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Chapter 3

Chapter 3 Neuropsychology Textbook Notes.docx

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McMaster University
Ayesha Khan

Neuropsychology Textbook Notes Fundamentals for Human Neuropsychology: Sixth Edition Chapter 3:Organization of the Nervous System Neuroanatomy: Finding your way around the brain -most brains structures are common amongst all mammals -100 years ago Lorente de No, made the first detailed description of a brain (mouse brain through a microscope) Describing Locations in the Brain Relative to Body Rostral- beak (latin) Caudal-tail (latin) Dorsal- back (latin)- top= superior Ventral-stomach (latin)-bottom-inferior *these descriptions of brain means the part is located towards the above body parts Relative to face Dorsal-top Ventral-bottom Anterior-front Posterior-back Lateral-sides Medial-middle Direction of cut (brain) Coronal- vertical cut (crown and down) Horizontal- horizontal cut Sagittal- hotdog cut, across mid-line length of brain -nervous system is symmetrical (left and right side) Ipsilateral: structures that lie on the same side of brain Contralateral: structures that lie on opposite sides of brain Bilateral: structures that lie on both of EACH side of the brain Proximal: structures close in distance Distal: structure far in distance Afferent: movement toward brain (central nervous system) Example: sensory info to brain Efferent: movement away from brain (peripheral nervous system)motor pathway to body -humans stand upright, whereas animals tend to have quadruped posture… likewise brain has similar spatial orientation, BUT not spinal cord -dorsal and ventral in quadrupeds= anterior and posterior in humans AWonderland of Nomenclature Ex. Precentral gyrus Other names: “the motor strip” “Jackson’s strip” -primary motor cortex (M1) -damaged by stroke in a patient = reduced motor ability An Overview of Nervous System Structure and Function • Central nervous system (CNS): brain + spinal cord • Peripheral nervous system (PNS): everything else  Somatic NS: cranial nerves+ spinal nerves -produces movement, transmits sensory info to CNS (5 senses)  Autonomic NS: sympathetic division + parasympathetic system -sympathetic: fight or flight -parasympathetic: rest and digest Support and Protection CNS is protected in 4 ways 1.Bone encasement: skull to brain, as vertebrae is to spinal cord Peripheral lies outside, regeneration capability (growing new axons and dendrites) 2. Triple-Layered Membranes, meninges: Outer: dura mater (tough, double layer) Middle: arachnoid membrane (thin, contours brain) Inner: pia mater (tough, clings to brain) 3. Cerebrospinal fluid: circulates in 4 ventricles of brain, spinal column, subarachnoid space -cushions CNS from shock and impacts -continuously made and drained circulatory system -outflow blockage= hydrocephalus (water brain)  retardation or death 4. Blood-brain barrier: CNS protected from chemicals by capillary cells forming tight junctions, to avoid permeability of harmful substances into CNS tissue Blood Supply -brain blood supply: 2 internal carotid arteries, 2 vertebral arteries (course up side of neck) -all four arteries connect at bases of brain, branch off into smaller arteries (irrigate the brainstem and cerebellum), then form 3 arteries that irrigate the forebrain -anterior cerebral artery (ACA) irrigates medial +dorsal (cortex) -middle cerebral artery (MCA) irrigates lateral (cortex) -posterior cerebral artery (PCA) irrigates ventral + posterior (cortex) Veins -returns deoxygenated blood to heart to re-oxygenate = external and internal cerebral and cerebellar veins Neurons and Glia -brain origin= neural stem cell (aka germinal cell) -stem cell is capable of self-renewal -when sem cells divides into 2 new cells, 1 dies (in adult) to maintain constant # -embryo: stem cells make progenitor cellsmake blasts (non-dividing) -blasts: some become neurons, others become glia -neurons differ (mainly) in size, length/branching of axons, complexities of dendritic activity 3 Types Of Neurons • Sensory Neurons -afferent Examples:  Bipolar neuron (retina): dendrite on one side, axon on other  Somatosensory (skin, muscle): dendrite and axon connected for speed of info transmission (no need to go through cell body) • Interneurons -associate sensoryAND motor activity in CNS Ex. Stellate cell(thalamus), pyramidal cell (cortex), purkinje cell (cerebellum) -branched dendrites, one axon • Motor neurons -efferent Ex. Motor neuron -brain stem location: to facial muscles -spinal cord location: to body muscles 5 Types of Glial Cells • Ependymal cell -round, small, secrets cerebrospinal fluid (CSF) • Astrocyte -star shape, symmetrical, nutritive and support • Microglial -small, mesodermally derived, defensive • Oligodendroglial -asymmetrical, forms myelin around axon in CNS • Schwann -asymmetrical, myelin in PNS Gray, White and Reticular Matter Gray matter: -“communities” -colour from blood vessels and neuronal cell bodies that are predominant in area White matter: “roads” -comprised mainly of axons extending to connect with other neurons -covered in fatty substance (insulating layer of glial cells) to give white colouration Reticular Matter: “suburbia” -mixture of cell bodies and axons = gray and white net appearance Layers, Nuclei, Nerves and Tracts Tract: large collection of axons projecting to/away from nucleus/layer in CNS (aka fiber pathway) -Tracts carry info within CNS Ex. Optic tract Nerves: fibers & fiber pathways the enter/leave CNS -however once they are in CNS, they are called TRACTS Ex.Auditory nerve The Origin and Development of the Central Nervous System • embryonic vertebrate brain: 3 chambers -adult fish, amphibian and reptile brain equivalent 1. prosencephalon (“front brain”)= olfaction 2. mesencephalon (“middle brain”)= vision, audition 3. rhombencephalon (hindbrain)= movement/balance • Mammalian embryos  prosencephalon forms cerebral hemispheres (telencephalon- “endbrain”) -remainder of prosencephalon  diencephalon “between brain” (includes thalamus(  back of brain metencephalon “across brain” + myelencephalon “spinal brain” -human brain is more complex than mammalian brain -3 main subdivisions of CNS: forebrain, brainstem, spinal cord= levels of function (newer parts replace function of older parts) BRAIN -begins as tube, hollow, 4 pockets = ventricles  lateral ventricles (1,2): C-shaped, under cerebral cortex  (3.4) extend into brainstem and spinal cord -all ventricles files with cerebrospinal fluid th -fluid flows from lateral4 ventriclecirculatory system The Spinal Cord -simplest part of CNS Spinal-Cord Structure and Spinal Nerves 5 regions of spinal nerves 1. cervical – 8 nerves 2. thoracic- 12 3. lumbar-5 4. sacral-5 5. coccygeal segment -segments are known as dermatomes (“skin cuts”) -each spinal segment is connected by SNS fibers tot eh body dermatome of the same number Dorsal root: fibers that converge as they enter spinal cord from dorsal part (posterior in humans), afferent -dorsal tracts= sensory Ventral root: fibers that leave spinal cord from ventral part (anterior in humans), efferent -ventral tract= motor -outer part of Spinal Cord (SC)= white matter -inner part of SC =gray matter, butterfly shape, ventral routes Bell-Megendie law: dorsal part of SC =sensory, ventral= motor -Magendie’s experiment has been called the most important ever conducted on the nervous system, allows neurologists to distinguish sensory
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