BSCI440 Lecture 1 1 24 Homeostasis Why multicellularity o Specialization Allows specialized cells to deal with certain perameters Multicellularity allows you to be a homeotherm while unicellular must make different enzymes to adapt to different temps Fig 1 4 slide 8 care about o Internal environment is maintained at optimum level homeostasis Fig 1 5 slide 9 Body fluid compartments o Plasma extracellular fluid inside blood o Interstitial fluid extracellular fluid inside tissues Plasma ISF ECF Tracing line on chalk board example o Stimulus position of chalk Measured by sensory structure Class giving him directions o What are we measuring what level do we want what is the stimulus o In you there are sensory structures measuring everything and there are comparators that sends signals to the effector organ o closed negative feedback always start with a stimulus Blood glucose fig 1 Design a Control System o Sensor o Reference Comparator o Effector for output Homeostatic loop Peripheral nervous system o CNS brain and spinal o PNS Sensory afferent Motor efferent Textbook Chapter 7 Please review Ch 4 CD Modules Nervous System I II Lecture 2 1 29 Organization of the nervous system 1 nerve cell neuron nerve collection of neurons axons from several neurons don t care about different kinds of neurons there are dendrites terminals and cell body a neuron gets input from several synaptic structures Glial cells occupy about half the volume of the bria o Schwan cells PNS o Oligodendrocyte CNS Both give insulation lay down myelin Astrocytes help regulate extracellylar K concentration of extracellular CFS o Capillaries in brain are not leaky Blood brain barrier Gases and other hydrophobic molecules can freely cross oxygen ethanol acids Hydrophilic molecules need selective transporters glucose amino Ex Amphedomine and methamphedomine meth more potent more lipid soluable leaves blood to CNS faster Picture on board of cell o High Na outside o High K inside Nerst equation E Ion R o E mV 61 5 Z x log ion ion o Ex if ratio of K to Na is 100 1 E 61 5 that s the value o Know it is negative if K is leaving going down concentration gradient to T ln Ion 1 outside o If Na is entering positive Equilibrium potential o If E equilibrium potential of that ion means ion is at rest no net ion o If inside 61 5 no net movement of Na z F If E Cl is below Vm the Cl out enter the cell If E Cl is above Vm Cl would leave cell bc inside is more negative All cells leak K and a little Na Neg and positive doesn t count as quantity just direction Membrane potential Vm Ion 2 R gas o More positive depolarization o More negative hyperpolarizaton Increase leakage of K hyperpolarization Increase permeability of Na depolarization Increase KCl outside depolarization K leaks slower o PG county lady putting KCl in patientients IV to euthanize Maximum depolarization E Na Permeability of an ion shows concentration of membrane potential Goldman Equation Ohms Law I V R I VG o I current o Any charge that moves current o Inversely proportional to resistance R o V voltage o G 1 R constant 1 987 cal mol deg T degrees K z ion valence F Faraday s Constant z 23 062 cal V mol Vm mV 61 5 log10 PK K in PNa Na in PCl Cl out PK K out PNa Na out PCl Cl in If approximating use K If you open Na channels depolarization Higher G Na larger amplitude of depolarization Local graded potential Hyperpolarize open Cl channels all cells can generate graded potentials o signal molecules will cause graded potentials on dendrites o if sensory neurons dendrites will be modified to receive sense stimuli ex corroded artery nerve endings are sensitive to blood pressure so if increased nerves will stretch o generated by signal molecules or physical stimuli Excitable Cells conduct action optentials message down length of cell Voltage gated ion channels Open Closed states determined by voltage difference across membrane Vm Threshold Closed state after opening is often referred to as channel inactivation Has a voltage sensor region Inactivation region Voltage gated Na channel red balls voltage sensors inactivation gate gets out of the way when gate is open but only for a little while refractory period fig 7 13 at peak voltage gated channels close and inactivate voltage gated K channels open resting potential 1 2 open Na channels depolarization phase causes Na to flow into cell 3 peak Na channels close and inactivate K channels open and repolarize faster due to K channels open longer refractory VG K channels open for longer time than necessary 4 red membrane potential blue conductance green voltage gated K channels Action Potential All or none o Either get an action potential or I don t o Why generate a graded potential that is at threshold or isn t Same amplitude and same duration on given neuron Cant add one action potential on top of another o b c of refractory period o AP are independent decrete events One direction dendrites to terminal Propagated non decremental Large diameter axon has less resistance increased flow Myelination of a neuron insulate Current flows very fast down axon AP jumps from node to node which is why mylenation incereases conduction velocity How far apart can they be in reality about half as far The information a nerve conducts is coded in the frequency the higher the frequency the greater the response of the action potential Amplitude and duration of AP cant change At terminal determines amount of signal molecules released Lecture 3 1 31 There will be a problem on action potential and membrane potential on the exam If there is a change in ion concentration everything changes affects the signal transduction of the nervous system and the heart Gap Junction Autocrines neurons that release signal molecules Synapse Ca comes in vesicles fuse to membrane release signal molecules In the terminal the voltage gated Ca channels open o Controls the amount of vesicles that move to membrane Amount of ca released determined by the frequency of AP Exocytosis Ca membrane fluid Complex of docking proteins don t worry about names Autoreceptors receptors on postsynaptic and presynaptic side Many neurons have receptors on the neuron Why must each vesicle contain the same number of NT molecules at any and at every moment Depression lack of signal molecules Neurotransmitters and Receptors Post Synaptic event Excitatory post synaptic graded potential depolarization o EPSP Depolarization o Threshold o Action Potential o Excitation Of o Post Synaptic Structure EPSP fast