Practice: Using a freezing point depression osmometer to measure serum osmolality. Practice: The refraction of light through the human eye. Practice: The effects of ultrasound on different tissue types. Practice: Leukocytes roll on blood vessel walls. Practice: Creating Fuel from Algae. Practice: How do organisms maintain a constant pH range?
Practice: The bicarbonate buffering system and titration curves. Practice: Neuronal membranes: Nature's capacitors. Practice: Doppler effect in living tissue. Practice: The effects of ear canal acoustics on hearing ability. Practice: The forearm as an example of a third-class lever.
Practice: The forces and torques acting on the hip joint. Practice: The chemical structure consequences of beta-lactams. Practice: Aldehydes and ketones. Practice: The effects of microgravity on muscle tissues. Practice: Comparing the stress exerted on the body by different running shoes.
Practice: Understanding the ballistics of gene bombardment. Practice: Analysis of image production by the human eye.
Practice: Alcohol production and absorption. Practice: The structure and function of glycogen. Practice: Elasticity and kinetics of vulcanized rubber. Practice: Preventing barotrauma in deep-sea divers. Practice: Pressure regulation and fluid dynamics of the respiratory system. Practice: Thermodynamics of gallium arsenide formation. Practice: Using ultrasounds to measure blood flow velocity.
Practice: The radioactivity of iodine Practice: Characteristics of various therapeutic radioisotopes. Practice: Understanding the properties of radioactive tracers. Practice: Melting point and thermodynamics of double-stranded DNA. Practice: Pure tone audiometry in diagnosing hearing loss.
Practice: Isothermal titration calorimetry in drug development. Practice: Mass spectrometry in the operating room. Practice: Separating enantiomers in a prescription drug.
Practice: Technetium decay and its cardiac application. Practice: The physics of eyesight correction. Practice: Flow and poiseuille's law in operation. Practice: The role of the bicarbonate buffer system in regulating blood pH.
Practice: Using optical traps to manipulate single DNA strands. Note that passive transmission of current in body tissues from the stimulating electodes also produces a stimulus artifact on the EMG. Please see the figure below Figure 3. This week, we will perform one experiment lab exercise 1 and one clinical evaluation lab exercise 2. The experiment will determine the effects of increasing stimulus strength on the EMG. Stimulus measured in milliamperes, mA is applied directly to the fibers of the ulnar nerve with stimulating electrodes on the skin.
The resulting EMG amplitude is recorded in mV. EMG amplitude measures the strength of contraction by the innervated muscle, which is relative to the number of motor units activated by the stimulus.
Recruitment of more motor units activation of additional motor neurons and their innervated muscle cells is accomplished by increasing the stimulus. Next, we will perform a nerve conduction study using EMG. Here, we will use the optimal stimulus strength from Experiment 1 to re-stimulate the ulnar nerve.
After recording the location of the stimulating electrode on the arm and obtaining the EMG, the stimulator will be moved to a secondary position, re-stimulating the ulnar nerve. This method of calculating conduction velocity is called the difference method. We will then use the information from our experiment to determine the conduction velocity transmission speed of the ulnar nerve in a nerve conduction study. Clean the areas where the electrodes will be attached with an alcohol pad.
Lightly abrade the skin in those areas. You will deliver mild electric shocks to either yourself or a volunteer experimental subject. The equipment you use to do this is carefully designed to keep the parameters of the electroshocks well within a safe range, and this experiment is safe and fun. Nevertheless, we ask that you place stimulating electrodes on the arms only , and only place electrodes on the same side of the body never on both arms at the same time. If you think you may be pregnant or if you suffer from known heart conditions or have an artificial heart pacemaker please do not volunteer as an experimental subject this week.
Objective: To determine the effect of stimulus strength on the response of the innervated abductor digiti minimi muscle. Overview: You will stimulate the abductor digiti minimi motor neuron with increasing amounts of current measured in milliAmps, read as AMP on LabScribe. You will measure the EMG muscle response each time in mV and record the value in your lab report. Of those three readings, put a mark next to the lowest current Amplitude value on your lab report; you will be using this value for exercise 2.
Click apply. Different sweeps may be selected any time by clicking on the Sweeps list on the bottom of the Main Screen , , etc. If analyzing data on the Main Screen while recording, the sweep you need to analyze is already selected. The Sweeps task bar is shown below. Objective: To measure the conduction velocity transmission speed of the ulnar nerve. You will use the AMP value which excited the maximal response in experiment 1 and stimulate the same abductor digiti minimi motor neuron further up the arm.
You will then use that previous experiment and the one you will conduct here to compare the time between innervation and the elicitation of the response for two points on the nerve. Several immunodulative therapies are in use to prevent new attacks; however, there is no known cure for MS.
Figure 3 Despite the severe outcome and considerable effect of demyelinating diseases on patients' lives and society, little is known about the mechanism by which myelin is disrupted, how axons degenerate after demyelination, or how remyelination can be facilitated.
To establish new treatments for demyelinating diseases, a better understanding of myelin biology and pathology is absolutely required. How do we structure a research effort to elucidate the mechanisms involved in developmental myelination and demyelinating diseases?
We need to develop useful models to test drugs or to modify molecular expression in glial cells. One strong strategy is to use a culture system. Coculture of dorsal root ganglion neurons and Schwann cells can promote efficient myelin formation in vitro Figure 1E. Researchers can modify the molecular expression in Schwann cells, neurons, or both by various methods, including drugs, enzymes, and introducing genes , and can observe the consequences in the culture dish.
Modeling demyelinating disease in laboratory animals is commonly accomplished by treatment with toxins injurious to glial cells such as lysolecithin or cuprizone. Autoimmune diseases such as MS or autoimmune neuropathies can be reproduced by sensitizing animals with myelin proteins or lipids Figure 3. Some mutant animals with defects in myelin proteins and lipids have been discovered or generated, providing useful disease models for hereditary demyelinating disorders.
Further research is required to understand myelin biology and pathology in detail and to establish new treatment strategies for demyelinating neurological disorders.
Myelin can greatly increase the speed of electrical impulses in neurons because it insulates the axon and assembles voltage-gated sodium channel clusters at discrete nodes along its length. Myelin damage causes several neurological diseases, such as multiple sclerosis.
Future studies for myelin biology and pathology will provide important clues for establishing new treatments for demyelinating diseases. Brinkmann, B. Neuron 59 , — Franklin, R. Remyelination in the CNS: From biology to therapy. Nature Reviews Neuroscience 9 , — Nave, K. Axonal regulation of myelination by neuregulin 1. Current Opinion in Neurobiology 16 , — Poliak, S. The local differentiation of myelinated axons at nodes of Ranvier. Nature Reviews Neuroscience 4 , — Sherman, D.
Mechanisms of axon ensheathment and myelin growth. Nature Reviews Neuroscience 6 , — Siffrin, V. Multiple sclerosis — candidate mechanisms underlying CNS atrophy. Trends in Neurosciences 33 , — Susuki, K. Molecular mechanisms of node of Ranvier formation. Current Opinion in Cell Biology 20 , — Cell Signaling. Ion Channel. Cell Adhesion and Cell Communication.
Aging and Cell Division. Endosomes in Plants. Ephs, Ephrins, and Bidirectional Signaling. Ion Channels and Excitable Cells. Signal Transduction by Adhesion Receptors. Citation: Susuki, K.
Nature Education 3 9 How does our nervous system operate so quickly and efficiently? The answer lies in a membranous structure called myelin. Aa Aa Aa. Information Transmission in the Body. Figure 1.
Figure Detail. Axonal Signaling Regulates Myelination. Figure 2: The fate of demyelinated axons. The case in the CNS is illustrated. Research in Myelin Biology and Pathology.
Figure 3. References and Recommended Reading Brinkmann, B. Waxman, S. The Axon: Structure, Function and Pathophysiology. New York: Oxford University Press, Article History Close.
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