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145 Cards in this Set
- Front
- Back
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What is the Amplitude of an Action Potential?
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80-100 mV
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What is the width of an Action Potential?
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1-3 ms
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Pharmacological seperation of currents via voltage clamp revealed what?
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Kinetics and Voltage Dependence
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What phase is due to the influx of Na+?
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Rising Phase
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What channels are stochastic/probabilistic?
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Single Channels
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What is the time referred to as Na+ channel inactivation?
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ABSOLUTE refractory period (second spike CAN NOT occur)
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What is the time referred to as Delayed K+ channel deactivation?
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RELATIVE refractory period (second spike can be elicited but requires a stronger stimulus)
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_____________ ensure that Aps are propagated in only one direction.
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Refractory Periods
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Under physiological conditions, AP travel only in _________ direction.
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Orthodromically (toward the distal terminals)
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Experimental initiation of AP would causes it to propagate _________.
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Antidromically
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Action potentials in Myelinated Nerves are ____________ at the Nodes of Ranvier.
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Regenerated
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What is an inflammatory demyelinating dx of the peripheral nerves that occurs from a viral infxn?
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Guillain-Barre Syndrome
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What kind of degeneration is in Guillain-Barre?
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Segmental Demyleination and WALLERIAN degeneration!!!!!!!
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What is the most common neurological cause of disability in young adults in the US?
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Multiple Sclerosis
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What involves the demylination of Oligodendrocytes?
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Multiple Sclerosis
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Why are there worsening/improving cycles with the symptoms?
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cycling of demylination/remyelination and Na+ channel Upregulation
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What are some symptoms seen with MS?
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muscle weakness, lack of coordination, disturbances in speech and vision
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PNS demyelinating disease?
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Guillain-Barre Syndrome
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CNS demyelinating disease?
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Multiple Sclerosis
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What is the name for the movement of negatively charged ions moving into the neuron?
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OUTward current
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What is a membrane capable of generating Aps?
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Excitable membranes
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What type of gate are Leak channels?
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NON gated channels
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Describe the flow of Ion Channels.
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PASSIVE
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What determines the direction and equilibrium of Ion Channels?
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Electrochemical driving force
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What determines the selective permeability of an Ion Channel?
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Ionic Charge
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Describe the Voltage Gated Sodium Channels
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made up of FOUR domains and each domain has 6 trans-membrane spans
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What forms the pore loop of Voltage Gated Sodium Channels?
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additional Hydrophobic regions
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What domain of the Voltage Gated Sodium Channel is believed to be voltage sensitive?
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S4
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What is responsible for the diversity seen in voltage gated channels?
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Genes! K+ is the most diverse
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L-type Voltage Gated Calcium Channels are ______ activated.
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HIGH voltage!!!! Eek!
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T-type Voltage-Gated Calcium channels are _______activated.
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Low voltage
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what is the treatment for Lambert Eaton Sydrome?
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Edrophonium (Tensilon)
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What are the symptoms seen with Lambert Eaton?
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muscle weakness
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What is a reduction of presynap. Ca+ channels and thus results in a reduced release of Ach?
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Lambert-Eaton Syn.
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Lambert Eaton Syndrome may be related to what?
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Lung and Breast Cx b/c they trigger the autoimmune response to generate Ab to Ca channels
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Who demonstrated animal electricity using a frog leg?
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Galvani
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Who measured the conduction velocity of a frog leg (27-30 ms)?
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Helmhotz
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Who wrote the Doctrine of the Neuron?
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Cajal
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Who discovered silver nitrate to stain nerve cells?
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Golgi
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Who named the synapses?
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Sherrington
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Who introduced intracellular recordings from the spinal cord motoneurons?
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Eccles
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Who did the voltage clamp and used a Atlantic squid giant axon and a Frog sciatic nerve?
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Hodgkin and Huxley
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Who introduced the patch clamp and single channel recording?
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Bert Sakmann
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what is a potential energy difference between 2 locations due to asymmetric charge distribution?
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voltage (mV)
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What is the net movement of charge from one place to another?
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Current (I, amps)
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What is the measure of how much energy (voltage) is needed to drive a current thru a conductor?
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Resistance (ohms) R
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What is a measure of how easily current can pass thru a conductor?
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Conductance (siemens) g
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What is a measure of the amount of electrical energy stored (or seperated) for a given electrical potential?
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Capacitance (farad) C
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When is a steady state reached on a Neuronal Membrane?
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when Capacitance is fully charged AND current thru resistance is stabilized. ( 2 C's)
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What is the Na+ concentration intracell and extracell for a human?
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Intracellular- 5-15; Extracellular 145 mM
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What is the K+ concentration Intracell and extracell for a human?
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Intracellular- 140; Extracellular 4-8 mM
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Neurons have a negative resting potential and the extracellular fluid is ____________.
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NEUTRAL!!!
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What determines Neuron SIZE and Membrane CAPACITANCE?
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time constant
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What is the importance of knowing the Time Constant?
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describes how voltage changes over time
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What is the importance of knowing the Length Constant?
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describes how voltage changes over a given space
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What is current charging the membrane capacitanceof flowing across the membrane leak channel called?
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Membrane Current
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What is current traveling along the length of the axon or dendrite?
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Axial Current
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Rectifying is ____________ and Nonrectifiying is ________________.
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Rectify---UNIdirectional; Nonrectify----Bidirectional
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A connexon consists of what?
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6 connexins
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Gap Junctions have what kind of speed of their transmission?
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RAPID , less than .1 ms
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What is the most common type of Charcot Marie Tooth Dx?
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Type 1a
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What is the cause of TypeX-linked Charcot Marie Tooth Dx?
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mutation in one of the connexin genes expressed by Schwann cells
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Type 1a Charcot Marie Tooth Dx is related to what protein?
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peripheral myelin protein 22
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What is it called when a mutation disrupts the connexin and thus it can not form a fxnl gap junction?
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Charcot Marie Tooth Dx
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How long does a Chemical synapse transmission lasts?
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from several msec to hundred msec
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Axodendritic synapses are usally _____________.
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Excitatory
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Axosomatic synapses are usually ______________.
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Inhibitory
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Axoaxonic synapses are usually ____________.
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modulatory
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What type of synapses are Asymmetric and have round vesicles?
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Excitable
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What type of synapses are Symmetric and have irregular vesicles?
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Inhibitory
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What receptor is involved with DIRECT gating?
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Ionotropic Receptors
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What receptor is involved with INDIRECT gating?
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Metabotropic Receptors
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What is the major excitatory neurotransmitter in the CNS?
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Glutamate
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What is it when neurotransmitters produce depolarizing graded potentials toward the potential?
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EPSP (Na influx, K efflux)
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What is it when Neurotransmitters produce Hyperpolarizing graded potentials AWAY from the threshold?
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IPSP (Cl influx, Ka efflux)
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what are the major inhibitory Neurotransmitters in the CNS?
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GABA and Glycine
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Ach Receptor uses a _______________ Gated Ion Channel.
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DIRECTly
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What blocks binding of Ach to its receptor?
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Curare
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What is a autoimmune disease with reduced fxn of Nicotinic Receptors?
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Myasthenia Gravis (droopy eyes and stained teeth)
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What is the treatment for Myasthenia Gravis?
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Edrophonium (Tensilon), an inhibitor for Acetycholinesterase
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Can Myasthenia Gravis occur via a VIRUS?
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yes, weird.
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What dx has symptoms of severe drooping of eyelids, eye muscles, oropharyngeal muscles and limb muscles?
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Myasthenia Gravis
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What is the conduction velocity of Myelinated axons to the skeletal muscle?
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5-120 m/sec
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What is the conduction velocity of Myelinated axons for aff. And eff. Innervation to the viscera?
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3-15 m/sec
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What is the conduction velocity of Unmyelingated axon for effer. And afferent?
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.6-2 m/sec
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What is blocked by removing Na and replacing with choline?
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I NA
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Are Carrier Proteins Active or Passive?
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Active
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What are the roles of Sodium Potassium Pump?
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1. Ionic Concentration 2. Osmotic Balance of Neuron
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Are Channel Proteins Active or Passive?
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passive
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What are Leak Channels?
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Nongated Ion Channels that are usually in open site. Flow during resting membrane potential
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What type of Gated Channel is closed at rest and is only open with a stimulus?
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Gated Ion Channels
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What is the equation for Capacitance?
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I/C or Q/V
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What is Capacitance?
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amt of electrical energy STORED or seperated for a given elect. Potential
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Current flow depends on what 2 things?
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Potential and Conductance
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What is movement of electrical charge that is measured in amps?
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Current------ I
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What is the def. for the difference in charges?
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Potential or Voltage------- V
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What is the ability of a charge to move?
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Conductance ------ g
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Conductance is measured in ______________.
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Siemens
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What is the inability of a charge to move?
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Resistance (Ohms)
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What is the equation for Ohm's Law?
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I= gV also I= V/R
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____________ move in same direction as current.
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Cations
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Which synaptic transmission is more common and can AMPLIFY?
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Chemical Transmission
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Where do Chemical Transmission synapse?
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Synaptic clefts with NTs
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Where do Electrical synapses occur?
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Gap Junction
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What is Rectifying Electrical synapse?
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Unidirectional current
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What is a mutation of the connexin gene in Schwann Cells called?
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Charcot Marie Tooth
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Describe the symmetric synapse of Chemical transmissions.
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INHIBITORY!!! Pre and post have similar thickness
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Describe the asymmetric synapse of Chemical transmission.
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EXCITATORY!!! Post syn is THICKER
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Transmitter release depends on ____________ being activated.
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type of receptor
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For Directly Gated Ion Channels, the recognition site for the NT is what?
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Ionotropic Receptor
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What type of Ion channel allows for slow and long synaptic actions?
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Indirectly Gated Ion channels
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What is the relationship of Ion Channels and Recognition Sites on Indirectly Gated Ion Channels?
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SEPARATE!!! Muscarinic Receptors
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Indirectly Gated Ion Channel, _____________ receptor. Directly Gated Ion Channel, __________________.
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Muscarinic, Ionotropic
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What is a dx with decreased Nicotinic Ach receptors in postsyn.?
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Myasthenia Gravis
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Neuronal Membrane are _____________circuits of _______________ and _________________.
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Parallel circuits of resistors and capacitors
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What of the Neuronal Membrane can be thought of as Capacitor in Parallel?
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Lipid Bilayer
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What of the Neuronal Membrane can be thought of Variable Restrictors?
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Ion Channels
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When opening a channel on the Neuronal Membrane @ time zero the Capacitance acts like what?
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a small Resistor
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What is the steady state of the NeuronalMembrane?
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when the capacitance is fully charged. (Leak channel charges up the membrane capacitance)
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In the steady state of the Neuronal Membrane the what is stabilized?
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Current thru resistance is stabilized. Change in current = 0.
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What is Change in Concentration/ Distance?
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Ficks Law of Diffusion. Simple Diffusion. J= D (d(ion)/dx)
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What determines time constant (t)?
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neuron SIZE and membrane CAPACITANCE.
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What is the fxn of knowing the time constant?
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describe how VOLTAGE changes over time
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What is the equilibrium potential of 1 ion that is present on both sides?
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Nernst Eqxn
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How would you calculate the membrane potential of all ions?
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Goldman eqxn
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what dx does ones Ab prod. against Ca channels lead to a decrease in voltage gated Ca channels, less Ach released and thus muscle weakness?
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Lambert Eaton
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What are some symptoms seen with Lambert Eaton Syndrome
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Dry mouth, constipation, dizzy with standing, muscle weakness
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What is the loss of voltage gated Ca channels in the PRE synpatic terminal?
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Lambert Eaton
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What is the way to diag. Lambert Eaton? Treatment?
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Diagnose with EMG and treat with Edrophonium
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What are 3 states of Ion Chanel Voltage Gated?
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1. Resting 2. Calcium Binding 3. Dephosphorylation
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What channel is made up of 4 domains and each domain is 6 transmembrane proteins of alpha helices?
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Sodium Channel
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What domain in Sodium Channels is voltage sensitive?
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S4
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What type of Calcium channel has a higher voltage activated, L or T type?
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L type
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What determines the selectivity of Sodium Channels?
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CHARGE
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What channel has a small diameter, large water cloud, and binding site?
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Sodium Channel
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What drug blocks the Na pore so it can not generate an action potential?
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TTX
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What determines the direction and equilibrium of Ion Channels?
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Electrochemical driving force
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Most cation-selective channels only allow one ion species to flow EXCEPT_____________.
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NMDA and nAchR
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Voltage gated Potassium Channels, what does I k mean?
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delayed rectifier, part of AP
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Voltage gated Potassium Channels, what does I c mean?
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Calcium-dependent K channel
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Voltage gated Potassium Channels, what does I ahp mean?
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slow afterhyperpolarization
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Voltage Gated K channels, what does I a mean?
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transient, repolarization
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Voltage Gated k channels, what does I m mean?
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muscarinic sensitive
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Voltage gated K channels, what does I h mean?
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activated by hyperpolarization
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Voltage gated K channel, what does I leak mean?
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contribute to E rest
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