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Ted Petit

PSYB65 Human Brain & Behaviour Lecture 2 –Function of the cerebral hemispheres, brain vascular supply, cerebral ventricles, cerebral coverings (Chapters 2, 14) Monday, September 17, 2012 Today’s Lecture:  Organization and structure of the human brain, especially the cortex  Different lobes of the cerebral cortex  Function of the lobes and the functions within each lobe  Inner structure of the brain such as the ventricles  Outer structure surrounding the brain (meninges), which are the coverings of the brain  Blood supply of the brain Introduction: Human Brain  As you move forward in the brain, the cortex is the newest evolutionarily  The cortex is NOT smooth for humans  There is some evolutionary pressure that wants humans to be smart  The cortex moves back smooth and covers the whole brain because there are no space , and it folds on itself; allthe cells line the little grooves and this leads to mountains and valleys (becomes NOT smooth) you can tell where each function ends and begins Basic Structure of the Brain  Sulcus/Sulci o The valleys in the brain o If there are huge (major one), it’s called fissure  Gyrus/Gyri o The individual mountains in the brain  SULCI (valleys) and GYRUS (mountains) o If you look at the top of the brain, the 2 sides of the brain are not connected from the top view, but they actually are connected How the brain is divided  The brain is divided into two HEMISPHERES (right and left), but they are not indentical  They are connected by a FIBER PATHWAY  The left controls the right and the rightcontrols the left o Right hemisphere controls/receives information from the left side of the body o Left hemisphere controls/receives information from the right side of the body  Example: person paralyzed on the right side due to brain damage on the left hemisphere  Incorrect terms: Left Brain, Right Brain can be used, but NOT the official terms to identify the left and right hemispheres The Hemispheres  The two sides are divided by the longitudinal fissures which divide the two hemispheres (left and right) o Also known as longitudinal sulcus  The two hemispheres areconnected  SLIDE2: CORPUS CALLOSUM the fibres move from the left to the right side and vise versa o Fibre pathway that connect the two hemispheres o Send fibre pathway which cross over the corpus callosum o Each part of the right hemisphere is connected to the adjacent (similar) part of the opposite hemisphere o Example: right occipital lobe is connected to the left occipital lobe o Excellent communication between each side of the hemispheres  The central portion of one side is connected to the similar side on the other SULCI  There are 3 main SULCI  when they are large  they are called FISSURES. o LONG TUDINAL fissure is from the right to left.  Seperates hemishpheres into left and right o CENTRAL fissure (or central sulcus): divides the brain in half from front to back, divides frontal lobe from the paritial lobe, anterior from posterior o SYLIAN (or LATERAL): it separates the frontal and the parietal  Runs up the sideof the brain  Separates the temporal lobe The Lobes within the Brain  Cerebral cortex divided into 4 lobes: 1. FRONTAL(in the front), 2. PARIETAL (behind the central sulci)(LOOK at the diagram,slide1), 3. OCCIPITAL(the very back), 4. TEMPORAL Function of the Lobe  Each lobe has one main primary function and a primary cortex (a major function) and an association cortex within each lobe  In each lobe, it is divided into two types of cortex (tissue): 1. PRIMARY Cortex (for each lobe): is the primary receptive(receiving) info from the outside (hot,cold,etc etc) o Responsible for performing basic input/out function o It is the area that is responsible for the primary input/output function within that lobe o Receives sensory information  Example: burn your finger and it processes what you do (move your finger away from the burning sensation  Each lobe has primary receptors 2. ASSOCIATIONAL Cortex: processes the higher order computing, it is the newest (most recent) evolutionarily there is a greater percentage of association cortex compared to primary cortex for humans and other primates. More evolved species have more of cortex. o Because people are trying to understand how the cortex works Brodmann’s numbers labels the functions on the brain. o Higher order functions, bigger than primary cortex o More complex orders o Each lobe has one associational cortex o More recently evolved o Thought processing part, whereas the primary cortex does basic input/output functions o More evolved the organism, more associational cortex there is o Higher percentage or ratio of associational cortex, much more intelligent  Example: humans have a small primary cortex and a huge associational cortex  Example: simple organisms such as frogs tend to have more primary cortex rather than associational cortex because they can’t process much high order of thoughts or memory  MOTOR cortex (for each lobe): controls the muscles, the output go to nerve, and to muscle to your hand. MUSCLE OUTPUT o Sensory input motor output. Brodmann: Organizing the Brain using numbered mapped concept (slide 3)  Mapped the brain  Placed numbers on different parts of the brain  For example: the occipital lobe is area 17  Area 4 and 6 is the primary area of the frontal cortex  Area 3,1,2  stripe of the parietal lobe  Area 17: the occipital lobe the info from eyes comes here. 17 is the primary area where the info from the eyes comes to  41: deals with hearing, the primary receptive area in the temporal lobe, info from ears goes here  How did Brodmann number them?  randomly Lobes of the Brain 1. Frontal Lobe (Slide 4 above)  Primary function: primarily involved in motor (muscle) control; walk, type, turn your head .blink your eyes o Involved in planning movements and inhibition of inappropriate behaviours  Associational cortex: o Long term planning of movement (ie: go to university in order to get an education and get a decent job in the future)  It starts at the most anterior part of the brain and it continues till the CENTRAL SULCUS (the division of the brain in half; valley)the PRECENTRAL GYRUS’s primary function is that it controls motor movements  When you want to move your arm, it starts in the FRONTAL lobe  As you move more anterior in the frontal lobe, it is involved in planning you won’t be anywhere without your frontal lobe  And inhibits inappropriate behaviours! OH SNAP.  The primary cortex is the PRIMARY MOTOR (get words out of your mouth; move, walk) o STRIP(Broadmann’s area 4 and 6) it is located in the PRECENTRAL GYRUS(mountain)  primary motor strip of the primary cortex  All the stuff in front of that strip is the associational cortex (planning long-term  Primary cortex deals with how you move, walk/run, type, turn head, blink  Associational cortex deals with planning, inhibition of appropriate behaviour, long-term planning  The way the motor strip is organized is not random  o Slide 5: the blue strip is the motor striparea 4 and 6  As you move away from the motor cortex(dark blue)(slide5)you move into the association cortex(lighter blue) the further you move away from the motor cortex(further anterior) it is higher in function (more planning) Motor Humunculous (Slide 6 below)  If you cut the strip if you stimulate close to the central sulcus, it causes twitching of the foot HUMUNCULOUS (little man) in the brain  Neurons in the different parts of the brain arrive at the cortex at different times and they layer upon each other  In the adult, the motor humunculous, if we take a slice in the middle of the motor strip (left image) and you bring it out and look at it (right image; corpus callosum; connects other hemispheres),  The part that controls the feet, and if you go up the brain, it’s the part that controls the knees, main torso, then its the part that controls your arm (where the neurons are found that control your arm), further down its the neurons that control your hands (more space devoted to the hands rather than the knees)  Side of the strips further down shows the part that controls your mouth and
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