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64 Cards in this Set
- Front
- Back
What is the nicotinic, cholinergic receptor?
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A ligand gated cation channel that antiports Na and K
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What activates the nicotinic, cholinergic receptor?
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ACh
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What does nicotinic, cholinergic receptor activation produce?
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depolarizing post-synaptic potentials.
*aka EPSPs. |
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What receptor is the site of action of nicotine?
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Nicotinic, cholinergic receptor
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What happens when ACh is released by a motor neuron and it binds to a nicotinic, cholinergic receptor?
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The receptor depolarizes skeletal muscle
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What is myasthenia gravis?
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The immune system makes Abs to the skeletal muscle nicotinic receptor resulting in muscle weakness.
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What is the 5-Ht3 ionotropic receptor?
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A ligand-gated cation channel that is selective for Na and K
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What is the GABA-A ionotropic receptor?
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A ligand-gated anionic channel that conducts Cl- current.
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What does GABA-A activation produce?
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Cl- selective anion channel that when activated by GABA mediates hyperpolarizing inhibitory postsynaptic potentials (IPSPs).
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What do benzodiazepines and barbiturates do?
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Act on the GABA-A receptor to make you sleepy!
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What is the pentameric glycine ionotropic receptor?
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A ligand-gated Cl anion channel that is activated by binding of glycine inhibitory IPSPs.
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What is the function of the pentameric glycine ionotropic receptor?
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Modulates excitatory neurons that mediate wake state and response to auditory and tactile stimuli.
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What is startle disease?
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"hyperplexia". Characterized by an abnormal response to auditory or tactile stimuli.
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What is the glutamate-activated cation channel?
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A ligand-gated channel that conducts Na and K that is activated by glutamate.
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What does activation of the glutamate-activated cation channel produce?
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EPSP and it is involved in long-term potentiation of memory.
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What channel is involved in Rasmussens encephalitis?
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NMDA (glutamate receptor)
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What is the purinergic ligand-gated cation channel?
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1. A post-synaptic ATP-activated cation channel that is permeable to Na, K and Calcium
2. involved in excitatory synaptic transmission and regulation of blood clotting. |
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What is the role of ATP in purinergic ligand-gated cation channels?
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Channels activated by synaptic co-release of ATP in catecholamine (NE) containing synaptic vesicles.
ATP-Ca channels are synergistic w/ alpha1 receptors and enhance NE mediated constriction. |
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What is the cystic-fibrosis transmembrane receptor? (CFTR)
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A ligand-gated channel that contains two internally homologous domains. It is a Cl- selective channel coupled to cAMP regulation.
*IMPORTANT transport pathway in secretory and absorptive epithelia in lung tissues. There are numerous mutations in this channel, one of which causes cystic fibrosis |
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What is the CIC Cl- channel?
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Cl- selective voltage-sensitive anion channel in skeletal muscle.
It regulates the regulation of electrical excitability in skeletal muscle. Modulates the threshold potential for activation in skeletal muscle. ALSO mediates Cl- transport in epithelia |
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What mutation causes becker and thompson myotonia? what marks becker and thompson myotonia?
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CIC Cl- channel; hyperexcitability of skeletal muscle causing delayed relaxation
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What is the tetrameric intracellular IP3 activated channel?
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VERY IMPORTANT CHANNEL IN SMOOTH MUSCLE!!!
1. intracellular cation channel permeable to Na, K and CALCIUM 2. Activated by binding of IP3 and Ca 3. mediates excitation-contraction in smooth muscle and participates in intracellular Calcium release. |
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What is the mechanism of action of the CIC Cl- channel?
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In smooth muscle ER, IP3 channel activation is coupled to alpha1-b receptor activation by NE, which in turn activates phospholipase C. PLC promotes the release of phospho-inositol bis phosphate (PIP2) w/ final conversion to IP3.
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What is the function of the tetrameric intracellular IP3 channel?
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Mediates excitation-contraction coupling in smooth muscle and participates in intracellular Ca release.
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What is the function of the tetrameric ryanodine receptor (RYR) Ca release channel?
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aka: CICR
Promotes rapid intracellular Ca release. |
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What is the RYR1 channel activated by? where is it located?
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Direct mechanical coupling to Cav channels in skeletal muscle.
located in skeletal muscle |
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What activates RYR2 and RYR3 channels? where is it located?
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Activated by elevation of cytoplasmic Ca due to plasma membrane Ca entry.
Located in heart, smooth muscle and neurons |
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What is dysregulation of the RYR3 receptor linked to? what drug is more selective for the RYR3 channel?
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malignant hyperthermia.
Dantrolene, an antagonist drug |
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What is the multi-meric ORAI store operated Ca channel?
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Located on the plasma membrane on non-excitable cells such as epithelial cells and lymphocytes.
*basically it is a plasma membrane Calcium channel. Orai is activated by IP3-activated Ca release and CICR from SER |
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What is STIM?
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An SER "calcium sensor" and is activated when SER Ca levels are lowered.
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What is another name for the ORAI channel?
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I-CRAC for Ca-release activated Ca current or SOC channel for store-operated Ca entry.
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What is the essential function of a channel?
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To form a aqueous channel pore so that ions flow across the hydrophobic membrane bilayer down the electrochemical gradient.
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What is the structure of most eukaryotic channels?
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Aqueous pores are located at the center of an oligomeric rosette-like arrangement of homologous subunits.
Ea. subunit is a polypeptide that weaves through the membrane several times |
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What are gap junctions?
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Protein channels that connect two cells w/ a large, unselective pore that allows ions and small molecules as large as 1 kDa to pass through.
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What is a connexin?
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A subunit that is an integral membrane protein that, (along w/ 5 other subunits) forms a gap junction.
Each subunit has four identifiable hydrophobic transmembrane segments |
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What effect does intracellular Ca concentration have on the probability a gap junction will be open/closed?
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*elevated [Ca] increase the probability that the gap junction will be closed.
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Where are the N1 AChRs located?
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At the neuromuscular junction
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Where are the N2 AChRs located?
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In the ANS on the postsynpatic membrane of the postganglionic sympathetic and parasympathetic neurons and in the CNS
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what change in the nicotinic receptor occurs during development?
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In fetal skeletal muscle the subunit composition is alpha2-beta-gamma-delta but in the adult there is a transition from gamma to epsilon, so the adult nicotinic receptor is alpha2-beta-epsilon-delta
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How many subunits does the nicotinic receptor have?
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5. The ACh receptor shows pentameric radial symmetry that corresponds to a rosette.
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How can ALL potassium channels be modulated?
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By reversible phosphorylation
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What is the structure of the Kv channel?
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4 identical tetrameric subunits w/ six transmembrane regions on ea. subunit.
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What is the structure of small and intermediate conductance calcium activated potassium Channels? (SKca and IKca)
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They have the same basic structure as the Kv channel, but these channels are voltage independent and only activated by Calcium.
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What is the voltage sensitive region of the Kv channel?
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region 4
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What is the structure of the inward rectifier Potassium channel?
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Kir is a tetramer w/ two membrane spanning regions.
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What is the structure of the dimeric tandem two-pore potassium channel (K2P)?
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Basically a tandem duplication of a Kir channel
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What is the hyperpolarization-activated, cyclic nucleotide-gated cation channel (HCN)?
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Plays a CRITICAL role in the automaticity of the heart and rhythmically firing neurons of the brain.
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What regulates HCN channels?
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Cyclic nucleotides and they are also voltage sensitive.
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What are CNG channels?
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A family of cation-selective channels that are directly activated by intracellular cGMP or cAMP.
These channels play a IMPORTANT role in visual and olfactory sensation. |
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What activates the CNG channel?
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binding of cAMP or cGMP
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What are the TRP channels?
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Sensory channels that transduce sensory information
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What activates the TRPV channel?
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Capsaicin, the "hot" ingredient of chili peppers. Appears to function in pain and temperature sensation
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What activates the TRPM channel?
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Menthol, the "cool"-tasting substance in eucalyptus leaves.
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What is the structure of the voltage-gated sodium channels? (Nav)
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Four domains, each domain containing the S1 to S6 structural motif that is homologous to the Kv K+ channel monomers. Each domain has 1 voltage sensing region.
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What unique structure are the Nav channels associated with?
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A unique family of auxiliary beta-subunits, modifying gating behavior and membrane localization of the channel-forming alpha-subunit.
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What do mutations in the Nav beta-subunit result in?
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Altered Nav function which causes Long QT (LQT3) syndrome.
*LQT3 occurs at fast cardiac paces (i.e. exercise/stress) |
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What is the structure of voltage-gated Calcium channels?
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Cav channels are multisubunit complexes (similar to Nav) that are called the alpha-subunit. the alpha subunit has four voltage sensor regions and in addition there are three accessory proteins that are involved in channel regulation. (alpha2-delta and a gamma subunit)
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What is the general structure of ligand-gated channels? What channels have this basic structure?
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*basic structure: pentamers w/ 4 transmembrane regions.
*channels that follow this: ACh, 5-HT, GABA, Glycine |
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What major structures are absent on ligand-gated channels?
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Phosphorylation sights, so they are NOT regulated by reversible phosphorylation
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What is the structure of the Glutamate channel?
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ligand channels that have only three membrane spanning regions per monomer
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What is the structure of the purinergic ligand-gated channels?
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A pentameric dimer w/ two membrane spanning regions
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What is the CFTR channel?
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a Cl- channel that modulates fluid balance in the lung alveoli.
*cystic fibrosis is caused by mutations in the NBD1/NBD2 regions |
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What is the structure of the CIC family of Cl- channels?
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have FIFTEEN (15!!!) membrane spanning regions on EACH monomer
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What is the structure of the ORAI channel and STIM?
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ORAI is a monomer until SER Ca levels decline.
The decline in SER [Ca] activates STIM aggregation. STIM aggregates causing ORAI aggregation and formation of Ca channels. |