Unit 5 Lecture 2 I The Brain A Structure i Embryological development procedures 3 regions of enlargements of the neural tube ii Forebrain Telencephalon and Diencephalon 1 Cerebral hemispheres 2 Basal nuclei 3 Diencephalon thalamus and hypothalamus iii Midbrain Mesencephalon iv Hindbrain Metacephalon 1 Pons 2 Cerebellum 3 Medulla Oblongata Myelencephalon v Brain Stem 1 Midbrain 2 Hindbrain except cerebellum II Meninges 3 layers of connective tissue separated by spaces or potential spaces i Protect spinal cord and brain A Epidural Space ONLY IN SPINAL CORD tough outer layer B Dura Mater C Sub Dural space D Arachnoid Mater E Subarachnoid space beneath Dura Mater thin transparent middle layer beneath arachnoid i Cerebrospinal fluid CSF circulates F Pia Mater transparent inner layer i Adheres to brain and spinal cord G Cerebrospinal Fluid CSF clear fluid that protect brain and spinal cord i Similar to blood plasma 1 More Vitamin C more Na Cl and H ions than blood plasma 2 Less protein Ca2 and K ions 3 pH of CSF effects breathing and cerebral blood flow ii Formed in Choroid Plexuses specialized capillaries I centricle s of roof 1 Surrounded by ependymal cells 1 layer a Fluid from blood stream is filtered as it moves through ependymal cells b Enters ventricles as CSF iii Constantly produced and reabsorbed 500mL daily 10 160 mL circulating 1 Circulates through ventricles and subarachnoid space covers brain and cord iv Functions 1 Hydraulic shock absorber 2 Transportation system H Ventricles 4 interconnected cavities within cerebral hemispheres and brain stem 1 Continuous with central canal 2 Allows continuous circulation of CSF III CSF Circulation Interventricular foramen i Lateral ventricle ii iii 3rd ventricle iv Cerebral aqueduct v 4th ventricle vi Central canal of cord circulates around cord vii Enters Sub arachnoid space through openings in roof of 4th ventricle B CSF continuously produced C Reabsorbed into blood through arachnoid villus i Project into blood filled dural sinuses IV Blood Brain Barrier A Protects brain B Helps maintain stable internal environment C Controls passage of materials from blood to cells in brain D Controlled by i Tight junctions seal endothelial cells of brain capillaries together become least permeable in body ii Thick basement membrane basal Lamina 1 Surrounds external surface of capillaries iii Feet of astrocyte processes cling to capillaries E Some materials can pass through barrier glucose fats fatty acids alcohol O2 CO2 F Can NOT pass most drugs metabolic wastes small amino acids some toxins V Cerebral Hemispheres or Cerebrum A Cerebral Cortex thin layer of gray matter 75 of all neuron cell bodies in B CNS Inner region of white matter bundles of myelinated nerve fibers which connect neuron bodies to other parts of CNS C 3 Functional Groups of Fibers i Commissural Fibers 1 Connect structures in each side or hemisphere brain or cord right and left sides 2 Examples a Gray commissure of cord b Corpus callosum right and left sides of cerebrum c Massa Intermedia right and left sides of thalamus ii Association Fibers 1 Connect areas within the same hemisphere 2 Long connect between lobes 3 Short connect between gyri within same lobe iii Projection fibers 1 Connect cerebrum with lower structures a Internal capsule to and from cerebrum open V or Boomerang Shape 2 Tracts can be specifically located D Lobes of Cerebral Hemispheres correspond to cranial bones i Frontal Parietal Temporal Occipital ii iii Surface of lobes Insular not visible from surface deep to lateral sulcus 1 Gyri gyrus sulci sulcus grooves or depressions ridges or convolutions separated by a Both arranged in distinct patterns with specific names 2 Precentral gyrus postcentral gyrus central sulcus lateral sulcus transverse sulcus iv All mapped for function 1 Highly organized 2 Sensory and motor function for opposite side of body a Left hemisphere 90 dominant for i Language Activities ii Analytical reasoning speech writing reading math and science b Right hemisphere non dominate i Non verbal functions patterns or spatial relationships Interpreting musical 1 Imagination artistic skills non verbal visual experiences 3 Cortex involved with consciousness a Perception of sensations i Voluntary motor control ii Higher mental processing memory logic judgment b Other regions have specific functions 4 Occipital vision 5 Frontal higher mental functions 6 Pre central gyrus primary motor 7 Post central gyrus sensory v Extensive Cortex Mapping beginning in 19th century 1 Brodmann s areas original 47 50 areas now 200 2 Primary Motor Areas a Pre central gyrus initiates voluntary skeletal muscles contraction b Origin of corticospinal tracts c Broca s Motor Speech Area directs muscle of tongue throat and lips articulating words 3 Primary Sensory Areas a Post central gyrus information from receptors in skin and proprioceptors b Visual Cortex receives sensory input from retinas c Auditory Cortex receive input from hearing receptors in ear d Smell Uncus Olfactory i Medial and deep to temporal lobe e Taste or Gustatory area 4 Homunculis Depicts results of Motor and sensory cortexes a Caricature of body that is proportioned to represent extent of innervation of specific body areas b Size represents degree of representation large expression and sensation area large head and hands 5 Association areas anterior portion of frontal lobes a Lateral parietal temporal and occipital lobes b Functions analyze and interpret sensory experiences i Especially with memory reasoning verbalizing judgment emotional feelings ii Communicate with motor cortex for proper response c Frontal lobes prefrontal areas i Higher intellectual processes ii Concentration planning complex problem solving iii Anterior and inferior prefrontal areas control of emotional behavior d Parietal lobes meaning of sensory information i Aid in understanding speech ii Choosing words to express thoughts and feelings iii Awareness of body parts from posterior regions e Temporal lobes toward posterior ends of lateral of area fissures i Complex sensory experiences ii Needed to understand speech read printed words remember visual scenes and music written and spoken words f Occipital analyze visual patters iii Wernicke s Area speech area understanding i Combine vision with other senses g General interpretive area intersection of parietal temporal occipital i Primary role in complex thought processing