The Nervous System. Functions of the Nervous System. 1. Gathers information from both inside and outside the body - Sensory Function. 2. Transmits. Nerves project from spine to internal organs, like the heart, lungs, liver, digestive tract, etc. • Stimulation of the Sympathetic system involves increased heart rate. Nervous System. Subdivisions. CNS (Central Nervous System). PNS(Peripheral Nervous System). ANS (Autonomic Nervous system.
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PDF | On May 15, , Alicia Garcia-Falgueras and others published THE HUMAN NERVOUS SYSTEM THIRD EDITION. The central nervous system includes the brain and spinal cord. The brain and spinal cord Besides being an anatomical structure, the axon hillock is also the . we must understand nervous system structure in order to understand brain function The neuroanatomy presented in this chapter provides the canvas on which.
Diseases that affect this area include Parkinson's disease and Huntington's disease. Cerebellum: mostly involved in precise motor control, but also in language and attention.
If the cerebellum is damaged, the primary symptom is disrupted motor control, known as ataxia. Broca's area: this small area on the left side of the brain sometimes on the right in left-handed individuals is important in language processing. When damaged, an individual finds it difficult to speak but can still understand speech.
Stuttering is sometimes associated with an underactive Broca's area. Corpus callosum: a broad band of nerve fibers that join the left and right hemispheres. It is the largest white matter structure in the brain and allows the two hemispheres to communicate.
Dyslexic children have smaller corpus callosums; left-handed people, ambidextrous people, and musicians typically have larger ones. Medulla oblongata: extending below the skull, it is involved in involuntary functions, such as vomiting, breathing, sneezing, and maintaining the correct blood pressure. Hypothalamus: sitting just above the brain stem and roughly the size of an almond, the hypothalamus secretes a number of neurohormones and influences body temperature control, thirst, and hunger.
Thalamus: positioned in the center of the brain, the thalamus receives sensory and motor input and relays it to the rest of the cerebral cortex. It is involved in the regulation of consciousness, sleep, awareness, and alertness.
Amygdala: two almond-shaped nuclei deep within the temporal lobe.
They are involved in decision-making, memory, and emotional responses; particularly negative emotions. Spinal cord The spinal cord carries information from the brain to the rest of the body.
The spinal cord, running almost the full length of the back, carries information between the brain and body, but also carries out other tasks. From the brainstem, where the spinal cord meets the brain, 31 spinal nerves enter the cord. Along its length, it connects with the nerves of the peripheral nervous system PNS that run in from the skin, muscles, and joints.
Motor commands from the brain travel from the spine to the muscles and sensory information travels from the sensory tissues — such as the skin — toward the spinal cord and finally up to the brain. The spinal cord contains circuits that control certain reflexive responses, such as the involuntary movement your arm might make if your finger was to touch a flame.
The circuits within the spine can also generate more complex movements such as walking. Even without input from the brain, the spinal nerves can coordinate all of the muscles necessary to walk. For instance, if the brain of a cat is separated from its spine so that its brain has no contact with its body, it will start spontaneously walking when placed on a treadmill.
The brain is only required to stop and start the process, or make changes if, for instance, an object appears in your path. White and gray matter The CNS can be roughly divided into white and gray matter. As a very general rule, the brain consists of an outer cortex of gray matter and an inner area housing tracts of white matter. Both types of tissue contain glial cells, which protect and support neurons.
White matter mostly consists of axons nerve projections and oligodendrocytes — a type of glial cell — whereas gray matter consists predominantly of neurons. Central glial cells Also called neuroglia, glial cells are often called support cells for neurons. In the brain, they outnumber nerve cells 10 to 1. Without glial cells, developing nerves often lose their way and struggle to form functioning synapses.
Just from looking down a microscope, however, it becomes very clear that not all neurons are the same. So just how many types of neurons are there? And how do scientists decide on the categories?
For the spinal cord though, we can say that there are three types of neurons: sensory, motor, and interneurons. Sensory neurons Sensory neurons are the nerve cells that are activated by sensory input from the environment - for example, when you touch a hot surface with your fingertips, the sensory neurons will be the ones firing and sending off signals to the rest of the nervous system about the information they have received.
The inputs that activate sensory neurons can be physical or chemical, corresponding to all five of our senses. Thus, a physical input can be things like sound, touch, heat, or light. A chemical input comes from taste or smell, which neurons then send to the brain. Most sensory neurons are pseudounipolar, which means they only have one axon which is split into two branches.
Motor neurons Motor neurons of the spinal cord are part of the central nervous system CNS and connect to muscles, glands and organs throughout the body. Secondly, control of the body can be somatic or autonomic—divisions that are largely defined by the structures that are involved in the response.
There is also a region of the peripheral nervous system that is called the enteric nervous system that is responsible for a specific set of the functions within the realm of autonomic control related to gastrointestinal functions. The nervous system is involved in receiving information about the environment around us sensation and generating responses to that information motor responses.
The nervous system can be divided into regions that are responsible for sensation sensory functions and for the response motor functions. But there is a third function that needs to be included. Sensory input needs to be integrated with other sensations, as well as with memories, emotional state, or learning cognition. Some regions of the nervous system are termed integration or association areas. The process of integration combines sensory perceptions and higher cognitive functions such as memories, learning, and emotion to produce a response.
The first major function of the nervous system is sensation—receiving information about the environment to gain input about what is happening outside the body or, sometimes, within the body. The sensory functions of the nervous system register the presence of a change from homeostasis or a particular event in the environment, known as a stimulus. The stimuli for taste and smell are both chemical substances molecules, compounds, ions, etc.
There are actually more senses than just those, but that list represents the major senses. Those five are all senses that receive stimuli from the outside world, and of which there is conscious perception.
Additional sensory stimuli might be from the internal environment inside the body , such as the stretch of an organ wall or the concentration of certain ions in the blood. The nervous system produces a response on the basis of the stimuli perceived by sensory structures. An obvious response would be the movement of muscles, such as withdrawing a hand from a hot stove, but there are broader uses of the term.
The nervous system can cause the contraction of all three types of muscle tissue. For example, skeletal muscle contracts to move the skeleton, cardiac muscle is influenced as heart rate increases during exercise, and smooth muscle contracts as the digestive system moves food along the digestive tract. Responses also include the neural control of glands in the body as well, such as the production and secretion of sweat by the eccrine and merocrine sweat glands found in the skin to lower body temperature.
Responses can be divided into those that are voluntary or conscious contraction of skeletal muscle and those that are involuntary contraction of smooth muscles, regulation of cardiac muscle, activation of glands. Voluntary responses are governed by the somatic nervous system and involuntary responses are governed by the autonomic nervous system, which are discussed in the next section.
Stimuli that are received by sensory structures are communicated to the nervous system where that information is processed. This is called integration.
Stimuli are compared with, or integrated with, other stimuli, memories of previous stimuli, or the state of a person at a particular time. This leads to the specific response that will be generated. Seeing a baseball pitched to a batter will not automatically cause the batter to swing. The trajectory of the ball and its speed will need to be considered.
Maybe the count is three balls and one strike, and the batter wants to let this pitch go by in the hope of getting a walk to first base. The nervous system can be divided into two parts mostly on the basis of a functional difference in responses. The somatic nervous system SNS is responsible for conscious perception and voluntary motor responses.
Voluntary motor response means the contraction of skeletal muscle, but those contractions are not always voluntary in the sense that you have to want to perform them.
Some somatic motor responses are reflexes, and often happen without a conscious decision to perform them. The autonomic nervous system ANS is responsible for involuntary control of the body, usually for the sake of homeostasis regulation of the internal environment. Sensory input for autonomic functions can be from sensory structures tuned to external or internal environmental stimuli.
The motor output extends to smooth and cardiac muscle as well as glandular tissue. The role of the autonomic system is to regulate the organ systems of the body, which usually means to control homeostasis. Sweat glands, for example, are controlled by the autonomic system.
When you are hot, sweating helps cool your body down.
That is a homeostatic mechanism. But when you are nervous, you might start sweating also. That is not homeostatic, it is the physiological response to an emotional state. There is another division of the nervous system that describes functional responses. The enteric nervous system ENS is responsible for controlling the smooth muscle and glandular tissue in your digestive system. It is sometimes valid, however, to consider the enteric system to be a part of the autonomic system because the neural structures that make up the enteric system are a component of the autonomic output that regulates digestion.
There are some differences between the two, but for our purposes here there will be a good bit of overlap. See Figure 5 for examples of where these divisions of the nervous system can be found. 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? Have you ever heard the claim that humans only use 10 percent of their brains? Maybe you have seen an advertisement on a website saying that there is a secret to unlocking the full potential of your mind—as if there were 90 percent of your brain sitting idle, just waiting for you to use it.
An easy way to see how much of the brain a person uses is to take measurements of brain activity while performing a task. An example of this kind of measurement is functional magnetic resonance imaging fMRI , which generates a map of the most active areas and can be generated and presented in three dimensions Figure 6. This procedure is different from the standard MRI technique because it is measuring changes in the tissue in time with an experimental condition or event.