Anatomy & Physiology 12 The Nervous System Essay


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Anatomy & Physiology 12 The Nervous System
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Question: Visit this site ( to see a virtual neurophysiology lab, and to observe electrophysiological processes in the nervous system, where scientists directly measure the electrical signals produced by neurons. Often, the action potentials occur so rapidly that watching a screen to see them occur is not helpful. A speaker is powered by the signals recorded from a neuron and it "pops" each time the neuron fires an action potential. These action potentials are firing so fast that it sounds like static on the radio. Electrophysiologists can recognize the patterns within that static to understand what is happening. Why is the leech model used for measuring the electrical activity of neurons instead of using humans?


The properties of electrophysiology are common to all animals, so using the leech is an easier, more humane approach to studying the properties of these cells. There are differences between the nervous systems of invertebrates (such as a leech) and vertebrates, but not for the sake of what these experiments study.

Question: Visit this site ( to read about a woman that notices that her daughter is having trouble walking up the stairs. This leads to the discovery of a hereditary condition that affects the brain and spinal cord. The electromyography and MRI tests indicated deficiencies in the spinal cord and cerebellum, both of which are responsible for controlling coordinated movements. To what functional division of the nervous system would these structures belong?


They are part of the somatic nervous system, which is responsible for voluntary movements such as walking or climbing the stairs.

Question: Watch this video ( to learn about the release of a neurotransmitter. The action potential reaches the end of the axon, called the axon terminal, and a chemical signal is released to tell the target cell to do something, either initiate a new action potential, or to suppress that activity. In a very short space, the electrical signal of the action potential is changed into the chemical signal of a neurotransmitter, and then back to electrical changes in the target cell membrane. What is the importance of voltage-gated calcium channels in the release of neurotransmitters?


The action potential depolarizes the cell membrane of the axon terminal, which contains the voltage-gated Ca2+ channel. That voltage change opens the channel so that Ca2+ can enter the axon terminal. Calcium ions make it possible for synaptic vesicles to release their contents through exocytosis.

Question: Watch this video ( to learn about summation. The process of converting electrical signals to chemical signals and back requires subtle changes that can result in transient increases or decreases in membrane voltage. To cause a lasting change in the target cell, multiple signals are usually added together, or summated. Does spatial summation have to happen all at once, or can the separate signals arrive on the postsynaptic neuron at slightly different times? Explain your answer.


A second signal from a separate presynaptic neuron can arrive slightly later, as long as it arrives before the first one dies off, or dissipates.

Question: Visit this site ( to learn about how nervous tissue is composed of neurons and glial cells. The neurons are dynamic cells with the ability to make a vast number of connections and to respond incredibly quickly to stimuli and to initiate movements based on those stimuli. They are the focus of intense research as failures in physiology can lead to devastating illnesses. Why are neurons only found in animals? Based on what this article says about neuron function, why wouldn't they be helpful for plants or microorganisms?


Neurons enable thought, perception, and movement. Plants do not move, so they do not need this type of tissue. Microorganisms are too small to have a nervous system. Many are single-celled, and therefore have organelles for perception and movement.

Question: When eating food, what anatomical and functional divisions of the nervous system are involved in the perceptual experience?


The sensation of taste associated with eating is sensed by nerves in the periphery that are involved in sensory and somatic functions.

Question: What happens across the membrane of an electrically active cell is a dynamic process that is hard to visualize with static images or through text descriptions. View this animation ( to really understand the process. What is the difference between the driving force for Na+ and K+? And what is similar about the movement of these two ions?


Sodium is moving into the cell because of the immense concentration gradient, whereas potassium is moving out because of the depolarization that sodium causes. However, they both move down their respective gradients, toward equilibrium.

Question: What responses are generated by the nervous system when you run on a treadmill? Include an example of each type of tissue that is under nervous system control.


Running on a treadmill involves contraction of the skeletal muscles in the legs, increase in contraction of the cardiac muscle of the heart, and the production and secretion of sweat in the skin to stay cool.

Question: In 2003, the Nobel Prize in Physiology or Medicine was awarded to Paul C. Lauterbur and Sir Peter Mansfield for discoveries related to magnetic resonance imaging (MRI). This is a tool to see the structures of the body (not just the nervous system) that depends on magnetic fields associated with certain atomic nuclei. The utility of this technique in the nervous system is that fat tissue and water appear as different shades between black and white. Because white matter is fatty (from myelin) and gray matter is not, they can be easily distinguished in MRI images. Visit the Nobel Prize website ( to play an interactive game that demonstrates the use of this technology and compares it with other types of imaging technologies. Also, the results from an MRI session are compared with images obtained from x-ray or computed tomography. How do the imaging techniques shown in this game indicate the separation of white and gray matter compared with the freshly dissected tissue shown earlier?


MRI uses the relative amount of water in tissue to distinguish different areas, so gray and white matter in the nervous system can be seen clearly in these images.

Question: Multiple sclerosis is a demyelinating disease affecting the central nervous system. What type of cell would be the most likely target of this disease? Why?


The disease would target oligodendrocytes. In the CNS, oligodendrocytes provide the myelin for axons.

Question: View the University of Michigan WebScope at: ( to see an electron micrograph of a cross-section of a myelinated nerve fiber. The axon contains microtubules and neurofilaments, bounded by a plasma membrane known as the axolemma. Outside the plasma membrane of the axon is the myelin sheath, which is composed of the tightly wrapped plasma membrane of a Schwann cell. What aspects of the cells in this image react with the stain that makes them the deep, dark, black color, such as the multiple layers that are the myelin sheath?


Lipid membranes, such as the cell membrane and organelle membranes.

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Disclaimer:  This course does NOT provide the education or experience needed for the diagnosing or treating any medical condition, all site contents are provided as general information only and should not be taken as medical advice.
Source:  OpenStax College. Anatomy & Physiology, OpenStax-CNX Web site., Jun 11, 2014
Briana Knowlton
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