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Reflexes
Biol 335 Lab
Rhode Island College
Dr. J. Montvilo
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Reflexes
•
A reflex is an automatic response by an
effector (usually a muscle) to some stimulus
(such as the stretching of a muscle or tendon)
•
A basic reflex usually involves a receptor
(such as a stretch receptor), an afferent
(sensory) neuron, the spinal cord, an efferent
(motor) neuron, and an effector (usually a
muscle)
•
Other reflexes may be more complicated
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Electromyogram
•
An electromyogram is the recording of the
electrical activity that occurs during the
contraction of a muscle; it is similar to the
electrocardiogram recorded from heart
muscles as they contract
•
This lab will involve recording
electromyograms of leg muscles as they
respond reflexively to stretch stimuli
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Achilles Tendon Reflex
(1)
•
Carefully follow the directions in the lab
manual
•
Place electrodes and attach leads to the
following areas:
• green — slightly above the main portion of
the Achilles tendon
• black — middle of the gastrocnemius (calf)
muscle
• red — 6 cm below the back of the knee
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Achilles Tendon Reflex
(2)
•
Practice generating the reflex until it can be
done consistently:
• the subject should sit with the leg dangling
• push up lightly on the bottom of the foot
• tap the Achilles (calcaneal)
tendon with a reflex hammer
• the foot should respond by
moving downwards as the
gastrocnemius contracts in
response
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Achilles Tendon Reflex
(3)
•
Make sure that the iWorx recording system is
set up properly
•
Check to make sure that it is recording
properly by hitting Record and having the
subject bend his or her foot downward
several times, with a pause in between; make
sure a good recording of these is seen and
copied into the journal
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Achilles Tendon Reflex
(4)
•
Using the pressure-sensitive reflex hammer,
produce and record at least five good actual
reflex recordings; paste one of these into the
journal
•
Calculate the average of five
response times for the reflex
from the recordings
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Achilles Tendon Reflex
(5)
•
Measure the impulse distance (path length) in
millimeters from the middle of the black
electrode to the spinal cord at the level of
the top of the hips
•
Calculate the nerve impulse conduction
velocity using the following equation
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Patellar Tendon Reflex
(1)
•
Carefully follow the directions in the lab
manual
•
Place electrodes and attach leads to the
following areas:
• green — on the lateral side of the knee
• black — on the top middle of the
quadriceps (anterior thigh) muscle, 12 cm
above the knee
• red — 10 cm above the black lead
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Patellar Tendon Reflex
(2)
•
Practice generating the reflex until it can be
done consistently:
• the subject should sit with the leg dangling
• tap the patellar (kneecap) tendon with a
reflex hammer
• the lower leg should respond by moving
outwards as the quadriceps contracts in
response
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Patellar Tendon Reflex
(3)
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Patellar Tendon Reflex
(4)
•
Make sure that the iWorx recording system is
set up properly
•
Check to make sure that it is recording
properly by hitting Record and having the
subject lift his or her lower leg several times,
with a pause in between; make sure a good
recording of these is seen and copied into the
journal
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Patellar Tendon Reflex
(5)
•
Using the pressure-sensitive reflex hammer,
produce and record at least five good actual
reflex recordings; paste one of these into the
journal
•
Calculate the average of five
response times for the reflex
from the recordings
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Patellar Tendon Reflex
(6)
•
Measure the impulse distance (path length) in
millimeters from the middle of the black
electrode to the spinal cord at the level of the
top of the hips
•
Calculate the nerve impulse conduction
velocity using the following equation
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•
Jendrassik’s Maneuver
(1)
Erno Jendrassik (1858-1921) discovered that
if a patient hooked his or her fingers together
and pulled the patellar reflex was enhanced
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•
•
Jendrassik’s Maneuver
(2)
Test the effect of Jendrassik’s maneuver on
the patellar reflex by repeating the patellar
tendon reflex experiment while the subject is
hooking their fingers together and pulling
(It is unclear whether this maneuver is simply
a distraction to the subject so that the reflex
is not inhibited by a conscious act of the
subject or whether a more neurological
mechanism is at work)
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Any questions?
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