Functions of the Nervous System. 1. Nervous system and endocrine system are the chief control centers in maintaining body homeostasis. 2. Nervous system. The Nervous System PowerPoint Notes. The anatomy and physiology of animals illustrate the complementary nature of structure and function. There are two. Human Anatomy & Physiology: Nervous System -–Central Nervous System, Ziser , Lecture Notes, 1. Central Nervous System. Brain & Spinal Cord. Brain.
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The Nervous System. Functions of the Nervous System. 1. Gathers information from both inside and outside the body - Sensory Function. 2. Transmits. The nervous system is the part of an animal's body that coordinates the A neuron is a nerve cell that is the basic building block of the nervous system. Neurons. The central nervous system includes the brain and spinal cord. The brain and nervous system is composed of excitable nerve cells (neurons) and synapses.
This preview shows page 1 - 3 out of 13 pages. Subscribe to view the full document. I cannot even describe how much Course Hero helped me this summer. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero. University of California, Berkeley. BIOL Chapter 12 Nervous System Notes.
The space between the arachnoid and the pia mater, the subarachnoid space, contains cerebrospinal fluid C. The ventricles of the brain contain vascular choroid plexuses, from which C. This fluid circulates through the ventricles, enters the subarachnoid space, and eventually filters into the venous system.
CSF protects the brain which basically floats. It serves to minimize damage from blows to the head and neck. Blood supply The brain is supplied by the cerebral branches of the vertebral and internal carotid arteries, the meninges mainly by the middle meningeal branch of the maxillary artery.
The spinal cord and spinal roots are supplied by the vertebral arteries and by segmental arteries. Peripheral nerves are supplied by a number of small branches along the course of the nerves. Peripheral nervous system A nerve is a collection of nerve fibers that is visible to the naked eye. The constituent fibers are bound together by connective tissue.
Each fiber is microscopic in size and is surrounded by a sheath formed by a neurilemmal cell comparable to the glial cells of the central nervous system. Hundreds or thou sands of fibers are present in each nerve. Thus, according to the number of constituent fibers, a nerve may be barely visible, or it may be quite thick.
A nerve as a whole is surrounded by a connective tissue sheath, the epineurium. Connective tissue fibers run inward from the sheath and enclose bundles of nerve fibers.
Such bundles are termed fasciculi funiculi ; the connective tissue that encloses them is called perineurium. Very small nerves may consist of only one fasciculus derived from the parent nerve. Finally, each nerve fiber and its neurilemmal sheath are enclosed by a connective tissue sheath termed endoneurium. Peripheral nerve fibers may be classified according to the structures they supply, that is, according to function. A fiber that stimulates or activates skeletal muscle is termed a motor efferent fiber.
A fiber that carries impulses from a sensory ending is termed a sensory afferent fiber. Fibers that activate glands and smooth muscle are also motor fibers, and various kinds of sensory fibers arise from endings in viscera. Consequently, a more detailed classification of functional components is sometimes required.
Spinal nerves The spinal roots, which are anchored to the spinal cord, consist of a dorsal root, attached to the dorsal aspect of the spinal cord, and a ventral root, attached to the ventral aspect of the cord. Each dorsal root which contains sensory fibers from skin, subcutaneous and deep tissues, and often from viscera also is formed by neuronal processes that carry afferent impulses into the spinal cord and which arise from neurons that are collected together to form an enlargement termed a spinal dorsal root ganglion fig.
The peripheral processes from the dorsal root ganglion neurons arise directly within the organ or structure from which they are conveying sensation. Each of the ventral roots which contain motor fibers to skeletal muscle, and of which many contain preganglionic autonomic fibers is formed by processes of neurons in the gray matter of the spinal cord.
While the projections from the motor neurons to skeletal muscle go directly to their termination in the muscle, the autonomic motor axons synapse on neurons in a ganglion hence the term preganglionic. The neurons in the ganglion postganglionic neurons have axons that reach their target on glands or smooth muscles. Basically, dorsal roots are afferent, ventral roots efferent. The corresponding dorsal and ventral roots join to form a spinal nerve. Each spinal nerve then divides into a dorsal and a ventral primary ramus.
Distribution of spinal and peripheral nerves The dorsal primary rami or just dorsal rami of spinal nerves supply the skin and muscles of the back. The ventral primary rami ventral rami supply the limbs and the rest of the trunk. The ventral rami that supply the thoracic and abdominal wall remain relatively separate throughout their course. In the cervical and lumbosacral regions, however, the ventral rami intermingle to form plexuses, from which the major peripheral nerves emerge.
When the ventral ramus of a spinal nerve enters a plexus and joins other such rami, its component funiculi or bundles ultimately enter several of the nerves emerging from the plexus.
Thus, as a general principle, each spinal nerve entering a plexus contributes to several peripheral nerves, and each peripheral nerve contains fibers derived from several spinal nerves. This arrangement leads to two fundamental and important types of distribution fig. Each spinal nerve has a segmental, or dermatomal, distribution. A dermatome is the area of skin supplied by the sensory fibers of a single dorsal root through the dorsal and ventral rami of its spinal nerve.
Dermatomes based largely on Foerster are shown in this figure. The mixture of nerve fibers in plexuses is such that it is difficult if not impossible to trace their course by dissection; hence, dermatomal distribution has been determined by physiological experimentation and by studies of disorders of spinal nerves. Methods have included stimulation of spinal roots, study of residual sensation when a root is left intact after section of the roots above and below it, study of the diminution of sensation after section of a single root, and study of the distribution of the vessicles that follow inflammation of roots and spinal ganglia in herpes zoster shingles.
Such studies have yielded complex maps, chiefly because of variation, overlap, and differences in method. Variation results from intersegmental rootlet anastomoses adjacent to the cervical and lumbosacral spinal cord and from individual differences in plexus formation and peripheral nerve distribution.
Overlap is such that section of a single root does not produce complete anesthesia in the area supplied by that root: at most, some degree of hypalgesia may result, particularly in the distal extremities, where overlap is less complete.
By contrast, when a peripheral nerve is cut, the result is a central area of total loss of sensation surrounded by an area of diminished sensation. There is little specific correspondence between dermatomes and underlying muscles. The general arrangement is that the more rostral segments of the cervical and lumbosacral enlargements of the spinal cord supply the more proximal muscles of the limbs, and that the more caudal segments supply the more distal muscles.
A muscle usually receives fibers from each of the spinal nerves that contribute to the peripheral nerve supplying it although one spinal nerve may be its chief supply. Section of a single spinal nerve weakens several muscles but usually does not paralyze them. Section of a peripheral nerve results in severe weakness or total paralysis of the muscles it supplies.
Moreover, autonomic dysfunction occurs in the area of its distribution. Cranial nerves The 12 pairs of cranial nerves are special nerves associated with the brain. The fibers in cranial nerves are of diverse functional types. Effectors: Muscles or glands which contract or secrete substances on receiving an impulse from the brain or the spinal cord.
Such a region of the nerve fibre is known as the excited region. Sympathetic and parasympathetic systems have functions which are opposite to each other. A receptor is any specialised tissue or cell sensitive to a specific stimulus.
Mechanoreceptors Receptors of touch, i. Chemoreceptors Receptors of taste of the tongue and smell of the nose due to chemical influence.
Photoreceptors Receptors of light present in rods and cones of the retina of eyes. Thermoreceptors Heat and cold receptors in the skin due to change in temperature. A nerve is a bundle of nerve fibers held together by layers of connective tissue.
Nerves can be sensory, motor, or mixed, carrying both sensory and motor fibers. The brain and spinal cord are surrounded by membranes called meninges that lie between the bone and the soft tissues. The outermost meninx is made up of tough, white dense connective tissue,contains many blood vessels, and is called the dura mater. It forms the inner periosteum of the skull bones.
In some areas, the dura mater forms partitions between lobes of the. The sheath around the spinal cord is separated from the vertebrae. The middle meninx, the arachnoid mater , is thin and lacks blood vessels.
It does not follow the convolutions of the brain. Between the arachnoid and pia maters is a subarachnoid space. The innermost pia mater is thin and contains many blood vessels and nerves. It is attached to the surface of the brain and spinal cord and follows.
The brain is the largest, most complex portion of the nervous system, containing billion multipolar neurons.
The brain can be divided into the cerebrum largest portion and associated with higher mental functions , the diencephalon processes sensory input , the cerebellum coordinates muscular activity , and the brain stem coordinates and regulates visceral activities. Structure of the Cerebrum 1. The cerebrum is the largest portion of the mature brain, consisting. Beneath the cortex lies a mass of white matter made up of myelinated nerve fibers connecting the cell bodies of the cortex with the rest of the nervous system.
Functions of the Cerebrum 1. The cerebrum provides higher brain functions, such as. Functional Regions of the Cerebral Cortex a. The functional areas of the brain overlap, but the cortex can. The primary motor areas lie in the frontal lobes, anterior to the central sulcus and in its anterior wall. Broca's area, anterior to the primary motor cortex, coordinates muscular activity to make speech possible.
Above Broca's area is the frontal eye field that controls the voluntary movements of the eyes and eyelids. The sensory areas are located in several areas of the cerebrum and interpret sensory input, producing feelings or sensations. Sensory areas for sight lie within the occipital lobe. Sensory and motor fibers alike cross over in the spinal cord. The various association areas of the brain analyze and interpret sensory impulses and function in reasoning, judgment, emotions, verbalizing ideas, and storing memory.
A general interpretive area is found at the junction of the parietal, temporal, and occipital lobes, and plays the primary role in complex thought processing. Most people exhibit hemisphere dominance for the language- related activities of speech, writing, and reading.
The non-dominant hemisphere specializes in nonverbal functions and controls emotions and intuitive thinking. The basal ganglia are masses of gray matter located deep within the cerebral hemispheres that relay motor impulses from the cerebrum and help to control motor activities by producing inhibitory dopamine.
Ventricles and Cerebrospinal Fluid 1. The ventricles are a series of connected cavities within the cerebral. The ventricles are continuous with the central canal of the spinal. Choroid plexuses, specialized capillaries from the pia mater,. Other portions of the diencephalon are the optic tracts and optic. The thalamus functions in sorting and directing sensory information arriving from other parts of the nervous system, performing the services of both messenger and editor.
The hypothalamus maintains homeostasis by regulating a wide variety of visceral activities and by linking the endocrine system with the nervous system. The hypothalamus regulates heart rate and arterial blood. The limbic system, in the area of the diencephalon, controls emotional experience and expression. By generating pleasant or unpleasant feelings about. The medulla oblongata also houses nuclei that control visceral functions, including the cardiac center that controls heart rate, the vasomotor center for blood pressure control, and the respiratory center that works, along with the pons, to control the rate and depth of breathing.
Other nuclei in the medulla oblongata are associated with coughling, sneezing, swallowing, and vomiting. Decreased activity in the reticular formation results in sleep; increased activity results in wakefulness. The cerebellum functions to integrate sensory information about.
The spinal cord begins at the base of the brain and extends as a slender cord to the level of the intervertebral disk between the first and second lumbar vertebrae. Structure of the Spinal Cord 1. The spinal cord consists of 31segments, each of which gives rise to. Two deep longitudinal grooves anterior median fissure and posterior median sulcus divide the cord into right and left halves. White matter, made up of bundles of myelinated nerve fibers nerve tracts , surrounds a butterfly-shaped core of gray matter housing interneurons.
The spinal cord has two major functions: Tracts carrying sensory information to the brain are called ascending tracts; descending tracts carry motor information from the brain. The names that identify nerve tracts identify the origin and termination of the fibers in the tract. The peripheral nervous system PNS consists of the cranial and spinal nerves that arise from the central nervous system and travel to the remainder of the body.
The PNS is made up of the somatic nervous system that oversees voluntary activities, and the autonomic nervous system that controls involuntary activities. The 12 pairs are designated by number and name and include the. Spinal Nerves 1. Thirty-one pairs of mixed nerves make up the spinal nerves. Spinal nerves are grouped according to the level from which they. Each spinal nerve arises from two roots: The cervical plexuses lie on either side of the neck and supply muscles and skin of the neck.
The lumbrosacral plexuses arise from the lower spinal cord and lead to the lower abdomen, external genitalia, buttocks, and legs. The routes nerve impulses travel are called pathways, the simplest of which is a reflex arc. Reflex Behavior 1. Reflexes are automatic, subconscious responses to stimuli that help. The knee-jerk reflex patellar tendon reflex is an example of a monosynaptic reflex no interneuron.
The autonomic nervous system has the task of maintaining homeostasis of visceral activities without conscious effort. General Characteristics 1. The autonomic nervous system includes two divisions: The parasympathetic division operates. Motor- Corticospinal Pathway- conscious control of skeletal muscle.
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This is only a preview. Load more. Search in the document preview. Neuroglia carry out a variety of functions to aid and protect components of the nervous system. The nervous system provides sensory, integrative, and motor functions to the body. Conscious or subconscious decisions follow, leading to motor functions via effectors.
Neuroglial cells fill spaces, support neurons, provide structural frameworks, produce myelin, and carry on phagocytosis. Microglial cells are small cells that phagocytize bacterial cells and cellular debris. Astrocytes are near blood vessels and support structures, aid in metabolism, and respond to brain injury by filling in spaces. Ependyma cover the inside of ventricles and form choroid plexuses within the ventricles. Schwann cells are the myelin-producing neuroglia of the peripheral nervous system.
Branching dendrites carry impulses from other neurons or from receptors toward the cell body. The axon transmits the impulse away from the axonal hillock of the cell body and may give off side branches.
Larger axons are enclosed by sheaths of myelin provided by Schwann cells and are myelinated fibers. The outer layer of myelin is surrounded by a neurilemma neurilemmal sheath made up of the ytoplasm and nuclei of the Schwann cell.