Neural Communication: Action Potentials Conduction Synaptic Transmission | BIOS 3500, Study notes of Physiology

Download Neural Communication: Action Potentials Conduction Synaptic Transmission | BIOS 3500 and more Study notes Physiology in PDF only on Docsity! 1/24/2011 Neural Communication: Action Potentials Conduction Synaptic Transmission January 24, 20n (A) Pearl Membrane potential (mV) After hyperpolarization doy 1 1 4 1 4 ie [ee cee (ee les} Time (msec) 1 msec Slow depolarization to threshold 1/24/2011 Principles of Action Potentials » All or Nothing Principle » The Refractory Period Refractory Periods Absolute Relative refractor refract Absolute refractory ae ede period: A second response is not possible regardless of strength or duration Relative refractory of the stimulus. period: A second response can be Voltage elicited, but requires a stronger stimulus,  Contiguous Conduction ‘Adjacent inactive area into Active area al which depolarization is peak of action spresding;willsgon reach Remainder of axon potential —_thresholé still at resting potential poe ee, OEE if" THete eters tee tete ete tt eset poter ; ~ - SEEPS EPTEE ET TESTE TT EEE EET Ditection of propeyation of action potenti aie Contiguous Conduction Previous active Adjecent rea that area retumed was brought to New adjacent toreating threshold by local Inactive area into which Potentisi:no current flow: now depolarization longer active; in. active at peak of spreading: retractory period action potential reach t Flemsinder of exon sill a resting potenti 1/24/2011 1/24/2011 A OUGODENDHOGY IE Myelination St godenareoyte 9 ve B SCHWANN CELL Layers ot myelin sheath Boron & woulsges: tes ea! rrysotoa% ana Ea. 1" Copyrignt @ 2009 by Sounder, an mpeint af Ebeyie; Ire. Nights reserved, Myelinated Fibers ‘Nodes of Ranvier ‘Myelin sheath Myolin sheath axon. Plasma. membrane (2) Myetinated ber 12 1/24/2011 Schwann Cells Cytoplasm ylop' Nucleus Schwann cell Node of Ranvier Oligodendrocytes Myelin sheath Ranvier  Theoretical] Relationship for Conduction Velocity Conduction Velocity Conduction velocities for three different types of nerve fibers Fiber type Diameter Conduction velocity (um) (m/sec) Ao Gmyelinated) 15.0 120 Nonmyelinated C 0.5 1 fibers Squid giant axon 500.0 25 (nonmyelinated) 1/24/2011 10 1/24/2011 11 21  Junction between presynaptic and postsynaptic  neurons  Electrical Synapses ◦ Two neurons connected by gap junctions  Chemical Synapses ◦ Chemical messenger is transmitted across the junction  separating the two neurons 22 1/24/2011 12 23  Between two neurons  Uses neurotransmitter(s)  Presyanaptic ◦ Releases neurotransmitter into synaptic cleft  Postsynaptic  ◦ Binds and responds to neurotransmitter 24 1/24/2011 15  Once in synaptic cleft needs to be removed   If not removed, continual activation of receptor   Acetylcholinesterase for example ◦ Talk more about when we get to NMJ 29  Neurotransmitters need to be ready at synaptic  terminal  Also taken back up ◦ Whole or degradation products  Anterograde ◦ From cell body to terminal  Retrograde ◦ Terminal to cell body 30 Synaptic Vesicle Transport 1 -Et Vesicle and peptide ‘Vesicles travel through the | | A non-peptide neurotransmitter is ‘neurotransmitter precursors and | Jaxon cn microtubule tracks | | synthesized in the nerve terminal enzymes are synthesized inthe || vi and transported intoa vesicle cell and are released from Golgi. : VV CELL BODY Boren & Boulpaep: Medical Fhysiclogy, 2nd Editon. Copyriant © 2009 oy Saunders, an imprint of Elseiey, Inc. All gts reserved. Anterograde Propeptide (precursor molecule) @ Fire! peptide @ Pr riemedctes Axonal transport Retrogrode transport Vesicles Release pool a ™ Release Depolarization + calcium 1/24/2011 16 1/24/2011 17 33  Simple diffusion too slow  Movement ATP driven along microtubules  Anterograde ◦ Mitochondria and vesicles ◦ ~ 400 mm/day  Retrograde ◦ Degraded vesicles ◦ Adbsorbed exogenous material 34 +30 ine T [ atone Activation of synapse Threshold potential Membrane potential (mV) in postsynaptic neuron T Time (msec) (b) Inhibitory synapse Summation of Synaptic Signals » EPSPs can be added together to generate a reponse » Temporal summation » Spatial summation 1/24/2011 20  Sacre” sama | eoemumnen oy a) ay a 4 = om ORE \ ji “aatung action ed) ahd eH potent ae ‘Soma = 3 al 2 a a inthe axon there are simple spikes, without PSPS, The timing, ofthe axonal spikes she same as that for spikes inthe some, orem & eulaaes: acl Physelopy, ane Eon, Ceppignt 3005 by nda, an mito Clee (eal ight sec a1 Postsynaptic Integration of EPSP & IPSP Excitatory presynaptic inputs Membrane pr potential Inhibitory presynaptic input Tire (msec) 1/24/2011 21 1/24/2011 22  Large molecules (approx. 2 to 40 amino acids)  Synthesized in neuronal cell body  Packaged in large, dense‐core vesicles present in  axon terminal  Neuromodulators ◦ don’t cause EPSP or IPSP ◦ bring about long term changes that modulate, depress or  enhance the action of the synapse 43 44