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Human Brain and Behaviour Lecture Notes Final.docx

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Ted Petit

Human Brain and Behaviour Lectures Lecture 1 September 10 , 2012  Nervous system: o Central nervous system = brain + spinal cord o Peripheral nervous system = nerves  Little difference between the brain and the spinal cord o They are one  3 major classifications of the brain: o Hindbrain  Medulla- responsible for basic life processes  Heartbeat, respiration…  If you damage this you're dead!  Cerebellum- sensory motor integration  Balance o Midbrain  Reticular formation  Damage to this = coma  Sleep wakeful dysfunctions o Forebrain  Thalamus (dorsal) top of head  Acts as a large relay center  Hypothalamus (ventral) below thalamus  Controls functions that keep the individual alive o Eating, drinking, fighting for food, sexual reproduction  Limbic System o Number of brain structures (not a single structure)  Hippocampus, amygdala  Deal with emotions/emotionality  Primitive organisms don‟t have one  Animals with larger limbic systems have increased emotional repertoire  i.e. dog vs turtle  cerebral cortex- part of forebrain o also known as „neo‟ cortex (newest part of brain)  dolphins have the biggest cortex o responsible for intellectual function Phylogenetic Development  cerebral cortex was a huge change in evolution allowing for intelligence  the size of a brain structure that controls a function is directly proportional to the need of that organism  ontogeny recapitulated phylogeny o your development mimics that of your development as an evolutionary species  most anterior structure of the brain= cortex o covers up the whole brain Triune theory of brain function  MacLean‟s theory  “3 brains in one” o 1. Reptilian Brain – brain stem  Controls basic life processes  Found even as far back as reptiles  We have not lost parts, we‟ve just added on o 2. Paleo-Mammalian/ Old Mammalian  Limbic system  Added on emotion o 3. New mammalian  Cerebral cortex Lecture 2 September 17 , 2012  Stroke/tumor in cerebral cortex or brain stem= death  Human brain is not smooth ; not enough space in the skull o Starts out smooth though turns wrinkly as it grows in the same space  1. Sulci (sulcus)- the „valleys‟ in the brain o If they‟re big= fissure  2. Gyri (gyrus) – the „mountains‟ in the brain  The brain is divided down the centre into two hemispheres (almost identical- right brain and left brain) o Right brain- controls left side/ receives sensory information from left o Left brain- control right side/receives info from right  Hemispheres are divided by the longitudinal fissure or „longitudinal sulcus‟  However, they are still connected via the corpus collosum o Each part of the hemisphere is connected with the adjacent part on the other hemisphere  There are 3 main sulci: o The longitudinal sulcus- divides hemispheres o The central sulcus- divides brain front to back (frontal lobe from parietal) o The sylvian sulcus or lateral sulcus- runs up the side of the brain; separates the temporal lobe  The cerebral cortex has 4 lobes o Each love has two different types of cortex  Primary- basic input/output function of that lobe, primary receiving area  Associational- higher order functioning, more complex. More recently evolved then more primitive organisms. Thought process and higher ratio of associational cortex to primary (in more evolved animals)  Broadman- mapped and numbered the brain The Lobes  FRONTAL LOBE o Starts in the front of the brain and goes back until it reaches the central suclus o Primary cortex function- motor (muscle) control…its what makes you move! o Planning and inhibition of inappropriate behaviour (delayed gratification) o Associational cortex function- long term planning (life goals) o Primary area: 4, 6 – broadman‟s area  Pre-central gyrus- right in front of central sulcus o Primary motor strip- everything in front of pre-central gyrus is associational  Not randomly places o Motor homunculus- „little man in the brain‟  Organization of brain function  PARIETAL LOBE o Starts at the central sulcus until it hits the occipital lobe o Primary cortex function- receive info from non-specialized sensory or somatosensory senses o Post-central gyrus is the primary strip  The rest is associational o Broadman areas 3,1,2 = primary somatosensory strip o Also has a homunculus o Genitals are on the sensory strip, don‟t need much motor control o In the homunculus, the pictures are big/small depending on how important that area is to humans o Associational cortex function: very complex, deals with body sensations (we‟ll return to this later)  OCCIPITAL LOBE o Just behind the parietal and temporal lobes o Primary function: receive and process info from the eyes (vision) o Broadman area 17= primary receptive area for vision o Uses vision to distinguish objects o Associational cortex function: higher order; understanding what the object is and what it does  TEMPORAL LOBE o Just below the sylvian fissure o Primary cortex function: hearing and listening  Receives info from ears o Uses audition primarily for speech o Primary receptive area = 41  Dorsal posterior portion of the lobe (back, top  The centre of the brain isn‟t solid o Cerebro-spinal fluid  Ventricles are continuous with the spinal/central canal o Lateral ventricles (2 of them)- one on each side of the hemispheres o Third ventricle- deethinside the thalamus, fluid flows through the cerebral aquaduct into the 4 ventricle o Fourth ventricle- found in the hindbrain near the cerebellum, connects to spinal canal  Squished ventricles can look like Alzheimer‟s or dementia How the blood gets to the brain  Internal caroid artery- main supply of blood into the brain or the vertebral artery.  2 vertebral arteries join together at the base of the brain to form the basilar artety  Comes together at the circle of willis o Like a roundabout o Separates basilar and caroid artery o Prevents damage because if the right/left side loses blood from a tumor or plaque, blood from the other side can go to the area that is lacking blood  Circle of willis arteries (one on each side) o Anterior cerebral artery  Supplies the anterior, medial and dorsal portion of the brain o Middle cerebral artey  Comes up the sylvian fissure  Supplies the lateral portion o Posterior cerebral artery  Posterior, medial and ventral portion of the brain Three protective membranes for the brain (meninges)  DURA „dura matter‟ o Thick fibrous layer o Very tough outermost layer  ARACHNOID MEMBRANE o Middle layer, very spongy o Blood vessels run beneath this layer  Run in the sub-arachnoid space (important when blood vessels break)  PIA MATTER o Very fine, thin delicate layer o Adheres to the surface of the brain o Follows all the sulci and gyri  Meningitis- affect these three layers, not the brain itself. Signs: deafness, headaches Lecture 3 September 24 , 2012 VASCULAR DISORDERS  You can get a blockage in the vascular system o Blood supply blockage 1. CEREBRO-VASCULAR ACCIDENTS (CVA) a. Refers to a stroke b. Refers to blockage of blood supply c. Ischema- the brain is not receiving enough oxygen/glucose i. Result of a stroke/blockage ii. Could also be from a heart attack, etc any type of lack of 02 to the brain iii. Ischema leads to an infart d. Infart- area of the brain that is dead e. CVA can be slow or fast, usually fast f. Larger the artery/blockage, the larger the brain damage 2. ENCEPHALOMALACIA a. Blood supply loss happens very slowly (years); different from CVA b. Softening of the brain tissue i. Looks like deteriorating tissue (like a bad fruit) c. Usually caused by a slow blockage of the arteries d. Usually associated with the elderly; sometimes a cause of dementia 3. TRANSIENT ISCHEMIC ATTACK a. Temporary, short lived (transient) b. Not enough 02 (ischemic) c. Seen in things like migraines i. There‟s constrictions, that‟s why migraines have loss of vision (blood vessels are constricting) d. Involves muscles around the blood vessels e. Vessels constrict-> brain is not getting 02 etc f. Mostly affects vision What causes the blockage?  Thrombosis- locally formed acclusion (blockage). Happens on the spot (i.e. blood clot- most common) o More common in the elderly; sedentary- less pumping of blood  Embolism- blockage that has formed elsewhere in the body; migrates in artery/blood supply and lodges in the brain o Clot breaks off in leg and travels through the vascular system and lodges in brain, heart etc o If it lodges in brain= stroke. In heart= heart attack o Cholesterol can build up and cause arteriosclerosis  Cerebral hemorrhage- massive bleeding of blood vessel into the brain itself o Can be life threatening depending on where it occurs- kills brain tissue  Sub-dural hemotoma- blood vessel breaks outside of the brain, between the dura and the brain o No bleeding in the brain itself o Creates pressure on the brain and squeezed CSF into one half of the brain o To „cure‟- open it up and get rid of the blood/bleeding, as long as you catch it in time o Symptoms may come and go, making it hard to discover  Angioma- collection of blood vessels that are enlarged or abnormal o Vessel breaks apart, forms webs then comes back together  Error during development o Very fragile; more prone to bursting  Aneurism- vascular dialation o Expanded blood vessel caused by localized problems and elasticity o Could lead to a stroke if blood vessel bursts o Caused by a weakening of blood vessels o Pressure builds up and then bursts  Leads to hemorrhaging, etc  Closed head injury- blow to the head that doesn‟t break into the brain o Brain swells and gets bruised  Minor= concussion (confusion, memory loss) o Skull doesn‟t allow brain to swell  It gets bigger and has nowhere to go  If it gets too big it goes into the foregnum??  It will compress the base of the brain- death o Usually damages the temporal lobe o Controcoup- damage on one side but you need to check the other side to see if the brain bounced back and caused damage on the other side  Brain cancer (tumors) o Glioma- account for just under ½ of brain tumors  From glia cells ~ 45%  Range from benign to highly malignant o Meningiomas- cancer of the meninges  Usually benign, do not put pressure on the brain, not usually life threatening  Infections o Cause swelling o Encephalitis- infection of the brain caused by an external toxic agesnt o Viral infections  Polio, rabies, herpes (can attack nervous system) o Bacterial infections  Most common= meningitis (can be caused by either a virus or bacteria) o Fungal infection (extremely rare)  See this in advanced stages of AIDS o Parasitic infection (relatively rare)  Common in less developed countries  Invade digestive system  Malaria, ameobic  There are 10 glial cells for every 1 neuron  The neuron closet to the corpus collosum is very long  Each axon makes 1 decision  Myelin sheath- speeds up action potential of neuron  PNS- Schwann cells (like myelin in the CNS) Multiple Sclerosis  Disease of the myelin  Chronic long term inflammatory disease of CNS myelin  Symptom: partial paralysis (most common)  Destroys glial cells therefore, destroys myelin  Symptoms o Can tell from symptoms where the disease attacked o Can be sensory or motor symptoms  Balance, vision and the ability to feel  Usually crippling rather than fatal (shortened life expectancy)  MS doesn‟t kill the patient, the immobility causes more infection which could kill  Onset- 20 to 40 years o Bad sign if it starts before or after  More common in colder climates; rare in tropics  Its where you grew up that matters  More common in families, but NOT genetic  Initial onset is rapid (days or shorter)  Early warning sign: cant walk  Symptoms can disappear  Some recover and never show another symptom or symptoms can come and go, some get progressively worse  Some people get it and never get a symptom (plasticity)  Symptoms initiated by trauma, illness or change in body temperature  Deterioration in myelin sheath  Occurs in small, localized areas o Referred to as plaques o Can be scattered across nervous system o Leaves the axon unprotected (no myelin)  Treatment: steroids to reduce inflammation and swelling  Myelin can regenerate but not with the quick recovery; takes time  Some sort of virus o Results in auto-immune disorder; body attacks itself and kills glial cells Lecture 4  Parkinson‟s disease is a result of dopamine insufficiency  Schizophrenia is over production of dopamine  Neuron membranes have channels that open up o Increased sodium outside of the cell. It comes in when the channels open o High density to low density o Sodium has a charge, makes inside of the cell more positive o When it hits threshold, channels open up and sodium comes in o Cells fire when this happens (action potential) because of positive ions o Action potential starts in the axon until it reaches the nerve terminal o Flows from the axon of one cell to the dendrite of the other o Goes to synapse  Synaptic vesicles inside the presynaptic membrane o Inside, there are transmitter substances o Transmitter substances are released into the synaptic cleft o Receptors on the membrane to receive transmitter substances o Stimulates the post synaptic side  TRANSMITTER o 1. Synthesis – it has to be made; first place to interfere with it o 2. Storage- has to be stored in the synaptic vesicle o 3. Release- when the neuron fires, the substance has to be released into the synaptic cleft o 4. Receptor- has to interact with the receptor o 5. Inactivate- reabsorb back into cell or break it down. Reuptake/inactivation  „mimicer‟ chemicals look just like the chemical (transmitter) ie. Cocaine- act like the chemical was released. It increases the receptor activation  „Blocker‟ chemicals block the receptors. Looks similar to transmitter substance, but not enough to activate the receptor  Once transmitters are in synaptic cleft, they activate the receptors. Until a certain point. Got to get rid of it! Different mechanisms to out it back to pre synaptic side.  Want to decrease inactivation  Classic Transmitters o 1.monoamines (biogenic amines)  Inactivation by REUPTAKE  Catecholamines  Dopamine (DA)  Norepinephrine (adrenaline) (NE)  Synthesis: TYROSINE -> DOPA -> DA -> NE  (Precursors = needed to make neurotransmitters)  dopamine can sometimes just be a precursors  SEROTONIN (5HT) -> real chemical composition  Synthesis- tryptophan -> 5OHT -> 5HT o 2. Acetylcholine  synthesis: choline +acetylCoA -> Ach  inactivated by breakdown  EPILEPSY o The repetitive discharge/firing of a hyper-excitable aggressive/collection of a neuron  Frequently associated with convulsions  Convulsions refer to behaviour  Not all forms of epilepsy lead to convulsions o Every neuron in the brain is acting in sync, so the brain/body does the same  Its best when each neuron does its own thing o Epilepsy is identical to learning/memory o Neurons = the more you use them, the easier it is to fire o Repetitive activation of hyper excitable neurons o It can be genetic  Relatively rare  Can tell what caused it based on age of onset  under Human Brain and Behaviour Lecture 5  Petit mal- minor type of epilepsy o No true behavioral convulsions o Characterized by rolling up of the eyes/twitch o Person loses awareness 5-20 seconds o Not as debilitating as a grand mal seizure o People might not even realize they have them- might space out for a bit o 50-75% of the time it exists by itself- sometimes, it can occur in patients with other types of epilepsy o EEG is broad waves with big spikes spaced apart Visual System  Function is dependent on anatomy and organization  Retinas are dived down the center of each eye  Visual world when looking straight out (visual field) divided down the center where your nose is o Right visual field and left visual field o Must be looking straight ahead  Part of retina for the outside portion of head is the temporal portion of the retina  Part closest to your nose is the nasal portion  Two nerves cross- optic chiasm – nerves in the back of your brain come together as they head towards the brain – then they pull away and that‟s called the optic tract  Part of your retina nerves from the temporal portion as it continues back it comes to the optic chiasm and stays on the same side of the brain- it does not cross!  The nasal portion of each retina (that half) whenever they go toward the optic chiasm they cross over and continue to the opposite side of the brain  Everything in the right side of the eye will hit the nasal portion of the right eye and the temporal portion of the left eye  Everything that you see in your right visual field goes to your left cortex- vice versa o Everything crosses over to the other side  Ask people to close one eye and move your hands and ask what they can see- you can tell exactly where the tumor is Patient‟s visual field- slide  2- completely blind in the right eye- you will see nothing in an area you can normally see in  3- if you slice through the optic chiasm- cutting off the fibers that cross over- the nasal portion of each eye will be damaged  4- affecting the outside portion of the right eye- going to destroy the left portion of the right eye‟s visual field  Neurons respond to bars of light at area 17, that‟s oriented in a specific direction  Associational cortex responds to more complex information such as a face  If you get damage to the back part of the occipital lobe you will be very blind- macular sparring; you wont be completely blind, there‟s a little spot in the middle where you can see- shouldn‟t be there but it is!  If you have a small tumor you will lose portions of vision in your opposite visual fields  If the damage is very small it can result in a schetoma- a small area where you cannot see – small area of blindness caused by damage to the occipital cortex o If its very small, you may not even notice it o Everyone has a naturally occurring schetoma- but you don‟t notice it  Visual objects are on right side, verbal things are on the left hand side generally  Visual agnosia- perceptual disorders o VISUAL AGNOSIA- inability to recognize o
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