10/14/14%1%Electrical)Signals:%Ac(on%Poten(al%Propaga(on%Lesson%23%::%BIOL%1108%::%15%October%2014%1%Unit:%Animal%Form%and%Func(on%Today ’s%Topic:%Ac(on%Poten(al%Propaga(on%Today’s%learning%objec(ves:%Be%able%to:%• describe%how%an%electrical%signal%moves%– down%an%axon%– from%one%neuron%to%the%next%• apply%what%you’ve%learned%to%real%world%situa(ons%2%10/14/14%2%Figure 48.11-5 OUTSIDE OF CELL INSIDE OF CELL Inactivation loop Sodium channel Potassium channel Action potential Threshold Resting potential Time Membrane potential (mV) +50 -100 -50 0 Na+ K+ Key 2 1 3 4 5 1 2 3 4 5 1 Resting state Undershoot Depolarization Rising phase of the action potential Falling phase of the action potential 3%4%Channels%in%the%cell%membrane%of%an%axon%%10/14/14%3%Δt%Δt%5%Ac(on%Poten(al%Propaga(on:%Speed%1)%2)%6%10/14/14%4%Ac(on%Poten(al%Propaga(on%Speed%Size%and%Structure%Myelina1on)Type)Axon)Diameter)Speed)Example)In)2m)Tall)Person)Giant%Squid%Unmyelinated%Up%to%1%mm%%100m/sec%Propulsion%NA%Mammals%Unmyelinated%2%μm%2m/sec%Warm%temperature%sensors%Toe%to%brain%in%1%sec%Mammals%Myelinated%5%μm%40m/sec%Pain%mechano%receptors%Toe%to%brain%in%50%ms%Mammals%Myelinated%20%μm%120m/sec%Motorneurons%to%muscle%Brain%to%toe%in%16%ms%7%8%Channels%in%the%cell%membrane%of%an%axon%%10/14/14%5%9%Ac(on%Poten(al%Propaga(on%Speed:%Structure%In%a%neuron,%signal%transmission%speed%is%affected%MOST%by%which%structure?%a)%dendrites%b)%axon%hillock%c)%axon%size%d)%myelin%sheath%10%D.)SQUID)drawing%credit:%dolphin4life.weebly.com%10/14/14%6%Figure 48.4 Nucleus Dendrites Stimulus Axon hillock Cell body Presynaptic cell Signal direction Axon Synapse Neurotransmitter Synaptic terminals Postsynaptic cell Synaptic terminals Signal%Movement%Between%Neurons%1)____________%synapses%2)____________%synapses%11%Figure 48.15 Presynaptic cell Postsynaptic cell Axon Presynaptic membrane Synaptic vesicle containing neurotransmitter Postsynaptic membrane Synaptic cleft Voltage-gated Ca2+ channel Ligand-gated ion channels Ca2+ Na+ K+ 2 1 3 4 Neuron%%to%%Neuron%Communica(on%for%Chemical%Synapses%12%10/14/14%7%5%groups%of%Neurotransmiaers%• Acetylcholine:%muscle%s(mula(on,%memory%forma(on,%learning%• Amino)Acids:)longbterm%memory%• Biogenic)Amines:)sleep,%mood,%aaen(on,%learning%– Used%for%nervous%system%disorders%and%treatments%• Neuropep1des:)pain%recep(on%• Gases)– Nitric%oxide%(local%regulators)%– Carbon%monoxide%(hypothalmic%hormone%release;%intes(ne%smooth%muscle%plasma%membrane%hyperpolariza(on)%13%Post%Synap(c%Responses%Excitatory%Post%%Synap(c%Poten(al%(EPSP):%Inhibitory%Post%%Synap(c%Poten(al%(IPSP):%How%does%the%membrane%poten(al%in%the%%postsynap(c%neuron%change%%with%an%EPSP%vs%an %IPSP?%Membrane%poten(al%(mV)%Time%0%0%b55%b70%Membrane%poten(al%(mV)%Time%0%0%b55%b70%14%10/14/14%8%15%Consider:%What%happens%when%you%have%excitatory%and%inh ib itory%synapses%firing%simultaneously?%Electrical%signals%are%kept%moving%in%one%direc(on%down%an%axon%by%which%of%the%following%occurrences?%%16%a)%potassium%leaving%the%cell%rapidly%when%voltagebgated%potassium%channels%are%open%b)%sodium%entering%rapidly%when%voltagebgated%sodium%channels%are%open%%c)%sodium%and%potassium%exchange%through%the%sodiumbpotassium%pump%d)%potassium%flowing%through%Ligandbgated%ion%channels%10/14/14%9%Nervous%System%Dis orders%• Schizophrenia:%distorted%percep(on%of%reality%by%fragmen(ng%brain%func(ons%(1%%of%world’s%popula(on)%• Depression:)depressed%mood,%abnormal%sleep,%appe(te,%and%energy%– Major%depression%(1%in%7%adults)%– Bipolar%disorder%(1%%of%world’s%popula(on)%• Drug)Addic1on:)compulsive%consump(on%and%lack%of%intake%control%(including%alcohol%and%nico(ne)%• Alzheimer’s)Disease:)progressive%mental%deteriora(on%(demen(a),%confusion,%and%memory%loss%– No%cure%but%some%drugs%relieve%symptoms%• 10%%of%people%age%65;%35%%of%people%age%85%• Parkinson’s)Disease:)progressive)motor%disorder;%muscle%tremors,%poor%balance,%flexed% posture,%shuffling%gait%– No%cure%but%some%drugs%manage%symptoms%• 1%%of%people%age%65;%5%%of%people%age%85%17%Animal%Form%and%Func(on:%Ac(on%Poten(al%Propaga(on%Today’s%learning%objec(ves:%Be%able%to:%• describ e%how%an%electrical%signal%moves%– down%an%axon%– from%one%neuron%to%the%next%• app ly%what%you’ve%learned%to%real%world%situa(ons%Think%about:%b