Physiology Lab

Experiment 4: Stretch Reflex

Group 4:Estreller

GarciaGarma

Ibay

Flow of Presentation:

I. Objectives of the Experiment

II. Brief Introduction

III. Activity Proper

IV. Results of the Experiment

V. Discussion

VI. Application

VII. Conclusion

VIII. References

I. Objectives

1) To elicit and observe examples of stretch reflexes

2) To analyze abnormal reflex responses from a knowledge of the reflex pathways

II. Brief Introduction

What is a reflex?!

A reflex is a protective, involuntary, and nearly instantaneous movement in response to a stimulus.

This term refers actually to a movement a reflex arc has elicited. (To be discussed in the succeeding slides…)

What about a muscle stretch reflex?!

This is a type of reflex wherein the stretching of a muscle serves as a stimulus. This is the simplest manifestation of muscle spindle function– it gets excited and in turn, causes reflex contraction of the large skeletal muscle fibers of the stretched muscle.

III. Activity

a) Materials• 2 reflex hammers

b) Procedure

The subject was asked to perform an appropriate movement in order to identify the tendon of the muscle to be tested. The subject relaxed and was comfortably supported in the limb to be tested, which was tapped briskly. The response was observed.

Using the rubber rim of the reflex hammer, the tendon was striked by holding the handle loosely and letting the head swing down toward the tendon.

This was repeated on another subject in order to elicit a more brisk and visible response. The subject was asked to make a “monkey grip” by pulling the hands apart while the knee and ankle jerks were elicited. He was then asked to voluntarily suppress the reflex as it was elicited.

IV. Results

Reflex Response (movement elicited)

Nature of response (brisk/weak)

1. Ankle Jerk dorsiflexion Brisk

2. Knee Jerk extension of the knee joint

Brisk

3. Triceps Jerk extension of the elbow joint

Brisk

V. Discussion

Let us discuss…

A) The Reflex Arc

A neural pathway that controls action reflexes

One of its characteristics in humans: its sensory neurons no longer pass directly into the brain but synapse in the spinal cord. This characteristic allows reflexes to occur very

quickly (1-2 milliseconds) It activates spiral motor neurons without delay of

routing signals through the brain, although the brain could still receive sensory input with the action occurs

A) The Reflex Arc

2 Types:

1. Autonomic reflex arc

2. Somatic reflex arc

A) The Reflex Arc

Components:

1. sense organ

2. afferent neuron

3. efferent neuron

4. effector

A) The Reflex Arc

So how does it work?

Mechanism:

When the sensory organ is stimulated, the sensory or afferent neurons connected to it carry this stimulus to the central nervous system (Brain and Spinal Cord).

Then, an efferent neuron will carry the message from the central nervous system to the effector which will react accordingly and have a given response.

A) The Reflex Arc

Remember the Bell Magendie Law?

Posterior/ afferent Sensory Anterior/ efferent Motor

A) The Reflex Arc

The Stretch Reflex: (process breakdown)

1) Stimulus: stretch of muscle

2) When the muscle stretches, the muscle spindles will too

3) Impulses to spindles from CNS by fast sensory fibers to efferent/motor neurons

4) Contraction happens

A) The Reflex Arc

The Stretch Reflex: (other points)

Classification: monosynaptic (to be discussed next) A pre-programmed response by the body to a stretch

stimulus in the muscle Coordinates normal movements and helps in making

sure the muscle won’t overstretch Neurotransmitter: Glutamate – which is also responsible

for fast pain reception

A) The Reflex Arc Classifications:

1) Monosynaptic Consists of 2 neurons: one sensory and one motor

neuron (hence, sometimes called a “2-neuron reflex”) It also refers to the presence of a single chemical

synapse between an afferent and efferent neuron Simplest reflex arc Ex. Patellar reflex

importance: used to test reflexes in general (where the absence or decrease of this reflex is known as Westphal’s sign and over reacting to it could be a sign of cerebellar diseases)

The Patellar Reflex (Monosynaptic reflex)

2) Polysynaptic One or more interneurons connect afferent and

efferent signals (2 or more synapses between afferent and efferent neuron)

Allows processes and inhibitions within the spinal cord

The effector organ voluntarily raises the organ involved before you are aware of pending dancer

Ex. Flexor or withdrawal reflex

importance: the body part withdraws itself when it encounters pain

The Withdrawal Reflex(Polysynaptic reflex)

Now that we know the mechanism of the stretch reflex as well as how the

reflex arc works, let’s dig in a little deeper and look into the receptors that are responsible for the impulses that transport

these signals – the Muscle spindles and Golgi tendon

organs!

B) Sensory Receptors

1) Muscle spindles• Other name: Neuromuscular spindles• Location: distributed throughout the belly of the muscle• Sends information about the muscle length and its rate in

change in length • Each spindle is built around tiny intrafusal muscle fibers that

are pointed at curls and attached to glycocalyx of the surrounding extrafusal skeletal muscle fibers

• The central region acts as a receptor end portion contract due to the Gamma motor fibers that originate from small type A gamma motor neurons in the anterior gray horn (also called Gamma Efferent fibers) in contradistinction to the large Alpha Efferent Fibers that innervate the extrafusal skeletal muscle.

[continuation of Muscle spindles]

• Can be excited in two ways: a. Lengthening of the whole muscle stretches the midpoint of

the spindle and excites the spindleb. Even if the length does not change, contraction of the end

portions of the spindle’s intrafusal fibers stretches the midpoint of the spindle and therefore excites the receptor

Muscle spindle reflex• 2 purposes of the simultaneous contraction of the muscle

spindle and large skeletal (voluntary) muscle:a. It keeps the length of the receptor region of the muscle

spindle from changing during the course of the whole contraction, thus, the coactivation keeps the muscle spindle reflex from contradicting the contraction

b. maintains the proper dampening function of the muscle spindle regardless of changes in length

[continuation of Muscle spindle]

[continuation of Muscle spindle]

Changes in muscle length are associated with changes in the joint angle, thus, muscle spindles provide information on position –

PROPRIOCEPTION!

B) Sensory Receptors

2) Golgi tendon organs• Other name: Neurotendinous spindles• Location: in muscle tendons• Transmit information about tendon tension and its

rate of change• receptor for inverse stretch reflex

B) Sensory Receptors

Purpose of these receptors:

Entirely for intrinsic muscle control Transmits information to the cerebellum and

cerebral cortex GAMMA motor fibers intrafusal

ALPHA motor fibers extrafusal

C) Kinds of Reflex

1) Superficial reflex

• Other name: cutaneous reflex • Polysynaptic • Several cells are connected between the cell that transmits

the afferent stimulus and the anterior horn cell • Standardized stimulus: tactile stimulus across a predefined

area of skin (skin, cornea or mucous membranes)• Common superficial reflexes: abdominal reflex, anal reflex,

cremasteric reflex, corneal and pharyngeal reflex

C) Kinds of Reflex

1) Deep reflex

• Other name: proprioceptive reflex • Monosynaptic• brisk contraction of the muscle inresponse to a sudden stretch caused

by sharp taps (from say, fingers or rubber hammers on the tendon of insertion of the muscle)

• Stretching receptors (muscle spindles) are stretched and send a stimulus via a peripheral nerve and posterior nerve root (afferent pathway of the reflex arc) to the anterior horn cell. This then sends a stimulus to the muscle, via the anterior nerve root and peripheral nerve (efferent pathway of the reflex arc), resulting in muscle contraction (monosynaptic reflex).

• Standardized stimulus: causes a rapid stretching of the tendon • Common deep tendon reflexes: triceps reflex, Achilles tendon reflex,

patellar reflex and biceps reflex.

For examination purposes, an important distinction between deep tendon and superficial reflexes is that the deep tendon reflex will be amplified when the patient’s attention is distracted, whereas the superficial reflex will not. In the case of a central or peripheral condition, these reflexes are absent.

What’s an important distinction between these two?

D) Pathological Reflexes

Reflexes observed in the abnormal or inappropriate motor responses of controlled stimuli initiated in the sensory organ that is appropriate to the reflex arc

May be initiated in the superficial reflexes of the skin and mucous membrane; in the deep tendon reflexes of the joints, tendons, and muscles; and in the visceral reflexes of the viscera and other organs of the body

The pathologic reflexes are thus syndromes of abnormal responses to otherwise normal stimuli.

E) Reflex Accuracy testing

This table will serve as a guideline in accurate reflex testing:

F) Reinforcement Techniques Valid test results are best obtained when the patient is relaxed

and not thinking about what you are doing After a general explanation, mingle the specific instructions with

questions or comments designed to get the patient to speak at some length about some other topic. If you cannot get any response with a specific reflex—ankle jerks are usually the most difficult—then try the following:1) Several different positions of the limb2) Get the patient to put slight tension on the muscle being tested.

One method of achieving this is to have the patient strongly contract a muscle not being tested

3) In the upper extremity, have the patient make a fist with one hand while the opposite extremity is being tested.

F) Reinforcement Techniques

If the reflex being tested is the knee jerk or ankle jerk, have the patient perform the "Jendrassik maneuver,“ (monkey grip) a reinforcement of the reflex:

The patient's fingers of each hand are hooked together so each arm can forcefully pull against the other. The split second before you are ready to tap the tendon, say "pull."

F) Reinforcement Techniques

How does the monkey grip help in eliciting a more accurate reflex response?

The patient is occupied with the maneuver, as the maneuver may prevent the patient from consciously inhibiting or influencing his or her response to the hammer. It serves as a distraction.

F) Reinforcement Techniques In general, any way to distract the patient from what you

are doing will enhance the chances of obtaining the reflex

Having the patient count or give the names of children are examples

 In cases of hyperreflexia, the physician may place his finger on top of the tendon, and tap the finger with the hammer Sometimes a reflex hammer may not be necessary to elicit hyperreflexia, with finger tapping over the tendon being sufficient as a stimulus.

VI. Application

Being knowledgeable of how each reflex is elicited and their expected normal responses could help the therapist in assessment

When the therapist is aware of his patient’s condition, the activities he would implement will be inclusive of the patients limitations and pathologic problems (like flaccidity and spasticity of muscle) making the therapy session and activities more appropriate and effective

Making sure activities will not further damage or worsen the clients’ current state – It will help secure the patient and avoid accidents

Importance as future OTs

VII. ConclusionMuscle stretch reflex is said to be the manifestation

of muscle spindle function. Whenever the tendon of the muscle is tapped, there will be contraction of the large skeletal muscle and the allied synergetic muscle.

It was discussed in this written report that each muscle group or stretched muscles has a specific tendon for striking using a reflex hammer (Achilles tendon for the ankle jerk, patellar tendon for the knee jerk, triceps tendon for the triceps tendon).

Certain movements are also observed during this experiment (for the ankle jerk, plantar flexion of the ankle joint is seen; extension of the knee by the knee jerk and extension of the elbow joint by the triceps jerk). Muscle stretch reflex is significant in determining and assessing the degree of facilitation in the spinal cord.

VIII. References

We would like to thank our credible resources for providing us with sufficient information to share for the discussion of our experiment’s presentation, and these are…

VIII. References

1) Hickman, C., Roberts, L., Larson, A., I’Anson, H., Eisenhour, D. (2006).

Reflex Arc.Integrated Principles of

Zoology (13th Edition) 33, 716-717.

2) Walker, H.K., Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition.,Chapter 72, Deep Tendon Reflexes, Butterworth Publications, 1990.

VIII. References

3) Chusid, J., Correlative neuroanatomy and functional neurology., 19th ed., Lange Medical Publications; Los Altos, CA: 1985.

4) Greenly, L., An Overview of Normal and Pathological Reflexes, JOURNAL OF CHIROPRACTIC MEDICINE, VOL. 2, 2003.

IX. Additional thanks to

Our professors, Mr. Nelson Alconcel, Ms. Cherry Gabuyo, Mr. Kim Medallon, Ms. Crismae Olay for facilitating in the conduction of the experiment

Our classmates for listening attentively!