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App Leads Plaque

The human brain undergoes noticeable physical changes during aging. Brain weight decreases and neuronal loss or shrinkage occurs, together with lowered protein concentrations. Catecholamine-metabolizing enzymes fall, as do the numbers of neurons in the substantia nigra and locus ceruleus. These changes do not necessarily signal a pathological change. There is, however, a gradual decline in memory skills and reduced postural reflexes in some individuals, although some people can retain excellent...

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Midbrain And Parkisons Disease

Log10 average clinical dose for daily treatment of schizophrenia ic50 molar concentration of drug required to inhibit haloperidol binding to D2 receptor by 50 Parkinson's disease is characterized by fine tremor of the hands at rest, and the characteristic 'pill-rolling' movement of the fingers and thumb. There is muscular rigidity, which is detected as an increase in resistance to passive limb movements, and hypokinesia, which is a decrease in the frequency of voluntary movement. Parkinson's...

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Apex of the inferior part of the 4th ventricle occurs in cell columns in the visual cortex which receive inputs 3rd cranial nerve supplies medial, inferior and oblique rectus muscles of the eye sense of smell neuroglial cell whose processes coil round neuronal axons the processes become the myelin sheath neuroglial CNS cells that produce myelin olive-shaped swelling situated bilaterally on the medulla oblongata a collection of olivary nuclei consisting of the accessory, inferior and superior...

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Cerebral Cortex Pictures

Time days hormone release during the menstrual cycle time days hormone release during the menstrual cycle Growth hormone GH , also called somatotropin STH , is a glycoprotein secreted by the anterior pituitary, and needed for normal growth. Without somatotropin the individual would develop to be a dwarf. The hormone has both direct and indirect actions. It has a direct diabetogenic, antiinsulin action, causing lipolysis in adipo-cytes, and is catabolic in muscle and liver, generating glucose...

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...

Components of the Basal Ganglia

Spiny Neurons Striatum

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...

Autonomic Nervous System Sympathetic Division

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...

Efferent Connections of the Reticular Formation

Reticulospinal Tract Mice

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...

Meninges and Tracts

Anterior Corticospinal 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....

Brain Vascularization Arterial Supply

Recurrent Artery Heubner

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

Superior Cerebral Veins

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...

Diagonal Band Of Broca

Diagonal Band 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

Dorsal Longitudinal Fasciculus

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...

Hypothalamospinal Projections

Somatotropic Organization The Brain

Central thalamus reticular formation hypothalamus periaqueductal grey PAG awareness of both intensified by emotion some pathways involved in pain perception some pathways involved in pain perception Nociception II Afferent Inputs to the Dorsal Horn and Ascending Pathways Afferent nociceptive inputs to the dorsal horn are carried by the AS and C fibers. AS fibers terminate in laminae I and V, and C fibers in laminae I and II substantia gelatinosa . Upon entering the cord, the fibers bifurcate or...

Extrapyramidal Motor Pathways

Rubrospinal Tract

The extrapyramidal pathways are those motor pathways that do not pass through the pyramids of the medulla oblongata. They consist of central pathways that modulate CNS motor areas in cerebral cortex, cerebellum, the brain stem, and spinal cord. The primary function of the extrapyramidal system is the 'fine-tuning' of voluntary movement to render it amenable to higher levels of conscious control. The absence of such fine-tuning becomes obvious in conditions such as parkinsonism see p. 370 , when...

Dynamic Nuclear Bag Fibers

Dynamic And Static Nuclear Bag Fibers

Receptive field of second order neuron So receptive field of second order neuron So Proprioceptors I The Muscle Spindle The term proprioceptor is used to include reception of sensation in the musculo-skeletal system, i.e. deep sensation. This includes joint capsules, ligaments, muscles and tendons. These are low-threshold, stretch-activated mechanore-ceptors, whose afferent signals are conducted centrally in relatively thick myeli-nated axons. The muscle spindle is an elongated organ lying in...

Picture Dermatomes

Secondary Afferent Neuron

Marginal nucleus substantia gelatinosa nucleus proprius reticular nucleus commissural nuclei Clarke's intermedilateral nuclei medial motor nuclei lateral motor nuclei central gray dorsal root fibers and termination areas in gray matter of cord topography of somatic motoneurons in cord dorsal root fibers and termination areas in gray matter of cord topography of somatic motoneurons in cord Segmental Organization of Spinal Cord In humans, the vertebral column serves as the central supporting...

Basal Ganglia Neurotransmitters and Receptors

Subcorticale Ganglia Dopamine Receptor

The dopaminergic nigrostriatal pathway is the largest brain pathway using dopamine as neurotransmitter, and has been extensively studied not least because of its importance in degenerative brain disease. It has been found recently that there is an interaction between striatal dopaminergic inputs and those that use as neurotransmitter the nucleoside ade-nosine. In addition, hybridization studies have revealed the presence of subtypes of dopamine and adenosine receptors, situated both pre- and...

Cerebral Cortex And Swimming

Mesolimbic Mesocortical Pathway

Norepinephrine, epinephrine, and dopamine are important CNS neurotransmit-ters, and their pathways and receptors have been mapped and localized to a large extent. Dopamine DA is the major cate-cholamine neurotransmitter of the mammalian CNS, comprising at least 50 of the total CNS catecholamine content. There are four major dopaminergic pathways in the brain. The mesolimbic pathway originates in the ventral tegmental region of the midbrain, near the substantial nigra, and projects to several...

The Spinocerebellar Module

Lateral Vestibular Nuclei And Red Nuclei

The spinocerebellum paleocerebellum is so called because the vermian and intermediate zones receive important inputs from the ventral and dorsal spinocere-bellar tracts. Through these inputs, the cerebellum monitors body position and movement. These zones also receive afferents from the upper extremities via the cuneocerebellar tract. The cerebellum also receives inputs from the contralateral accessory olivary nuclei. The cerebellum integrates this information and projects it to the cerebral...

Habenular Nucleus

Pouch Luschka

Development of the Rhombencephalon Cerebellum and Ventricular System The cerebellum develops from dorsal thickenings of the alar plates in the rostral metencephalon. These extensions of the alar plates are called the rhombic lips. With the combined effects of their growth and the deepening of the pontine flexure, they approach each other in the midline overlying the fourth ventricle. Fusion of the rhombic lips results in the formation of the cerebellar plate. The developing cerebellum becomes...

Transverse Section of Pons

Medial Longitudinal Fasciculus

The pons metencephalon lies beneath anterior to the cerebellum and is around 2.6 cm in length. The pons has been arbitrarily divided into the dorsal or posterior tegmentum, and a basal or anterior part, sometimes referred to as the pons proper. Transection of the caudal pons at the level of the facial colliculi shows the fourth ventricle prominently, as well as the middle cerebellar peduncles. The term colliculus refers to the visible swellings caused by the mass of the nucleus. The superior...

Blood Supply and Venous Drainage of Spinal Cord

Vertebral Venous Plexuses

The spinal cord is supplied with arterial blood by descending arteries that run the length of the spinal cord, and by radicular arteries that arise at the segmental level. The descending arteries comprise the paired posterior spinal arteries, and the unpaired anterior spinal artery. The posterior spinal arteries arise either from the posterior inferior cerebellar arteries see p. 43 , or from the vertebral arteries. They descend the cord on the dorsal posterior surface, medial to the dorsal...

Cerebral Hemispheres Internal Structures

Internal Capsule Thalamus

The cerebral hemispheres contain the lateral ventricles, white matter, which consists of nerve fibers embedded in the neuroglia, and the basal nuclei basal ganglia . Each hemisphere possesses a lateral ventricle, which is lined with a layer of ependyma and filled with cerebrospinal fluid CSF . The ventricle has a body located in the parietal lobe, and horns, the anterior, posterior and inferior horns, which extend into the frontal, occipital and temporal lobes respectively. The body of the...

The Neural Plate and Neural Tube

Ganglion White Matter

Development of the central nervous system commences on day 18, with the formation of the neural plate in the ectoderm anterior to the primitive pit. The neural plate seems to be chemically induced by so-called inducing substances that are secreted by the prechordal plate and the cranial end of the notochordal plate in the underlying mesoderm. The cells in this area of ectoderm begin to differentiate into a thick plate of pseudo-stratified columnar neuroepithelium, forming the neural groove and...

Transverse Section of Medulla Oblongata

Medulla Level Hypoglossal Nerve

The spinal cord becomes the medulla oblongata, which also contains white and gray matter, but the arrangement changes, due to the embryonic expansion of the central canal to form the hindbrain vesicle, which will become the fourth ventricle. Development of the ventricle pushes dorsally situated structures more dorsolaterally. The transition is clearly seen in transverse section. The spinal cord becomes the medulla, which initially resembles the upper cervical segments. The substantia gelatinosa...

Dorsal View of Brain Stem

Inferior Colliculus Medial View

The dorsal surface of the brain stem, and particularly that of the medulla and pons, is obscured by the cerebellum. When this is removed, the bilateral swellings caused by the ascending cuneate and gracile fasciculi can be seen, as well as the corresponding tubercles, which are the swellings caused by their nuclei. Dorsal to the olives are the inferior cerebellar peduncles, which climb to the lateral aspect of the fourth ventricle and then swing into the cerebellum between the middle and...

Laminae and Nuclei of the Spinal Cord Gray Matter

Clarke Nucleus And Spinal Cord

The gray matter of the cord is butterfly-shaped, with the so-called dorsal posterior horns forming the upper wings of the butterfly shape. These are linked by a thin gray commissure in which lies the central canal. In the thoracic and upper lumbar segments the gray matter extends on both sides to form lateral horns. The lower wings of the butterfly shape are formed by the ventral anterior horns of the gray matter. The size of the gray matter is greatest at segments that innervate the most...