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b. Explain why in multiple sclerosis the action potentials take longer to reach their muscle and neurological targets or do not reach them at all, resulting in muscle spasms and weakness in one or more limbs, bladder dysfunction, local sensory losses, visual disturbances and other neurological deficits.
c. Explain the speed of action potential in the normal person. Be sure to provide documentation using any example from the literature (provide the pdf-version of the article) and summary that supports your conclusion.
i. A neuron propagates action potential along its axon and then transmits this signal across a synapse by releasing neurotransmitters. Neurotransmitter triggers a reaction between another neuron or effector cell, which in turn stimulate or inhibit the receiving cell.
ii. An action potential is caused by the stimulus received by the dendrites of nerve cells. This stimulus causes the sodium channels to open. Opening of these channels causes the interior potential to go from -70 mV up to -55 mV. This allows for the cell to reach its action potential. When this potential is reached voltage gated sodium channels open and drive the potential inside the cell membrane to increase to around 30 mV. This is called depolarization. This action potential is conducted along the length of the fiber and causes the next adjacent space to open voltage-gated sodium ion channels to open. Once depolarized the sodium channels close and the potassium channels open, which allow for the membrane to repolarize to around -90 MV in a process called hyperpolarization. Hyperpolarization prevents the neuron from receiving another stimulus. After hyperpolarization the membrane goes back to its resting potential of -70 mV.
iii. Mye...
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...xin.
2. Different species of dinoflagellates have different polyketide synthases, these synthases allow for the biosynthesis of saxitoxins.
d. What is its toxic dose? Is this an oral or iv dose?
i. The oral dose in humans that can result in human death is 1 to 4 mg. Unfortunately no further information can be found on this matter. However information of the LD50 for mice is available the oral and iv dosages are 3–10 μg/kg and 3400 ng/kg respectively.
e. If saxtoxin is such a powerful toxin in people who eat contaminated shellfish, why does the toxin not poison/kill the host shellfish?
i. The host/shellfish must have adopted a sodium ion channel that saxitoxins cannot bind to. For example some puffer fish have undergone a mutation that changes the amino acid sequence that makes its sodium channel insensitive to the toxin.
f. Sources:
i
In the beginning phases of muscle contraction, a “cocked” motor neuron in the spinal cord is activated to form a neuromuscular junction with each muscle fiber when it begins branching out to each cell. An action potential is passed down the nerve, releasing calcium, which simultaneously stimulates the release of acetylcholine onto the sarcolemma. As long as calcium and ATP are present, the contraction will continue. Acetylcholine then initiates the resting potential’s change under the motor end plate, stimulates the action potential, and passes along both directions on the surface of the muscle fiber. Sodium ions rush into the cell through the open channels to depolarize the sarcolemma. The depolarization spreads. The potassium channels open while the sodium channels close off, which repolarizes the entire cell. The action potential is dispersed throughout the cell through the transverse tubule, causing the sarcoplasmic reticulum to release
When a chemical signal is transmitted, the presynaptic neuron releases a neurotransmitter into the synapse. The signal is then sent to the postsynaptic neuron. Once the postsynaptic neuron has received the signal, additional neurotransmitter left in the synapse will be reabsorbed by the presynaptic
Multiple sclerosis (MS) is a disease affecting the myelination of the central nervous system, leading to numerous issues regarding muscle strength, coordination, balance, sensation, vision, and even some cognitive defects. Unfortunately, the etiology of MS is not known, however, it is generally thought of and accepted as being an autoimmune disorder inside of the central nervous system (Rietberg, et al. 2004). According to a study (Noonan, et al. 2010) on the prevalence of MS, the disease affects more than 1 million people across the world, and approximately 85% of those that are affected will suffer from unpredictably occurring sessions of exacerbations and remissions. The report (Noonan, et al. 2010) found that the prevalence of MS was much higher in women than in men, and that it was also higher in non-Hispanic whites than in other racial or ethnic groups throughout the 3 regions of the United States that were studied.
Action potentials in neurons are facilitated by neurotransmitters released from the terminal button of the presynaptic neuron into the synaptic gap where the neurotransmitter binds with receptor sites on the postsynaptic neuron. Dopamine (DA) is released into the synaptic gap exciting the neighboring neuron, and is then reabsorbed into the neuron of origin through dopamine transporter...
Multiple sclerosis (MS) is generally thought to be an autoimmune disease that attacks the myelin sheaths, or oligodendrocytes that cover nerve axons in the central nervous system (PubMed Health 2013). This immune response causes inflammation, which triggers immune cells to destroy axons “along any area of the brain, optic nerve, and spinal cord” (PubMed Health 2013). When the myelin sheath “is damaged, nerve signals slow down or stop” thus hindering the propagation of action potentials and limiting function (PubMed Health 2013).
According to National Multiple Sclerosis Society, Multiple Sclerosis (MS) is an unpredictable, often disabling disease of the central nervous system (CNS) that disrupts the flow of information within the brain, and between the brain and body. The central nervous system (CNS) comprises of the brain and the spinal cord. CNS is coated and protected by myelin sheath that is made of fatty tissues (Slomski, 2005). The inflammation and damage of the myelin sheath causing it to form a scar (sclerosis). This results in a number of physical and mental symptoms, including weakness, loss of coordination, and loss of speech and vision. The way the disease affect people is always different; some people experience only a single attack and recover quickly, while others condition degenerate over time (Wexler, 2013). Hence, the diagnosis of MS is mostly done by eliminating the symptoms of other diseases. Multiple sclerosis (MS) affects both men and women, but generally, it is more common in women more than men. The disease is most usually diagnosed between ages 20 and 40, however, it can occur at any age. Someone with a family history of the disease is more likely to suffer from it. Although MS is not
Neurons dispatch signals to other cells through thin fibers called axons, that cause chemicals acknowledged as neurotransmitters to be released at junctions identified as synapses. A synapse gives a command to the cell and the entire communication process typically takes only a fraction of a millisecond.
Multiple Sclerosis (MS) is a complicated chronic deteriorating disease that has an effect on the central nervous system (CNS). This disease causes destruction of the myelin around the nerve fibers. “The exact etiology of Multiple Sclerosis is unknown; however, it is thought to be an immune mediated disease. MS is characterized by CNS inflammation, demyelination, and axonal loss” (Compston & Coles, 2008). Typically, it is described by early relapses and remissions of neurological signs of the CNS. This is known as relapsing-remitting MS (RRMS). MS can be identified by a variety of known risk factors. Multiple Sclerosis can be brought on by a mixture of inherited and environmental risk factors such as smoking or an exposure to a virus like Epstein Barr. The inflammatory process has an interesting role on the central nervous system.
Primarily, the term MS refers to a chronic disorder that attacks the central nervous system (CNS). It is most common in temperate continents such as Europe and Australia with Asiatic and African continents having a lower risk of the disease (Wiley Online Library, 2013). A search organised by the Multiple Sclerosis Society (2013) has estimated that there are 127,000 people living with MS in the United Kingdom. Further research by Chipps, Clanin, and Campbell (1992, pp. 158-167) shows that MS disorder more likely affects women than men with its symptoms occurring between the ages of 20 and 40 in most cases and is quite uncommon in childhood and old age. The nerve cells known as neurons in the brain constantly transmit and receive signals. They invoke emotions, activities and cognition that constitute the day to day experiences of humans. Under normal circumstances, these signals travel on a protected insulation path known as the myelin sheath. This insulation is vital as it enables signals to reach their target. In Multiple Sclerosis, the myelin sheath gets disintegrated causing the nerve fibre to be damaged leading to a disruption in the abili...
The brain is part of the central nervous system, which consists of neurons and glia. Neurons which are the excitable nerve cells of the nervous system that conduct electrical impulses, or signals, that serve as communication between the brain, sensory receptors, muscles, and spinal cord. In order to achieve rapid communication over a long distance, neurons have developed a special ability for sending electrical signals, called action potentials, along axons. The way in which the cell body of a neuron communicates with its own terminals via the axon is called conduction. In order for conduction to occur, an action potential which is an electrical signal that occurs in a neuron due to ions moving across the neuronal membrane which results in depolarization of a neuron, is to be generated near the cell body area of the axon. Wh...
Dendrites are located on either one or both ends of a cell.The peripheral nervous system then takes the sensory information from the outside and sends the messages by virtue of neurotransmitters. Neurotransmitters are chemicals that relay signals through the neural pathways of the spinal cord. The neurotransmitter chemicals are held by tiny membranous sacs located in the synaptic terminals. Synaptic terminals are located at the ends of nerve cells. The release of neurotransmitters from their sacs is stimulated once the electrical nerve impulse has finished travelling along a neuron and reaches the synaptic terminal. Afterward, neurotransmitters travel across synapses thus stimulating the production of an electrical charge that carries the nerve impulse onward. Synapses are junctions between neighboring neurons. This procedure is reiterated until either muscle movement occurs or the brain picks up on a sensory reaction. During this process, messages are being transmitted from one part of the body onto the next. The peripheral and central nervous system are two crucial subdivisions of the nervous system. The brain and spinal cord make up the central nervous
Neurotransmitters are chemicals made by neurons and used by them to transmit signals to the other neurons or non-neuronal cells (e.g., skeletal muscle; myocardium, pineal glandular cells) that they innervate. The neurotransmitters produce their effects by being released into synapses when their neuron of origin fires (i.e., becomes depolarized) and then attaching to receptors in the membrane of the post-synaptic cells. This causes changes in the fluxes of particular ions across that membrane, making cells more likely to become depolarized, if the neurotransmitter happens to be excitatory, or less likely if it is inhibitory.
B. Has a hard time moving in spaces, especially if its crowded like a mall or an airport. Will run into people or objects.
Action potentials are started at one end of the node, flow passively through the myelinated axon, and pop out the other side to jump to the next node. This jumping of action potentials is called saltatory.
Synaptic transmission is the process of the communication of neurons. Communication between neurons and communication between neuron and muscle occurs at specialized junction called synapses. The most common type of synapse is the chemical synapse. Synaptic transmission begins when the nerve impulse or action potential reaches the presynaptic axon terminal. The action potential causes depolarization of the presynaptic membrane and it will initiates the sequence of events leading to release the neurotransmitter and then, the neurotransmitter attach to the receptor at the postsynaptic membrane and it will lead to the activate of the postsynaptic membrane and continue to send the impulse to other neuron or sending the signal to the muscle for contraction (Breedlove, Watson, & Rosenzweig, 2012; Barnes, 2013). Synaptic vesicles exist in different type, either tethered to the cytoskeleton in a reserve pool, or free in the cytoplasm (Purves, et al., 2001). Some of the free vesicles make their way to the plasma membrane and dock, as a series of priming reactions prepares the vesicular ...