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BSCI440Lecture 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 compartmentso Plasma- extracellular fluid inside bloodo 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 directionso What are we measuring, what level do we want, what is the stimuluso In you, there are sensory structures measuring everything and there are comparators that sends signals to the effector organBlood glucose fig 1- Design a Control System o Sensoro Reference + Comparatoro Effector for output- Homeostatic loop- o closed, negative feedback, always start with a stimulus- Peripheral nervous system:o CNS- brain and spinalo PNS- Sensory- afferent Motor- efferentTextbook Chapter 7(Please review Ch 4)CD Modules NervousSystem I & IILecture 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 briao Schwan cells (PNS)o Oligodendrocyte (CNS) Both give insulation, lay down myelin - Astrocytes- help regulate extracellylar K+ concentration of extracellular CFSo Capillaries in brain are not leaky Blood brain barrier Gases and other hydrophobic molecules can freely cross (oxygen, ethanol) Hydrophilic molecules need selective transporters (glucose, amino acids)- Ex. Amphedomine and methamphedomine- meth more potent, more lipid soluable, leaves blood to CNS faster- Picture on board of cello High Na outsideo High K+ inside- Nerst equationo 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 outsideo If Na is entering, positive- Equilibrium potentialo If E=equilibrium potential of that ion, means ion is at rest, no net iono If inside = -61.5, no net movement of Na- All cells leak K+ and a little Na- 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- Neg and positive doesn’t count as quantity, just direction- Membrane potential (Vm)o More positive= depolarizationo 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)Ohms Law I=V/Ro I = currento Any charge that moves = currento Inversely proportional to resistance (R)o V = voltageo G= 1/R I=VG Permeability of an ion shows concentration of membrane potentialGoldman EquationE Ion = R T ln [Ion]1z F [Ion]2R = gas constant = 1.987 cal/mol-degT = degrees Kz = ion valenceF = Faraday’s Constant 23,062 cal/V-molVm (mV) = - 61.5 log10 PK+[K+]in + PNa+ [Na+]in + PCl-[Cl-]out z PK+[K+]out + PNa+ [Na+]out + PCl-[Cl-]in If approximating, use KIf you open Na channels, depolarizationHigher G Na, larger amplitude of depolarizationLocal/ graded potentialHyperpolarize= open Cl channels all cells can generate graded potentialso signal molecules will cause graded potentials on dendriteso 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 stretcho generated by signal molecules or physical stimuliExcitable Cells conduct action optentials, message down length of cellVoltage-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 regionVoltage gated Na channelred balls- voltage sensorsinactivation gate gets out of the way when gate is open, but only for a little whilerefractory periodfig 7.13at peak voltage gated channels close and inactivatevoltage gated K channels open1. resting potential2. open Na channels- depolarization phase, causes Na to flow into cell3. peak- Na channels close and inactivate, K channels open and repolarize faster dueto K channels open longer4. refractory, VG K channels open for longer time than necessary red- membrane potential blue- conductance green- voltage gated K channelsAction Potential All or noneo Either get an action potential or I don’to 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 anothero b/c of refractory periodo AP are independent decrete events One direction (dendrites to terminal) Propagated (non-decremental)Large diameter axon has less resistance, increased flowMyelination of a neuron- insulateCurrent flows very fast down axonAP jumps from node to node which is why mylenation incereases conduction velocityHow far apart can they be- in reality about half as farThe information a nerve conducts is coded in the frequency, the higher the frequency, thegreater the response of the action potential Amplitude and duration of AP cant change At terminal- determines amount of signal molecules releasedLecture 3 (1/31)There will be a problem on action potential and membrane potential on the examIf there is a change in ion concentration, everything changes- affects the signal transduction of the nervous system and the heart Gap JunctionAutocrines- neurons that release signal moleculesSynapse- In the terminal, the voltage gated Ca++ channels open- Ca comes in, vesicles fuse to membrane, release signal moleculeso 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 namesAutoreceptors- receptors on postsynaptic and presynaptic side- Many neurons have receptors on the neuronWhy must each vesicle contain the same number


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UMD BSCI 440 - Homeostasis

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