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Bio 350, Exam 1
Bio 350
| Question | Answer |
|---|---|
| Parts of the neuron? | Soma (cell body), axon, axon hillock, dendrites, nodes of ranvier, myelinated areas of the axon, terminal branches, bouton terminaux, bouton en passage. |
| Four types of macroglial cells? | 1. Olgiodenrocytes (myelination, 15) 2. Schwann Cells(myelination, 1) 3. Astrocytes (regulate synaptic activity/blood-brain barrier) 4. Ependymal Cells (form the epenthelial lining of the brain, aid circulation of spinal fluid) |
| Three types of neurons? | 1. Unipolar neurons 2. Bipolar neurons 3. Multipolar neurons |
| Astrocytes? | Supporting cells (store glycogen, physical support, nutrition, provides matrix, etc.) with large, star-shaped bodies. End feet. Maintain [K+] in extracellular space, take up synaptic zones (regulate synaptic activity), form blood-brain barrier. |
| Ependymal Cells? | Support cells. Form the epithelial lining of the ventricals of the brain and the central canal of the spinal cord. Give rise to the epithelial layer surrounding the choroid plexis. Ciliary motions aid the circulation of spinal fluid. |
| Blood-brain barrier? | Formed by astrocytes. Prevents viruses or diffusion throughout the brain (between spinal fluid and capillaries). Formed by tight junctions. |
| Microglia? | Activated during injury or disease (phagocytes). Major antegen present in the brain; physiologically & embryologically different from other tissues in the brain, as they arise from mesoderm. |
| Unipolar neurons? | Single, primary process which gives rise to many branches (1 axon, branches serve as dendrites). Found in invertebrates. Regulates involuntary movements (autonomic nervous system). |
| Bipolar neurons? | Oval shaped soma with q-processors. Dendrites convey info, which the exons transmit. Found in sensory cells (retina of the eye, mechanoreceptors, olfactory epithelium of the nose, etc.) |
| Multipolar neuron? | Single axon and several dendrites. Degree of branching, length, intricacy, and soma shape greatly varies based on function/synaptic connections. Predominates the vertebrate nervous system. |
| Sensory v. Motor neurons? | Afferent neurons (sensory) convey information from the tissues and organs to the brain. Efferent neurons (motor) transmit signals from the CNS to the effector cells. |
| Interneurons? | Connects neurons within specific regions of the CNS. Connect sensory and motor neurons. Can be inhibitory. |
| Two principals of communications? | 1. Dynamic polarization (electrical signals flow only from the dendrite to the axon) 2. Connective specificity (each connection serves a specific purpose) |
| Monosynaptic reflex? | Single synapse between afferent and efferent neurons. Ex. Knee-jerk reflex. |
| Polysynaptic reflex? | Multiple synapses between afferent and efferent neurons. Ex. Withdraw reflex. Polysynaptic circuts are initiated at the spinal cord level, modified by the brain's higher processing centers. Ex. flexion & crossed-extension reflex. |
| Neuronal convergence v. Neuronal divergence? | Neuronal convergences involves several signals processed by a single neuron; neuronal divergence involves several signals being sent out by one neuron. |
| Intensity of stimulus? | Depends on: 1. Amplitude of stretch (stimulus) 2. Duration |
| Imput, Trigger, Conductive, and Output components of the neuron? | I- dendrite/soma (Chemical) T- axon hillock (Chemical) C- axon (Chemical) O- bouton terminaux/terminal branches (Electrical) |
| Graded membrane potential? | Receptor proteins activate ion channels (influx of Na+), causing a change in membrane potential (graded--depends on the strength of the stimulus). Passive spread over cell membrane. @ Axon hillock, inital strength of receptor is reduced to 1/3. |
| Action potential? | Individual stimuli summed together (graded) can reach a threshold and create an action potential. |
| Integration zone? | Reads the signal & determines whether the action potential has been reached. All or nothing. Depends on the duration and strength of the receptor potential. Output depends on frequency. Neurotransmitters are released. |
| Which potentials are graded? | Motor and synaptic |
| Purpose of ion channels? | Speed the diffusion if polar ions |
| Way in which neurons vary? | At the molecular level. Local interneurons may lack a conductile component, lack a steady state resting potential, be sponataneously active, express different ion channels, use different chemical transmitters. Greatly affect brain function & behavior. |
| Ion channels? | Pathways. Tightly embedded protein structures that allow only specific ions (K+, Na+, Ca 2+, Cl-, etc) to cross. Open/close in response to various chemical, mechanical, and electrical stimuli. Ions surrounded by waters of hydration. |
| 4 Major types of ion channels? | 1. Stretch/pressure 2. Voltage 3. Ligand 4. Protein phosphoryaltion/dephosphorylation |
| Bertil Hille hypothesis? | Ion channels have narrow regions that act as selectivity filters. Ions shed waters of hydration and form electrostatic reactions with polar A.A. Electrostatic & diffusional forces propel molecule through the rest of the channel. |
| George Eisenman theory? | Na+ will bind to A.A. that have a highly negative charge (C=O/-O) and K+ will bind to A.A. with a small negative charge (C=O; OH-). |
| Three functional states of ion channels? | 1. Open and active (resting) 2. Closed and activatable 3. Closed (refractory) |
| Ligand-gated channels? | Open with a specific ligand binds to the surface of the channel. Prolonged exposure to lignad can cause desensitation, which can leave the channel in a refractory state. Anagonists (inhibitory) and agonists (stimulatory). |
| Phosphorylation-gated channels? | Open with the binding of P. Energy is derived from the transfer of Pi. |
| Voltage-gated channels? | Open/close in response to the electrical potential difference across the membrane. Energy is derived from these electrical changes, resulting in conformational changes. |
| Three types of gating? | 1. Conformational changes 2. Blocking particle 3. General structure change |
| Gating? | In-between stage of the more stable conformation states of the ion channel. |
| Stretch/pressure-gated channels? | Channels gain energy from the mechanical forces passed to the channel from the cytoskeleton. |
| Rate of transition between states depends on? | 1. Calcium binding 2. Changes in membrane potential 3. Protein phosphorylation/dephosphorylation |
| Calcium binding? | Voltage-gated channels open & receive an influc of Ca 2+, which inactivates the channel by binding to a specific recognition site (calmodulin molecule). |
| Dephosphorylation & transition states concerning Ca 2+? | Increase in [Ca 2+] may cause inactivation due to dephosphorylation. At pathologically high levels of Ca 2+, there may be irreversible inactivation of the channel by the recruitment of proteolytic enzymes. |
| Neurological dangers of high levels of Ca 2+? | Cystic fibrosis, migranes, epilepsy |
| Neurological dangers of ion channel problems? | Cystic fibrosis, skeletal muscle disease, cardiac arrythmea. |
| Densensitization? | May be an intrinsic property of ineractions between ligand and the channel, or due to phosphorylation of the channel molecule by protein kinase. Can be reactivatable or irreversible. |
| Binding of endogenous/exogenous ligands? | Binding of exogenous ligands (toxins, drugs) may block the binding of agonists by the means of reversible or irreversible reactions. Exogenous agents can make the channel favor an open state by binding to a regulatory site (irreversible). |
| Basic components of ion channels? | Glycoprotein element, central aqueous pore (spanning the length of the channel), consisting of 2 or more subunits. Beta and gamma subunits can be added; they modify the gating of the central pore. |
| Secondary structures of ion channels (spanning proteins)? | Based off of ACh-gated receptor channels. Spannng helix containing 20 hydrophobic A.A. residues and are connected by cytoplasmic/extracellular loops (hydrophilic residues). |
| Hydrophobicity plot? | Determines A.A. sequences and the traits of A.A. Hydrophobic A.A. will have a postive value. The portion of the channel made of lipophobic A.A. spans the membrane and stand out as large regions of hydrophobicity. |
| Ligand-gated channel structure? | Genes coded that are activated by glycine, GABA, and acetylcholine. Composed of 5 closely related subunits, each of which has 4 alpha helixes. Members of the family vary in their ligand-ion specificity. |
| Gap-junction channel structure? | Found at electrical synapses. Composed of hemi channels, each of which has 6 subunits and 4 transmembrane regions. Serves as a conduit between the cytoplasm of pre- and post-synaptic cells. |
| Voltage-gated channel structure? | Generate action potential and are activated by depolarization. Selects for Na+, Cl-, K+, Ca 2+. Contains 4 regions of basic motif, 6 transmembrane segments. 5th & 6th are connected by a loop through the P-region, which forms the selectivity filters. |
| Where does most bonding take place? | C-terminus end, which is very reactive. |
| Voltage-gated K+ channel structure? | 4 subunits, each of which corresponds to one repeated domain of voltage-gated Na+ channels. 6 transmembrane segments and a pore-forming P-region. |
| Inward-rectified K+ channel structure? | Activated by hyperpolarization. 2 transmembrane segments connected by a pore-forming P-region. |
| Two-pole domain K+ channel structure? | Contributes to the resting state (conductance) of the channel. Each repeat with two P-regions. |
| Glutamic-gated channel structure? | Found in GLURO subunits containing 2 transmembrane regions. Higher organisms contain 3. |
| Membrane potential formula and definition? | Vm = Vi - Vo. Change in electrical potential or voltage across the neuronal membrane due to seperation of (+) & (-) at a given time. Seperation of charges is maintained b/c of the lipid layer, which blocks the diffusion of ions. |
| Resting membrane potential? | Vr. Vo = 0, so Vr = Vi, usually -80 to -60 mV. Electrical signaling involves brief changes in the Vr, caused by changes in the electric current flow by movement of cations & anions. |
| Net movement of cations? | Direction of current. K+ & organic ions out, Cl-/Ca 2+/Na+ in. |
| Electrostatic potential? | Change in the Vr that does not lead to the opening of ion channels--passive responses of the membrane, such as very small changes in Vr. |
| Vr determination? | Vr is determined by resting ion channels (non-gated/ "leaky"). |
| Vr 4 facts? | 1. Vr is determined by non-gated and ion-gated channels. 2. Results from the passive influx of individual ions 3. Voltage is established when the membrane is permeable to one or more ions 4. Glial cells's resting channels are selective for K+. |
| Glial cell's Vr | Vr = -75 mV. Passive, moves down the concentration gradient. Outside accumulates a (+) & the inside has a (-). Excess charges collect locally on either side of the membrane. |
| Limiting "leaky" diffusion? | 1. Being self-limiting. 2. Chemical driving force (conc. gradient) 3. Electrical driving force(electrical potential differences across the membrane) |
| Equilibrium potential formula? | Ek = Electrical driving force + Chemical driving force |
| Nerve cell permeability? | Na+, K+, and Cl-. Large organic ions, charged proteins, and A.A. are unable to penetrate the lipid bilayer. |
| Na+ Chemical gradient and Electrical potential difference | C.G.- Na+ is more concentrated outside the cell. E.P.D.- Na+ is driven into the cell by (-) E.P.D. across the membrane |
| Determination of Vr of nerve cells? | Determined by the proportion of open ion channels--more K+ than Na+. |
| Resting cells with only K+ channels? | K+X are in equilibrium & Vm = Ek+. Slight influx of Na+ depolarizes the membrane slightly from Ek+. K+ are more numerous, so new Vm is closer to K+ (-75 mV) than Na+ (-55 mV). New Vr established. flow of K+ = flow of Na+ (depends on magnitude of ion flux) |
| Membrane depolarization X& K+ efflux? | More membrane depolarization, the grater the electrochemical driving force (more K+ efflux). |
| Conductance of Na+/K+ at rest? | Conductance of K+ is high (depends on the # of open channels). Outward force acting on K+ is enough to produce a K+ efflux equal to Na+ influx. |
| Na+/K+ pump? | Prevented by K+/Na+ pump, which transports ions across the membrane against their gradient. Has catalytic binding sites for K+, Na+, & ATP. 1 ATP moves 3 Na+ & 2 K+. |
| Ca 2+ pump? | Located in the plasma membrane. Transports Ca 2+ out of the cell (Ca 2+ within the cell moved by ER). 2 Ca 2+ are moved for each ATP hydrolysed & 2 protons transported in the opposite direction. |
| P-ATPase | Both Na+/K+ and Ca 2+ pumps are formed from P-ATPase with the transmembrane domain containing 10 membrane-spanning alpha helices. |
| Differences between ion channels and pumps? | Channels: faster, passive Pumps: slower, active, ATP |
| Co-transporters/Secondary Active Transport? | Cotransporters move one type of ion actively against its gradient by using energy stored in the electrochemical gradient of the 2nd ion. Secondary active transport does not use ATP; rather, a previously existing concentration gradient is used. Symporters. |
| Antiporters? | Ions are transported in an opposite direction. Exchanger. |
| Action potential & ion fluxes? | Action potential abolishes the balance of ion fluxes. Increases in membrane permeability to Na+ cause a net (+); the regenerative positive feedback cycle drives the membrane potential towards Na+ equilibrium potential of +55 mV. K+ efflux continues. |
| Inhibitory ions? | Cl- |
| Repolarization? | Gradual reclosing of voltge-gated channels & the opening of K+ channels (slow). Produces a net efflux of postive charge from the cell, which continues until the cell returns to its resting potential. |
| Limitations of the Goldman equation? | In excess amounts of 1 ion, reduces to the Nerst eqn. Can't be used to determine how rapidly the Vm changes in response to permeability & isn't suitable for determining the magnitude of the individual ion currents. |
| Generate --> Travel -(Potential-> Response (Action) | |
| Compare neurons to batteries? | 1. Conductors/Resistors: ion channels 2. Batteries: concentration gradient of relevant ions 3. Capacitors: ability of membrane to store charge. |
| Axon hillock & Action potential | Once a signal has reached the axon hillock, it'll be regenerated. |
| Membrane & Axioplasmic resistance? | Determines the efficency of conduction. Subthershold voltage signal decreases in amplitude w/ distance. Potential variation depends upon Rm in a unit length of Ra. |
| Lambda? | = sq.rt. of Rm/Ra. Determines the degree to which a depolarizing current decreases as it passively spreads--function of the diameter of the neuronal processes. High lambda experience minimal decay & have lower threshold. 37% Delta Vm = lambda. |
| Spatial summation? | Depolarizing produced at one synnapse is never enough to trigger an action potential. The summation of all imputs must be added at the trigger zone to initiate an action potential. |
| Demyelination? | Low lambda, leaky/decay. Found in diseases like MS. |
| More current means more efficent depolarization--recruited at low levels of current. | |
| Role of Nodes of Ranvier? | Keeps action potential from dying out. Have many Na+ channels, generating intense depolarization, boosting the amplitude of the action potential. Myelination slows the potential as it crosses the node. Saltatory conduction. |
| Action potential*? | Caused by depolarization o the membrane beyond hte threshold. Short term charge in the electrical potential such that the inside of the membrane becomes positive with respect to the outside*. |
| Saltatory Conduction? | As the action potential moves down the axon it jumps from node to node. |
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