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Psyc 6, week 1

by: Sabrina Straus

Psyc 6, week 1 PSYC 6

Sabrina Straus

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Class notes and textbook notes chapter 2 9/14/16
Introduction to Neuroscience
Catherine Cramer
Class Notes
psych, neuroscience, intro
25 ?




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This 6 page Class Notes was uploaded by Sabrina Straus on Wednesday September 14, 2016. The Class Notes belongs to PSYC 6 at Dartmouth College taught by Catherine Cramer in Fall 2016. Since its upload, it has received 8 views. For similar materials see Introduction to Neuroscience in Psychology (PSYC) at Dartmouth College.


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Date Created: 09/14/16
2. 9/13/16  Class Notes  NEURONS AND GLIA  ~Brain volume  > 35­40% neurons  >25­35% other cells  >15­20% fluid compartments (blood, cerebrospinal fluid)  >10­15% extracellular space       I.  Basic components of neurons    A.  cell body (soma)    nucleus    B.  dendrites  (dendritic tree)    dendritic spines­info coming into the neurons+decides whether to pass on info    C.  axon­sending wing of neuron, surrounded by myelin    axon hillock­beginning of axon    Microtubules­have proteins to move vesicles down the terminals    D.  membrane    ion channels­make cells excitable and able to communicate  E.  synapse­can be anywhere on the cell body or dendritic tree    axon terminal (button)­output    synaptic vesicles­contain neurochemicals that are released    presynaptic membrane    postsynaptic membrane    synaptic cleft    Neurotransmitter­diffuse across synaptic cleft (slow process)          II.  Classifying neurons     A.  By shape    Unipolar(often in spinal neurons), bipolar (one dendrite and one axon), multipolar (most  common)    Pyramidal (common in cortex layer), stellate, projection   *invertebrates are more likely to have bigger neurons    B.  By function    receptor cell­have to make a neuro signal    interneuron­majority/ get signal and send out    Motoneuron­strictly output    neurosecretory cell­hormone output        III.  Glial cells  (neuroglia, glia)    A.  In the central nervous system (brain & spinal cord)    astroglia (astrocytes)­providing physical support for surrounding neurons} feature of blood  brain barrier    Microglia­clean up by breaking down dead cells    Oligodendroglia­producing myelin    Myelin­speed transition    nodes of Ranvier­exposed part of axon    ependymal cells       B.  In the peripheral nervous system      satellite cells      Schwann cells        IV.  Cytoarchitecture    laminar organization­layers in brain composed of different cells    cerebellar cortex­6 layers    cerebral cortex ­ Brodmann’s areas=each has a different function and different organization of  neurons  ~~Structurally, the neuron can be divided into four functional zones: the  ​ input, integration,  conduction and output zones. ​   The input zone is comprised of dendrites, which are activated by  chemicals that they encounter.  The integration zone is the body of the neuron, where  information is processed.  The conduction zone consists of the axon, which sends outgoing  information away from the cell body.  There is typically one axon, but that axon can divide into  multiple axon collaterals, which exert the effect of the axon on many other neurons.  Finally, the  output zone, composed of axon terminals, send these messages out of the neuron through the  cell membrane.    Chapter Notes  Chapter 2: Neurons and Glia  ~structure of different types of cells in the nervous system  ­neurons​ sense changes in the environment, communicate changes to other neurons, and  command the body’s responses to these sensations  ­Glia​ contribute to brain function by insulating, supporting, and nourishing neighboring neurons    Progression of neuroscience  ­began with the development of the compound microscope  ­fixing of tissues with formaldehyde and creating thin slices with m ​ icrotome  ~resulted in ​histology ​ (microscopic study of the structure of tissues)  ­introduction of stains:   1. Nissl​ stain (stained the nuclei of all cells as well as the surrounding clumps in order to  distinguish between neurons and glia and allows for the study of the arrangement or  cytoarchitecture​ of neuron)  2. Golgi Stain​­revealed that the neuronal cell body (region of the neuron around the  nucleus) is only a small fraction of the total structure of the neuron + shows that neurons  have 2 parts (central region that contains the nucleus (ce ​ ll body/ soma/ perikaryon) ​  +  thin tubes (​neurites­​  2 types { ​axons and dendrites)​   a. Axons: act like wires that carry the output of the neurons  b. Dendrites: act as the antennae of the neuron to receive incoming signals or input  ~Golgi believed that the neurites of different cells are fused together to form a  continuous reticulum while Cajal argued that the neurites of different neurons are not  continuous with each other and communicate by contact (n ​ euron doctrine: ​  cell theory  applies to neurons)  ­Prototypical Neuron:  > Neuron consists of ​soma, dendrites, and the axon  ​ and the inside of the neuron is  separated from the outside by the neuronal membrane  1. Soma: spherical central part of the neuron  a. Cytosol​: fluid inside cell  b. Organelles​: membrane enclosed structures within the soma\  c. Cytoplasm​: everything within the cell membrane but excluding the nucleus  d. Nucleus​:has a double membrane called the nuclear envelope and within the  nucleus are chromosomes (contain a double­strand of DNA)(genes: segments of  DNA determine the specific parts of DNA that are used to assemble the cell)  i. Gene expression: reading of DNA  1. Promoter: where RNA synthesizing enzyme (RNA polymerase)  binds to initiate transcription  a. Transcription factors: regulate binding of polymerase to  promoter  2. terminator/stop sequence  3. Introns and exons: undergo splicing (remove introns)    ii. Proteins: final product of gene expression which give neurons their unique  characteristics  1. Protein synthesis: assembly of protein molecules (occurs in  cytoplasm) built with amino acids  a. Translation: assembling of proteins from amino acids  2. mRNA: carries genetic message to sites of protein synthesis in  cytoplasm (made of 4 dif. Nucleic acids)  a. Transcription: process of assembling a piece of mRNA  >Neuronal genes, genetic variation, and genetic engineering  ­genome: entire length of DNA that comprises the genetic info in our  chromosomes­> diseases (missing gene, mutations)  >Rough Endoplasmic Reticulum/Nissl bodies: protein synthesis occurs in ribosomes  (translate instructions to make protein) attached to ER  >Smooth ER+Golgi­SER folds protein/golgi delivers  >Mitochondrion­inner membrane:cristae and between the cristae is the matrix+cellular  respiration (pulls in pyruvic acid and oxygen­>krebs cycle+electron transport chain­> ATP  >Neuronal membrane: encloses cytoplasm  >Cytoskeleton: gives the neuron shape (consisting of microtubules, microfilaments, and  neurofilaments)  ~microtubules: long pipe consisting of tubulins  ~microfilaments: made of actin  ~neurofilaments: strong    2. Axon:transfer of information over distances in the nervous system  ~speed that the signal sweeps down the axon is the nerve impulse (thicker the axon=faster  impulse)  a. Axon hillock­thick branch  b. Axon collaterals: branches (recurrent collateral is a branch that returns to its  original cell)=terminal arbor  c. Axon proper  d. Axon terminal:comes in contact with the synapse}i​ nnervation  *Two noteworthy features distinguish the axon from the soma:  1. No rough ER extends into the axon, and there are few, if any, free ribosomes  in mature axons.  2. The protein composition of the axon membrane is fundamentally different  from that of the soma membrane/no protein synthesis  *The cytoplasm of the axon terminal differs from that of the axon in  several ways:  1. Microtubules do not extend into the terminal.  2. The terminal contains numerous small bubbles of membrane, called  synaptic vesicles , that measure about 50 nm in diameter.  3. The inside surface of the membrane that faces the synapse has a particularly  dense covering of proteins.  4. The axon terminal cytoplasm has numerous mitochondria, indicating a  high energy demand.  ~~~summary:Axon (energy aka filled with mitochondria) terminals form synapses with the  dendrites or somata of other neurons. When a nerve impulse arrives in the presynaptic axon  terminal, neurotransmitter molecules are released from synaptic vesicles into the synaptic cleft.  Neurotransmitter then binds to specific receptor proteins, causing the generation of electrical or  chemical signals in the postsynaptic cell. Soma has the ribosomes. Dendrite tree receives  signals.  3. Synapse  a. Presynaptic: axon terminal  b. Synaptic cleft: in between pre and post  i. Synaptic transmission: transfer of info at the synapse from one neuron to  another (electric impulse­> chemical(n ​ eurotransmitter​ stored in and  released from synaptic vesicles within the terminal)­>crosses cleft­>  electric  c. Postsynaptic: dendrite or soma  4. Axoplasmic transport:flow of material down the axon (soma to terminal) (Wallerian  degeneration is when flow of materials is interrupted)  a. Kinesin moves material from soma to terminal} anterograde transport  b. Dynein moves material terminal to soma} Retrograde transport  5. Dendrites­extend from soma and covered with synapses and receptors that detect  neurotransmitters  a. Dendritic spines:receive synaptic input/ isolate various chemical reactions that  are triggered by some types of synaptic activation. Spine structure is sensitive to  the type and amount of synaptic activity  >Classifying Neurons  Structure  1. Number of neurites  a. Single neurite:unipolar  b. 2=bipolar  c. 3+=multipolar  2. Dendrites  a. Cerebral cortex  i. Stellate cells (star shaped)  ii. Pyramidal cells (pyramid shaped)  b. Spiny dendrites (all pyramidal)  c. Aspinous  3. Connections  a. Primary sensory neurons: neurites in sensory surfaces of body  b. Motor neurons: axons that form synapses with muscles  c. Interneurons: form connections with other neurons  4. Axon length  a. Golgi type I or projection neurons:long ex: pyramidal  b. Golgi type II or local circuit neurons; short ex:stellate  Gene Expression  ~ex: Green fluorescent protein  6. Glia  1. Astrocytes: regulating the chemical content of the extracellular space by enveloping  synaptic junctions and restricting the spread of neurotransmitter molecules + have  receptors to trigger electrical and biochemical events  2. Myelinating Glia  a. oligodendroglial and Schwann cells~provide layers of membrane to insulate  axons called myelin but the exposed part is the node of ranvier  i. Oligodendroglial cells: found only in the central nervous system (brain and  spinal cord) + contributes myelin to several axons  ii. Schwann cells: found only in the peripheral nervous system (parts outside  the skull and vertebral column) + myelinates only a single axon  7. Other non­neuronal cells  1. Ependymal cells: line fluid­filled ventricles to direct cell migration during brain  development  2. Microglia: function as phagocytes to remove debris left by dead or degenerating neurons  and glia  3. vasculature: arteries, veins, and capillaries that deliver via the blood essential nutrients  and oxygen to neurons. 


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