Nervous system, Neurons, and History of the Brain
Nervous system, Neurons, and History of the Brain
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This 7 page Class Notes was uploaded by Megan Hodges on Sunday October 11, 2015. The Class Notes belongs to at University of California - Los Angeles taught by in Summer 2015. Since its upload, it has received 17 views.
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Date Created: 10/11/15
Wednesday September 23 2015 Chapter 2 Cells and Structures The Anatomy of the Nervous System The Nervous System Is Composed of Cells Neuron main component of the nervous system Consists of three parts dendrites integrating cell body protected by a myelin sheath an axon and an axon terminal Glial cells similar cells that participate in structure formation and information processing Also known as glia These are non neural brain cells Neurons are larger and produce more signals than a glial cell Santiago Ramon and Caj al demonstrated that neurons are not entirely continuous There are synapses are in between their two discoveries became known as the neuron doctrine 1 neurons are structurally metabolically and functionally different and independent of one another 2 signals travel across a tiny gap the synapse The Neuron Has Four Principle Divisions Input Zone dendrites and the cell body covered with synapses receive information from other neurons Dendrites may be branched Integration Zone the soma cell body evaluates the information and determines if another signal is necessary Conduction Zone axon carries signals in the form of an electrical currentsignal Output Zone axon terminals releasetransmit the signal to the receiving dendrites of another neuron neurotransmitters chemical form now Neuron shape ts function Most brain neurons interneurons integrate information and communicate with other neurons Larger neuron more inputoutput greater distance and quicker transmission of messages Multipolar neurons many dendrites one axon MOST COMMON bipolar neuron single dendrite one axon SENSORY SYSTEMS VISION unipolar monopolar neuron branch in both directions that acts as the dendrite and the axon cell body is in the center TOUCH INFO FROM BODY TO SPINAL CORD Information is Received Through Synapses info travels from pre to postsynaptic neuron components of a synapse presynaptic membrane axon terminal synaptic vessels contain neurotransmitters medium by which a neuron shares information vessels are fused to the membrane to release the neurotransmitters neurotransmitter receptors on the dendrites react to the neurotransmitters speci c match They make the neuron more or less likely to release neurotransmitters They are proteins postsynaptic membrane dendrites or cell body synaptic cleft gap neural plasticity remodeling of interactions between neurons due to changes in composition and shape of the dendrites and the neurotransmitter receptors Visualizing the Cellular Structure of the Brain Golgi stains ll the whole cell useful in determining shape of cells Nissl stains outline all cell bodies because dyes are attracted to RNA used to measure cell body size and density of cells in regions Autoradiography cells are manipulated into taking photographs of themselves immunocytochemistry ICC uses the af nity of antibiotics for proteins In situ hybridization uses RNA or DNA to identify a neuron with a speci c turned on gene ICC can be used to identify IEG immediate early genes Review anterograde labeling page 26 Horseradish peroxidase taken up by axon and transported to cell body used to identify certain cells of origin of an axon The Axon is Specialized for Integrating and Transmitting Information Axon hillock where axon projects from Cone shaped Innervate provide neural input to axon branch 2 axon collateral axon transport materials produced in cell body are carried to axon and dendrites and from the axon back to the cell body carried by microtubules Glial Cells Protect and Assist Neurons provide chemical signals raw materials and structure to neurons Wednesday September 23 2015 oligodendrites and Schwann cells provide a myelin sheath cover to the axon Fatty insulating substance speed up transmission of a signal nodes of Ranvier gaps between myelin segments where the axon is exposed used to speed up transmission of signal signal jumps from one node to the next multiple sclerosis break down of myelin sheath Astrocytes are found around and in between neurons They also can help control blood ow to more or less active brain regions secrete chemicals to regulate formation of synapses and the formation of tough outer membranes around the brain microglial cells mobile clean up sites of injury because glial cells continue to divide they can cause brain tumors and can also cause edema in response to injury swelling of brain tissue Neurons and Glial Cells form Information Processing Circuits The Nervous System Extends Throughout The Body gross neuroanatomy visible to naked eye CNS brain and spinal cord PNS everything else 1 nerves collections of neurons cranial conducted directly to brain spinal regular intervals to spinal cord autonomic nerves that connect to internal organs viscera There are 12 pairs of cranial nerves innervate head and neck directly never join with spinal cord REVIEW PAGE 31 Spinal nerves 31 pairs emerge through spinal cord at regularly spaced openings each nerve is made of a group of motor bers projecting from ventral side and a group of sensory bers projecting from dorsal side named according to segment of spinal cord they are attached to The autonomic nervous system sympathetic and parasympathetic axons of the sympathetic leave the middle of the spinal cord and the innervate the sympathetic ganglia after traveling a short distance axons from the sympathetic ganglia travel to the major organs of the body immediate action increase blood pressure increase heart rate etc ght or ight parasympathetic axons travel long distances to parasympathetic ganglia close to the organs they serve relaxation rest and digest stage different effects because different neurotransmitters spinal cord 2 re exes The Outer Surface of the Brain cerebral cortex outer covering of the brain made up largely of nerve cell bodies gyrus ridge in the cortex sulcus separate the gyri folding increases surface area increase metabolic processes frontal temporal parietal and occipital lobes sylvian ssure separates temporal lobe central sulcus divides parietal and frontal lobe cortex complex cognitions corpus callosum connect right and left hemispheres postcentral gyrus mediates sense of touch strip of parietal cortex precentral gyrus essential for motor control occipital lobe vision temporal auditory and memory Wednesday September 23 2015 gray matter interneurons receives and processes white matter myelin transmits info Three Customary Orientations for Viewing the Brain and the Body sagittal plane right and left coronal plane frontaltransverse plane anterior front and posterior back horizontal upper and lower medial toward the middle lateral toward the side ipsilateral relative to another location on the same side contralateral opposite side relative superior above inferior below head is referred to as anterior or rostral tail end is described as posterior or caudal proximal means near the center and distal means toward the end of a limb affarent carries info into a region of interest efferent away from region of interest dorsal toward or at back ventral toward or at belly Subdivisions in the Brain neural tube early CNS made of cells and the interior is lled with uid few weeks three separate swellings forebrain midbrain and hindbrain forebrain 50 days telencephalon cerebral hemispheres later and diencephalon thalamus and hypothalamus later hindbrain later cerebellum pons medulla brainstem midbrain pons and medulla combined within and between brain regions are nuclei and tracts bundles of axons The Brain is Described In Terms of Both Structure and Function each side of the brain controls the opposite side of the body The Cerebral Cortex Performs Complex Cognitive Processing most prominent kind of neuron in the cerebral cortex pyramidal cell cortical column information processing units Important Nuclei Are Hidden Beneath the Cerebral Cortex basal ganglia consists of caudate nucleus putamen and globus pallidus plays a critical role in control of movement curled around the basal ganglia is the limbic system emotion and learning amygdala emotional regulation and perception of odor hippocampus and fornix learning and memory cingulate gyrus direction of attention olfactory bulb sense of smell hypothalamus sex and aggression hormonal systems of the body thalamus traf c cop directing all incoming sensory information to the appropriate regions of the cortex for further processing and receiving instructions back from the cortex to control which sensory information is transmitted hypothalamus hunger thirst temperature regulation sex and many more controls the pituitary gland serves as brains interface with hormonal systems of the body The Midbrain Has Sensory and Motor Systems doesn t encompass a lot of tissue more rostral bumps are the superior colliculi and the caudal bumps are the inferior colliculi together referred to as the tectum superior processes visual information and the inferior processes information about sound substantia nigra loss of its neurons leads to Parkinson s disease reticular formation loose collection of neurons stretching right down into the medulla reticular neurons are important in a variety of behaviors including sleep and arousal The Brainstem Controls Vital Body Functions cerebellum highly convoluted three layered instead of six layered motor coordination and control cognition learning pons adjacent motor contro land sensory nuclei medulla transition from brain to spinal cord conveying all motor and sensory bers to and from the body as well as driving respiration and heart rate which is why brainstem injuries are often lethal Wednesday September 23 2015 Specialized Support Systems Protect and Nourish the Brain meninges protective membranes around the brain and spinal cord Between dura matter and pia matter that adheres tightly to the surface of the brain arachnoid suspends the brain in a bath of cerebrospinal uid CSF has shock absorbing action to protect the brain also provides nutrients and signaling chemicals meninges can become in amed by infections and this squeezes the brain the result is meningitis sometimes this can form large tumors meningiomas bening do not invade ventricular system lled with CSF series of chambers each hemisphere contains a lateral ventricle extending into all four lobes of the hemisphere these are lined with choroid plexus produces CSF by ltering blood CSF ows from lateral ventricle into the third ventricle and then into the fourth ventricle that lies between the cerebellum and the pons second crucial uid blood brain tissue consumes 20 of the body s energy stroke a clot a narrowing or rupture interrupts the supply of blood to a discrete brain region causing the affected region to stop functioning or die warning signs numbness or weakness altered vision dizziness severe headache confusion or dif cult speaking capillaries in the brain are resistant to passage of large molecules across their walls the blood brain barrier evolved to help protect the brain from infections and blood borne toxins but it also make she delivery of drugs to the brain more dif cult Brain Imaging Techniques Reveal the Structure and Function of the Human Brain CAT x ray energy is used to generate images x ray radiation absorbed is proportional to the density of tissue through which the x ray has passed useful for visualizing problems such as strokes tumors or cortical shrinkage MRI provides higher resolution images than CT and because MRI uses magnetic elds and radio waves it has fewer damaging effects magnet causes protons to line up parallel Then the protons are knocked over by a powerful pulse of radio waves When this pulse is turned off the protons relax back into their original con guration emitting radio waves as they go Detectors measure the radio waves which differ for tissues of varying densities can reveal subtler changes in brain such as loss of myelin PET provides a means to measure brain activity during behavioral tasks short lived radioactive chemicals are injected into the bloodstream and radiation detectors encircling the head map the destination of these chemicals in the brain radioactive glucose is selectively taken up and used by the most active parts of the brain a moment to moment color coded portrait of brain activity can be created faster and is able to track quick changes in brain activity TMS focal magnetic currents are used to brie y stimulate the cortex of alert subjects directly without any lasting physical alterations or surgery allows experimenters to activate a discrete area of the brain while simultaneously tracking any resulting changes in behavior MEG large array of ultra sensitive detectors measures the minuscule magnetic elds produced by the electrical activity of cortical neurons this is used to construct real time maps of brain activity during ongoing cognitive processing Responds quickly to moment by moment changes in brain activity excellent for studying rapidly shifting patterns of brain activity in cortical circuits Notes Chapter 1 An Introduction to Brain and Behavior Nature and Nurture Building the Minds Machine the scientific study of the nervous system The first scholars to study the relationships between brain and behavior called themselves philosophers because it was philosophy that established the foundations of scientific discovery and methods for creating new knowledge Biological psychology the field that relates behavior to bodily processes 0 Same as behavioral neuroscience brain and behavior and physiological psychology 0 Main goal is to understand the brain structures and functions that respond to experiences and generate behavior Modern era of psychology is characterized by objective experimentation and use of the scientific method to test hypotheses The role of the brain was uncertain to scholars in antiquity In mummified people the brain was considered as having no importance and was often thrown out while other organs were kept due to their importance in the afterlife of struggle and reward The heart was even preserved within the body No mention of the bran in the bible but the heart is mentioned a lot considered mental capacities to be properties of the heart 0 Thought the brain system was a cooling system for hot blood from the heart ascribed emotion perception and thought to the functioning of the brain had experience treating head injuries of gladiators and proposed that behavior results from the movement of animal spiritsquot from the brain through nerves to the peripheral body produced neuroanatomical illustrations of brain and nerve structures Religious dogma dominated Renaissance science with the result that scientific writing from that era often presents the brain as a mysterious and intricate gift from God Michelangelo s depiction of God in the Sistine Chapel bears a striking resemblance to the brain Did he secretly believe in neuroscience outside of its relation as a gift from god tried to explain how the control of behavior might resemble the workings of a machine proposing the concept of spinal re exes and a neural pathway for them He argued that free will and moral choice could not arise from a mere machine 0 Notion of there was a nonmaterial soul in the body that governed through a point of contact in the brain 0 Rejected today the notion that the rain coordinates and controls behavior specific behaviors feelings and personality traits were controlled by discrete regions of the brain Wrong in the sense that one could read a persons character by feeling the persons head 0 Established the different brain regions specialize in specific behaviors damage to region of left frontal lobe caused speech problems Whole brain is active most of the time but when performing particular tasks certain brain regions become even more activated Overall size of the brain matters but not as much as people think consciousness and other aspects of human experience can be seen as properties of the nervous system Pavlov classical conditioning wanted to link a specific brain region to the formation of long term memory an engram Gave us the idea that memory is not localized to only one region of the brain cognitive processing could be accomplished by networks of active neurons 0 type of plastic connection between neurons that remains a hot topic in neuroscience Theoretical perspective modern day psychologist may draw upon 0 Systematic description of behavior 0 Evolution of the brain and behavior I Evaluate similarities between species and look for specific differences in behavior and biology that have evolved as adaptations to different environments 0 Life span development of the brain and behavior I process by which an individual changes in the course of its lifetime I Observing the way a particular behavior changes during ontogeny may give us clues to its functions and mechanisms 0 The biological mechanisms of behavior I group of nerve cells that make up an individual behavior and experiences alter the physiology of the brain neural plasticity 0 Can alter the size and interconnections between neurons 0 Can modify the rates at which neurons are born in the adult brain haracteristics shared among species throughout ancestry Arose from a common ancestor uses the tools of neuroscience to discover how biological and social factors continually interact and affect each other as behavior unfolds o Testosterone in males example how natural selection might have shaped our own behaviors including specific cognitive abilities 0 Sexual selection was crucial for evolution of the human brain focuses on factors that have a lasting effect on patterns of the turning on or off of specific genes without changing the structure of the genes themselves 0 lasting inactivation of a gene exploits new brainimaging technologies that identify brain regions activated under differing decision making circumstances 0 Early research suggest we have two major neuroeconomic systems I One that assesses the relative value of the choices valuable I Sifts through the evaluated choices in order to make a conscious decision the personal private awareness of our emotions intentions thoughts and movements and of the sensations that impinge upon us Three kinds of studies that probe brainbehavior relationships 0 alter a structure or function of the brain or body to see how this alteration changes behavior physical alteration behavioral effect to compare results to control group is the same individuals tested before the somatic intervention occurred I entire other groups are used for a basis of comparison 0 alters or controls the behavior of an organism and looks for resulting changes in body structure or function 0 quantifies the cooccurrence of a behavior and somatic change Must have a one goes up while the other goes down both go same direction I Does not reveal 0 Relations between body and brain are each affects the other in an ongoing cycle of bodily and behavioral interactions we can understand complex systems by discussing their smaller parts 0 Aims to identify