Myasthenia gravis literally translates to “grave muscle weakness;” since 1672‚ when the disease was first recorded‚ to the early twentieth-century‚ the majority of patients diagnosed with it ended up passing away. Medical practitioners back then did not know myasthenia gravis is an autoimmune disease that attacks the neuromuscular junction‚ causing weakness and abnormal fatigue of the muscles. Nor‚ did they have sophisticated treatment options‚ such as drugs and surgery‚ to care for their patients
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the stimulus going to the receptor surface. Receptors are electrically polarized cells and therefore have a resting membrane potential. Stimuli produce‚ in the appropriate receptors‚ a change in the electrical properties that is known as the receptor or generator potential. The two ways in which sensory stimuli can act on receptors to change their resting membrane potential (RMP) are by directly acting on ion channels or causing production of second messengers that act on ion channels. The two types
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Chapter 48 Nervous Systems Lecture Outline Overview: Command and Control Center The human brain contains an estimated 1011 (100 billion) neurons. Each neuron may communicate with thousands of other neurons in complex information-processing circuits. Recently developed technologies can record brain activity from outside the skull. One technique is functional magnetic resonance imaging (fMRI)‚ which reconstructs a 3-D map of the subject’s brain activity. The results of brain imaging and other
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Excitation Contraction Coupling Process The sequence of events that converts action potentials in a muscle fiber to a contraction is know as excitation contraction coupling. In order for a skeletal muscle fiber to contract‚ it has to get a signal from the nervous system. The part of the nervous system that it gets a signal from is called a motor neuron. An electoral signal‚ called an action potential travels down the axon and to the axon terminal. At the end of the motor neuron are structures
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and nervous systems maintain internal coordination – Endocrine system: communicates by means of chemical messengers (hormones) secreted into to the blood – Nervous system: employs electrical and chemical means to send messages from cell to cell 12-2 Overview of the Nervous System • Nervous system carries out its task in three basic steps • Sense organs receive information about changes in the body and external environment‚ and transmit coded messages to the brain and spinal cord (CNS: central
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BIOLOGY 2113 Unit IV Review Guide Chapters 13-17 Chapter 13 – True or False 1. The nervous system consists of the brain‚ spinal cord‚ and nerves. 2. The afferent nervous system consists of all outgoing motor pathways. 4. Ependymal cells engulf and destroy microbes and cellular debris in inflamed or degenerating brain tissue. 5. Oligodendrocytes form myelin sheaths around nerve fibers in the CNS. 6. Nerve fibers with many Schwann cells forming a thick myelin sheath are called myelinated fibers
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| | |Look at Figure 6.1‚ the cardiac action potential. The period of time between the |Absolute refractory period of cardiac muscle | |beginning of the cardiac action potential and the approximate middle of phase 3 is | | |the __________________ refractory
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Mid-Term Review 1. Chemicals that cause birth defects are: a. morphogenic c. homeostatic b. homophobic d. teratogenic 2. A person with X‚X‚ and Y sex chromosomes must be a. heterosexual c. male b. homosexual d. bisexual 3. Which controversy deals with the question of whether development is a gradual‚ cumulative change or a sequence of distinct stages? a. nature vs. nurture c. stability vs. change b. continuity vs. discontinuity d. evolution vs. creation 4. Knowing how to ride a bicycle is
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(+) ions (Ca++) can pass into the muscle fiber which depolarizes the membrane potential. As this happens the voltage-gated sodium channels are triggered opens and allows sodium ions (NaCl-) enters the fiber and action potential spreads along the entire membrane to initiate excitation-contraction coupling. Following the depolorization of the membrane‚ repolarization occurs‚ which reestablishes the negative membrane potential. The ACh within the synaptic cleft is also degraded by AChE so that ACh cannot
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Overview Snake venom is the poison fluid normally secreted by venomous snakes when biting. It is produced in the glands‚ and injected by the fangs. Snake venom is used to immobilize and/or kill prey‚ and used secondarily in defence. It is a clear‚ viscous fluid of amber or straw colour. There are two main types of venom produced by snakes‚ containing primarily either: *Neurotoxins - these attack the nervous system. *Hemotoxins - these attack the circulatory system. While most snakes’ venom contains
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