Physio Lab 1-3

Experiment 1 Muscle Tonus Allison Eunice B. Servando

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Objectives 1. What is responsible for muscle tonus? What muscles of the body are specially kept in tone? Responsible for muscle tonus is the sensory muscle spindle which measures muscle stretch. Skeletal, cardiac and smooth muscles are type of muscles in the body that should be kept in tone; measured by the amount of tension or resistance to movement in muscle. In skeletal muscle, a state of tension that is maintained continuously minimally even when relaxed increases in resistance to passive stretch. In smooth muscle, steady tension maintained in the walls of hollow vessels; regulated mainly by autonomic innervation but influenced, e.g. in the walls of arterioles, by local variables: temperature, chemical factors or intravascular pressure, contributing to auto regulation of appropriate blood flow. Muscle tonus is also caused by nerve impulses through successive flow and is influenced by receptors found in the muscle and tendons. 2. Why muscles have to be kept in tone? When is muscle tonus physiologically lost? Muscle tone is the maintenance of partial contraction of a muscle, important for the generation of reflexes, maintenance of posture and balance and controlling proper function of other organ systems. That is why most muscles should be kept in tone in order to facilitate other organs and sense to carry out proper function. Physiologically, muscle tone is lost when there is damage in the peripheral nerve, termed as flaccidity and an exaggerated tone, termed as

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spasticity by overstimulation. Procedures 1. What have you observed in the characteristic position of the limbs of the frog after suspending it? (Procedure #1) Lower Limbs of the frog were extended and no motions were observed. Muscle tone is firm and normal. 2. What observations can you get from the position of the limbs of the frog when spinal shock had worn off? (Procedure #2)

Short twitches or reflexes were observed initially while the lower limbs were extended and this was followed by a decrease in muscle tone and contraction. 3. What are the differences, in terms of position, found between the right and left lower limbs after cutting the right sciatic nerve? (Procedure #3) They are not aligned anymore because after cutting the right sciatic nerve, right limb went flabby and loose while left lower limb was still raised and tight. 4. What are the differences, in terms of firmness, found in the gastrocnemius? Right leg is flaccid and limp while Left leg is firmer and toner 5. What have you observed in the position of the limbs of the frog after destroying the spinal cord? The lower limbs of the frog both became flaccid and limp. III.

Report and Conclusion 1. Define muscle tonus, give its importance. A state of continuous partial muscle contractions is known as muscle tone. These contractions are not strong enough to produce movement, but do tense and firm the muscles. For example, even when the body is at rest, certain muscle fibers in all muscles are contracting. This activity is directed by the brain and cannot be controlled consciously. In doing so, they keep the muscles firm, healthy, and ready for action. Muscles with moderate muscle tone are firm and solid, whereas ones with little muscle tone are limp and soft. Muscle tone is important because it helps human beings maintain an upright posture. Without muscle tone, an individual would not be able to climb up a stairs or simply, stand up. Muscle tone is also important in maintaining body heat because like most typical muscles, it is a principal function to generate heat. 2. Describe spinal shock, its duration according to species. It is a state of transient physiological reflex depression of cord function below the level of injury with associated loss of all sensorimotor functions. When the spinal cord is suddenly transected in the upper neck, at first, essentially all cord functions, including the cord reflexes immediately become depressed to the point of total silence, a reaction called spinal shock. The 'shock' in spinal shock does not refer to circulatory collapse, and should not be confused with neurogenic shock. In all vertebrates, transection of the spinal cord is followed by a period of spinal shock during which all spinal reflex responses are profoundly depressed. Subsequently, reflex responses return and become hyperactive. The duration of

spinal shock is proportionate to the degree of encephalization of motor function in the various species. In frogs and rats, it lasts for minutes; in dogs and cats, it lasts for 1-2 hours; in monkeys, it lasts for days; and in humans, it usually lasts for a minimum of 2 weeks. Conclusion: When there is an impaired function of the motor neurons it will result in weakness in the lower limbs of the frog. The muscle becomes flaccid and unresponsive prior to an injury or damage.

Experiment 2 Genesis of Tetanus Allison Eunice B. Servando

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Objectives 1. Define tetanus and give the different types and characteristics of tetanic contraction. It is defined as a sustained muscle contraction evoked when the motor nerve that innervates a skeletal muscle emits action potentials at a very high rate. During this state, a motor unit has been maximally stimulated by its motor neuron and -remains that way for some time. This occurs when a muscle's motor unit is stimulated by multiple impulses at a sufficiently high frequency. The different types include incomplete and complete tetanic contraction. The characteristics of

this type of contraction include the following: a). A shortening or tensing of a part or organ especially of a muscle or muscle fiber b). Is accompanied by prolonged and continuous “jerky” movement c).

Characterized by uncontrollable and

sometimes painful muscular contractions 2. Give the importance of tetanus with respect to muscular activity in man. During the muscular activity of man, calcium concentrations in tissues decreases which will lead to an uncontrollable contraction in muscles, a condition known as tetany. The back-and-forth movement of calcium ions that generates muscular contraction is a coordinated. However, when calcium concentrations in your bodily fluids change, membrane potentials are disrupted and your muscles begin to function abnormally. A drop in blood calcium level can lead to tetanic muscle contractions that act as a compensatory mechanism each stimulus causes a twitch. If stimuli are delivered slowly enough, the tension in the muscle will relax between successive twitches. If stimuli are delivered at high frequency, the twitches will overlap, resulting in tetanic contraction. When tetanized, the contracting tension in the muscle remains constant in a steady state. This is the maximal possible contraction. During tetanic contractions, muscles can shorten, lengthen or remain constant length. Muscles may exhibit some level of tetanic II.

activity, leading to muscle tone, in order to maintain posture. Results and Conclusion 1. Define tetanic contraction A tetanic contraction is a more sustained contraction than a twitch. It is produced by a series of stimuli bombarding the muscle in rapid succession (Thibodeau, 1990). 2. Describe incomplete and complete tetanus Incomplete tetanus occurs when there is a partial relaxation between muscle twitches. Complete tetanus is a sustained contraction with no relaxation observed between twitches. Muscle twitches are fine movements of a small area of muscle. 3. What is the significance of tetanic contraction? Contraction of muscle fibers limits the severity of connective tissue damage, and that muscle damage accompanied by disruption of the muscle connective tissue network requires a relatively longer recovery time. Conclusion

Application of electrical stimulus by Harris stimulator causes muscle twitching or “jerking” movement of the lower extremities. Response varies according to the intensity of stimulus applied. In our experiment we obtained a result; at frequency 1-4, degree of the response is almost the same but at frequency 5, response was greater.

Experiment 3 Synaptic Fatigue Allison Eunice B. Servando

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Objectives 1. What is the primary seat of fatigue in an intact body? It is the synapse 2. What is the effect of acetylcholine at the synapse? Acetylcholine binds to a receptor on an adjoining cell which activates it resulting in the continuation of a nerve impulse, the movement of muscle, or many other responses in a variety of different tissues. Binding of acetylcholine to its receptors on the postsynaptic cell opens up ligand-gated sodium channels. These allow an influx of Na+ ions, reducing the membrane potential. This reduced membrane potential is called an excitatory postsynaptic potential or EPSP. If depolarization of the postsynaptic membrane reaches threshold, an action potential is generated in the postsynaptic cell. 3. Differentiate between synapse and myoneural junction.

Myoneural junction is the junction between a nerve fiber and the muscle it supplies this is also called neuromuscular junctions while a synapse, it is the junction between two neurons (axon-to-dendrite).

CONCLUSION: In relation to the reflex arc, stimulation of left and right sciatic nerve (Receptor,Afferent/Efferent Nerve) is followed by responses from both gastrocenimus muscles (Effector Organ). The contraction occurred bilaterally because the neurons on one side make connections not only on the same side but also with neuron on the opposite side, the neurons meeting, and their impulse are integrated in the Central Nervous System (Central IntegratingArea). Since the sciatic nerve, CNS, and effector organ are not the primary seats of fatigue, because if it were so, then the muscles contraction would not be obtained from impulse of stimulus passing thru the afferent and efferent nerve fiber via CNS. Therefore, the synapse is responsible for the cessation of muscle contraction, which is primary seat of fatigue in an intact body.