Na
preganglionic fiber postganglionic fiber preganglionic fiber postganglionic fiber schematic arrangement of autonomic nervous system
Info Qir
nucleus of the. horizontal limb of the diagonal band localization of estrogen receptors in ratforebrain frontal view through preoptic region Feedback control is part of the body's homeostatic mechanisms. Living organisms have developed tight control over their internal environment, which in mammals includes temperature regulation, appetite, water and salt balance, blood pressure, sexual function and behavior, and regulation of the thousands of biochemical and electrochemical changes that occur....
Basal Ganglia Lesions in Striatum and Subthalamic Nucleus
Some previously unexplained disturbances of motor function, especially those involving hyperkinetic disturbances, have been found to be due to neurochemical lesions in the striatum or the subthalamic nucleus. In principle, the hyperkinesias may be explained perhaps oversimplified as an abnormally high flow of impulses through the thalamocortical pathway due to a disturbance of the normal balance between direct pathway excitation and indirect pathway inhibition of pallidothalamic pathways see p....
Gh
LH luteinizing hormone GH growth hormone FSH follicle-stimulating hormone ACTH adrenocorticotropic hormone
Oculomotor Nuclei and Nerves
The main aim of eye movement is to focus external objects on to the fovea of the eye see p. 236 , and to keep the focus on the fovea. The eye has to be stabilized even when the head moves. Each eye has six extraocular muscles, and each eye has five movements, which are governed by three bilateral groups of brain stem oculomotor nuclei. The extraocular muscles are the inferior, medial, lateral, and superior rectus muscles, and the inferior and superior oblique. The muscles enable the eye to...
Basal Ganglia Neurotransmitters
The neurotransmitters of the basal ganglia have been studied extensively, in view of their importance in human disease. Very many neuroactive substances have been described in the basal ganglia, but the functional significance of most of them is still unknown. Nevertheless, the study of basal ganglia neurotransmitters and their neuronal distribution is helping to throw light on basal ganglia function in both health and disease. The inputs to the striatum from the cerebral cortex appear to be...
Sleep and The Reticular Formation
The reticular formation plays a role in the rhythmical cycle of sleep and wakefulness. Evidence for its role can be obtained by using the electroencephalogram, or EEG, which is a surface recording of electrical patterns. Further evidence is obtained from experimental evidence based on lesioning of selected areas in the reticular formation. The EEG obtained during sleep suggests that the brain passes through several stages of sleep. Wakefulness is characterized by high frequency, low voltage...
Caba
amacrine and bipolar actions on ganglion cells The accurate projection of visual inputs from the retina to the brain requires the preservation of the order of the original visual layout on the retina, the so-called retinotopic map. The map is plotted on the retina in terms of an orderly arrangement of photoreceptors and their associated ganglion cells. Thus, adjacent visual inputs are plotted by adjacent ganglion cells, somewhat analogous to the plotting of pixels by a computer. The picture...
I Xjv
constriction constriction secretion I Autonomic Nervous System Agonists and Antagonists Agonists activate the receptors with which they interact, while antagonists block the binding of the agonist to the receptor. Both agonists and antagonists of the ACh receptor, especially the mus-carinic receptor, and of the cate-cholaminergic receptors, have several important therapeutic implications, many of which have been developed. Muscarinic agonists include ACh, muscarine, carbachol, methacholine, and...
X
wavelength less than order of head diametersound direction localized wavelength more than order of head diameter -sound direction not localized phase difference calculated as d.sin XIX degrees d.sin L v msec, where d metres v sound velocity metres sec phase differences in sound localization The vestibular apparatus is part of the labyrinth in the inner ear. It evolved partly from the lateral line organ, which in fish enables them to orientate in water and sense changes in water movement. The...
Control of Posture
Posture is body position, which is designed to maintain support against the force of gravity. Put another way, it is the arrangement of vertical position relative to the body supports in contact with the ground. In humans, the support area when standing is covered by the feet, a relatively small area, and the center of gravity is high. Therefore relatively little tilt will destabilize the vertical position. The body is equipped with mechanisms that sense changes in the orientation of the body...
Afferent Connections to the Reticular Formation
The reticular formation receives much afferent input, both from the spinal cord and from other parts of the brain. The lateral column of the reticular formation is an important reception area for incoming sensory and other afferent inputs inputs from collaterals arising from ascending spinal sensory tracts and from spinoretic-ular tracts are especially prominent. The lateral column is made up of nuclei consisting chiefly of small cells, including the parvicellular nucleus in the medulla and...
Info Kmm
I I I I I I I 0.2 2 20 lowest threshold frequency for eel I Primary afferent fibers from the cochlea enter the brain stem at the level of the cerebellopontine angle. They synapse first in the ipsilateral cochlear nuclear complex in the medulla. The complex lies partly on the surface of the brain stem at the junction between the medulla and pons. The complex comprises three nuclei, the dorsal, posterolateral, and antero-ventral cochlear nuclei. Each nucleus has a sonotopic representation of the...
Control of Extraocular Muscles
The extraocular muscles and their nerves determine the velocity of movement and position of the eyes. They have to stabilize the gaze and keep the object in focus, regardless of head movement, or movement of the object. This is achieved through the versatility of eye movements and through several reflexes. Gaze is stabilized through five systems that are controlled by the abducens, oculomotor, and vestibular nuclei in the brain stem. The optokinetic reflex keeps the object in focus during head...
Jil
polarization of cilia towards striola polarization of cilia away from striola, polarization of cilia away from striola, The eye is structured to collect light and perform initial processing of visual inputs. The eyeball is a roughly spherical structure, with a strong outer layer of dense connective tissue, called the sclera, which protects the inner layers. The sclera is continuous with the dura mater of the brain. Beneath the sclera is the choroid, a vascular layer, and beneath the choroid is...
Components of the Basal Ganglia
The term basal ganglia refers to five subcortical nuclei situated bilaterally in the white matter of the cerebral hemispheres. The word ganglia is inappropriate, as these are not strictly ganglia, but nerve cell nuclei. These nuclei are the caudate nucleus, putamen, subthalamic nucleus, substan-tia nigra, and the globus pallidus. In more recent texts, the reader may find the nucleus accumbens and the olfactory tubercleincluded with the basal ganglia as associated nuclei. The globus pallidus and...
The Reticular Formation
The term brain stem is used here to define the anatomically visible brain areas referred to as the medulla, pons, and mesencephalon. In some texts not this one it also encompasses the diencephalon. The brain stem is not a functional unit, and can be thought of as two distinct parts i the reticular formation, which appears to exert a form of control over the spinal cord and over ii the cranial nerve nuclei. The term 'reticular formation' is derived from the microscopic appearance of the region...
Info Krx
The receptor organ of hearing is the organ of Corti. These lie in the scala media within the cochlea in spiraling banks, supported on the basilar membrane. Each organ has pillar cells, which arch to form a tunnel of Corti. Adjoining the pillar cell is a single inner hair cell, which has hair cells stereocilia close to an overlying gelatinous tectorial membrane, but not attached to it. The scala tympani and media are filled with perilymph, which is high in Na . On the other side of the tunnel...
Layout of the Autonomic Nervous System
The autonomic nervous system ANS carries all efferent impulses from the central nervous system, except for motor innervation of skeletal muscle. The ANS is mainly outside voluntary control and regulates i the heart beat, ii contraction of smooth muscle, iii all exocrine and some endocrine organs, and iv some of intermediary metabolism. Afferent sensory fibers run in the same nerve bundles that carry efferents, but only the efferents will be considered here. The ANS is anatomically and...
Autonomic Nervous System Sympathetic Division
The sympathetic preganglionic neuron cell bodies are situated in the thoracic and upper two or three lumbar segments of the spinal cord. The cell bodies lie in the lateral horn of the spinal gray matter. The usually short preganglionic fibers leave the spinal cord in the ventral nerve root, and join the spinal nerve. These fibers synapse with the postganglionic fibers, either in one of the sympathetic ganglia, which lie in a bilateral longitudinal, paraverte-bral chain on either side of the...
Trigeminal Function and Pathology
The trigeminal nerve is the principal sensory nerve of the head, and also innervates the masticatory muscles. The sensory fibers carry modalities of temperature, touch, pain, pressure, and proprioceptive information from the tem-poromandibular joint and the muscles of mastication. Sensory inputs converge on to different central sensory nuclei. Pressure and touch terminate in the principal nucleus, pain and temperature in the spinal nucleus, and proprioceptive afferents in the mesen-cephalic...
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electrical stimulation of nerve NA norepinephrine ACH acetylcholine_ reciprocal presynaptic regulation of neurotransmitter release lateral hori cell body of preganglionic neuron lateral hori cell body of preganglionic neuron relationship between the sympathetic chain and a typical thoracic spinal nerve
O 1
laminar organization of olfactory bulb The auditory system, in common with the other senses, consists of two main divisions peripheral and central. The peripheral components are the ear and the nerves, which carry impulses to and from the ear. The central components are the CNS pathways and centers, which process auditory information. The ear is conveniently divided into outer, middle, and inner ears. The outer ear consists of the external ear or pinna, and the ear canal, or external auditory...
Stria Terminalis Bed Nucleus
ventropostero-medial nucleus of thalamu BNST bed nucleus of stria terminalis BNST bed nucleus of stria terminalis cranial nerve VII, IX, orX taste bud d dark cell i intermediate cell I light cell t taste pore b basal cell taste bud adenylate cyclase taste receptor sweet raste Na channel The sense of smell is mediated by the olfactory system. This is the detection of airborne chemicals by specialized receptors in the olfactory mucosa. Animals that rely heavily on olfaction for survival and...
The Cerebrum
The cerebrum or forebrain is the largest part of the human brain and is housed in the concavity produced by the vault of the skull. It consists of the diencephalon and telencephalon. The diencephalon consists of the third ventricle and the structures that define its rostral, caudal, superior, and inferior boundaries. It is situated in the midline of the brain, and most of its components are bilateral and symmetrically arranged, with free communication between the two sides of a given...
S
Reissner's membrane scala media stria basilar membrane scala tympani moving direction Sound is caused by changes in pressure in a medium such as air. For example, the initial vibration of a loudspeaker diaphragm sets up a cone of rapidly moving air molecules. This moving boundary compresses the air immediately in front of it. If the loudspeaker continues to vibrate, the pressure differences will continue to move away from the original source of the air disturbance at a rate dependent on the...
Efferent Connections of the Reticular Formation
The raphe nuclei and medial column are the principal sources of efferent projections from the reticular formation to other brain areas. The medial column contains large cell bodies in the gigantocellular, ventral reticular, and pontine reticular nuclei. These cells put out long ascending and descending axons with many collaterals that interconnect ascending and descending neurons. Many of these collaterals also travel to the cranial nerves. Descending reticulospinal fibers travel either crossed...
Summary of Brain Development
The nervous system develops from the neural plate, which is an ectodermal thickening in the floor of the amniotic sac. During the third week, the plate forms paired neural folds that fuse to form the neural tube and neural canal. By the end of the fourth week, the open ends, the neuropores, become fused at either end and close. The formation of the neural tube is termed neurulation. Even before neurulation begins, the brain starts to develop from the rostral front end of the tube, which expands...
Jl
The electrical gap junction has been isolated from nervous tissue and characterized. All gap junctions studied consist of pairs of protein cylinders called connex-ons. One connexon is presynaptic, and the other is postsynaptic. The two connexons meet in the extracellular gap between the two cells, through homophilic interactions, and the two hemichannel cylinders align end-to-end to form a hollow tube, with a central channel, about 1.5-2.0 nm in diameter, which connects the cytoplasm of the two...
Autonomic Nervous System Parasympathetic Division
The parasympathetic division of the autonomic nervous system PNS consists of preganglionic fibers that originate in three main areas of the central nervous system. These are the midbrain or tectum, the medulla, and the sacral outflow. The outflows emerge from two main regions, i the brain stem cranial outflow, and ii the sacral outflow. Preganglionic fibers are generally much longer than the postgan-glionic fibers and often the ganglia lie on the organ innervated. The midbrain nuclei are the...
Cns
y-motoneuron sets desired spindle length the stretch reflex as feedback servosystem Sensory fibers, including those from the muscle spindle, pass into the dorsal roots and from there into the spinal cord. Once in the cord, the sensory fibers split into ascending and descending branches, and also give off collaterals that terminate in different areas of the gray matter of the cord. The dorsal root fiber axons that leave the ganglion and enter the cord are of different diameters depending on...
Meninges and Tracts
The nervous system consists of two main divisions the central nervous system CNS , consisting of brain and spinal cord, and the peripheral nervous system, consisting of cranial and spinal nerves, and their associated ganglia. Three membranes surround both spinal cord and brain dura mater, arachnoid mater, and pia mater. The dura mater is a tough, fibrous coat that encloses the spinal column and cauda equina, which is a bundle of nerve roots from the lumbar, sacral and coccygeal spinal nerves....
Ipsp
Central synapses II Types of Synapse Synaptic contact between cells in the CNS is made at several sites. Synapses may be axodendritic, dendrodendritic, axoax-onic, or axosomatic, the last indicating that an axon may synapse with the cell body. Dendrodendritic and axoaxonic synapses are relatively rare. This diversity of synaptic contact makes possible a vast array of control mechanisms for enhancement or inhibition of electrical activity and for integration and regulation see also p. 97 ....
Cranial Nerve Paralysis
Interruption of the corticonuclear supply to the brain stem nuclei supranuclear , or damage to the nuclei nuclear , causes paralysis of the muscles they innervate, and decreases or deletes their other cranial and visceral actions. Interruption is often the result of cerebral or brain stem vascular strokes that damage the pyramidal tract. Paralysis may result if structures peripheral to the nuclei infra-nuclear are damaged. The lesion may be caused by injury, by cardiovascular accident, or tumor...
Thalamic Nuclei Projections to Cerebral Cortex
There are highly precise point-to-point reciprocal connections between thalamic nuclei and the cerebral cortex. All thalamic nuclei except the reticular nucleus send ipsilateral projections to the cerebral cortex, and all cortical areas receive inputs from the thalamus. Thalamic nuclei that communicate with cortical regions are termed specific nuclei. All the specific nuclei lie in the ventral tier of the lateral nuclear group. The thalamus projects efferents to the cortex in the thalamic...
Info Yxf
measurement of synaptic current NMDA receptor measurement of synaptic current NMDA receptor classification of glutamate receptors
Info Pfa
I threshold absolute sensory threshold curve 0 2.5 5.0 7.5 10 stimulus intensity arbitrary units Mechanoreceptors transduce a physical stimulus into an electrical impulse by means of which the organism is able to localize the stimulus and gain some perception of its intensity and duration. In humans, this is achieved through mechanoreceptors such as Meissner's, pacinian, and Ruffini's corpuscles. Vertebrate mechanoreceptors are relatively inaccessible for study, but much has been learnt about...
The Glossopharyngeal Nerve
The glossopharyngeal nerve IX is mainly sensory in function, but does have some preganglionic parasympathetic and motor fibers. On route to the brain stem, the nerve leaves the mucous membrane of the oropharynx and runs between the middle and superior constrictor muscles. Where the nerve enters the brain at the base of the skull, it joins the vagus, spinal accessory, and the sympathetic internal carotid branch of the superior cervical ganglion. The glossopharyngeal runs together with the vagus...
The Accessory Hypoglossal and Vagus Nerves
The vagus, accessory, and hypoglossal nerves are X, XI, and XII, respectively. The vagus is the main parasympathetic nerve, having very extensive motor and sensory components see also p. 240 the auto-nomic nervous system . The accessory nerve is purely motor, and consists of cranial and spinal divisions. The cranial part has a linear set of rootlets that project bilaterally from the medulla, and lie just caudal to the vagal roots. The spinal part projects from the five most rostral segments of...
The Facial Nerve
The facial VII nerve contains motor, parasympathetic, and sensory fibers. It supplies several facial muscles, including those involving facial expression. It also supplies the posterior digastric, stapedius, and stylohyoid muscles. The nerve has two roots the nervus intermedius, which contains the parasympathetic and sensory fibers, and the facial nerve proper, which contains the motor fibers. The motor nucleus of the facial nerve lies in the pons and receives fibers from the facial region of...
The Cerebellum II Cellular and Lobular Arrangement
The lobules and fissures of the cerebellum are more easily understood if it is imagined that the surface of the cerebellum has been flattened as shown opposite. Using this representation, many of the areas of the cerebellum can be quickly and easily drawn schematically, and their relationship to other cerebellar structures understood. The medial vermal cerebellum has been subdivided into lobes running down the middle. These are, from dorsal to ventral, the lingula, culmen, declive, folium,...
Info Hul
Central synapses III Synaptic Integration When the neurotransmitter binds to its postsynaptic receptor on a CNS cell, it may initiate a postsynaptic potential PSP . The PSP may be an excitatory postsynaptic potential EPSP if the membrane potential decreases, or an inhibitory postsynaptic potential IPSP if the membrane potential increases. The EPSP, like the EPP at the neuromuscular junction, is a local graded potential. For an EPSP, after an initial synaptic delay of around 0.5 msec, the...
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Central Synapses I The Stretch Reflex Synapses between cells in the central nervous system may be excitatory or inhibitory. Such duality of control is essential for integration and regulation of central control of sensory information and motor regulation. The stretch reflex is a powerful and easily understood example. A monosynaptic reflex arc in the spinal cord consists, typically, of a sensory afferent 1a fiber, which synapses excitatorily with a motoneuron in the ventral horn of the spinal...
Ch3 I
Mg2 , Co2 ions aminoglycosides botulinum toxin block ACh release NMJ blockers tubocurarine suxamethonium
Brain Vascularization Arterial Supply
The brain receives its blood supply via two pairs of arteries, the internal carotid and vertebral arteries. The internal carotid arises from the common carotid and courses upward to the surface of the brain, giving off numerous preterminal branches, until it appears just laterally to the optic chiasm. The vertebral arteries run upwards and unite to form the basilar artery, which extends along the pons. As it runs up the pons, the basilar artery gives off small pontine tributaries, and the...
Venous Drainage of the Brain
Venous blood is drained from the brain through fine veins, which form themselves in pial venous plexuses. These drain into larger cerebral veins that traverse the subarachnoid space and drain into the sinuses of the dura mater, which lie between the meningeal and periosteal layers of the dura. The dural sinuses drain posteriorly and superiorly and meet at the confluence of the sinuses, which is situated near the internal occipital protuberance. Two transverse sinuses arise from the confluence...
The Cranial Nerve Nuclei
During embryonic development, there is a vertical column in the brain stem from which the different nerve fiber types are derived. As the fetus develops, the column splits into different columns, which migrate away from it. In the mature nervous system, afferent cranial nuclei tend to lie more laterally in the brain stem, while efferent nuclei lie medially. The most medially placed of the somatic efferent nuclei are termed general somatic efferent nuclei, and lie caudally to rostrally in the...
Trigeminal Innervation
The trigeminal nerve is primarily sensory, and covers a large area of the skin of the face, dura mater, major in-tracranial blood vessels, the teeth, and the oronasal mucosa. The nerve also supplies the masticatory muscles with both sensory afferents and motor efferents. The three main divisions of the trigeminal sensory nuclei are the principal, mesen-cephalic, and spinal nuclei. The trigemi-nal sensory gasserian ganglion lies near the apex of the petrous temporal bone and gives rise to three...
Diagonal Band Of Broca
5-hydroxyindoleacetic acid 5-HIAA metabolic disposition of 5-HT methysergideNHCH CH3 CH2OH ch3 y amine ergot alkaloids Cholinergic Pathways and Muscarinic Receptors Cholinergic neuron systems occur in the peripheral and central nervous systems. In the CNS, they are widespread, and release ACh opposite muscarinic M and ni-cotinic N receptors. M receptors outnumber N receptors 10-100-fold in the CNS. In the CNS, major cholinergic pathways originate from cell bodies in the septum, diagonal band of...
The Midbrain
The midbrain can be divided into three main parts the tectum quadrigeminal plate the tegmentum, which is a continuation of the pons tegmentum and the very large crus cerebri, which contains the corticofugal fibers. The midbrain contains two cranial nerve nuclei, the oculomotor and trochlear nuclei. The most prominent nuclear mass in the midbrain is the substantia nigra, a huge area darkly pigmented with melanin, a metabolic byproduct of dopamine breakdown. The sub-stantia nigra, which sends...