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44 Cards in this Set
- Front
- Back
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What is the net charge inside a cell at rest?
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-70mV
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Which is more permeable across the cell membrane, Na or K?
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K
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What are the two forces that will make an ion want to move across a membrane?
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Electrical force & Concentration force
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For Na, where are the forces wanting to move it?
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Both into the cell.
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For K, where are the forces trying to move it?
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Concentration force: out of cell
Electrical force: into cell On the whole, K is going to move out of the cell. |
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What are the 'driving forces' for
Na K Cl ??? |
Na-> 140 mV inward
K-> 24 mV outward Cl-> 45 mV outward |
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Adding ouabain to the extracellular fluid will do what?
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It will poison the Na/K pump. You will see an immediate 5 mV depolarization to -65 mV.
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What is the estimated level of threshold for an action potential?
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About -50 mV.
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Depolarization takes the membrane potential to where (charge)?
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From about -50 mV (threshold) to about 30 mV.
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At rest, where is Na and K (in general).
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More Na outside cell, more K inside cell.
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What allows Na to enter the Na-channel?
What can block this? |
The Selectivity filter.
Tetrodotoxin (puffer fish). |
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Which end of the protein has the inactivation gate?
At rest, is it open or closed? |
The intracellular end.
Open. |
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While the Na inactivation gate is closed, what is this period?
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The Absolute Refractory Period.
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When does the Na activation gate open?
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Once threshold is reached.
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How does Calcium act on voltage-gated channels?
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Stabilizes the membrane and increases threshold.
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How does tetrodotoxin act on voltage-gated channels?
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Blocks Na channels from extracellular side.
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How does local anesthetic act on voltage-gated channels?
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Insert in the conductance pore and block Na permeability increases.
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How does batrachtotoxin act on voltage-gated channels?
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From poisonous frogs, irreversibly opens Na channels.
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How do Scorpion toxins act on voltage-gated channels?
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Block K channel opening.
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How does TEA (Tetraethylammonium) act on voltage-gated channels?
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Blocks voltage-gated K channels, but only from the intracellular fluid side of the channel.
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Antidromic is toward where?
Orthodromic is toward where? |
Antidromic--toward cell body
Orthodromic--toward axon terminal |
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Myelin is formed by what cells in the CNS?
In the PNS? |
CNS--Oligodendrocytes
PNS--Schwann cells |
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What are the breaks in myelin called?
What is the conduction along myelinated nerves, from node to node, called? |
Nodes of Ranvier.
Saltatory Conduction. |
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A function of membrane proteins in excitable cell membranes is as?
a. protection against invasion of foreign organisms b. ports for release of cellular waste c. voltage dependent gates d. openings for filtration of mitochondria |
C
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Propagation of a nerve impulse is enhanced by extracellular myelin deposition because
a. myelin is a better conductor than the nerve cell membrane b. the creation of the nodes of Ranvier causes the impulse to move at a greater velocity c. myelin enhances the electrogenic pump d. myelin enhances the movement of Na intracellularly |
B
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The primary ion respnsible for maintenance of the resting membrane potential is?
a. Ca b. K c. Na d. Cl |
B
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During the absolute refractory period
a. the nerve can be stimulated to produce an action potential b. the nerve cannot be stimulated to produce an action potential c. Na and K conductance is low d. the membrane potential is at its resting level |
B
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The magnitude of an action potential which reaches the nerve terminus has a direct effect on?
1. the amount of Ca conductance into the nerve terminus 2. the extracellular Ca concentration 3. the quantity of NT substance released from the presynaptic ending 4. the magnitude of the post synaptic potential |
1 & 3
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Inhibitory post-synaptic potentials usually result in
a. excitation of presynaptic cell membranes b. the opening of chloride channels c. the elevation of threshold potentials d. the opening of Na channels |
B
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All of the following are true of the action potential of along a single axon process except?
a. propagated in an all or none fashion b. has a reduction in amplitude from the time it starts until the time it ends c. is unidirectional in living cells d. is always supra-threshold |
B
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The ion primarily responsible for NT release from the presynaptic terminal is
a. K b. Na c. Ca d. Mg |
C
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Although Na ions are smaller they do not diffuse through the nerve cell membranes, as well as, K ions. This is due to
a. their charge b. their hydration sphere c. their molecular weight d. their insolubility in water |
B
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During the propagation of a nerve action potential all of the following are true except
a. there are more Na channels than K channels open per unit time b. all ion channels are open c. as the action potential travels down the nerve process it becomes gradually smaller d. the action potential creates a local current |
C
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As the action potential begins to return to resting levels the nerve reaches a point during repolarization where it can be stimulated to fire another action potential. All of the following are true regarding this state, except?
a. another maximal action potential can be generated b. only an action potential of lower than maximal amplitude can be generated c. this is called the relative refractory period d. this point is at or below the original threshold potential |
B
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The magnitude of an action potential which reaches the nerve terminus would have a direct effect on?
1. the amount of calcium-conductance into the nerve bouton 2. the extracellular calcium concentration 3. the quantity of NT substance released from the presynaptic ending 4. the magnitude of the post synaptic potential |
1 & 3
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Which of the following would exhibit the fastest conduction velocity?
a. a small diameter unmyelinated axon b. a small diameter myelinated axon c. a large diameter unmyelinated axon d. a large diameter myelinated axon e. all would conduct equally |
D
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Which of these statements is true
a. TEA will immediately depolarize a neuron by 5 mV b. TTX (tetrodotoxin) will immediately hyperpolarize a neuron by 10 mV c. Ouabain will immediately depolarize a neuron by 5 mV d. TEA will immediately hyperpolarize a neuron by 10 mV e. Ouabain will immediately hyperpolarize a neuron by 10 mV |
C
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The repolarization phase of the action potential
a. is characterized by a higher than normal K permeability b. is associated with the relative refractory period c. begins when the inactivation gates reopen d. is the period during which the membrane potential changes from -70 to 30 mV e. all of the above are correct |
A
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Most inhibitory synapses
a. are located on dendrites b. are located on cell bodies c. are located on neurons d. involve an increase in Na permeability e. involve an increase in Ca permeability |
B
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During the period of the after hyperpolarization
a. the Na channel inactivation gates are closed b. the membrane potential is more negative than the resting membrane potential c. K permeability is lower than normal d. a new action potential cannot be generated e. all of the above |
B
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The driving force on an ion
a. is the difference between the membrane potential and the Nernst potential b. is partially determined by the concentration gradient of the ion c. is partially determined by the charge on the ion d. all of above e. A & B, but not C |
D
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The resting membrane potential primarily results from
a. Na/K pumps b. Cl pumps c. Ca ionophores d. K permeability e. Na ionophores |
D
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Which of the following blocks the voltage gated Na channel?
a. Ouabain b. Kurtkilbane c. Tetrodotoxin d. TEA e. 2, 3-dinitrophenol |
C
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During the depolarization phase of the action potential, which is incorrect
a. Na permeability is greater than K permeability b. K permeability is greater than at rest c. both gates in the Na channel are open d. the voltage-gated K channel gates are closed e. all of above correct |
D
Not a good ? |
