Anatomy and phys lecture 16
Anatomy and phys lecture 16 PHCL2600
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This 5 page Class Notes was uploaded by Legacy Tanner on Tuesday October 6, 2015. The Class Notes belongs to PHCL2600 at University of Toledo taught by Williams,F in Fall 2015. Since its upload, it has received 25 views. For similar materials see Funct Anat and Pathophysiol I in Pharmaceutical Sciences at University of Toledo.
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Date Created: 10/06/15
Anatomy Lecture 16 Repolarization Phase 4 and 5 o Voltagegated K channels are open More K ions leave the neuron Build up of negative charges inside of the membrane surface 0 Na channel inactivation gates open 0 lnactivated Na channels return to resting state 0 Repolarization phase is produced by the slowing opening of voltagegated K channels Na in ux and K out ow causes the change in membrane potential from 30mv to 70mv Hyperpolarization Phase 6 o More negative membrane potential than at rest Voltagegated K channels close slowly they remain open longer Na channels are in the resting state 0 K channels close returning potential to resting levels 0 Summary pic in phone Refractory periods 0 Membrane does not respond to further stimulation 0 2 refractory periods 0 Pic in phone 0 Absolute refractory period No amount of stimulation will produce a second AP Coincides with Na channels activation and inachann Channels will not respond Inactivated Na channels must rst return to the resting state 0 Relative refractory period K channels are open and enough Na channels are in normal close position Stimulation greater than threshold can produce a second AP 0 Need enough Na to counteract K ef ux Membrane is hyperpolarized to some degree 0 Types of propagation ways impulse travels 0 Continuous propagation or continuous conduction Unmyelinated axons and muscle bers Goes all the way down every part of axon o Salutatory propagation or salutatory conduction Myelinated axons propagation is more rapid Skips and travels via Nodes of Ranvier Propagation of action potentials 0 AP propagation begins at the trigger zone near the axon hillock AP regenerates over and over at adjacent areas from trigger zone Propagated AP is not the same as initial AP lt propagates away from the initiation site one way It cannot reverse direction 0 Previous axon segment is in the absolute refractory period 0 Pic in phone 0 Continuous propagation Step by step depolarization and repoarization Flow of ions voltagegated Na channels in each adjacent segment of the membrane Short distance propagation of the action potential 0 Salutatory propagation Each nodal area depolarizes to threshold triggering an AP lons cross the membrane only at the nodes AP leaps from node to node 0 Salutatory conduction Uneven distribution of voltagegated channels 0 Many Na and K channels at the Node of Ranvier Few channels at region cover by myelin Myelin increases the resistance to the flow of ions across the membrane 0 Pic in phone 0 Local anesthetics Lidocaine It is used topically to relieve itching burning and pain from skin in ammations It is injected as a dental anesthetic or as a local anesthetic for minor surgery Prevent opening of voltagegated Na channeb Nerve impulses cannot pass the anesthetized region 0 Speed of propagation factors 3 major factors affect AP propagation Amount of myelination Myelinated axons propagate AP more rapidly Axon diameter Propagation is faster in largediameter axons Temperature Propagation at lower speeds when axons are cooled Neurotransmission o Presynaptic neuron transmits info and postsynaptic neuron receives info 0 Pic in phone 0 Properties of synapses Electrical synapses Action potential conduct directly between 2 cells 0 GapjuncUons Chemical synapses Electrical signal is transferred from 1 neuron to another using chemical anaHng o It needs neurotransmitters Pic in phone 0 Types of chemical synapses o Synapse is the junction between a neuron and a second ce ex Neuron 0 Types Axodendritic axon and dendr e Axosomatic axon and cell body Axoaxonic axon and axon Pic in phone
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