Class Note for ECOL 182R at UA
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Date Created: 02/06/15
ECOL 182 Spring 2008 Lecture 6 Nervous system and brain Dr Regis Ferriere Department of Ecology amp Evolutionary Biology University of Arizona What are the key questions and key terms What cells are unique to nervous systems xneurons glia How do neurons generate and conduct signals membrane potential action potential How do neurons communicate With one another synapses neurotransmitter summing potentials How is the nervous system organized CentralPeripheral AfferentEfferent How are complex functions controlled by the brain xlocalization lateralization limbic system What types of cells do we find in nervous systems Neurons are the functional units of nervous systems Neurons are excitable Generate and propagate electric signals action potentials Signals code for information received by or delivered to external or internal environment Different functional types of neurons Sensory neurons transduce information from environment Afferent neurons carry information into nervous system lnterneurons integrate and process information Efferent neurons carry commands to organs What types of cells do we find in nervous systems B Specialized neurons A Generalized neuronal anatomy Cell body Cerebellum W Dendrites r39 Cell body Axon Retina Cerebral cortex 0 Anatomy of neurons LIFESeFigured43Part2 WWWWMWM l r xVery diverse But several common features VCell body contains nucleus and most organelles dendrites receive electric signals axon conducts action potentials away to other cells Axon What types of cells do we find in nervous systems A Myelinproducing Schwann cells Site and direction of myelin growth Nodes of Flanvier Nucleus of Schwann cell 8 Mitochondria Axon Glial cells glia are much more numerous Do not transmit electric signals Physically support and orient neurons supply neurons with nutrients insulate axons How do neurons generate and conduct signals A RESEARGI METHOD RESEARCH METHOD Outside axon Outside axon Time LIFE 89 Figure 445 Part 2 m mnmwtormwvrwmn xm u u Ar m l LIFE 8a Figure 445 Part 1 mmmsmmww a IfYWAM n u w h gm Difference in electric potential across membrane membrane potential At rest resting potential How do neurons generate and conduct signals A Na K pump ATPase B Na K channels Outside of cell outside of Ge 0 O Voltagegated Sodium 0 Na 0 o 0 K channel 0 Nat channel 0 potassium pump 0 0 0 0 O 0 x 39 J 1 3 i L K9 0 o o w P 0 o 0 Closed 0 o 0 Inside of cell 0 Na o o 0 Inside of cell 0 O O 0 Open 0 Electric current across membranes is carried by m xMajor ions involved Na K Ca2 CI39 Ion pumps amp ion channels generate membrane potentials xSodiumpotassium pump moves Em and w ut VWhen K channels open K leave When Na channels open Na enter How do neurons generate and conduct signals new on K HYDemn m c nnnn c w rm mm M 1 cal t a39 mum hypmpvla xuil Membranes can be depolarized or hyperpolarized Depolarization can be triggered by external signals Ifdepolarization reaches threshold gositive feedback membrane potential becomes gt O action potential Then channels close Na channels haverefractory perioq How do neurons generate and conduct signals A Electrical stimulus Point A Pain 8 Oscuoscope screen loss of signal inlA E PDIH B iagamquot quot 2 Time PmmA PDlnlB Action potentials travel along axons to axon erminals wit 1out How do neurons communicate Communication occurs at synapses Chemical synapses are most common type Arrival of action potential Presvnap ccequot causes release of neurotransmitter xContained in vesicles that fuse with presynaptic if membrane hence release Action potential diffusion through synaptic cleft Synapticclefrt 2 Acetylcholine in motor Axon Motor neuron I Muscle fiber I 39W quoti Acetylcholine molecules in vesicle neurons quotNew Neurotransmitter can bind to Petswap mquot receptors on oostsvnaotic 395 Se Figure 4413 HITMscfwrocnmoanrqmrnrwi V l r i b m m r ne Acetylcholine l 1 7 receptor How do neurons communicate Excitatory synapses QMi quot Jim hillock Action B potential U D 7 o EPSPS Threshold Membrane potential rtIV M i i i i i 11 2 3 412123 Synapsenumber I I I I I I I I eeting potential Millisecond s Synapses between neurons can be excitatory or inhibitory The postsynaptic cell sums excitatory and inhibitory inputs L b ar i 1 4 9 How is the neural network organized Morpholoqical orqanization xCentral nervous system CNS brain and spinal cord Spinal cord communicates information between brain and rest of body can issue commands to body without input from brain VPeripheral nervous system PNS cranial and spinal nerves How is the neural network organized Functional orqanization Two main components Neural Neural ariarents efferents depending on direction of mfg information flow and whether we re aware of CONSC OUS VOLUNTARY the information gt gt UNCONSCIOUS AUTONOMIC from to a peripheral Glands smooth Efferent component 13212 iiili mquot from CNS to peripheral parts of body LIFE Be Figure 461 m mncrmwsmoanmmmm r m How does the human brain develop Brain forms from 3 swellings at anterior end of neural tube xhindbrain midbrain forebrain Forebrain develops into cerebral hemispheres telencephalon underlying thalamus and hypothalamus diencephalon Midbrain and hindbrain develops into brain stem Vcerebellum LATERAL VIEWS DORSAL VIEWS 25 days Forebrain 7 Neural tube Midbrain Hindbrain D g 1 a O O 0 gr u 100 days Adult brain Cerebral hemisphere Thalamus Hypothalamus Cerebrum Pnuitary How is our behavior controlled A Central sulcus E Central Primary somalor Primary motor cortex sulcus sensory cortex ariea lobe Frontal lohe Occipital 39 lobe Passively viewing wards Listening to words Primary visual Olfactory area bulb Temporal lobe Cerebellum Face Spinal cord recognition Speaking words Generating words LIFE Be gure 465 Pan 1 Different functions can be linked to different regions of the brain functional deoqraphv of the brain Cerebral hemispheres divided into temporal lobes process auditory information frontal lobes many motor functions parietal lobes many sensory receptors occipital lobes process visual information Cerebral cortex layers of neurons covering cerebral hemispheres 7 LIFEBeFi uI485Pan2 mummwmmwmr How are our emotions controlled Cerebral hemispheres Hypothaamus Pituitary Amygdala Spinal cord Emotions as well as instincts and Iohvsioloqical drives controlled by limbic system at the core of the forebrain VAmygdala controls fear responses Hippocampus necessary for memory Limbic system is evolutionarily very ancient What happens when we sleep Sleep and dreaming are reflected in electrical patterns in cerebral cortex Electrical patterns detected by electrodes on scalp and recorded as changes in voltage between electrodes through time In humans five patterns correspond to five stages of sleep that we go through in repeated seduences 1 stage of rapideye movement REM sleep preceded by J4 nonREM stages including 2 that are deep restorative Each sequence of 5 stages lasts 1h302h Dreams during REM stage Inhibitory commands from brain almost completely paralyze skeletal muscles No acting out of dreams We still know very little about the function ofosleep What happens when we sleep B 0 Awake II l l 739 Awake e NonREM REM Stage 1 Stage 1 Stage 2 Stage 2 Stage 3 Stage 3 Stage 4 Stage 4 Time hours HEM 2395 0 1 0 Time seconds FE 89 Figure 45111 Part 2 m mmwmm mmm arms aw walnut2 mm H FWLD o How do we learn memorize things Learning modification of behavior by experience Memory ability to retain what is learned xSome learning and memory processes have been localized to specific brain areas Different types of memory shortterm longterm xShortterm memories 1015 min are transferred to long term memory xReinforcement a factor hippocampus involved Learning leading to longterm memory must involve long lastinq svnaotic chanqes xLongterm potentiation highfrequency stimulation that makes svnabses more sensitive to future stimulations xLongterm depression continuous small stimulation reduces responsiveness How did nervous system and brain evolve A s eeeeeee ne 5 Eanhworm a Snuid rain stem The power of the nervous system as an information processor results from the organization of neurons into networks Nervous system vary in size and complexity In animal species with increasingly complex sensory and behavioral abilities information is increasingly centralized Brains vary in size and complexity ln vertebrate species of similar size brains can show immense differences
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