Ec Theory

An increase in the strength of a muscle’s contraction is necessary to perform a task. Subsequently, the brain increases the number of simultaneously active motor units within the muscle by a process known as the motor unit recruitment. Physical muscle movement in humans involves movement of fibers which are hundreds of cylindrically shaped cells bound together by connective tissue. It is essential for individuals, mainly professionals who work to promote health, to understand the mechanisms in the body. Resting skeletal muscles in vivo exhibit a phenomenon known as tonus, a constant state of slight tension that serves to maintain the muscle by motor centers in the brain and spinal cord. However, muscle

Introduction: According to the “Human Physiology Laboratory Manual “,BIOL 282 ,page 31 , the reason of performing this experiment is to learn how the muscle contraction occurs based on the molecular level and what kind of factors are involved .As a matter of fact, skeletal muscles contain a lot of nuclei because of the cell fusion while being developed and are made of cylindrical cells that have myofibrils. The myofibrils contain sarcomeres and the

Rationale, Significance and Hypothesis. An extrinsic factor, which exerts a dominant influence on skeletal muscle fiber phenotype, is the nervous system. Buller et al. (1960) elegantly demonstrated the plastic nature of skeletal muscle fibers in response to changes in innervation type. Later, Lφmo and Westgaard (Lφmo and Westgaard, 1974; Westgaard and Lφmo, 1988) demonstrated that depolarization of muscle with specific patterns and frequencies of electrical activity are sufficient to cause changes in mature muscle fiber phenotypes. However, how myofibrillar gene expression and structural organization is affected by the frequency of impulses during activity, the amount of activity over time, or other characteristics of patterned activity is essentially unknown. To answer these questions will require the isolation and study of subsets of muscle-specific proteins in relation to different electrical activation patterns in vivo, an issue that cannot be easily addressed in preparations currently used in the study of muscle development and maintenance. However, using novel in vivo approaches can, in part, circumvent this difficulty.

Martini, F. H., Nath, J. L., and Bartholomew, E. F. “Muscle Tissue.” Anatomy & Physiology. 9th

Lightly myelinated Aδ fibers and unmyelinated C fibers have thinner axons and a higher threshold of activation. Nociceptors of Aδ fibers can be either mechanosensitive or thermosensitive. Polymodal nociceptors (of C fibers), may respond to both mechanical and thermal stimuli, as well as chemicals [261-263]. When nociceptors are activated, the fibers transmit action potentials along the axon to the spinal cord [264, 265]. The spinal cord mediates sensory and motor communication between the periphery and the brain, and is organized into four regions; cervical, thoracic, lumbar, and sacral. The gray matter contains cell bodies of neurons and glia and is divided into the dorsal horn, intermediate column, lateral horn, and ventral horn. The dorsal horn is comprised of sensory nuclei that receive and process incoming sensory information [266], and like the rest of the spinal gray matter, is organized histologically into parallel laminae based on the size and density of neurons [267]. In general, laminae I to IV are involved in exteroceptive sensation whereas laminae V and VI are involved in proprioceptive sensations [263]. Nociceptors terminate in the dorsal horn laminae in a

The spinal motor neurons undergo an aging-related gradual loss due to the interaction of multiple factors; the neurons undergo a programmed cell death along with a decrease in signaling by growth factors and protein uptake. This process leads to the denervation of muscle fibers. The surviving motor axons or motor end plates can send some collaterals to innervate the denervated muscle fibers which explains the formation of enlarged motors end

Although the cause of fibromyalgia is unknown, there are many explanations for what occurs in the nervous system of people afflicted with fibromyalgia. Specific to this are the various reasons for the intense perception of pain. A change to the myofascia surrounding the muscles has been found to be one of the leading causes of pain and other muscular symptoms of fibromyalgia in the majority of cases. Myofascia is the thin, whitish membrane comprised of a material called 'ground substance' that envelopes and protects the muscle like a sack and which is responsible for supporting and connecting all of the body's muscles together[2]. Normally, neurotransmitters pass easily from the interneurons on one side of the myofascia to create action potentials in the motor neurons attached to the muscles. In the case of people with fibromyalgia, however, often the myofascia has lost its elastic properties and hardened. The ground substance within the myofascia, which is usual in a fluid state, has become more like a solid gel. This change in the myofascia hinders or entirely prevents the neurotransmitters from reaching the motor

Annie is a swimmer who has started to suffer from sever muscle fatigue. Muscle fatigue is a decrease in force during lengthy contractions. Skeletal Muscle is made out of fascicles, which are then made up of muscle fiber cells and those cells are made of micro fibrils (Stanfield, C, 2017). All of these items make up a motor unit, which cause muscle units to contract due to the startup of the action potential that release neurotransmitters that depolarizes the muscle membrane (Stanfield, C, 2017). The neurotransmitters are released in an area known as the neuromuscular junction (Stanfield, C, 2017). In this junction. In the junction action potentials that are entering the axon terminal starts the free movement of acetylcholine that then goes into the synaptic cleft (Stanfield, C, 2017). The acetylcholine then travels through a cleft which binds to a nicotinic receptor on the motor end plate that then opens the ion channels that leads to the freedom of calcium from the sarcoplasmic reticulum (Stanfield, C, 2017). In order to determine why she was beginning to have muscle fatigue Annie had to face a series of test. One of the tests that Annie could have taken was an Electromyography, also known as an EMG.

After each nerve impulse, the amount of ACh released by the presynaptic motor neuron decreases due to a temporary depletion of ACh stores. This is a normal phenomenon known as presynaptic rundown. MG results in a reduction of the available AChR at the postsynaptic membrane as well as a flattening of the postsynaptic folds. Therefore, even without the phenomenon of presynaptic rundown, MG can result in an inefficient neuromuscular transmission due to a reduction in the number of AChRs at the motor end plate. The inefficient neuromuscular transmission and presynaptic rundown phenomenon account for the fatigability seen in MG due to the progressive decrease in the amount of muscle fibers that are activated with each successive nerve impulse. Patients begin to exhibit symptoms of fatigue when there is a reduction of approximately 70% of the available AChRs.

Skeletal muscle contraction and relaxation is vital for voluntary body movements to occur. Skeletal muscles contract when myofibrils composed of actin and myosin slide past each other, which contracts the muscle by altering its length. The gastrocnemius muscle in Rana pipiens, which is attached to the sciatic nerve, can be stimulated to find threshold and maximal stimulus voltage. Once threshold is reached, contraction amplitude increases with stimulus voltage until the maximal voltage is reached, at which point it levels off. Altering the interstimulus interval can induce twitch summation in the gastrocnemius, leading to one combined contraction with a high amplitude. Increased stimulus frequency can be used to induce a tetanic

The nerve consists of two different motor fibers: the somatic motor component and the parasympathetic motor component. The somatic motor component controls the movement of four extrinsic muscles and the parasympathetic motor component controls the sphincter pupillae and ciliary muscles (McKinley, O'Loughlin, & Bidle, 2017, p. 44). CN III can be divided into two major branches: the superior division and inferior division (Jaffee & Stewart, 2016). The superior branch is composed of motor fibers that innervate the levator palpebrae superioris and the superior

The F-wave, H-reflex, and T-reflex are considered as indices of spinal motor neuron excitability. We previously studied the spinal motor neuron excitability during MI of isometric thenar muscle activity. The persistence and F/M amplitude ratio during MI of thenar muscle activity under 50% MVC was significantly increased than at rest [10]. Taniguchi et al. [11] reported that the F/M amplitude ratio after volitional relaxation for 3 hours was significantly decreased. When subjects did volitional relaxation and MI of thumb abduction simultaneously, the F/M amplitude ratio was maintained at before volitional relaxation level. This indicated that MI can increase the spinal motor neuron excitability. Whereas, Kasai et al. [9] reported that the H-reflex amplitude was not unchanged during MI of wrist flexion movement. Also, Oishi et al. [12] reported that there are various results in the H-reflex amplitude during MI in speed skater. Thus, it might be suggested that the spinal motor neuron excitability was not always increased during MI, although MI can increase the central nervous

Homeostasis is achieved through the central nervous systems process of receiving, integrates and responding to information (Marieb & Hoehn, 2014). The peripheral nervous system acts as a communication line carrying impulses through nerves extending from the brain, spinal cord and ganglia, transmitting the impulses via the spinal cord and cranial nerves, back and forth from the brain (Marieb & Hoehn, 2014). The peripheral nervous system is subdivided into the sensory and motor divisions. The sensory, which picks up on stimuli, sending impulses from the receptors to the central nervous system (Marieb & Hoehn, 2014). And the motor division, with a motor nerve structure that transmits the impulse from the central nerves system to the effectors known as the muscles and glands (Marieb & Hoehn, 2014), thus allowing movement to occur. The motor division also divides into the somatic nervous system and autonomic nervous system. The somatic nervous system, which is a voluntary response that travels through nerve fibres, allowing conscious control of skeletal muscular movement (Marieb & Hoehn, 2014). The autonomic nervous system unconsciously controls muscle and glands. The visceral motor nerve fibres regulate a person’s smooth

Frog skeletal muscle is used as an animal model to study muscle contraction. The objectives of this experiment is to demonstrate the physiological responses of skeletal muscle to electrical stimuli using frog gastrocnemius, to understand twitch, summation, tetanus and fatigue, to investigate the relationship between initial tension and force of contraction, to explore the differences between human and frog skeletal muscle. The threshold voltage is 0.4V. The minimum voltage required to give a maximal response is 5V. Stimulus voltages and muscle response shows a linear relationship from 0.4V to 5V and reaches plateau at 6V. The optimal initial tension at which maximum force of contraction could be

The study of the response of the sciatic nerve and the neuromuscular to the Rana pipens was constructed by the Comparative Animal Physiology lab manual for both the nerve compound action potential (Lab five) and the neuromuscular junction (Lab six) (Norris, et al.,2016). In order to analyze the responses of the sciatic nerve and the gastrocnemius of a Rana pipens, one exercise was selected from Lab five and five exercises were selected from Lab six. Both lab five and Lab six had a study length of three weeks to be performed. Therefore, the first experiment focused on the nerve compound action potentials, while the second experiment focus on the neuromuscular junction. In the first experiment, the only exercise analyzed (Exercise one), was the determination of the threshold voltage and the relationship between stimulus intensity and compound action potentials(CAP). On the second experiment, five exercises were analyzed, these experiments focused on the stimulus intensity and strength of contraction, the effect of stretch on contractile force, the effect of paired pulses on contraction force(summation), muscle tetanus, and muscle and nerve fatigue.