Lecture 20 - 1.) Name general characteristics of the ANS....

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1.) Name general characteristics of the ANS. ANS is entirely motor . Reflexes respond to sensory info going into CNS through afferent nerves with sensory receptors in skin or viscera. Input from viscera evaluated and acted on at subconscious level via autonomic reflexes . ANS effectors : Cardiac muscle, smooth muscle, glandular epithelium. In ANS, motor neurons in spinal cord send out axons that make synapses with second- order neurons located outside of CNS in ganglia ( singular= ganglion) . Axons of ganglia make synaptic connections with cardiac muscle, smooth muscle, or glandular epithelium. Axons of first neurons called preganglionic axons and neurons themselves called preganglionic neurons . Axons of second-order neurons called postganglionic axons and neurons themselves called postganglionic neurons . 2.) Three branches of ANS. S ympathetic, parasympathetic, and enteric (highly complex network of neurons found in walls of gut) . 3.) Para-/sym-pathetic branches vs. Somatic efferent system (effectors, control, pathways, actions, neurotransmitters). Somatic Efferent Para-/Sym-pathetic Effectors Skeletal muscles Cardiac/smooth muscle, glandular epithelium Control Voluntary Involuntary Pathway Axon of motor neuron in CNS synapses with skeletal muscle fibers Axon of motor neuron in CNS synapses with 2 nd neuron in ganglion ; this 2 nd neuron sends axon that synapses with visceral effector Action Always excites (muscle always contracts) Excitatory/inhibitory, depends if innervations para-/sym-pathetic Neurotransmitters Acetylcholine Acetylcholine, norepinephrine 4.) Para-/Sym-pathetic efferent pathways vs. somatic efferent pathways Both have first motor neurons in the spinal cord . BUT, Para-/Sym-pathetic involve groups of 2 nd -order neurons located in ganglia outside of CNS. Axons of 1 st motor neurons synapse with 2 nd -order neurons, which send their axons to visceral effectors (cardiac/smooth muscle, glandular epithelium). 5.) Three groups of autonomic ganglia. State which division of ANS they’re associated with. 1- Associated with sympathetic division . Ganglia are called paravertebral ganglia and are arranged like a string of beads along either side of vertebral column. Beads of ganglia and whole string called sympathetic trunk . 2- Associated with sympathetic division . Ganglia are called collateral ganglia. 3- Associated with parasympathetic division . Ganglia are called terminal ganglia or intramural ganglia . They belong to the parasympathetic division and are located either close to organ being innervated or are within the walls of organ itself. In gut, neurons in these ganglia input into enteric branch of ANS.
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This note was uploaded on 11/13/2010 for the course BIOLOGY 203 taught by Professor Bridges during the Fall '10 term at Purdue University-West Lafayette.

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Lecture 20 - 1.) Name general characteristics of the ANS....

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