Nervous system

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The nervous system consists of the central nervous system (CNS) and the peripheral nervous system (PNS).

The central nervous system includes the brain and spinal cord. The brain is the control center of the nervous system and contains billions of neurons. The brain coordinates all body activities and maintains homeostasis. The spinal cord transmits signals from the brain to the rest of the body through nerves.

The peripheral nervous system connects the CNS to the rest of the body. It includes all the neurons that extend from the brain and spinal cord to the limbs and organs.

The main functions of the nervous system are:

• Transmission of signals: The nervous system transmits electrochemical signals between different parts of the body that allow communication and coordination. These signals are transmitted through nerve fibers that connect various organs and muscles to the CNS.
• Control and regulation: The nervous system controls and regulates many bodily functions such as movement, digestion, respiration, excretion, etc. The brain monitors the internal and external environment of the body and sends signals to maintain homeostasis.
• Processing and perception: The brain processes and interprets various signals received through our sensory organs like the eyes, ears, nose, tongue, and skin. It allows us to perceive the world around us. The brain processes all our senses, thoughts, memories, movements, emotions, etc.
• Storage and retrieval: The nervous system stores all our experiences, memories, habits, skills, thoughts, and emotions in the form of neural connections. The brain is able to encode, consolidate and retrieve various information.

The main parts of the nervous system are:

• Brain: Consists of cerebrum, cerebellum and brain stem. Responsible for intelligence, thoughts, perception, and movement.
• Spinal cord: Transmits signals from the brain to the rest of the body.
• Nerves: Bundles of neurons that transmit signals between the CNS and the muscles, organs and senses.
• Neurons: Basic structural and functional units of the nervous system. Responsible for transmitting electrical and chemical signals.

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Transcript:-
The nervous system is made up of the brain, the spinal cord, and the nerves. The network of nerve cells and fibers regulates the body's responses to internal and external stimuli. Neurons constitute a major part of the human nervous system. The undifferentiated supporting cells, which form the packing around neurons constitute the neuroglia.

Neurons are highly specialized. Consisting of a cell body or cyan with a nucleus and the nerve fibers. The nerve fibers are of two types, axon and dendrites or dendron. Axon is a single, usually very long fiber, which is branched only at the tip. Dendrites are usually short and branched, and through these stimuli are carried to the cell body.

Based on the number and position of fibers, neurons are classified into three types. Unipolar. These are neurons with two processes which join the cell body at one pole. Bipolar. These are neurons with two fibers, which originate from the opposite poles of the cell body. Multipolar. These are neurons with more than two fiber.

Based on their function, neurons are classified into three types, sensory afferent, or receptor neurons. These are receptors that are responsible for converting external stimuli from the environment into internal stimuli, such as olfactory receptors or connect receptors, such as the taste receptors, which conduct information to the central nervous system motor efferent or effector neuron.

These are located in the central nervous system and conduct information away from it to the effectors, muscles, glands, organs, et cetera. Inter neurons. These connect other neurons within a region and relay stimuli. They are usually confined to the central nervous system. Every neuron has the cell body or sight on, and, uh, fibers, dendrites, and ax.

Cyan is the Bulbus central body of a neuron. Like all cells, the entire neuron is surrounded by a cell membrane neuroma. The cell body consists of a nucleus and masses of r n A called niel granules surrounding the nucleus. The cell body also contains a network of neuro fibrils, some of which may pass into dendrites and ax.

The nerve fibers that receive impulses and conduct them towards the cell body are dendrites, and those that carry them away from the cell body are axons. Most peripheral nerve fibers are surrounded by a sheath of myelin, myelin sheath segmentally, which is a complex of fat and protein. The myelin sheath is also surrounded by the delicate neur.

The nuclei present below the numa are called sheath nuclei, or nuclei of schwan cells. The mile in material is constricted at intervals. These regions are called nodes of rambi Axons terminate by branching into many fine filaments called terminals or tele dendri. A nerve fiber with myelin sheath is called myelinated fibers.

For example, cranial nerves and a nerve fiber without myelin sheath is called non myelinated fiber, such as sympathetic nerves. The functional contact between axons and dendron that forms a junction is referred to as a synapse. The nerve impulse is not an electrical. But it is a wave of physiochemical activity in the nerve, which travels from the cell body to the axon, and along this structure to another nerve cell or non nervous tissue, such as muscle, and is accompanied by a potential change as a result of this change in the electrical charge in the area occupied by the impulse.

A difference in potential occurs between the two areas outside and inside the cell membrane. Conduction of nerve impulse involves the following events, resting potential or polarized state and action potential. Like other cell membranes, the membrane surrounding the neuron is also selectively permeable.

When the nerve fiber is not conducting the impulse that is in the resting phase, it is normally polarized. Measurement across the membrane shows that about 20 times as much positive potassium ions, K plus, are concentrated within the cells as outside the cell. As for positive sodium ions and a plus, there is about 10 times as much sodium outside the cell as inside the membrane is electrically polarized.

Inside of the membrane is negatively charged while outside the membrane. It is positively charge. The magnitude of the electric potential difference is measured in terms of millivolts MV in the resting cell. The ions represent minus 70 mv potential difference across the membrane. In other words, the inside of the cell is always 70 mv negative to the outside, and this is called the resting.

An action, potential, or impulse is a sequence of rapidly occurring events that decrease and reverse the membrane potential and then eventually restore it to the resting state. An action potential has two main phases, depolarization and repolarization. During depolarization, the membrane becomes more permeable or depolarizeslocally under the influence of a stimulus.

So that the voltage gated sodium channels allow sodium ions to rush into the cell. This exchange establishes a potential difference between the active and inactive regions of the neuron and the current flows between the two regions. This shift in the membrane potential as a result of depolarization wave along along the neuron is called action, potential, or nerve.

As a result at the region of depolarization, inside becomes positively charged and outside, negatively charged. The positive sodium ions are more within the cell than outside the cell, and the positive potassium ions are more outside the cell than inside the cell. Immediately after the depolarization waves along the neuron voltage gated potassium channels open, allowing potassium ions to flow.

Thus, the depolarized region undergoes repolarization to get back to the resting level, the synapse or junction between two neurons is the most important part of the nervous system. The axon terminal of one neuron synapses with the dendritic terminal of another neuron. The cell membrane of the neurons of the axodendritic connections do not join, but are separated by a distance of about 200 angstrom.

And this gap is known as synaptic gap or cleft. During synaptic transmission, chemical transmitters, neurotransmitters diffuse across the synapse. Neurotransmitters are chemical substances which transmit the impulse through the synapse. There are at least eight different neurotransmitters among them. Ace Coline is the main transmitting.

Other agents include norepinephrine or norad, adrenaline and serotonin, and three amino acids, including glycine. The nervous system may be divided into three parts, central nervous system, c n s. This includes the brain and the spinal cord, peripheral nervous system, p n s. This includes the cranial nerves and the spinal.

Autonomous nervous system, a n s. This is also called vegetative nervous system, as it is not under the control of the will that is involuntary and includes sympathetic and parasympathetic nerves. The human brain is perhaps the most highly specialized and well-developed organ of the body. It is lodged in a protective bony vault called the cranium in the.

It weighs about 1.4 kilograms, 1,400 grams, and is composed of about 12,000 million neurons. The brain is covered by three membranes called meninges. The outer membrane is fibrous and tough and is called durata. The middle membrane is called arachnoid, and the innermost membrane is called py. Between the arachnoid and the Pieter, there is a space called subarachnoid space, which contains a fluid called the cerebro spinal fluid.

The meninges with the cerebro spinal fluid are protective in function. The brain consists of three main parts, the cerebrum, the cerebellum, and the brains. The cerebrum is divided into right and left cerebral hemispheres by a deep depression. The longitudinal fisher, the surface of the cerebral hemispheres is wrinkled, and the depressions are called fishers.

The shallow depressions called sai give rise to convolution. The portions of convolutions are called gyri. The surface layer is composed of gray matter called cerebral cort. Gray matter is also present in the interior of the cerebrum, which constitute the basal ganglia. The nervous matter found between the cortex and the basal ganglia is called white matter, which is mainly composed of nerve fibers.

Each cerebral hemisphere is composed of four lobes, frontal, parietal, temporal, and occipital lobe. The cerebral hemispheres, also encloses cavities called ventricles, two lateral ventricles, and a third ventricle COR eight nucleus is structure found on the side walls of the lateral and third ventricles.

The two cerebral hemispheres are connected by a nervous tract called corpus callosum. Associated with this is gray material composed of putamen and globus. P. All these together constitute the corpus trium, the gray material that bounds The third ventricle laterally is the thalamus below each thalamus and forming the floor of the third ventricle is the hypothalamus pineal body is found attached to the roof of the third ventricle, and the pituitary gland is located below the hypothalamus.

Cerebral cortex is regarded as the center of intelligence, memory, and imagination. Corpus Stria is concerned with voluntary movements, movements of upper and lower extremities, head eyes, and body, et cetera. The thalamus acts as a relay station for sensory pathways and stimulation of this area gives rise to exaggerated sensations of pain and.

The hypothalamus plays an important part in the regulation of the body temperature, blood pressure, as well as the regulation of water, fat, and carbohydrate metabolism. The cerebellum is a miniature of the cerebral hemispheres in appearance attached to the brainstem by three pairs of massive bundles of nerve tissues called edun.

Like the cerebrum, it has a cortex of gray matter and an interior of both gray and white matter. The cerebellum is also divisible into two lateral hemispheres, which are connected in the middle by verus a structure called dentate nucleus is present in the white matter of cerebellum. The cerebellum coordinates impulses from sensory organs and is responsible for muscular movements as well as maintaining equilibrium.

The brain stem is a massive bundle of nerve tissue associated with the base of the cerebral hemispheres. It is divided into three areas, mid-brain pons and medela oblongata. The mid-brain is directly connected to the base of the brain. Pons is a massive rounded structure found below the mid. Mad Oblongata is found below the Ps, which is directly continuous with the spinal cord at the Foramen Magnum.

The fourth ventricle is present in the ponds and made oblongata, and is connected to the third ventricle by a canal called aqueduct toils. The brainstem controls respiration and cardiovascular function. It has a cardiac center and also centers of defecation, thetic, et cetera. Medela also controls certain reflexes like cough reflex, sneezing, reflex, saliva, reflex, et cetera.

The spinal cord is a massive nerve column contiguous with the brainstem emerging through the four aimon magnum and terminating at the upper border of the second lu vertebra. It is much shorter than the vertebral canal in which it rests measuring about 18. It is also covered by the three membranes or meninges, the outmost durata, the middle arachnoid, and the innermost py.

The cerebral spinal fluid is present in the space between the arachnoid and py. The cylindrical spinal cord has a dorsal septum and a deep ventral fisher. There are two swellings. The first one is known as cervical swelling at the level of the sixth spinal nerve. And the other is lu swelling at the level of the third lumbar spinal nerve, the spinal cord is divided into five regions.

Cervical, thoracic, lumber, sacral and coxal across section of the spinal cord at any level reveals the following structures. The gray matter of the spinal cord is internally located and is arranged in the form of a letter H surrounded by the white matter. The upper arms of the H are called dorsal horns, and the lower ones, the ventral horns, the central bar of gray matter of the spinal cord is pierced by the central canal.

The posterior part of the spinal cord with nerves is called , and the slender terminal part is called pH termin. The spinal cord carries stimuli to the brain and also conveys impulses from the brain to various parts of the body. It also carries out reflex actions. There are 12 pairs of cranial nerves originating from the brain.

Cranial nerves of the right part of the brain go to the left part of the body, and those of the left part of the brain go to the right part of the body. Consequently, the right cerebral hemisphere is concerned with sensations and movements of the left side of the body, and the left cerebral hemisphere is concerned with the stimuli and movements of the right part of the body.

Cranial nerves are either sensory or motor, or both mixed. There are 31 pairs of spinal nerves originating from the spinal cord. The spinal nerves are named after the five regions of the spinal cord. There are eight pairs of cervical, 12 pairs of thoracic, five pairs of lu, five pairs of sacral, and one pair of coxid spinal nerves.

The spinal nerves innovate the various parts of the body, bring stimuli to the spinal cord, and carry impulses from the spinal cord to various organ. In general, peripheral nerves are classified as sensory motor or mixed, depending on the direction in which they carry impulses. Sensory nerves carry impulses towards the central nervous system from internal organs or from external stimuli, whereas motor nerves carry impulses from the central nervous system to organs and muscle.

Mixed nerves contain both types of neurons which carry impulses toward and away from the central nervous system. The autonomous nervous system includes the sympathetic and parasympathetic nervous systems. The spinal nerves from thoracic and lumber regions are connected to the sympathetic chain through ganglia, which constitute the sympathetic nervous system.

The sympathetic chain has nerves going to the heart and blood vessels, lungs, stomach, sex, organs, and endocrine glands. These nerves are stimulatory in nature. Hence increase the activities of these organs, nerve fibers from the third, seventh, ninth, and 10th. Cranial nerves and also the upper roots of the second, third, and fourth sacral.

Spinal nerves are connected to the parasympathetic chain. The parasympathetic nerves also go to internal organs like the heart, stomach, lungs, bladder, and endocrine glands. These nerves are inhibitory in nature and hence decrease the activities of these organs. The organs of senses include the olfactory organs, sense of smell, the is sense of hearing, the eyes, the sense of sight, the tongue, the sense of taste and the skin sense of.

The receptors of all these sense organs are located in the cranial region and their sensory paths are over cranial nerves. The receptors for the sense of smell are situated very high in the interior of the nose between the median septum and the superior turbinate bone. The olfactory receptors consist of long, narrow pigmented cells, which have six to eight protoplasm Fila.

Extending from their free borders projecting into the open olfactory cleft. The impulses that are initiated in the olfactory cells travel to the brain by way of the olfactory nerve, where they are interpreted as various types of odors. The ear can be divided into three areas, external, middle, and internal.

The external ear or pinner, is composed of the oracle. An oblong flat fold of skin situated on the lateral aspects of the head. An external auditory canal leads from the oracle external air to the middle ear, which terminates at the timan membrane or eardrum. The middle ear contains three small bones within the middle air chamber, and these are Malus, incus, and Sta.

The Inea contains the cochlear semi canals, the utricle and sac. The cochlear and semi canals are tubular systems composed of membranes, tissue, and are called the membranes labyrinth. These tubules contain a fluid. The endolymph, the boney labyrinth is filled with a fluid called peri. The anterior part of the vestibular apparatus or the cochlear serves for hearing, whereas the posterior part of the vestibular apparatus mainly comprising semicircular canals plays a role in the maintenance of equilibrium.

The eyeball is almost spherical in shape and measures about 2.5 centimeters in diameter. Nearly one six of the surface area is exposed, and the remaining part is protected by the orbit into which it fits. The eyeball is composed of three layers, tunica, fibrosis, tunica, vascu, and tunica nervosa or retina.

The tunica fibro is the outer coat of the eyeball. This tough layer is divided into two unequal region. A transparent, exposed portion, the cornea and the larger opaque posterior portion, the sclera. The cornea is covered externally by a thin, transparent membrane called conjunctiva Tica. Vascu is the middle coat of the eye and is also known as uv.

It is divided into three regions. A vascular pigmented choroid coat the Cary body consisting of circular and radial smooth muscle fibers and a colored partition called the iris with a black hole in the center called the pupil Tica nervosa, or retina, is the innermost coat, which is further differentiated into three, a layer of rods and cones, a layer of bipolar neurons and a layer of optic nerve fiber.

There are about 115 million rods and 6.5 million cones. The retina is the light sensitive area containing the receptors of sight. The bi convex lens is located behind the pupil and separates the hollow interior of the eye into anterior and posterior cavities. The anterior cavity contains a fluid, the aqueous.

And is divided into anterior and posterior chambers by the iris. The posterior cavity is filled with a jelly-like substance, the vitreous humor, the region where the optic nerve leaves the eye is referred to as the optic disc. This area contains no visual elements and hence is called the blind spot. The eyes are adapted for binocular vision, which provides the basis of stereoscopic vision.

The sclera gives shape to the eyeball and protects its inner parts. Muscles attached to the sclera control. Eye movements, its posterior part is pierced by the optic nerve and also by blood vessels. The cornea is responsible for focusing light rays and the pigmented and vascular choroid coat absorbs light rays so that they are not reflected back to the eyeball.

The cornea also nourishes the retina. The iris regulates the amount of light entering the eyeball, and the color of the eye is also due to the iris, the colored smooth muscle. The ciliary muscles regulate the shape of the lens, which is suspended by the ciliary body. The convex lens with the Cary body forms the accommodation apparatus focusing objects on the retina.

Rods are dark light receptors containing Rodin or Visual purple. They are responsible for black and white vision. The cones are color receptors containing IO dosin or visual violet. They are meant for color, vision, aqueous humor, vitreous humor, and the lens serve as refractory media and help in focusing li rays on the retina.

The tongue is a highly muscular organ of delution taste and speech. It is partly oral and partly pharyngeal in position. The tongue is attached by its muscles to the hyoid bone, mandible, soft palate, and the pharyngeal wall. The sense of taste is a function of taste buds in the mouth. Adults have 3000 to 10,000.

Taste bud. The taste buds are found on three types of pail of the tongue. A large number of taste buds found on the walls on the troughs that surround the circum valley pail, which form a V line at the posterior tongue. Taste buds are also located on fungi form pail on the anterior surface of the tongue.

A few numbers of taste buds are present on the folate pail located in the folds at the lateral surfaces of the. The taste bud is composed of epithelial cells, some of which are supporting cells called sustentacular cells, and others are taste cells. The taste cells are continually being replaced by new epithelial cells.

That's why some taste cells are young cells and others are mature. The tips of Tay cells are arranged around a taste pour from the tip of each taste cell. Several microvilli protrude outwards into the taste pour, and get entry into the mouth cavity. These microvilli provide the receptor surface for the sense of taste.

In the taste cells matte, there is a network of nerve fibers that are stimulated by the taste cells and transfer sensory information to the brain. The skin has nerve endings through which the sensory information of touch is transmitted to the brain. Four types of touch sensations are identified. Cold heat, pain and contact hairs on the skin magnify the sensitivity and act as an nearly warning system for the body.

Nails survey protective function. The skin, hair, and nails altogether form the system of the body. These animated videos simplify and thereby provide a better understanding of the anatomy and functions of this complex system, which comprises the brain, spinal cord neurons, nerves, impulses, and neurotransmitters, sensory organs, their coordination and the working of the various types of nervous systems which manage the human body and its function.