Physiology Manual Spring 2007

Table of Contents Nerve and Muscle Frog Gastrocnemius Sciatic Preparation………………………………………2 The Simple Muscle Twitch……………………………………………………3 Effect of Temperature on SMT………………………………………………..4 Effect of Two Successive Stimuli……………………………………………..5 Effect of Multiple Stimuli……………………………………………………..8 Effect of Fatigue……………………………………………………………….9 Effect of Autonomic Drugs on Frog’s heart…………………………………..10 Nervous System Sensory System………………………………………………………………..11 Reflexes………………………………………………………………………..16 Motor System …………………………………………………………………19

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NERVE AND MUSCLE Idea: Isolated muscles removed from the body can be made to contract either: - Directly by electrical stimulation - Or indirectly through the activation of the motor nerve. Preparation Used for Demonstration: The frog’s gastrocnemius muscle-sciatic nerve preparation.

Important Definitions:

• •

The Threshold: it is the minimum voltage needed to elicit a response if applied for a specific time. Stimulus: It is the change in the environment which causes the excitable tissue to respond. It may be : 1. Physical e.g. temperature 2. Mechanical 3. Chemical 4. Electrical which is the most commonly used because it is similar to the natural stimulants inside the body, its intensity and duration can be controlled and they don’t cause tissue damage.

The Apparatus: The Kymograph, a student stimulator, frog board and a writing lever.

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EXPERIMENT 1 the Simple Muscle Twitch (SMT) Objectives: • • •

To be able to define a simple muscle twitch To understand its phases and their timings To relate them to the action potential in the nerve

Definition: The skeletal muscle contractile response to a single stimulus of sufficient strength and duration is called the simple muscle twitch. Phases: 1. 1-latent period (o.o1 second): It is the time that elapses between the application of the stimulus and the beginning of the muscle. Causes: •

The time of propagation of the impulse in the nerve.

•

The time of transmission of the impulse through the motor end plate.

•

The time of spread of the action potential in the muscle.

•

The time of development of mechanical response in the muscle.

2. Contraction period (0.04 second): It is the period of contraction and performance of the work. 3. Relaxation period(0.05 second): It is the period of muscle relaxation and return to its original length

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Experiment 2 Effect of Temperature on the SMT Objectives: • To grasp the steps of the experiment • To comment on the effect of warm and cold saline on the simple muscle twitch and its causes STEPS: -

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The SMT is recorded at room temperature (25 °C) Pour warm saline solution (37° C) and then record SMT again Bring the temperature of the preparation to room temperature by normal ringer’s solution. Put ice cold ringer (4 °C) on the preparation then record the SMT.

Observation:

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Warming the muscle decreases the latent, contraction and relaxations periods and increase the amplitude of contraction. This is because it increases enzymatic reaction in the muscle, increases the metabolism (ATP delivery) and decreases the viscosity.

-

The maximum temperature after which there is no further increase in amplitude of contraction is 45°C.

-

The effect of cooling is the reverse .i.e. all periods are prolonged and the amplitude of contraction is decreased.

-

The minimum temperature below which there is no further decrease in the amplitude of contraction is 5°C

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Experiment3 Effect of Two Successive Stimuli Objectives: • To define motor units, phases of stimulation and types of stimuli • To understand the concept of summation • To analyze the curves according to the timing of the second stimulation Remember: Muscles Are Organized Into Motor Units •

Types of stimulus (according to the strength of stimulus): 1. Subthresold (sub minimal) stimulus: producing no response. 2. Threshold (minimal): it is the minimum voltage needed to elicit a response if applied for a specific time. 3. Sub maximal (supra minimal): producing a stronger contraction. 4. Maximal stimulus: producing a maximal contraction. At this voltage, all the motor units are recruited 5. Supramaximal stimulus: producing no further increase in the amplitude of the contraction.

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Principles: 1. The refractory period of the skeletal muscle corresponds to duration of action potential (1-3msec) and the mechanical response starts by the end of the action potential.

2. The skeletal muscle recovers its excitability before it starts to contract therefore; a second stimulus applied to the muscle during the contraction or the relaxation phases gives a response. 3. -Two successive stimuli are applied and the effect of the second stimulus arriving during the latent, contraction, and relaxation phases of the SMT obtained by the first stimulus is recorded. Comment: -when the second stimulus is applied in the latent period (refractory period) of the first SMT no response is observed. -when the second stimulus occurs in the contraction phase of the first stimulus a stronger contraction is recorded due to the summation of the muscle response of the two stimuli.

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- When the second stimulus occurs in the early relaxation phase of the first stimulus the muscle shows a summated response with two peaks. (Bi-hump curve)

-if the second stimulus occurs at the end of relaxation of the SMT Two contractions are produced in which the second contraction higher than the first. (WHY?)

NB: The second contraction is higher due to availability of Calcium from the first contraction.

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Experiment 4 Effect of Multiple Successive Stimuli OBJECTIVES: • To define Tetanus and clonus

•

To understand the effect of changing the frequency of the multiple successive stimuli on SMT Principles: -Repeated stimulation of the muscle at the early relaxation phase results in clonus. -Repeated stimulation while increasing the frequency of contraction of the muscle at the contraction phase of the previous stimulus results in TETANUS i.e. contractions without relaxations.

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Experiment 5 The Effect of Fatigue on SMT Objectives: To understand the phenomenon of fatigue, its causes and its sites -The phenomenon of Fatigue: Fatigue is the inability of the muscle to contract after repetitive contractions. Comment: Repeated stimulation of the nerve- muscle preparation produces progressive decline in the height of contraction of the recorded twitches with prolongation of their duration (latent period, contraction, relaxation) Site of fatigue is: the neuromuscular junction. Causes of fatigue: -Accumulation of metabolites e.g. lactic acid. -Depletion of muscle ATP, glycogen. -Diminished transmission of the neuromuscular junction

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Experiment 6 The Effect of Autonomic Drugs on the Frog’s Heart Objectives: • To analyze the effect of different autonomic drugs on the frog\s heart contraction. Procedure: A) Effect of adrenaline on frog’s heart: -record the normal beats of the heart. -pour adrenaline and record the effect. Comment: Adrenaline a sympathomimetic drug increases heart rate and force of contract as it activates beta adrenoceptors. B) Effect of acetylcholine on frog’s heart: - record the normal beats of the heart. - Pour acetyl choline and record the effect. Comment: -Acetylcholine a parasympathetic drug, decreases the heart rate as it stimulates the muscarinic receptors. C) Effect of atropine: - record the normal beats of the heart - pour atropine and record the effect. - pour acetylcholine and record the effect - wash with ringer. - pour acetylcholine, observe. - pour atropine then record the effect Comment: - Atropine applied before acetylcholine blocks the inhibitory effect of the acetylcholine thus the heart continues to beat normally. -Atropine applied after acetylcholine does not block the inhibitory action of the acetylcholine.

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Nervous System Why is a neurological examination performed? A complete and thorough evaluation of a person's nervous system is important if there is any reason to think there may be an underlying problem, or during a complete physical. Damage to the nervous system can cause problems in daily functioning. Early identification may help to identify the cause and decrease long-term complications. A complete neurological examination may be performed:

• • •

During a routine physical. Following any type of trauma. if the person has any of the following complaints:

o o o o o o o o o

headaches blurry vision change in behavior fatigue change in balance or coordination numbness or tingling in the arms or legs decrease in movement of the arms or legs injury to the head, neck, or back fever

Sensations The term sensations refer to the conscious awareness of conditions in the external environment or with in the body Sensations are detected by sensory receptors that change the mechanical, thermal or chemical energy into electrical energy termed the receptor potentials. If the receptor potentials reach threshold value, a nerve impulse will be transmitted to the central nervous system for integration and interpretation. A Sensory Unit: consists of a single peripheral neuron and its terminal ending. According to the type of stimuli the receptors detect: 1. Mechanoreceptors: detect the mechanical pressure or stretching. They provide sensations of touch, pressure, vibration, proprioception, hearing and equilibrium. 2. Thermo-receptors: detect changes in temperature. 3. Nociceptors: detect pain. 4-Chemorecptors: detect chemicals in the mouth (taste) nose (smell) and chemicals in the body e.g. oxygen.

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EXAMINATION OF SOMATIC SENSATIONS

1. EXAMINATION Of SPINOTHALAMIC SENSATIONS: 1-Crude Touch: - It is tested by a piece of cotton placed on the skin. - It is poorly localized - Firm areas of the skin as soles, palms require a heavier stimulus than normal, while hairy areas parts of skin require a lighter stimulus than normal because of the numerous nerve endings around the hair follicles. 2- Pain Sensations: - Tested by pricking the skin with a mounted needle. - The patient must report when the stimulus elicits pain and not when the stimulus can be detected as touch or pressure. - Compare both sides i.e. arm to arm and leg to leg. Types of pain Acute pain One common type of pain is acute pain, currently defined as pain lasting less than 3 to 6 months, or pain that is directly related to tissue damage. This is the kind of pain

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that is experienced from a paper cut or needle prick. Other examples of acute pain include Touching a hot stove or iron. This pain will cause a fast, immediate, intense pain with an almost simultaneous withdrawal of the body part that is being burned. More of an aching pain might be experience a few seconds after the initial pain and withdrawal. Chronic pain is continuous pain that persists for more than three months, and beyond the time of normal healing. It ranges from mild to severe and can last weeks, months, or years to a lifetime. The cause of chronic pain is not always evident, although it can be brought on by chronic conditions such as arthritis and fibromyalgia. Chronic pain can often interfere with a patient’s quality of life, sleep, and productivity. The experience of physiological pain can be grouped according to the source and related nociceptors (pain detecting neurons). •

Cutaneous pain is caused by injury to the skin or superficial tissues. Cutaneous nociceptors terminate just below the skin, and due to the high concentration of nerve endings, produce a well-defined, localized pain of short duration. Examples of injuries that produce cutaneous pain include paper cuts, minor cuts, minor (first degree) burns and lacerations.

•

Somatic pain originates from ligaments, tendons, bones, blood vessels, and joints. It is detected with somatic nociceptors. The scarcity of pain receptors in these areas produces a dull, poorly-localized pain of longer duration than cutaneous pain; examples include sprains and broken bones.

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Visceral pain originates from body's viscera, or organs. Visceral nociceptors are located within body organs and internal cavities. The even greater scarcity of nociceptors in these areas produces pain that is usually more aching and of a longer duration than somatic pain. Visceral pain is extremely difficult to localize, and several injuries to visceral tissue exhibit "referred" pain, where the sensation is localized to an area completely unrelated to the site of injury. Myocardial ischaemia (the loss of blood flow to a part of the heart muscle tissue) is possibly the best known example of referred pain; the sensation can occur in the upper chest as a restricted feeling, or as an ache in the left shoulder, arm or even hand.

Referred pain can be explained by the findings that pain receptors in the viscera also excite spinal cord neurons that are excited by cutaneous tissue. Since the brain normally associates firing of these spinal cord neurons with stimulation of somatic tissues in skin or muscle, pain signals arising from the viscera are interpreted by the brain as originating from the skin. The theory that visceral and somatic pain receptors converge and form synapses on the same spinal cord pain-transmitting neurons is called "Conversion Projection Theory". •

Phantom limb pain is the sensation of pain from a limb that has been lost or from which a person no longer receives physical signals. It is an experience almost universally reported by amputees and quadriplegics.

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2. EXAMINATION OF DORSAL COLUMN SENSATION: A) Touch sensations: -Fine touch 1. Tactile localization: Definition: It is the ability to locate the point touched the skin accurately with eyes closed. - It is tested by touching the skin of various parts of the subject’s body simultaneously. 2. TWO point discrimination: Definition: It is the ability to distinguish two simultaneously applied touch stimuli as separate with minimal distance between them with eyes closed. Procedure: - Ask the subject to close his eyes. - With the blunt points of a compass touch the skin simultaneously and painlessly on different areas as the back of the hand ,the palm of hand, back, finger tips…etc. - Start with pints very close then increase the distance between the two points. - Record the least distance between the two points at which the subject feels as two points touched and not as one (threshold distance) for each area. The threshold distance in: Back of the neck = mm Back of the hand= mm Finger tip= mm Palm of hand= mm What can u conclude from these data? The two point discrimination test shows that the more sensitive the area (greater number of receptors), the closer the compass points can be placed and still be felt separately, i.e. the smaller the threshold distance.

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B-STEREOGNOSIS: Def: it is the ability of identifying common objects placed in the hand while eyes are closed .it depends on: touch sensation, temperature, Fine touch, and stretch receptors. Procedure: Place different, but familiar objects one after the other in the subject’s hands with eyes closed, and ask him to name them one after the other. Loss of this ability is called Astereognosis. c- Pressure Sense: Def: it is the ability to weigh objects and discriminate between different weighs. d- Vibration Sense: Def: This composite sensation consisting of touch and rapid alteration of deep pressure sensations. It is tested by placing the base of a vibrating tuning-fork, with a low rate of vibration over bony prominences e.g. (medial malleolus).

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Examination of Reflexes Objectives:

• • •

•

To understand the components of a Reflex Arc To differentiate between the types of reflexes To be able to elicit reflexes, to know their centers and effect of UMNL or LMNL on them To be able to define some terms as Babiniski’s sign and Jendrassik’s maneuver

A reflex action is an automatic (involuntary) neuromuscular action elicited by a defined stimulus. 1 A reflex action is mediated via the reflex arc. A reflex arc is the neural pathway that mediates a reflex action. In higher animals, these pathways do not pass through the brain, but synapse in the spinal cord. This characteristic allows reflex actions to occur relatively quickly by avoiding the delay of routing signals through the brain, although the brain will receive sensory input while the reflex action occurs. Reflexes of clinical importance can be classified as: Superficial

Deep

Visceral

Planter

Biceps

Light

Abdominal

Triceps

Accommodation

Cremasteric

Knee

Micturition

Anal

Ankle

Defecation

Clinical Significance of Reflex testing The presence of the response indicates: 1. The muscle spindle, afferent (sensory) and efferent (motor) neuromuscular junctions, and the muscle are working appropriately.

neurons,

2. An appropriate balance of excitatory and inhibitory inputs from the higher brain levels. 3. The integrity of the vertebral segments (center) of the spinal cord. Tests for simple muscle reflexes, such as the patellar reflex, are basic to any physical exam when motor nerve or spinal damage is suspected. These tests can help locate the damage, because motor nerves above the damage aren't affected, but nerves that originate at or below the injury will produce abnormal reflexes.

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For each Reflex, you should be able to determine:

Reflex

Planter

Biceps

Stimulus Patient is lying on bed, supine position. Gently scratch the outer edge of the foot with blunt object Elbow is 90 degress while the forearm semiprone. place your thumb on the biceps tendon, strike it with the small end of the hammer.

Center

L5-S1

C5-C6

Action

Muscle

Flexor of the outer 4 toes and the ankle becomes dorsiflexed

Flexion and supination

UMNL Fanning of the later four toes with dorsi flexion of the Big toe (Babiniski positive)

Biceps Brachii

Hyperreflexia

LMNL

Hyporeflexia or absent reflex

Hyporeflexia or absent reflex

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Triceps

Knee

Ankle

Semiflex the elbow 90 degrees and hold the arm from the bicep’s side. Hit the triceps tendon just above the olecranon. Subject is asked to sit while his knee hangs freely or on the other knee. Hit the patellar tendon Slightly dorsiflex and evert the ankle of the subject with your hand. Strike the tendon of the Gastrocnemius.

C6-C7

Extension of the arm

L2-L3-L4

Extension of the knee

S1- S2

Planter flexion of the ankle

Triceps

Hyperreflexia

Hyporeflexia or absent reflex

Quadriceps Femoris

Hyperreflexia

Hyporeflexia or absent reflex

Gastrocnemius

Hyperreflexia

Hyporeflexia or absent reflex

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Motor System Examination Muscle state Assess the 3 Ss: size, shape, and symmetry of a muscle. Atrophy, hypertrophy, or abnormal bulging or depression in a muscle is an important diagnostic finding in the presence of different muscle diseases or abnormalities. Hypertrophy occurs with commensurate strength from use and exercise; on the other hand, hypertrophy with weakness is seen commonly in Duchenne muscular dystrophy. The shape may also be altered when the muscle or tendon is ruptured. Muscle tone Muscle tone is the permanent state of partial contraction of a muscle and is assessed by passive movement. The muscle may be hypotonic or hypertonic. Hypotonia is defined as decreased tone and may be seen in lower motor neuron lesions, spinal shock, and some cerebellar lesions. Hypertonia may manifest as spasticity or rigidity. Pyramidal lesions result in spasticity that may manifest as a clasp-knife phenomenon (ie, resistance to passive movement with sudden giving way, usually toward the completion of joint flexion or extension). Rigidity refers to increased tone associated with extrapyramidal lesions; it may result in a cogwheel (stepwise) or lead-pipe (uniform) resistance to passive movement. Muscle Power The muscles are tested against resistance. Use this muscle-strength scale when assessing and documenting muscle strength.

Score

Description

0

Absent voluntary contraction

1

Feeble contractions that are unable to move a joint

2

Movement with gravity eliminated

3

Movement against gravity

4

Movement against partial resistance

5

Full strength

Ataxia

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Ataxia, a medical term originated from the Greek language meaning "without order," refers to disturbances in the control of body posture, motor coordination, speech control, and eye movements. Several brain areas, including the cerebellum and the spinocerebellar tracts, substantia nigra, pons, and cerebral cortex control these functions. Injuries in one or more of these areas or in the spinal cord may lead to some form of ataxia. Birth trauma, medication toxicity, drug abuse, infections, tumors, degenerative disorders, head injury, stroke, or aneurysm, as well as hereditary neurological disorders also may cause ataxia.

1. Romberg's test - The test is primarily used to differentiate sensory ataxia from cerebellar ataxia - Romberg's sign detects proprioceptive sensory loss by demonstrating loss of postural control in darkness - The test is usually performed by having an examiner observing the patient's postural stability when standing with the feet close together, initially with eyes open and then with eyes closed - Romberg's sign is present when a patient is able to stand with feet together and eyes open, but sways or falls with the eyes closed A positive Romberg's sign indicates one or more of these problems: • •

•

Vertigo or Vestibular Ataxia - problems with the balance organs in the inner ear or sensory feedback. These can be caused by Cerebellar Ataxia - this is dysfunction caused by damage to the cerebellum or to nervous pathways connecting to it. The cerebellum is responsible for assimilating sensory data, for example limb position and visual data, and coordinating movements resulting from that. Proprioceptive Dysfunction. Proprioceptive sensors are located in the muscles and joints and feedback positional data to the cerebellum. Damage anywhere along the pathway from the proprioceptive sensors to the cerebellum can give rise to cerebellar ataxia.

2. Dysmetria Limb dysmetria is an inability to place and position a limb correctly, in both range and direction, across the plane of more than one joint - a dysmetric limb mainly has difficulties with the initiation and termination of limb movements, and a limb with terminal dysmetria often moves beyond the target (hypermetria), or fails to reach the target (hypometria) during a voluntary movement; hypermetria is more suggestive of cerebellar disease than hypometria

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Finger to Nose Test: past-pointing refers to terminal limb dysmetria, and can be seen during finger-nose testing with the upper arm abducted to 90 degrees => elbow movement is tested by asking the patient to sequentially touch his nose ---> upper limb hypermetria will cause the patient's finger to strike his face because the patient cannot control the amplitude of the elbow movement

•

Lower limb dysmetria is tested by heel-knee testing in the supine position => the one leg is elevated and the heel is placed on the opposite knee => the heel is then run smoothly down the leg to the top of the foot. Severe leg dysmetria will cause the heel to overshoot and miss the knee, and/or oscillate widely as it runs down the leg to finally overshoot the foot in an uncontrolled manner

3. Dysdiadochokinesis Dysdiadochokinesis refers to the fragmentation of rapid alternating muscle movements seen in cerebellar disease - dysdiadochokinesis is best tested by asking the patient to slap his thigh with the palm of his hand and then flipping the hand over to slap the thigh with the back of his hand, while the examiner listens for the regular smoothness of repetitive discrete slaps of the hand against the thigh and also observes the smoothness and rhythm of the repetitive wrist movements

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