ses intracellular calcium ions from reserves in endoplasmic reticulum Has

Ses intracellular calcium ions from reserves in

This preview shows page 21 - 25 out of 37 pages.

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
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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
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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.
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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
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  • Spring '14
  • AGRAWAL
  • motor neurons, ganglionic neurons

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