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Neuro Lecture 1.docx

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Michelle French

Neuro: Lecture 1 October-27-12 8:47 PM Cell membrane info • Permeability, simple diffusion, facilitated diffusion, active transport, secondary active transport (substance carried up gradient without ATP catabolism by using other people's energy •Channels made of membrane spanning proteins o Pore loops of the protein molecules dangle inside the channel o Selective, made of many subunits o Gated channels • Most channels can be closed off • 2 shapes, one is open, other is closed Voltage gated channels •Some membrane channels are sensitive to the potential difference across the membrane •Conformation changes causing a pore to be created •The voltage sensing mechanism is in the 4th trans membrane domain of the protein, the S4 segment •S4 sticks out the side of the protein (like a wing) •The natural position of the S4 'wing' is up towards the outer surface of the cell membrane •But when the membrane is polarized, the positively charged wing is attracted downwards to the negatively charged inner surface of the membrane •Membrane depolarized to -50 MV. No more electrical attraction so S4 wing migrates up •When up, stuff can go through Ligand gated channels •Cell membrane receptors are part of the body's chemical signalling system •Ligand binding with receptor triggers stuff at membrane e.g. activation of an enzyme Endocytosis •Membrane pinches inward to make a vesicle, usually receptor mediated to capture proteins, from outside to inside Exocytosis •Partial or complete fusion of vesicles with cell membrane for bulk transmembrane transport of specific molecules, from inside to outside •Intracellular material is packed in vesicles and either secreted or delivered to the plasma membrane by exocytosis •Two mechanisms o Exocytosis 1: fast, called kiss and run • Secretory vesicles dock and fuse with the plasma membrane at specific locations called fusion pores • Vesicle can connect and disconnect several times before contents are empties • Since o
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