UNC-Chapel Hill EXSS 276 - EXAM 3 REVIEW (18 pages)

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EXAM 3 REVIEW



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EXAM 3 REVIEW

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Pages:
18
School:
University of North Carolina at Chapel Hill
Course:
Exss 276 - Human Physiology
Human Physiology Documents
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EXAM 3 REVIEW Chapter 12 Nervous Tissue o Nervous System Cells o Neurons nerve cells conduct electrical signals action potential Neurogilia provide support to neurons Make up about volume of CNS Astrocytes of CNS star shaped cells largest and most numerous of neuroglia Oligondedrocytes of CNS smaller and contain fewer processes compared to astrocytes o Responsible for forming and maintain the myelin sheath around CNS axon Shwann Cells of PNS myelinates a single axon participate in axon regeneration Neurons have excitable tissue cause a change in voltage to become either more positive or negative Fast process Short duration and specific Parts of neuron Dendrites receive input Axon carries impulse action potential Cell body basic functions of neuron Axon hillock sums graded potentials Axon terminal forms synapse and releases neurotransmitters o Myelination o Function to speed up operation o Sheath consists of fat and protein covering o Node of Ranvier gaps in myelin sheath What allow action potential to move along axon propagate speed o types that produce myelin sheaths Schwann cells in PNS Oligodendrocytes in CNS o White vs Grey Matter o White Composed primarily of myelinated axons Whitish color To try to help secrete linkage from one to another Conduction Brain and spinal cord are highly myelinated Speed fast Provides link between areas region o Grey Contains neuronal cell bodies dendrites unmyelinated axons axon terminals and neuroglia Grey because the Nissl bodies impart appears gray color and there is little or no myelin in the areas Neural processing Analysis Interpretation Higher order of thinking o Blood brain barrier o Barrier around the brain that controls permeability of different substances Very selective o To transport glucose for neuron tissue keep drugs out as well as pathogens o Astrocytes help form blood brain barrier o To get through blood brain barrier Fat soluble materials O2 CO2 C2H5OH free diffusion Glucose active transport Water soluble materials slow process in Drugs proteins blocked o Disruption dizziness unconsciousness death Trauma to head can cause leakage of proteins into plasma o Ion Channels o Leak Channels randomly open close Plasma membrane have many more potassium ion K leak channels than sodium ion Na leak channels and the potassium ion leak channels are leakier than the sodium ion lean channels Membranes permeability to K is much higher than its permeability to Na Move down its gradient Leak channels and ion pumps complement each other to maintain a constant electrical potential Found in all cells of all types of neurons o Ligand gated channels open when ligand chemical binds with receptor neurotransmitters hormones and particular ions can open or close o ex acetylcholine neurotransmitter opens cation channels that allow Na and Ca2 to diffuse inward and K to diffuse outward located in the dendrites o mechanically gated channels open through a mechanical stimulus touch pressure vibration sound waves tissue stretching force distors the channel from its resting position opening the gate found at dendrites found in sensory receptors o voltage gated channels opens in response to a change in membrane potential voltage electrical signal open when meeting threshold 55mV participate in the generation and conduction of action potentials in the axons and axon terminal of all types of neurons o Resting Membrane Potential o Small buildup of charges along the potential membrane o This causes a potential energy because of the positive and negative charges The greater the difference in charge across the membrane the larger the membrane potential voltage o Overall net charge between the extracellular fluid and cytosol are equal neutral o Normally 70mV Due to sodium potassium pump K leak channels let even more positives out o Established by leak channels There are more potassium leak channels than there are sodium channels so more positive potassium ions go out of cell than positively sodium ions that diffuse in o Maintained by the Na K pump Maintain high K inside neuron and high Na outside neuron o Establishing Membrane Potential o Factors that contribute to RMP Na K pumps Sodium in potassium out Na moves against gradient ATP 3 potassium K moves out 2 sodium Na move in o more positive out more negative inside Anion impermeability inability of most anions to leave the cell Anions inside cell are not free to leave because they are attached to non diffusible molecules such as ATP and large proteins o Na increases inside becoming more negative Ion and ion channel disparities unequal distribution of ions o o o o Large and charged Permeability of Na is low because of few sodium leak channels o Sodium ions diffuse slowly inward down gradient As more K move out of cell inside becomes more negative Graded potential o Small deviation local change from the resting membrane potential that makes the membrane either more polarized inside more negative or less polarized inside less negative Travel few mm only Very local changes occurring in dendrites and cell body of a neuron o Occurs when a stimulus causes mechanically gated or ligand gated channels to open or close in an excitable cell s plasma membrane o Establishing resting membrane potential o Membrane potential becomes more positive excitatory or more negative inhibitory Excitatory potential More positive o Ex ligand gated Na channel Ligand binds activation Positive moves in to make less negative As it opens ligand dissociated from receptor increases in potential and then it closes and goes back to resting membrane potential Quick bc it needs to go back to rmp 70mV Inhibitory potential More negative o Ex ligand gated Cl channel o Hyperpolarizing negative potential o More negative because Cl ions move into cell Graded Potential Strength o Directly proportional to signal Bigger signal more change o Local quick travel across dendrites o Do not exhibit a refractory period Temporal Summation o Process by which graded potentials add together As they get closer bigger summation Spatial Summation o Magnitude direction o All graded potential has to arrive simultaneously o Sum of inputs from different sources o Dendrites receive both excitatory and inhibitory signals o 3 1 2 1 o Action Potential o A sequence of rapidly occurring events that decrease and reserve the membrane potential and then eventually restore it to the resting state o Occurs in the membrane of the axon of a neuron when depolarization reaches threshold 55mV


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