OPTM4106 Structure of neuron and synapse 2024 PDF

OPTM4106 Structure of neuron and synapse Dr. Jason Charng [email protected] Acknowledgement of country The University of Western Australia acknowledges that its campus is situated on Noongar land, and that Noongar...

OPTM4106 Structure of neuron and synapse Dr. Jason Charng [email protected] Acknowledgement of country The University of Western Australia acknowledges that its campus is situated on Noongar land, and that Noongar people remain the spiritual and cultural custodians of their land, and continue to practise their values, languages, beliefs and knowledge. Artist: Dr Richard Barry Walley OAM Objectives Neuron structure Neuron message propagation Retina – neurotransmitters and glial cells  Neuron (type of Cell ( Consists of contains the where soma/cell body E nuclear of the neuron E receive dendrites Cell axon => carries electron information along information the length of neuron Information flow: Dendrites -> cell body -> axon -> terminals -> effector cell https://qbi.uq.edu.au/brain/brain-anatomy/types-neurons Dendrites Branches from cell body Can be extensive m T Receives signal from axon endings of other neurons (i.e. synapse) Made up of neurofilaments https://www.ncbi.nlm.nih.gov/books/NBK11536/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5556172/ Soma Metabolic centre of the neuron Maintains normal neuron functioning Produce proteins required Neurons classified by shape of cell body and the pattern of processes from it https://www.ncbi.nlm.nih.gov/books/NBK11536/  4 Types , according to the cell body pattern of processes Neuron classification & Unipolar Only one process extends from cell body Branches to form dendrite and axon Bipolar One axon and one dendrite that extend from either end of the cell body Pseudounipolar E Nodendrites Single axon that bifurcates Cusually Sensory neuron serves sensory neurons) Multipolar Multiple tapering dendrites Single axon Hu large amount of dendrites of dendrites - allows large amount https://qbi.uq.edu.au/brain/brain-anatomy/types-neurons Axons aka nerve fibre Carries electrical message to the next neuron Can extend for long distances Myelination allows faster information transmission Terminate in axon terminal Y released When neuron transmitters are. https://qbi.uq.edu.au/brain/brain-anatomy/axons-cable-transmission-neurons Neuronal functional classification PUPIL PATHWAY Neurons can be classified by their function Afferent – transfer information carry information to from the periphery to CNS the CNS · Efferent – transfer information carry information from from CNS to the periphery the CNS. http://syllabus.cwru.edu/YearThree/neuroscience/NeurLrngObjectives/Pupil.htm  rapid rise & fall in membrane Action potential El. Used potential by most neurons to Propagate electrical massage. Transitory change in the resting large to a Rapid deactivation of membrane potential of the neuron Refers amount of - > - Not channels & the Nat Transmit electrical signal along influx of opening efflux of KT. 70 mU due to the relative more Idue to the neuron - sodium ions outsidethe cell. ofNat channels) Four steps This by is achieved the sodium pumping Hypopolarisation Potassium ATP channels Depolarisation sodium out of the neuron When reached the threshold (-55). , O O ↓ fire 70 to -55 is the neuron will Repolarisation. - achieved via neuron transmitters Hyperpolarisation binding to the ligand gated of the channels channels at which induces synapse causing opening. Action potential at axon terminal – influx of Not neurotransmitter release & Photoreceptors bipolar cells use graded potential instead. Resting potential of a neuron is around - 70 MV. https://www.moleculardevices.com/applications/patch-clamp-electrophysiology/what-action-potential to -55  Presynaptic inhibition Inhibit the postsynapic Inhibition before the neuron via the is release excitatory signal reaches of GABA- synapse GABA imnotropic – GABAA receptors: chloride ions into cell this make the cell negative more ↓ – GABAB receptors: G-protein metabotropic HYPERPOLARISATION - coupled receptors, open K+ ↑ (make less likly to fire neuron potential) Accen channels make the cell more negative. https://pubmed.ncbi.nlm.nih.gov/28825683/ Neuronal support cells Glial cells => Support cells for neuron – Structural support – Maintain homeostasis maintaining micro environment – Myelination of apcons - for neuronal function Glial cells of the CNS – Astrocytes – Oligodendrocytes – Microglia Glial cells of the PNS – Satellite cells – Schwann cells – Macrophages https://qbi.uq.edu.au/brain-basics/brain/brain-physiology/types-glia  Responsible for a myriad of important functions. Retina glial cells – Müller cell the retina principle glial cells ~ in. Runs through the entire retina Provides lactate to photoreceptors Clears metabolic waste Facilitates neurotransmitter recycling (i.e. glutamate) Facilitates photopigment recycling Maintains ionic balances Optic fibre transferring light onto photoreceptors https://pubmed.ncbi.nlm.nih.gov/25873768/ Retina glial cells – Astrocytes All restricted to the retinal most entirely nerve fibre Cell bodies and processes layer. found in RNFL Peak distribution on ONH Axonal and vascular glial sheaths, maintain blood- retina barrier of inner retina blood vessels https://webvision.med.utah.edu/ Retina glial cells – Microglia Found in every retinal layer Specialised macrophages Remove damaged neurons – Maintain homeostasis of The space btw retinal neural neuroretinal Cells microenvironment Mediate immune cells entry to retina https://webvision.med.utah.edu/  at ① Action potentials arriving the acconal terminal Synapse Depolarization at the of membrane terminal cause potential the opening of voltage gated cat channels. Between axon terminal O I Influx of cat into the neuron which synaptic cause the membrane of the and dendrite Mammals – chemical synapse for information to propagate to the next helion. resicle to fuse with the cell membrane. via which releases neurotransmitters neurotransmitter exocytosis. (the quantity of released is related to the no. of cat that entered).  Neurotransmitters of the retina. (to relay signals stage ofthe retinal to the next Released by all photoreceptor a bipolar subtypes circuit). Glutamate – excitatory GABA – inhibitory E Glycine – inhibitory Horizontal cells release glutamate to cone photoreceptors as a part of their feedback pathways. Red arrows – glutamate release Blue arrows – GABA release Green arrow – glycine release Summary General overview of neuronal structure Information propagation along and between neurons Glial cells of the retina Major neurotransmitters of the retina