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Psychology (9,695)
PSYB64H3 (201)
Chapter 3

Chapter 3 Textbook Notes for Physio Psych PSYB64

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Janelle Leboutillier

CHAPTER 3: CELLS OF THE NERVOUS SYSTEM Fugu/Puffer Fish: Delicacy that has deadly tetrodotoxin (TTX) 100s die each year bc it blocks APs (specifically, blocks Na ion movement) Neurons and Glia 1 : 10-50 = neuron: glia ratio Structure of Neurons: Membrane: o Double phospholipid (fatty phosphate-containing molecs) layer o 2 main types of embedded proteins 1)ion channels Voltage-gated Ligand-gated (chemical-based, whether drugs or natural) 2)ion pumps Na-K pumps o Maintain diffs in chem. comp btwn intra and extra o Prisoner exchange of sending 3 Na out: 2 K in o Costs a lot of energy (20-40% of energy reqd by brain) Ca pumps o Only Ca out o Release of neurotrans depends on low levels on intra Ca Cytoskeleton: o Maintains shape of neuron o Filaments x 3: 1) microtubules: Largest (25nm diameter), hollow tubes Move various materials within cells o Anterograde (= forward) transport: soma axon terminal o Retrograde (= backward) transport: axon terminal soma Alzheimers: o Memory loss, cog + physical decline, death o Neurofibrillary tangles consisting of tau protein bc high tau lvls Normally, tau connects adjacent microtubules and holds them in place o Bc enzymes high tau lvls neuron adds phosphate tau disconnects and forms tangles neuron collapses in on itself o Amyloid plaques (amyloid = abnormal protein) Beta amyloid = specific type that works with tau to break apart microtubules 2) neurofilament Most common 10nm, hair-like Structural support 3) microfilament Smallest, 3-5nm Mostly found in neuron branches Change shape and length of branches during dev and for learning Soma: o Nucleus: contains DNA, directs cell fxns Nucleolous: substructure that builds ribosomes Ribosomes= produce proteins on their own or w/ the ER o Endoplasmic reticulum: RER: ribosomes on surface, proteins constructed here SER: no ribosomes, transports proteins to GA o Golgi Apparatus: packages the completed proteins into vesicles (made out of membrane material) o Mitochnodria: extracts O2 and pyruvic acid from sugar in intra fluid and ATP (adenosine triphosphate) for energy source Dendrites: o Greater surface area of a dendrite, the more connections/synapses can be formed o Dendritic spines: knobs sometimes formed by dendrites which provide even more space for synapses to occur can change shape based on amount of activity occurring at synapse related to learning + memory abnormal ~s mental retardation unusually long and thin (how they are in early dev) FMRP = Fragile X mental retardation protein = necessary for normal maturation Axon: o Axon hllock: Cone-shaped segment that lies at junction of axon and cell body APs start here and then go down length of axon o Larger axons = faster at signalling But, myelin allows for rapid signalling even though smaller axon diameter Most of CNS neurons + PNS motor neurons = myelinated o Only some PNS sensory are myelinated, more likely for the larger diameter ones Myelin is formed by certain types of glia Does not cover length of an axono Hillock is uncovered and between each sement of myelin, there is a bare space of axon membrane called node of Ranvier o Larger axons have thicker myelin and greater distances between nodes of Ranvier Advantages of myelin: o Allow axons to be smaller without sacrificing transmission speed o Reduces energy reqs of neurons by decreasing amount of work done by Na/K pumps o Since myelin segments wrap around so tightly, there is little to no extracellular fluid between myelin and axon membrane. Therefore, no need for ion channels under myelin! Only the axon hillock and nodes of ranvier will have ion channels Multiple Sclerosis: o Progressive demyelination of nervous sys o Neural signalling wont work properly o range of symptoms from increased fatigue to vision/mobility problems to death
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