Midterm 1

• Central Nervous System: Incased by bone (skull / spine)
• Peripheral nervous system: umbrella term
• Technical challenges for studying brain: neurons and glia are very small, cannot be seen by naked eye
• Compound microscope: 17th century neuroscience begins
• Nissil Stain: aka Cresyl Violet, stains nucleic acids, mainly RNA and ribosomes on RER, this allows distinguishing btw cell types in the brain since glia not stained
• Formaldehyde: allows jello-like brain to be sectioned
• Laminar Structure: cytoarchitecture that nissil stain revealed, showing six different layers of the brain. Darker areas mean more cells
• Nissil Stain limitations: could not resolve unitary nature of nerve cell bc complex shapes and branching packed together
• Golgi Stain: silver chromate solution, differentiates between cell body (soma) and neurites (axons and dendrites)
• Golgi's Reticular Theory: neurites of different cells are fused into a continuous reticulum (nerve net) that permits bidirectional flow of information
• Santiago Ramon y Cajal: used the golgi stain and a light microscope to draw neurons and neural circuits, developed Neuron Doctrine
• Neuron Doctrine: neuron is the basic functional unit of the nervous system, distinct cells with synapses between so not continuous. Axons: send the signal Dendrites: receive the signal, unidirectional information flow
• Both theories (Golgi and Cajal) correct in some ways depending on organism, both awarded Nobel Prize
• Three properties of Neuron: 1) Morphologically heterogenous in size and shape, very diverse. 2) Conduct bioelectric signals across long distances with no loss of strength. 3) possess specific connections with other nerve cells and with muscles and glands
• Three parts of neuron: 1) Soma: the cell body containing nucleus and organelles. 2) Dendrites: projections from the soma that receive information from other neurons. 3) Axon: the long extension of the neuron that carries electrical signal away from the cell body to terminal buttons
• The Nucleus: DNA packaged in chromosomes. in order for genes to be expressed, transcription of DNA into mRNA occurs. RNA processing like alternative splicing occurs with mRNA exiting nucleus via pores and then being translated into proteins at ribosomes
• Ribosomes and RER: ribsomes are the site of protein translation. If free, the protein will stay in the cytosol. if bound to the RER, the protein will be inserted into the membrane or exocytosed. LOTS in neurons
• SER: Smooth ER folds proteins into 3D structure after translation, regulates the internal Ca2+ concentration with cascade of signals
• Golgi apparatus: "post-office," modifications of translated proteins
• Mitochondria: site of cellular respiration where the Kreb's Cycle makes ATP for energy. Neurons require a lot so especially abundant at synapses where NT synthesized
• Mitochondria in Psychiatry: monoamine oxidase inhibitors (MAOi) were some of the first antidepressants.
• Neuronal Cell Membrane: membrane is a lipid bilayer. On the outside is hydrophilic and on the inside hydrophobic. Ions cannot pass through without channel
• Cytoskeleton: critical for stability and function of neuronal processes, dynamic.
• Three proteins of cytoskeleton: Microtubules (tubulin), Neurofilaments (intermediate filaments), Microfiliments (actin)
• Tau: a microtubule associated protein (MAP) that stabilizes axonal MTs by interacting with tubulin. Hyperphosphorylation of p-Tau leads to neurofibrillary tangles. Insoluble aggregates form and axon cannot send signal. Neuronal death. Major feature of Alzheimer's.
• Chronic Traumatic Encephalopathy: accumulation of p-TAU due to repetitive head trauma. Symptoms include behavior and mood changes, memory loss, cognitive impairment, dementia
• The Axon: No RER or free ribosomes. Three parts: 1) Axon hillock (beginning). 2) Axon proper (middle and collateral). 3) Axon terminal (end)
• Axon terminal: pre-synaptic vesicles to send signal, large number of mitochondria to meet energy demand
• The synapse: presynaptic membrane is filled with NT. Postsynaptic membrane is filled with receptors. Synaptic cleft: space between where the NT is released into.
• Axoplasmic transport: no protein translation in axon so proteins made in the soma must be transported to axon terminals. In the cytoskeleton, MTs form tracks that allow packets of proteins to travel with motor proteins
• Wallerian degeneration: axons cannot be sustained when separated from their cell body bc axoplasmic transport is interrupted
• Two types of axoplasmic transport: anterograde: soma to axon terminal using kinesin. Retrograde: axon terminal to soma using dynein. When one motor protein is activated the other is deactivated
• Dendrites: the antennae of neurons, on the receiving side so covered with NT, high ribosome content, some have spines to increase efficiency with surface area
• Spines: 1st described by Cajal, contain NT receptors. Studies of kids with developmental disorders reveal fewer spines. 2 photon microscopy allows in-vivo visualization of activity for 1st time. Spines are dynamic.
• Axons vs Dendrites: axons: longer, thinner, uniform diameter, fewer branches, usually presynaptic. Dendrites: Shorter, thicker, tapered, highly branched, postsynaptic
• Classifications of Neurons: Unipolar vs. Bipolar vs. Multipolar. Number of neurites on soma. Motor vs. Sensory vs. Interneurons, Morphology of soma, morphology of dendrites, axonal length, type of neurotransmitter released.
• Motor Neurons: Neurons that carry impulses from the CNS to the musculature
• Sensory Neurons: convert physical stimuli into electrical signals. From dorsal root ganglia to skin.
• Interneurons: connections only with other neurons in brain and spinal cord
• Morphology of Soma: stellate cells (star) vs pyramidal cells (pyramid)