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because it is the most complex and complicated system in the human body.
Th nervous system and the endocrine system coordinate and control the body. Together they regulate our responses to the environment and maintain homeostasis.
the endocrine system functions by means of hormones,wheres the nervous system functions by means of electric impulses.
For the study purposes, the nervous system may be divided into the central nervous system (CNS), consisting of the brain and spinal cord, and the peripheral nervous system (PNS), consisting of all nervous tissue outside the brain and spinal cord.
By Functionally, the nervous system can be divided into the somatic nervous system, which controls skeletal muscles, and the visceral or autonomic nervous system (ANS), which controls smooth muscle, cardiac muscle, and glands.
The ANS regulates responses to stress and helps to maintain homeostasis. Two types of cells are found in the nervous system: Neurons, or nerve cells, that make up the conducting tissue of the nervous system. And the Neuroglia, the connective tissue cells of the nervous system that support and protect nervous tissue
► THE NEURON:
The neuron is the basic functional unit of the nervous system. Each neuron has two types of fibers extending from the cell body: the dendrite, which carries impulses toward the cell body, and the axon, which carries impulses away from the cell body. Some axons are covered with myelin, a whitish, fatty material that insulates and protects the axon and speeds electric conduction. Axons so covered are described as myelinated, and they make up the white matter of the nervous system. Unmyelinated tissue makes up the gray matter of the nervous system. Each neuron is part of a relay system that carries information through the nervous system.
A neuron that transmits impulses toward the CNS is a sensory neuron.and a neuron that transmits impulses away from the CNS is a motor neuron. There are also connecting neurons within the CNS. The point of contact between two nerve cells is the synapse. At the synapse, energy is passed from one cell to another by means of a chemical neurotransmitter.
► NERVES:
Individual neuron fibers are held together in bundles like wires in a cable. If this bundle is part of the PNS, it is called a nerve. A collection of cell bodies along the pathway of a nerve is a ganglion. A few nerves (sensory nerves) contain only sensory neurons, and a few (motor nerves) contain only motor neurons, but most contain both types of fibers and are described as mixed nerves.
The ANS regulates responses to stress and helps to maintain homeostasis. Two types of cells are found in the nervous system: Neurons, or nerve cells, that make up the conducting tissue of the nervous system. And the Neuroglia, the connective tissue cells of the nervous system that support and protect nervous tissue
► THE NEURON:
The neuron is the basic functional unit of the nervous system. Each neuron has two types of fibers extending from the cell body: the dendrite, which carries impulses toward the cell body, and the axon, which carries impulses away from the cell body. Some axons are covered with myelin, a whitish, fatty material that insulates and protects the axon and speeds electric conduction. Axons so covered are described as myelinated, and they make up the white matter of the nervous system. Unmyelinated tissue makes up the gray matter of the nervous system. Each neuron is part of a relay system that carries information through the nervous system.
A neuron that transmits impulses toward the CNS is a sensory neuron.and a neuron that transmits impulses away from the CNS is a motor neuron. There are also connecting neurons within the CNS. The point of contact between two nerve cells is the synapse. At the synapse, energy is passed from one cell to another by means of a chemical neurotransmitter.
► NERVES:
Individual neuron fibers are held together in bundles like wires in a cable. If this bundle is part of the PNS, it is called a nerve. A collection of cell bodies along the pathway of a nerve is a ganglion. A few nerves (sensory nerves) contain only sensory neurons, and a few (motor nerves) contain only motor neurons, but most contain both types of fibers and are described as mixed nerves.
THE BRAIN:
human brain is the central organ of the human nervous system, and with the spinal cord makes up the central nervous system.
The brain consists of the cerebrum, the brainstem and the cerebellum. It controls most of the activities of the body, processing, integrating, and coordinating the information it receives from the sense organs, and making decisions as to the instructions sent to the rest of the body.
The cerebrum is the largest part of the brain. It is composed largely of white matter with a thin outer layer of gray matter, the cerebral cortex. It is within the cortex that the higher brain functions of memory, reasoning, and abstract thought occur.
The cerebrum is divided into two hemispheres by a deep groove, the longitudinal fissure. Each hemisphere is further divided into lobes with specialized functions.
The diencephalon contains the thalamus, the hypothalamus, and the pituitary gland. The thalamus receives sensory information and directs it to the proper portion of the cortex. The hypothalamus controls the pituitary and forms a link between the endocrine and nervous systems. The brainstem consists of the midbrain, the pons, and the medulla oblongata. The midbrain contains reflex centers for improved vision and hearing. The pons forms a bulge on the anterior surface of the brainstem. It contains fibers that connect different regions of the brain. The medulla connects the brain has vital centers for control of heart rate, respiration, and blood pressure.
The cerebellum is under the cerebrum and dorsal to the pons and medulla. Like the cerebrum, it is divided into two hemispheres. It helps to control voluntary muscle movements and to maintain posture, coordination, and balance.
Within the brain are four ventricles (cavities) in which cerebrospinal fluid (CSF) is produced. It is produced by the specialised ependymal cells in the choroid plexuses of the ventricles. This fluid circulates around the brain and spinal cord, acting as a protective cushion for these tissues. Covering the brain and the spinal cord are three protective layers, together called the meninges. The outermost and toughest of the three is the dura mater. The middle layer is the arachnoid. The thin, vascular inner layer, attached directly to the tissue of the brain and spinal cord, is the pia mater
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THE SPINAL CORD :
The spinal cord extends from the medulla oblongata to between the first and second lumbar vertebrae. It has a central area of gray matter surrounded by white matter. The gray matter projects toward the back and the front as the dorsal and ventral horns. The white matter contains the ascending and descending tracts (fiber bundles) that carry impulses to and from the brain. Thirty-one pairs of spinal nerves connect with the spinal cord.
These nerves are grouped in the segments of the cord as follows:
Cervical 8
Thoracic 12
Lumbar 5
Sacral 5
Coccygeal 1
Each nerve joins the cord by two roots. The dorsal, or posterior, root carries sensory impulses into the cord; the ventral, or anterior, root carries motor impulses away from the cord and out toward a muscle or gland. A simple response that requires few neurons is a reflex. In a spinal reflex, impulses travel through the spinal cord only and do not reach the brain. An example of this type of response is the knee-jerk reflex used in physical examinations. Most neurologic responses, however, involve complex interactions among multiple neurons (interneurons) in the CNS.
The Autonomic Nervous System The autonomic nervous system (ANS) is the division of the nervous system that controls the involuntary actions of muscles and glands. The ANS itself has two divisions:
the sympathetic nervous system and the parasympathetic nervous system.
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THE SPINAL CORD :
The spinal cord extends from the medulla oblongata to between the first and second lumbar vertebrae. It has a central area of gray matter surrounded by white matter. The gray matter projects toward the back and the front as the dorsal and ventral horns. The white matter contains the ascending and descending tracts (fiber bundles) that carry impulses to and from the brain. Thirty-one pairs of spinal nerves connect with the spinal cord.
These nerves are grouped in the segments of the cord as follows:
Cervical 8
Thoracic 12
Lumbar 5
Sacral 5
Coccygeal 1
Each nerve joins the cord by two roots. The dorsal, or posterior, root carries sensory impulses into the cord; the ventral, or anterior, root carries motor impulses away from the cord and out toward a muscle or gland. A simple response that requires few neurons is a reflex. In a spinal reflex, impulses travel through the spinal cord only and do not reach the brain. An example of this type of response is the knee-jerk reflex used in physical examinations. Most neurologic responses, however, involve complex interactions among multiple neurons (interneurons) in the CNS.
The Autonomic Nervous System The autonomic nervous system (ANS) is the division of the nervous system that controls the involuntary actions of muscles and glands. The ANS itself has two divisions:
the sympathetic nervous system and the parasympathetic nervous system.
The sympathetic nervous system: motivates our response to stress, the so-called “fight-or-flight” response. It increases heart rate and respiration rate, stimulates the adrenal gland, and delivers more blood to skeletal muscles.
The parasympathetic system: returns the body to a steady state and stimulates maintenance activities, such as digestion of food. Most organs are controlled by both systems and, in general, the two systems have opposite effects on a given organ.
► Functions of nerves within the parasympathetic nervous system include: Dilating blood vessels leading to the GI tract, increasing the blood flow. Constricting the bronchiolar diameter when the need for oxygen has diminished Dedicated cardiac branches of the vagus and thoracic spinal accessory nerves impart parasympathetic control of the heart (myocardium) Constriction of the pupil and contraction of the ciliary muscles, facilitating accommodation and allowing for closer vision
The parasympathetic system: returns the body to a steady state and stimulates maintenance activities, such as digestion of food. Most organs are controlled by both systems and, in general, the two systems have opposite effects on a given organ.
► Functions of nerves within the parasympathetic nervous system include: Dilating blood vessels leading to the GI tract, increasing the blood flow. Constricting the bronchiolar diameter when the need for oxygen has diminished Dedicated cardiac branches of the vagus and thoracic spinal accessory nerves impart parasympathetic control of the heart (myocardium) Constriction of the pupil and contraction of the ciliary muscles, facilitating accommodation and allowing for closer vision
► Functions of nerves within the Sympathetic nervous system include:
Diverts blood flow away from the gastro-intestinal (GI) tract and skin via vasoconstriction
Blood flow to skeletal muscles and the lungs is enhanced (by as much as 1200% in the case of skeletal muscles)
Dilates bronchioles of the lung through circulating epinephrine, which allows for greater alveolar oxygen exchange
Increases heart rate and the contractility of cardiac cells (myocytes), thereby providing a mechanism for enhanced blood flow to skeletal muscles
Dilates pupils and relaxes the ciliary muscle to the lens, allowing more light to enter the eye and enhances far vision
Provides vasodilation for the coronary vessels of the heart
Constricts all the intestinal sphincters and the urinary sphincter
Inhibits peristalsis
Stimulates orgasm.
Vegitables,fruit, milk,menta m and physical exsercis is important factors to increase your brain activities.
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