Electrophysiology of Cell Membranes: Understanding Voltage, Ions, and Membrane Potentials, Quizzes of Philosophy of psychiatry

Download Electrophysiology of Cell Membranes: Understanding Voltage, Ions, and Membrane Potentials and more Quizzes Philosophy of psychiatry in PDF only on Docsity! TERM 1 What is a potential? DEFINITION 1 an energy state of an object that has the ability (potential) to do work (expend energy). TERM 2 For charged molecules and in electrical circuits, the potential to do work is expressed as what? DEFINITION 2 voltage TERM 3 For membrane potentials, voltage is measured where? DEFINITION 3 between two compartments separated by a membrane (usually inside and outside of a cell). TERM 4 A difference in electrical potential can help to do what? DEFINITION 4 move ions and other charged molecules across the membrane in either direction depending upon the conditions TERM 5 Why have a membrane potential? DEFINITION 5 useful for controlling intracellular environmenttransport of metabolic precursors into and out of the cellenergy link for metabolic processes TERM 6 What important things in the NS are coded as changes in membrane potential? DEFINITION 6 almost all rapid signals within the nervous system including external and internal stimuli and communication between cells TERM 7 The movement of ions across a membrane is essentially the same as what? DEFINITION 7 an electrical circuit TERM 8 . In a simple electrical circuit, the ability to move (potential or voltage) charged particles (electrons) is created how? DEFINITION 8 through chemical reactions in a battery TERM 9 Ohm's Law DEFINITION 9 The electrons move through a conductor (wire) and some resistance (load) according to Ohms Law: (I=V/R, also rearranged to V=IR) where:I = electrical current in amperesV= voltage in voltsR= resistance in ohms TERM 10 Ohm's law demonstrates what? DEFINITION 10 that voltage current and resistance are all interdependent.also shows that if any component is 0, (e.g. no voltage, very high resistance) no current will flow. TERM 21 How do cells create and maintain concentration gradients? DEFINITION 21 by actively transporting (pumping) ions from one side of the membrane to the other usually against a concentration gradient.sodium potassium pump TERM 22 What does the Na-K pump move? DEFINITION 22 This pump (a protein complex in the membrane) moves 3 sodium ions out of the cell and 2 potassium ions into the cell at the cost of an ATP molecule (energy). in this process the exchange of 3 sodium ions out and 2 potassium ions in not only acts to establish a concentration gradient, but also an electrical gradient (net -1 each cycle). TERM 23 Transport mechanisms that create an electrical potential/concentration difference and are called what? DEFINITION 23 electrogenic TERM 24 The Na+/K+ pump takes up what % of energy used by the brain? DEFINITION 24 20-40% of the energy used by the brain and is largely responsible for the generation of the concentration gradients necessary to maintain a resting membrane potential. TERM 25 What happens if the pump is inhibited through poison or insufficient ATP stores? DEFINITION 25 the membrane potential will gradually approach 0 as the ion concentration gradients across the membrane are lost TERM 26 which component of the membrane is highly resistant to the passage of charged elements (ions)? DEFINITION 26 The highly hydrophobic component of membranes TERM 27 The movement of ions across the membrane (current) is made possible by what? DEFINITION 27 special protein elements inserted into the membrane (ion channels) which will allow ions to pass through them or special enzyme proteins to transport ions across the membrane (transporters, ion pumps). TERM 28 How can a cell change its permeability? DEFINITION 28 This can be done by changing the properties or numbers of ion channels in their membrane. This includes opening or closing existing channels or changing the number of channels in the membrane. TERM 29 resting membrane potential DEFINITION 29 The net potential of all the different ions distributed across a membrane in a cell which has not been stimulated TERM 30 dynamic equilibrium DEFINITION 30 A dynamic equilibrium exists once a reversible reaction ceases to change its ratio of reactants/products, but substances move between the chemicals at an equal rate, meaning there is no net change. TERM 31 For the resting membrane potential, the contribution a particular ion will have on the net potential is determined how? DEFINITION 31 by how permeable the membrane is to that ion TERM 32 Ions that cannot cross the membrane (permeability is near 0), can contribute to what? DEFINITION 32 a charge difference across the membrane, but not current flow of the particular ion TERM 33 The control of how permeable the cell membrane is to a particular ion mediated how? DEFINITION 33 through ion channels TERM 34 The control permeability is a function of what? DEFINITION 34 how selective channels are for a particular ion, and the opening and closing of channels . TERM 35 passive channels or leakage channels DEFINITION 35 act basically like selective holes in the membrane and allow some types of ions to pass freely into and out of the cell TERM 46 Graded responses can be of what type? DEFINITION 46 can be depolarizing (opening sodium or calcium channels) or hyperpolarizing (open potassium or chloride channels). TERM 47 Depolarizing postsynaptic potentials tend to do what? DEFINITION 47 excite the postsynaptic cell and are called excitatory postsynaptic potentials (EPSPs). TERM 48 Hyperpolarizing potentials do what? DEFINITION 48 are inhibitory and called inhibitory post synaptic potentials (IPSPs) TERM 49 If there are no other ion channels that are opened as a result of the local depolarization effect, what happens? DEFINITION 49 the discharge of the membrane capacitance will continue to spread passively across the membrane (electrotonic conduction).The electrical potential (voltage) sustaining the depolarization declines in amplitude exponentially as a function of distance and time and is effective over very short distances, usually several hundred microns or less than a millimeter TERM 50 Adding graded potentials does what? DEFINITION 50 While graded potentials dont travel very far, they can interact to summate or subtract from each other on the postsynaptic membrane.The two primary mechanisms involved are temporal and spatial summation. TERM 51 temporal summation DEFINITION 51 takes place at a single synapse and uses the frequency of incoming action potentials. TERM 52 temporal summation relies on what? DEFINITION 52 the fact the time needed for a postsynaptic potential to be generated and die away (synaptic delay) is substantially longer than the shortest interval between action potentials arriving at presynaptic terminals (1 ms). If multiple action potentials arrive at a synapse before the prior potential has completed, it will cause the release of more neurotransmitter, open more ion channels and add to the postsynaptic potential. TERM 53 An increased frequency of action potentials and their temporal summation at the synapse can produce what? DEFINITION 53 a larger postsynaptic potential that has a greater chance of activating the postsynaptic neuron. TERM 54 spatial summation DEFINITION 54 greater effects can be produced by the combined effects of multiple synapses spatially across the neuronal membraneLike waves, the peaks and troughs can combine either in an additive or subtractive fashion in space TERM 55 The decline in magnitude of graded potentials as they spread across the membrane results from what? DEFINITION 55 membrane capacitance, potassium (leakage channels; e.g. Carrying a leaky bucket) and the cytoplasmic resistance to ionic movement. TERM 56 what solves the problem of signals only travelling a short distance? DEFINITION 56 excitable cells contain areas of the cell which have Voltage gated ion channels that can open and close in response to membrane depolarization or hyperpolarization TERM 57 significance of voltage gated channels and perpetuating the action potential DEFINITION 57 Because voltage gated channels respond to changes in membrane polarization, they can be activated quickly and spread over relatively large areas by sequentially activating adjacent voltage gated channels in the membrane (if they are there). This type of activation can both greatly magnify and sustain the initial depolarization across the membrane. TERM 58 primary voltage gated channels DEFINITION 58 the primary types are for potassium, sodium and calcium. TERM 59 what is the primary driving force for action potentials? DEFINITION 59 For action potentials along axons, the activation of voltage gated sodium and potassium channels by depolarization is the primary driving forces for action potentials. TERM 60 factors that determine the membrane voltage pattern DEFINITION 60 determined by the timing, number and types of channels opened and closed. The process is dependent upon some basic properties of voltage gated sodium and potassium ion channels. TERM 71 threshold. DEFINITION 71 The amount of membrane depolarization needed to activate voltage sensitive ion channels (usually sodium channels)Threshold is defined as the level of depolarization needed to produce action potentials 50% of the time. TERM 72 If the depolarization is large enough to activate voltage gated sodium channels, then what? DEFINITION 72 an action potential is generatedwill be of the same amplitude regardless of the magnitude of stimulus that drove the membrane above threshold. TERM 73 what happens as the action potential is initiated? DEFINITION 73 voltage gated potassium channels will also begin to open.Their rate of opening lags slightly behind the sodium channels, but begins to influence the membrane potential more as the sodium channels are inactivated and sodium permeability decreases. Accordingly, the membrane potential will begin to decline TERM 74 after-hyperpolarization DEFINITION 74 a period of time in which the potassium permeability remains high after the sodium conductance has returned to resting levels. remains until potassium conductance returns to resting levels. TERM 75 how does an action potential propagate? DEFINITION 75 Once initiated, action potentials move over membranes by sequentially producing enough depolarization to open voltage gated sodium channels in the adjacent membrane.This activation is accomplished by the same wave mechanism as in passive conduction except that additional depolarization is created by the sequential opening of voltage gated channels across the membrane. A wave of depolarization will move across the cell membrane or down an axon (propagation or conduction). TERM 76 absolute refractory period DEFINITION 76 Refractoriness is the fundamental property of any object of autowave nature not to respond on stimuli, if the object stays in the specific refractory state. TERM 77 During the rest recovery phase of the membrane, a new depolarization cycle can be produced how? DEFINITION 77 if the stimulus is large enough (usually much above the resting membrane threshold). TERM 78 relative refractory period DEFINITION 78 continues until the membrane resting potential returns TERM 79 Refractory periods in also membranes help to insure what? DEFINITION 79 that action potentials travel primarily in one direction in cell processes. TERM 80 If an axon, essentially a tube, is stimulated in the middle, the action potential can spread how? DEFINITION 80 in both directions, both orthodromic (normal direction of conduction toward the effector zone) and antidromic (abnormal direction, usually toward the receptor zone. TERM 81 if the AP is generated in a trigger zone or at one end of an axon, what happens? DEFINITION 81 the wave of depolarization progresses down the axon, followed by a wave of repolarization in which the membrane is in an absolute or relative refractory period. This essentially blocks the depolarization from reversing. TERM 82 The excitable regions of a cell are characterized by what? DEFINITION 82 high concentrations of voltage gated ion channels (usually for sodium). TERM 83 The non-excitable cell or region of the cell can still have functions associated with what? DEFINITION 83 graded potentials TERM 84 Action potentials can be induced in any area of an excitable cell that contains what? DEFINITION 84 enough voltage sensitive channels to initiate and sustain the depolarization cascade (Hodgkin Cycle). TERM 85 In neuronal cell bodies, the axon arises from where? DEFINITION 85 a specialized region of the cell body, that includes the axon hillock, at the junction of the cell body and axon and axon initial segment TERM 96 how are sensory axons divided? DEFINITION 96 into groups Ia,Ib,II,III, and V. TERM 97 function of sensory axons 1a, 1b DEFINITION 97 motor afferent: golgi tendon organ TERM 98 function of sensory axons II DEFINITION 98 sensory afferent: touch, pressure, hair, joint TERM 99 function of sensory axons III DEFINITION 99 sensory afferent: hairfree nerve endings: fast pain, temperature TERM 100 function of afferent sensory axons IV DEFINITION 100 sympathetic, sensory afferent: slow pain, temp, mechanoreceptors