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20 Cards in this Set
- Front
- Back
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Where are α1 receptors located?
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-Vascular smooth muscle of the skin and splanchnic regions
-GI and bladder sphincters -Radial muscles of the iris |
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What do α1 receptors produce?
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Excitation (eg contraction or constriction)
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What are α1 receptors sensitive to?
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-Equally sensitive to NE and epinephrine
-Only NE released from adrenergic neurons is present in high enough concentrations to activate α1 receptors |
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Describe the mechanism of action for α1 receptors
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Gq protein, stimulation of phospholipase C and increase in inositol 1,4,5-triphosphate (IP3) and intracellular [Ca2+]
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Where are β1 receptors located?
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-SA node
-AV node -Ventricular muscle of the heart |
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What do β1 receptors produce?
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Excitation (increased HR, increased conduction velocity, increased contractility)
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What are β1 receptors sensitive to?
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-Sensitive to both NE and epinephrine
-Most sensitive than the α1 receptors |
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Describe the mechanism of action for β1 receptors
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-Gs protein
-Stimulation of adenylate cyclase and increase in cAMP |
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Where are the α2 receptors located?
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-Presynaptic nerve terminals
-Platelets -Fat cells -Walls of the GI tract |
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What do α2 receptors produce?
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Inhibition (relaxation or dilation)
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Describe the mechanism of action for α2 receptors?
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Gi protein inhibition of adenylate cyclase and decrease in cAMP
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Where are the β2 receptors located?
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-Vascular smooth muscle of skeletal muscle
-Bronchial smooth muscle -The walls of the GI tract and bladder |
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What do β2 receptors produce?
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Relaxation (eg, dilation of vascular smooth muscle, dilation of bronchioles, relaxation of the bladder wall)
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What are β2 receptors sensitive to?
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-More sensitive to epinephrine than to NE
-Most sensitive tp epinephrine than the α1 receptors |
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Describe the mechanism of β2 receptors
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Gs protein, stimulation of adenylate cyclase and increase in cAMP
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Where are nicotinic receptors located?
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-The autonomic ganglia (N_N) of the sympathetic and parasympathetic nervous system
-At the neuromuscular junction (N_M) -The adrenal medulla (N_N) -The receptors in these locations are similar but not identical |
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What activates nicotinic receptors?
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Ach or nicotine
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What do nicotinic receptors produce?
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Excitation
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Describe blocking of the nicotinic receptors
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Blocked by ganglionic blockers (eg, hexamethonium) in the autonomic ganglia, but not at the neuromuscular junction
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Describe the mechanism of action of nicotinic receptors
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-ACh binds to α subunits of the nicotinic ACh receptors
-The nicotinic ACh receptors are also ion channels for Na and K |
