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The brain and the spinal cord are the central nervous system, and they represent the main organs of the nervous system. The spinal cord is a single structure, whereas the adult brain is described in terms of four major regions: the cerebrum, the diencephalon, the brain stem, and the cerebellum. The regulation of homeostasis is governed by a specialized region in the brain.
- Anatomy and physiology of the nervous system
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- Anatomy and physiology of the nervous system
The nervous system consists of the brain, spinal cord, sensory organs, and all of the nerves that connect these organs with the rest of the body. Together, these organs are responsible for the control of the body and communication among its parts. The brain and spinal cord form the control center known as the central nervous system CNS , where information is evaluated and decisions made.
Anatomy and physiology of the nervous system
The nervous system consists of the brain, spinal cord, sensory organs, and all of the nerves that connect these organs with the rest of the body. Together, these organs are responsible for the control of the body and communication among its parts. The brain and spinal cord form the control center known as the central nervous system CNS , where information is evaluated and decisions made. The sensory nerves and sense organs of the peripheral nervous system PNS monitor conditions inside and outside of the body and send this information to the CNS.
Efferent nerves in the PNS carry signals from the control center to the muscles, glands, and organs to regulate their functions.
The majority of the nervous system is tissue made up of two classes of cells: neurons and neuroglia. Neurons, also known as nerve cells, communicate within the body by transmitting electrochemical signals. Neurons look quite different from other cells in the body due to the many long cellular processes that extend from their central cell body.
The cell body is the roughly round part of a neuron that contains the nucleus, mitochondria, and most of the cellular organelles. Small tree-like structures called dendrites extend from the cell body to pick up stimuli from the environment, other neurons, or sensory receptor cells.
Long transmitting processes called axons extend from the cell body to send signals onward to other neurons or effector cells in the body. Each neuron in the body is surrounded by anywhere from 6 to 60 neuroglia that protect, feed, and insulate the neuron. Because neurons are extremely specialized cells that are essential to body function and almost never reproduce, neuroglia are vital to maintaining a functional nervous system.
The brain , a soft, wrinkled organ that weighs about 3 pounds, is located inside the cranial cavity, where the bones of the skull surround and protect it. The approximately billion neurons of the brain form the main control center of the body.
The brain and spinal cord together form the central nervous system CNS , where information is processed and responses originate. The brain, the seat of higher mental functions such as consciousness, memory, planning, and voluntary actions, also controls lower body functions such as the maintenance of respiration, heart rate, blood pressure, and digestion. The spinal cord is a long, thin mass of bundled neurons that carries information through the vertebral cavity of the spine beginning at the medulla oblongata of the brain on its superior end and continuing inferiorly to the lumbar region of the spine.
The white matter of the spinal cord functions as the main conduit of nerve signals to the body from the brain. The grey matter of the spinal cord integrates reflexes to stimuli. Nerves are bundles of axons in the peripheral nervous system PNS that act as information highways to carry signals between the brain and spinal cord and the rest of the body.
Each axon is wrapped in a connective tissue sheath called the endoneurium. Individual axons of the nerve are bundled into groups of axons called fascicles, wrapped in a sheath of connective tissue called the perineurium. Finally, many fascicles are wrapped together in another layer of connective tissue called the epineurium to form a whole nerve.
The wrapping of nerves with connective tissue helps to protect the axons and to increase the speed of their communication within the body. The meninges are the protective coverings of the central nervous system CNS. They consist of three layers: the dura mater, arachnoid mater, and pia mater. CSF is formed from blood plasma by special structures called choroid plexuses.
The choroid plexuses contain many capillaries lined with epithelial tissue that filters blood plasma and allows the filtered fluid to enter the space around the brain. Newly created CSF flows through the inside of the brain in hollow spaces called ventricles and through a small cavity in the middle of the spinal cord called the central canal. CSF also flows through the subarachnoid space around the outside of the brain and spinal cord.
CSF is constantly produced at the choroid plexuses and is reabsorbed into the bloodstream at structures called arachnoid villi. What are known as the special senses—vision, taste, smell, hearing, and balance—are all detected by specialized organs such as the eyes , taste buds , and olfactory epithelium. Sensory receptors for the general senses like touch, temperature, and pain are found throughout most of the body. All of the sensory receptors of the body are connected to afferent neurons that carry their sensory information to the CNS to be processed and integrated.
Did you know that DNA testing can help you discover your genetic risk of acquiring certain health conditions that affect the organs of our nervous system? The brain and spinal cord together form the central nervous system, or CNS. The CNS acts as the control center of the body by providing its processing, memory, and regulation systems. The CNS is also responsible for the higher functions of the nervous system such as language, creativity, expression, emotions, and personality.
The brain is the seat of consciousness and determines who we are as individuals. The peripheral nervous system PNS includes all of the parts of the nervous system outside of the brain and spinal cord. These parts include all of the cranial and spinal nerves, ganglia, and sensory receptors. The SNS is the only consciously controlled part of the PNS and is responsible for stimulating skeletal muscles in the body.
The ANS controls subconscious effectors such as visceral muscle tissue, cardiac muscle tissue, and glandular tissue. There are 2 divisions of the autonomic nervous system in the body: the sympathetic and parasympathetic divisions. The enteric nervous system ENS is the division of the ANS that is responsible for regulating digestion and the function of the digestive organs.
The ENS receives signals from the central nervous system through both the sympathetic and parasympathetic divisions of the autonomic nervous system to help regulate its functions. Neurons function through the generation and propagation of electrochemical signals known as action potentials APs. An AP is created by the movement of sodium and potassium ions through the membrane of neurons.
See Water and Electrolytes. A synapse is the junction between a neuron and another cell. Synapses may form between 2 neurons or between a neuron and an effector cell. There are two types of synapses found in the body: chemical synapses and electrical synapses. The axons of many neurons are covered by a coating of insulation known as myelin to increase the speed of nerve conduction throughout the body.
In both cases, the glial cells wrap their plasma membrane around the axon many times to form a thick covering of lipids. The development of these myelin sheaths is known as myelination.
Myelination speeds up the movement of APs in the axon by reducing the number of APs that must form for a signal to reach the end of an axon. The myelination process begins speeding up nerve conduction in fetal development and continues into early adulthood.
Myelinated axons appear white due to the presence of lipids and form the white matter of the inner brain and outer spinal cord. White matter is specialized for carrying information quickly through the brain and spinal cord. The gray matter of the brain and spinal cord are the unmyelinated integration centers where information is processed. Reflexes are fast, involuntary responses to stimuli. Reflexes are integrated in the gray matter of the spinal cord or in the brain stem.
Reflexes allow the body to respond to stimuli very quickly by sending responses to effectors before the nerve signals reach the conscious parts of the brain.
This explains why people will often pull their hands away from a hot object before they realize they are in pain. All sensory receptors can be classified by their structure and by the type of stimulus that they detect. Structurally, there are 3 classes of sensory receptors: free nerve endings, encapsulated nerve endings, and specialized cells. Free nerve endings are simply free dendrites at the end of a neuron that extend into a tissue. Pain, heat, and cold are all sensed through free nerve endings.
An encapsulated nerve ending is a free nerve ending wrapped in a round capsule of connective tissue. When the capsule is deformed by touch or pressure, the neuron is stimulated to send signals to the CNS. Specialized cells detect stimuli from the 5 special senses: vision, hearing, balance, smell, and taste.
Each of the special senses has its own unique sensory cells—such as rods and cones in the retina to detect light for the sense of vision. Functionally, there are 6 major classes of receptors: mechanoreceptors, nociceptors, photoreceptors, chemoreceptors, osmoreceptors, and thermoreceptors. By: Tim Taylor. Last Updated: Nov 2, Now please check your email to confirm your subscription. There was an error submitting your subscription. Please try again. Email Address. All Rights Reserved.
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The nervous system is the master controlling and communicating system of the body. Every thought, action, and emotion reflects its activity. Its signaling device, or means of communicating with body cells, is electrical impulses, which are rapid and specific and cause almost immediate responses. The nervous system does not work alone to regulate and maintain body homeostasis ; the endocrine system is a second important regulating system. We only have one nervous system, but, because of its complexity, it is difficult to consider all of its parts at the same time; so, to simplify its study, we divide it in terms of its structures structural classification or in terms of its activities functional classification.
Neurons transmit nerve impulses along nerve fibers to otheneurons 2. Information Technology Solutions. Divided into 3 main regions: Cerebrum, Cerebellum, and the Brain Stem. Peripheral nervous system. Together, a combination of nerves, hormones, bacteria, blood, and the organs of the digestive system. The nervous system is a system in the body which sends signals around the body.
The nervous system is a complex network of nerves and nerve cells neurons that carry signals or messages to and from the brain and spinal cord to different parts of the body. It is made up of the central nervous system and the peripheral nervous system. The central nervous system CNS is made up of the brain and spinal cord. The brain controls most body functions, including awareness, movements, sensations, thoughts, speech and memory. The spinal cord is connected to the brain at the brain stem and is covered by the vertebrae of the spine.
Anatomy and physiology of the nervous system
Like all body systems, the nervous system goes through inevitable age-related changes, including a loss of brain cells, but ageing does not necessarily lead to confusion or dementia. The nervous system controls the activities of all body organs and tissues, receiving input from sensory organs and responding via effector organs. However we do understand, to some degree, how age affects it, as well as the nervous system as a whole. This fifth article in our series on the anatomy and physiology of ageing describes the age-related changes occurring in the brain, spinal cord and peripheral nerves.
Endocrine System Physiology. The sight, smell or thought of food can also stimulate your salivary glands. Do you want to master the endocrine system, and what it's made of? Look no further, here is the quiz of your dreams! The quiz that will let you know every least bit of information you want.
The nervous system is responsible for our thoughts, our emotions, our senses, and our movements. The brain, nerves, and spinal cord are all members of this important process. How much do you know about the nervous system?
The picture you have in your mind of the nervous system probably includes the brain , the nervous tissue contained within the cranium, and the spinal cord , the extension of nervous tissue within the vertebral column. The brain is contained within the cranial cavity of the skull, and the spinal cord is contained within the vertebral canal of the vertebral column.
Practice Test: The Nervous System and Nervous Tissue
Сьюзан вздохнула: - Программа принимает ключ только в цифровой форме. Мне кажется, что тут содержится некий намек на то, что это за цифра. В тексте названы Хиросима и Нагасаки, города, разрушенные атомными бомбами. Может быть, ключ связан с количеством человеческих жертв, оценочной суммой нанесенного ущерба в долларах… - Она замолчала, снова вчитываясь в текст. - Слово разница особенно важно.
Все в комнате дружно повернули головы. Диаграмма чем-то напоминала бычий глаз.
Никакой коммерческий производитель и мечтать не мог о создании шифровального чипа, потому что нормальные алгоритмы такого рода со временем устаревают. Но Цифровая крепость никогда не устареет: благодаря функции меняющегося открытого текста она выдержит людскую атаку и не выдаст ключа. Новый стандарт шифрования. Отныне и навсегда. Шифры, которые невозможно взломать.
Мне даже не сказали, что вы придете. Беккер поспешил переменить тему: - У вас на голове огромная шишка. Больно.
Это был краеугольный камень метода грубой силы. Именно этим принципом вдохновлялся Стратмор, приступая к созданию ТРАНСТЕКСТА. Он недвусмысленно гласит, что если компьютер переберет достаточное количество ключей, то есть математическая гарантия, что он найдет правильный.
Стратмор мысленно взвешивал это предложение.