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Receptors (Adrenergic (Transmission of the neurotransmitter norepinephrine…

- - - - Alpha 1
        
        Located in the eye, skin and visceral vessels, skeletal muscle vessels. stomach and intestine, and liver. When Ne binds to Alpha 1, a rise of cytoplasmic concentration of Ca2+ as a second-messenger occurs.The stimulation of these receptors causes contraction of smooth muscles
      - Alpha 2
        
        Located on presynaptic terminal buttons and in the brain and produce a decreased release of NE when activated by it in the synaptic cleft, producing a negative feedback over the amount of NE released.
    - - Beta 1
        
        Located in the heart, Force the contraction of cardiac muscles promoting and increase in heart rate.
      - Beta 2
        
        Located in the skeletal muscle arterioles and bronchioles, and liver. It promotes the relaxation of the smooth muscles and promote vasodilation.
- - - - Nicotine and ACh stimulate the nicotinic receptors. The receptors are ligand-gated channels located in the CNS, neuromuscular junctions, and autonomic ganglia. Binding the ACh receptor to the the channel causes it to open allowing Na+ to diffuse inward and K+ to diffuse outward. Since the Na+ gradient is larger than the K+ gradient, the net effect is depolarization and the nicotinic receptors are excitatory.
    - - Muscinaric and ACh stimulate the ACh receptors in visceral organs. These G-protein-coupled receptors are stimulated by ACh that is released by postganglionic parasympathetic axons to produce parasympathetic nerve effects in the heart, smooth muscles, and glands. The G-proteins bind with the receptor proteins to open and close the channel and activate different membrane enzymes. Thus the effects are excitatory and inhibitory. There are 5 different types of muscinaric receptors.
        
        M3
        
        Causes depolarization and the contraction of the smooth muscle and secretion of glands. ACh binds with G-proteins opening the Ca2+ channels and increasing the systolic Ca2+
        
        M4
        
        Decrease cAMP in the cell and produce inhibitory effects
        
        M2
        
        Causes hyperpolariaztion in the heart. ACh binds with G-proteins to open K+ channels
        
        M5
        
        Causes depolarization and the contraction of the smooth muscle and secretion of glands. ACh binds with G-proteins opening the Ca2+ channels and increasing the systolic Ca2+
        
        M1
        
        Mediate excitatory effects