ses intracellular calcium ions from reserves in endoplasmic reticulum • Has excitatory effect on target cell • In smooth muscles • Vesse ls constriction • Closi ng sphincters • Alph a receptors • Alph a-2 ( α 2 ) • Lower s cAMP levels in cytoplasm • Has inhibitory effect on the cell • Helps coordinate sympathetic and parasympathetic activities • When sympathetic division is active: • NE is released • Binds to α 2, on parasympathetic efectors (neuromuscular and neuroglandular) and inhibits their activity • Beta (β) receptors • Affect membranes in many organs (skeletal muscles, lungs, heart, and liver) • Trigg er metabolic changes in target cell via G proteins • Stimu lation increases intracellular cAMP levels
• Thre e Main Types of Beta Receptors 1. Beta- 1 (β 1 ) 2. Beta- 2 (β 2 ) 3. Beta- 3 (β 3 ) • Three Main Types of Beta Receptors 1. Beta-1 (β 1 ) • Incre ases metabolic activity, skeletal muscle • Heart , increase heart rate and force of contraction 10. Beta- 2 (β 2 ) ( inhibition ) • Trigg ers relaxation of smooth muscles along respiratory tract • Easie r breathing, respiratory therapy 11. Beta- 3 (β 3 ) 1. Leads to lipolysis, the breakdown of triglycerides in adipocytes 2. Make fatty acids available for other tissues • Symp athetic Stimulation and the Release of Ach • Choli nergic (ACh) sympathetic terminals • Inner vate sweat glands of skin and blood vessels of skeletal muscles and brain • Stimu late sweat gland secretion and dilate blood vessels
• Symp athetic Stimulation and the Release of NO • Nitrox idergic synapses • Relea se nitric oxide (NO) as neurotransmitter • Neuro ns innervate smooth muscles in walls of blood vessels in skeletal muscles and the brain • Produ ce vasodilation and increased blood flow Summary: Sympathetic Division • Inclu des: • 2 sets of chain ganglia • 3 collateral ganglia • two adrenal ganglia • Prega nglionic fibers shorts, post ganglionic are long • ganglia are near spinal cord • Adren al: very short fibers direct to bloodstream • Exten sive divergence: • a single sympathetic motor neuron can control a variety of visceral effectors producing a complex and coordinated response. • All preG neurons release ACh at synapses with ganglionic neurons • Most postG neurons release NE • a few release Ach or NO • The effector response depends on the 2nd messenger triggered by activation of G proteins by NE o E to α or β receptors.
16-4: The Parasympathetic Division • Auton omic Nuclei • Prega nglionics neurons • Are contained in the mesencephalon, pons, and medulla oblongata • Assoc iated with cranial nerves III, VII, IX, X • In lateral gray horns of spinal segments S 2 –S 4 • Gangl ionic Neurons in Peripheral Ganglia • Term inal ganglion • Near target organ • Usual ly paired • Intra mural ganglion • Embe dded in or within tissues of target organ • Orga nization and Anatomy of the Parasympathetic Division • Paras
- Spring '14
- motor neurons, ganglionic neurons