terminals for Neefs Hammer
5. Input Termnals for Primary Coil
6. Wooden Base
7. Pointer
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12. • It is used to deliver the electrical stimulus to
the tissues.
• It consists of two copper wires held together
by a piece of Perspex.
4. STIMULATING ELECTRODE
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13. It records the movement on a moving surface
It consists of
1. A metal gear box, with heavy base vertical
rotating axle connected to it.
2. The cylinder also called drum attached to the
shaft and rotates with it.Smoked/Glazed paper
3. Cone Wheels
5. KYMOGRAPH
SHERRINGTON-STARLING RECORDING DRUM
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14. 4. Gear Control- for slow, neutral and fast
gears.
5. Clutch for turning the drum on and off.
6. Two horizontal contact arms project from
the vertical shaft at the lower end.
7. Contact Block makes contact with the
striker to complete the circuit
8. Two terminals. Seen at the base and used
to convey current through base of drum
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15. Primary Circuit Secondary Circuit
Power Source Secondary Coil
Key Stimulating Electrodes
Kymograph Short Circuiting Key
Primary Coil
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16. • Tunning fork (100 Hz) with a writing
point is used for measuring time
intervals.
• Set to vibrate and made to write on the
fast rotating drum
• So each wave is 0.01 sec (10 msec).
6. TIME TRACER
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17. GASTROCNEMIUS – SCIATIC NERVE
PREPARATION
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18. • Pithing is a process by which brain
and spinal cord is destroyed.
• The frog will be passive and no pain
will be experienced.
• Sufficiently alive for experimental
purposes.
• Circulation and cutaneous respiration
are unimpaired and the muscle will
twitch when stimulated
A. PITHING OF FROG
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19. • Gastrocnemius muscle bigger,
stronger and less easily fatigued
• Sciatic nerve longer and easy to
stimulate.
B. GASTROCNEMIUS – SCIATIC NERVE PREPARATION
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20. Nutrient solution
Conventionally, normal saline (0.65% NaCl solution) is used for all skeletal muscle
experiments & Ringer’s solution for all heart experiments.
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21. 7. FROG BOARD
This is used to place the nerve in muscle
experiments and the frog as such in heart
experiments.
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22. • A plastic chamber to keep the
muscle moist - ringer’s solution.
• A block carrying the stimulating
electrodes
• The writing lever is fixed on the
other wall of the trough.
• From the base of the trough a
drainage is provided with a clamp.
8. LUCA’S MOIST CHAMBER / MUSCLE TROUGH
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23. • This lever has a handle fulcrum and writing
point.
• The position of the writing point is adjusted
using the afterload screw.
Other types of levers
• Afterload lever
• Isometric Lever
• Starlings Heart Lever
9. ISOTONIC MUSCLE LEVER
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24. Gastrocnemius muscle
Sciatic nerve
Writing lever
Fulcrum
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25. When nerve is stimulated, muscle contracts,
shortening causes upward movement of lever.
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26. • Its a vertical rod fixed to a heavy
triangular base.
• A muscle trough, femur clamp, muscle
lever, frog board is fitted using X
Blocks
• Should be placed on the right side of
the drum with the apex of the base
towards the drum
10. MYOGRAPH STAND
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28. SIMPLE MUSCLE TWITCH
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29. Aim To record a simple muscle twitch
Apparatus Inductorium, Kymograph, Recording Drum, Myograph Stand,
Frog Board, Muscle Lever
Principle A single induction shock passed in to the nerve results in a
momentary twitch like contraction of the muscle followed by
relaxation.
A standard simple muscle twitch is 7-9 cm in amplitude and has a total duration of 0.1s
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30. • Prepare a gastrocnemius sciatic preparation, mount it on myograph stand
• Arrange drum at maximum speed, fast gear
• Connections for induced current are made including drum in primary circuit
• Position of lever is adjusted, recording one inch from the lower edge of the
cylinder
• Record a base line
• Record a simple muscle twitch
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PROCEDURE

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32. • Hold the axle of the drum and rotate it so that the strikers touch the
contact knob, and the Point of Stimulation (PS) is marked as a vertical
arc by the lever.
• Point of Contraction (PC) , Point of Maximum Contraction (PMC) and
Point of Relaxation (PR) using the muscle lever
• Time Tracer marked and duration calculated.
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33. PS PC
PR
SIMPLE MUSCLE TWITCH
1 1 2 3 4 1 2 3 4 5
CP RP
LP
PMC
Ps - Point of Stimulation
Pc - Point of Contraction
PR - Point of Relaxation
PMC - Point of Max Contraction
LP - Latent Period
CP - Contraction Period
RP - Relaxation Period
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34. Period between the Ps and Pc, Normal 0.01-0.012 sec
Causes
1. The time taken for the generation of impulse
2. The time taken for the impulse to travel along the nerve fibre
3. Neuromuscular delay
4. The time taken for the impulse to spread across the muscle fibre
5. Mechanical Inertia of the Lever
LATENT PERIOD
Factors influencing Latent Period are Site of Stimulation, Temperature, pH, Fatigue
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35. CONTRACTION PERIOD
Pc – PMC
0.04 s
Factors affecting CP
• Fatigue increases CP
• Increase in temperature shortens CP
RELAXATION PERIOD
PMC- PR
0.05-0.06 s
Fatigue and Temp Opposite effect
AMPLITUDE
Initial Length of Muscle
Intensity of Stimuli
Distance of fulcrum from point of tying of thread
Fatigue
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Isometric Muscle Contraction Isotonic Muscle Contraction
Length Contraction without shortening Shortens in length while contracting
Latent Period
CP / RP
No Change
Longer
No Change
Shortened
Tension Tension is greater, depends on the
stimulus
Tenison is comparatively less and
depends on load
Work done Does no work Does work
Heat produced Heat produced more Heat produced is less
Example Postural Muscles contraction Lifting a weight up with hand

37. EFFECT OF TWO SUCCESIVE STIMULI ON
MUSCLE CONTRACTION
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38. Aim To study the effect of two successive stimuli on muscle
contraction
Apparatus Inductorium, Kymograph, Recording Drum, Myograph
Stand, Frog Board, Muscle Lever
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Separate the two strikers and adjust the angle between
them so as two separate contractions are obtained.

40. PS1
PC
PR
PS2
Second stimulus applied soon after
relaxation phase
Response: Beneficial effect
Second curve bigger & has shorter latent
period
Cause for Beneficial effect
• Rise in temperature
• Viscoelastic Changes
• Decrease in pH
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Reduce the angle between the strikers so that the second
falls during the relaxation period of the first

42. PS1
PC PR
PS2
Second stimulus applied during relaxation phase
Response: Superposition - partial fusion of
contractions. Second part bigger due to beneficial effect
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43. PS1 PC PR
PS2
Second stimulus applied during
contraction phase
Response: Wave summation
occurs
Amplitude increased – taller &
wider curve due to fusion of
contractions
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44. Quantal summation
When skeletal muscle stimulated using
higher strength of stimulus then several
motor units are activated that results in
increase force of contraction
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45. 1 2
1 4
3 1 2 3 4 5
PS1
PC PR
Contraction period Relaxation period
Latent period
PS2
Second stimulus
applied during latent
period
Response: No
response for second
stimulus because it
falls during refractory
period
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REFRACTORY PERIOD
Refractory Period is the period after the application of the first
stimulus during which a second stimuli of adequate strength fails to
produce a response.
Absolute Refractory Period Relative Refractory Period
Second Stimulus fails whatever its
intensity is.
Second stimuli of stronger intensity can
produce a response

47. THANK YOU !
saran.adhoc@gmail.com
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