Presentation on theme: "Neuropsychology (Neuroanatomy)"— Presentation transcript:
1Neuropsychology (Neuroanatomy) Dr . Bakhshani NMZahedan University of Medical SciencesDepartment of Clinical Psychology and Psychiatry
2Structure of the Vertebrate Nervous System Neuroanatomy is the anatomy of the nervous system.Refers to the study of the various parts of the nervous system and their respective function(s).The nervous system consists of many substructures, each comprised of many neurons.
3Structure of the Vertebrate Nervous System Terms used to describe location when referring to the nervous system include:Ventral: toward the stomachDorsal: toward the backAnterior: toward the front endPosterior: toward the back endLateral: toward the sideMedial: toward the midline
5Figure 4.2: Terms for anatomical directions in the nervous system. In four-legged animals, dorsal and ventral point in the same direction for the head as they do for the rest of the body. However, humans’ upright posture has tilted the head, so the dorsal and ventral directions of the head are not parallel to those of the spinal cord.Fig. 4-2, p. 83
6Structure of the Vertebrate Nervous System The Nervous System is comprised of two major subsystems:The Central Nervous System (CNS)The Peripheral Nervous System (PNS)
7Figure 4.1: The human nervous system. Both the central nervous system and the peripheral nervous system have major subdivisions. The closeup of the brain shows the right hemisphere as seen from the midline.
8Structure of the Vertebrate Nervous System The Central Nervous System consists of:BrainSpinal Chord
9Structure of the Vertebrate Nervous System The spinal cord is the part of the CNS found within the spinal column and communicates with the sense organs and muscles below the level of the head.The Bell-Magendie law states the entering dorsal roots carry sensory information and the exiting ventral roots carry motor information.The cell bodies of the sensory neurons are located in clusters of neurons outside the spinal cord called dorsal root ganglia.
10Figure 4.3: Diagram of a cross-section through the spinal cord. The dorsal root on each side conveys sensory information to the spinal cord; the ventral root conveys motor commands to the muscles.Fig. 4-3, p. 84
11Structure of the Vertebrate Nervous System The spinal cord is comprised of:grey matter-located in the center of the spinal cord and is denseley packed with cell bodies and dendriteswhite matter – composed mostly of myelinated axons that carries information from the gray matter to the brain or other areas of the spinal cord.Each segment sends sensory information to the brain and receives motor commands.
12Spinal Cord Runs through the vertebral canal Extends from foramen magnum to second lumbar vertebraRegionsCervicalThoracicLumbarSacralCoccygealGives rise to 31 pairs of spinal nervesAll are mixed nervesNot uniform in diameterCervical enlargement: supplies upper limbsLumbar enlargement: supplies lower limbsConus medullaris- tapered inferior endEnds between L1 and L2Cauda equina - origin of spinal nerves extending inferiorly from conus medullaris.Spinal Cord
13Meninges Connective tissue membranes Spaces Dura mater: outermost layer; continuous with epineurium of the spinal nervesArachnoid mater: thin and wispyPia mater: bound tightly to surfaceForms the filum terminaleanchors spinal cord to coccyxForms the denticulate ligaments that attach the spinal cord to the duraSpacesEpidural: external to the duraAnesthestics injected hereFat-fillSubdural space: serous fluidSubarachnoid: between pia and arachnoidFilled with CSFMeninges
14Cross Section of Spinal Cord Anterior median fissure and posterior median sulcusdeep clefts partially separating left and right halvesGray matter: neuron cell bodies, dendrites, axonsDivided into hornsPosterior (dorsal) hornAnterior (ventral) hornLateral hornWhite matterMyelinated axonsDivided into three columns (funiculi)VentralDorsallateralEach of these divided into sensory or motor tractsCross Section of Spinal Cord
15Cross section of Spinal Cord Commissures: connections between left and right halvesGray with central canal in the centerWhiteRootsSpinal nerves arise as rootlets then combine to form dorsal and ventral rootsDorsal and ventral roots merge laterally and form the spinal nerve
16Organization of Spinal Cord Gray Matter Recall, it is divided into hornsDorsal, lateral (only in thoracic region), and ventralDorsal half – sensory roots and gangliaVentral half – motor rootsBased on the type of neurons/cell bodies located in each horn, it is specialized further into 4 regionsSomatic sensory (SS) - axons of somatic sensory neuronsVisceral sensory (VS) - neurons of visceral sensory neur.Visceral motor (VM) - cell bodies of visceral motor neuronsSomatic motor (SM) - cell bodies of somatic motor neurons
18White Matter in the Spinal Cord Divided into three funiculi (columns) – posterior, lateral, and anteriorColumns contain 3 different types of fibers (Ascend., Descend., Trans.)Fibers run in three directionsAscending fibers - compose the sensory tractsDescending fibers - compose the motor tractsCommissural (transverse) fibers - connect opposite sides of cord
19White Matter Fiber Tract Generalizations Pathways decussate (most)Most consist of a chain of two or three neuronsMost exhibit somatotopy (precise spatial relationships)All pathways are pairedone on each side of the spinal cord
21Descending (Motor) Pathways Descending tracts deliver motor instructions from the brain to the spinal cordDivided into two groupsPyramidal, or corticospinal, tractsIndirect pathways, essentially all othersMotor pathways involve two neuronsUpper motor neuron (UMN)Lower motor neuron (LMN)aka ‘anterior horn motor neuron” (also, final common pathway)
22Pyramidal (Corticospinal) Tracts Originate in the precentral gyrus of brain (aka, primary motor area)I.e., cell body of the UMN located in precentral gyrusPyramidal neuron is the UMNIts axon forms the corticospinal tractUMN synapses in the anterior horn with LMNSome UMN decussate in pyramids = Lateral corticospinal tractsOthers decussate at other levels of s.c. = Anterior corticospinal tractsLMN (anterior horn motor neurons)Exits spinal cord via anterior rootActivates skeletal musclesRegulates fast and fine (skilled) movements
23Corticospinal tracts Location of UMN cell body in cerebral cortex Decussation of UMN axon in pyramids or at level of exit of LMNSynapse of UMN and LMN occurs in anterior horn of s.c.LMN axon exits via anterior root
24Extrapyramidal Motor Tracts Includes all motor pathways not part of the pyramidal systemUpper motor neuron (UMN) originates in nuclei deep in cerebrum (not in cerebral cortex)UMN does not pass through the pyramids!LMN is an anterior horn motor neuronThis system includesRubrospinalVestibulospinalReticulospinalTectospinal tractsRegulate:Axial muscles that maintain balance and postureMuscles controlling coarse movements of the proximal portions of limbsHead, neck, and eye movement
25Extrapyramidal TractNote: 1. UMN cell body location 2. UMN axon decussates in pons 3. Synapse between UMN and LMNoccurs in anterior horn of sc3. LMN exits via ventral root4. LMN axon stimulates skeletalmuscle
26Extrapyramidal (Multineuronal) Pathways Reticulospinal tracts – originates at reticular formation of brain; maintain balanceRubrospinal tracts – originate in ‘red nucleus’ of midbrain; control flexor musclesTectospinal tracts - originate in superior colliculi and mediate head and eye movements towards visual targets (flash of light)
27Main Ascending Pathways The central processes of first-order neurons branch diffusely as they enter the spinal cord and medullaSome branches take part in spinal cord reflexesOthers synapse with second-order neurons in the cord and medullary nuclei
28Three Ascending Pathways The nonspecific and specific ascending pathways send impulses to the sensory cortexThese pathways are responsible for discriminative touch (2 pt. discrimination) and conscious proprioception (body position sense).The spinocerebellar tracts send impulses to the cerebellum and do not contribute to sensory perception
29Nonspecific Ascending Pathway Include the lateral and anterior spinothalamic tractsLateral: transmits impulses concerned with pain and temp. to opposite side of brainAnterior: transmits impulses concerned with crude touch and pressure to opposite side of brain1st order neuron: sensory neuron2nd order neuron: interneurons of dorsal horn; synapse with 3rd order neuron in thalamus3rd order neuron: carry impulse from thalamus to postcentral gyrus
30Specific and Posterior Spinocerebellar Tracts Dorsal Column Tract1. AKA Medial lemniscal pathway2. Fibers run only in dorsal column3. Transmit impulses from receptors inskin and joints4. Detect discriminative touch andbody position sense =proprioception1st O.N.- a sensory neuronsynapses with 2nd O.N. in nucleus gracilis and nucleus cuneatus of medulla2nd O.N.- an interneurondecussate and ascend to thalamus where it synapses with 3rd O.N.3rd-order (thalamic neurons)transmits impulse to somato-sensory cortex (postcentral gyrus)Spinocerebellar TractTransmit info. about trunk and lower limb muscles and tendons to cerebellumNo conscious sensation
31Spinal Cord Trauma and Disorders Severe damage to ventral root results in flaccid paralysis (limp and unresponsive)Skeletal muscles cannot move either voluntarily or involuntarilyWithout stimulation, muscles atrophy.When only UMN of primary motor cortex is damagedspastic paralysis occurs - muscles affected by persistent spasms andexaggerated tendon reflexesMuscles remain healthy longer but their movements are no longersubject to voluntary control.Muscles commonly become permanently shortened.Transection (cross sectioning) at any level results in total motor andsensory loss in body regions inferior to site of damage.If injury in cervical region, all four limbs affected (quadriplegia)If injury between T1 and L1, only lower limbs affected (paraplegia)
32Spinal Cord Trauma and Disorders Spinal shock - transient period of functional loss that follows the injuryResults in immediate depression of all reflex activity caudal to lesion.Bowel and bladder reflexes stop, blood pressure falls, and all muscles (somatic and visceral) below the injury are paralyzed and insensitive.Neural function usually returns within a few hours following injuryIf function does not resume within 48 hrs, paralysis is permanent.Amyotrophic Lateral Sclerosis (aka, Lou Gehrig’s disease)Progressive destruction of anterior horn motor neurons and fibers of thepyramidal tractsLose ability to speak, swallow, breathe.Death within 5 yrsCause unknown (90%); others have high glutamate levelsPoliomyelitisVirus destroys anterior horn motor neuronsVictims die from paralysis of respiratory musclesVirus enters body in feces-contaminated water (public swimming pools)
33Structure of the Vertebrate Nervous System The Peripheral Nervous System (PNS) is comprised of the:Somatic Nervous SystemAutonomic Nervous System
34Structure of the Vertebrate Nervous System The Somatic Nervous System consists of nerves that:Convey sensory information to the CNS.Transmit messages for motor movement from the CNS to the body.
35Structure of the Vertebrate Nervous System The autonomic nervous system regulates the automatic behaviors of the body (heart rate, blood pressure, respiration, digestion etc).The autonomic nervous system can be divided into two subsystems:The Sympathetic Nervous System.The Parasympathetic Nervous System.
37Structure of the Vertebrate Nervous System The sympathetic nervous system is a network of nerves that prepares the organs for rigorous activity:increases heart rate, blood pressure, respiration, etc. (“fight or flight” response)comprised of ganglia on the left and right of the spinal cordmainly uses norepinephrine as a neurotransmitter at the postganglionic synapses.
38Structure of the Vertebrate Nervous System The parasympathetic nervous system facilitates vegetative, nonemergency responses by the organs.decreases functions increased by the sympathetic nervous system.comprised of long preganglion axons extending from the spinal cord and short postganglionic fibers that attach to the organs themselves.dominant during our relaxed states.
39Structure of the Vertebrate Nervous System Parasympathetic Nervous System (cont’d)Postganglionic axons mostly release acetylcholine as a neurotransmitter
40Structure of the Vertebrate Nervous System The brain can be divided into three major divisions:Hindbrain.Midbrain.Forebrain.
42Structure of the Vertebrate Nervous System The Hindbrain consists of the:Medulla.Pons.Cerebellum.Located at the posterior portion of the brainHindbrain structures, the midbrain and other central structures of the brain combine and make up the brain stem.
43Figure 4.8: The human brainstem. This composite structure extends from the top of the spinal cord into the center of the forebrain. The pons, pineal gland, and colliculi are ordinarily surrounded by the cerebral cortex.
44Structure of the Vertebrate Nervous System The medulla:Located just above the spinal cord and could be regarded as an enlarged extension of the spinal cord.responsible for vital reflexes such as breathing, heart rate, vomiting, salivation, coughing and sneezing.Cranial nerves allow the medulla to control sensations from the head, muscle movements in the head, and many parasympathetic outputs to the organs.
46Figure 4.9: Cranial nerves II through XII. Cranial nerve I, the olfactory nerve, connects directly to the olfactory bulbs of the forebrain. (Source: Based on Braus, 1960)
47Structure of the Vertebrate Nervous System Ponslies on each side of the medulla (ventral and anterior).along with the medulla, contains the reticular formation and raphe system.works in conjunction to increase arousal and readiness of other parts of the brain.
48Structure of the Vertebrate Nervous System The reticular formation:descending portion is one of several brain areas that control the motor areas of the spinal cord.ascending portion sends output to much of the cerebral cortex, selectively increasing arousal and attention.The raphe system also sends axons to much of the forebrain, modifying the brain’s readiness to respond to stimuli.
49Structure of the Vertebrate Nervous System The Cerebellum:a structure located in the hindbrain with many deep folds.helps regulate motor movement, balance and coordination.is also important for shifting attention between auditory and visual stimuli.
50Structure of the Vertebrate Nervous System The midbrain is comprised of the following structures:Tectum – roof of the midbrainSuperior colliculus &inferior colliculus– swellings on each side of the tectum and routes for sensory informationTagmentum- the intermediate level of the midbrainSubstantia nigra - gives rise to the dopamine-containing pathway
51Structure of the Vertebrate Nervous System The forebrain is the most anterior and prominent part of the mammalian brain and consists of two cerebral hemispheresConsists of the outer cortex and subcortical regions.outer portion is known as the “cerebral cortex”.Receives sensory information and controls motor movement from the opposite (contralateral) side of the body.
52Figure 4.10: A sagittal section through the human brain. (Source: After Nieuwenhuys, Voogd, & vanHuijzen, 1988)Fig. 4-10, p. 90
53Structure of the Vertebrate Nervous System Subcortical regions are structures of the brain that lie underneath the cortex.Subcortical structures of the forebrain include:Thalamus - relay station from the sensory organs and main source of input to the cortex.Basal Ganglia - important for certain aspects of movement.
54Structure of the Vertebrate Nervous System The limbic system consists of a number of other interlinked structures that form a border around the brainstem.Includes the olfactory bulb, hypothalamus, hippocampus, amygdala, and cingulate gyrus of the cerebral cortexassociated with motivation, emotion, drives and aggression.
55Figure 4.12: The limbic system is a set of subcortical structures that form a border (or limbus) around the brainstem.Fig. 4-12, p. 91
56Structure of the Vertebrate Nervous System HypothalamusSmall area near the base of the brain.Conveys messages to the pituitary gland to trigger the release of hormones.Associated with behaviors such as eating, drinking, sexual behavior and other motivated behaviors.Thalamus and the hypothalamus together form the “diencephalon”.
57Figure 4.14: Routes of information from the thalamus to the cerebral cortex. Each thalamic nucleus projects its axons to a different location in the cortex. (Source: After Nieuwenhuys, Voogd, & vanHuijzen, 1988)Fig. 4-14, p. 92
58Structure of the Vertebrate Nervous System Pituitary gland - hormone producing gland found at the base of the hypothalamus.Basal Ganglia - comprised of the caudate nucleus, the putamen and the globus pallidus.Associated with planning of motor movement, and aspects of memory and emotional expression .
59Fig. 4-15, p. 93 Figure 4.15: The basal ganglia. The thalamus is in the center, the basal ganglia are lateral to it, and the cerebral cortex is on the outside. (Source: After Nieuwenhuys, Voogd, & vanHuijzen, 1988)Fig. 4-15, p. 93
60Structure of the Vertebrate Nervous System Basal forebrain is comprised of several structures that lie on the dorsal surface of the forebrain.Contains the nucleus basalis:receives input from the hypothalamus and basal gangliasends axons that release acetylcholine to the cerebral cortexKey part of the brains system for arousal, wakefulness, and attention
61Fig. 4-16, p. 93 Figure 4.16: The basal forebrain. The nucleus basalis and other structures in this area send axons throughout the cortex, increasing its arousal and wakefulness through release of the neurotransmitter acetylcholine. (Source: Adapted from “Cholinergic Systems in Mammalian Brain and Spinal Cord,” by N. J. Woolf, Progress in Neurobiology, 37, pp. 475–524, 1991)Fig. 4-16, p. 93
62Structure of the Vertebrate Nervous System Hippocampus is a large structure located between the thalamus and cerebral cortex.critical for storing certain types of memory.
63Structure of the Vertebrate Nervous System The central canal is a fluid-filled channel in the center of the spinal cord.The ventricles are four fluid-filled cavities within the brain containing cerebrospinal fluid.Cerebrospinal fluid is a clear fluid similar to blood plasma found in the brain and spinal cord:Provides “cushioning” for the brain.Reservoir of hormones and nutrition for the brain and spinal cord.
64Fig. 4-17, p. 94 Figure 4.17: The cerebral ventricles. (a) Diagram showing positions of the four ventricles. (b) Photo of a human brain, viewed from above, with a horizontal cut through one hemisphere to show the position of the lateral ventricles. Note that the two parts of this figure are seen from different angles. (Photo courtesy of Dr. Dana Copeland)Fig. 4-17, p. 94
65The Cerebral CortexThe cerebral cortex is the most prominent part of the mammalian brain and consists of the cellular layers on the outer surface of the brain.comprised of grey matter and white matter.divided into two halvesjoined by two budndles of axons called the corpus callosum and the anterior commissure.more highly developed in humans than other species.
66The Cerebral Cortex Organization of the Cerebral Cortex: Contains up to six distinct laminae (layers) that are parallel to the surface of the cortex.Cells of the cortex are also divided into columns that lie perpendicular to the laminae.Divided into four lobes: occipital, parietal, temporal, and frontal.
68Fig. 4-22, p. 98 Figure 4.22: Columns in the cerebral cortex. Each column extends through several laminae. Neurons within a given column have similar properties. For example, in the somatosensory cortex, all the neurons within a given column respond to stimulation of the same area of skin.Fig. 4-22, p. 98
69The Cerebral CortexThe four lobes of the cerebral cortex include the following:Occipital lobeParietal lobeTemporal lobeFrontal lobe
70Fig. 4-23, p. 99 Figure 4.23: Areas of the human cerebral cortex. (a) The four lobes: occipital, parietal, temporal, and frontal. (b) The primary sensory cortex for vision, hearing, and body sensations; the primary motor cortex; and the olfactory bulb, a noncortical area responsible for the sense of smell. (Source for part b: T. W. Deacon, 1990)Fig. 4-23, p. 99
71The Cerebral Cortex Occipital lobe: Located at the posterior end of the cortex.Known as the striate cortex or the primary visual cortex.Highly responsible for visual input.Damage can result in cortical blindness.
72The Cerebral Cortex Parietal lobe Contains the postcentral gyrus (aka “primary somatosensory cortex”) is the primary target for touch sensations, and information from muscle-stretch receptors and joint receptors.Also responsible for processing and integrating information about eye, head and body positions from information sent from muscles and joints.
73Figure 4.24: Approximate representation of sensory and motor information in the cortex. (a) Each location in the somatosensory cortex represents sensation from a different body part. (b) Each location in the motor cortex regulates movement of a different body part. (Source: Adapted from The Cerebral Cortex of Man by W. Penfield and T. Rasmussen, Macmillan Library Reference. Reprinted by permission of The Gale Group.)Fig. 4-24, p. 99
74The Cerebral Cortex Temporal Lobe Located on the lateral portion of the hemispheres near the temples.Target for auditory information and essential for processing spoken language.Also responsible for complex aspects of vision including movement and some emotional and motivational behaviors.
75The Cerebral Cortex The Frontal lobe: Contains the prefrontal cortex and the precentral gyrus.Precentral gyrus is also known as the primary motor cortex and is responsible for the control of fine motor movement.Contains the prefrontal cortex- the integration center for all sensory information and other areasof the cortex. (most anterior portion of the frontal lobe)
76Figure 4.25: Species differences in prefrontal cortex. Note that the prefrontal cortex (blue area) constitutes a larger proportion of the human brain than of these other species. (Source: After The Prefrontal Cortex by J. M. Fuster, 1989, Raven Press. Reprinted by permission.)Fig. 4-25, p. 100
77The Cerebral Cortex The Prefrontal cortex (cont’d) responsible for higher functions such as abstract thinking and planning.responsible for our ability to remember recent events and information (“working memory”).allows for regulation of impulsive behaviors and the control of more complex behaviors.
78The Cerebral CortexVarious parts of the cerebral cortex do not work independently of each other.All areas of the brain communicate with each otherThe binding problem refers to the question of how the visual, auditory, and other areas of the brain produce a perception of a single object.perhaps the brain binds activity in different areas when they produce synchronous waves of activity