Autonomic and Sensory NS

Autonomic and Sensory NS - Biol 121 Anatomy &...

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Nervous System Notes - #3 The Autonomic Nervous System Sensory Nervous System Autonomic Nervous System Review Organization of the Nervous System Central Nervous System (CNS) Peripheral Nervous System (PNS) Afferent - Sensory neurons to CNS Efferent - motor neurons from CNS to effector organs Somatic - Voluntary, conducts impulses from CNS to skeletal muscles Autonomic - involuntary, impulses to cardiac, smooth muscles, and glands Sympathetic Parasympathetic A. Definition of the autonomic nervous system (ANS ) Autonomic motor nerves innervate organs not under voluntary control Effector organs include cardiac muscle, smooth muscle and glands Unlike somatic motor neurons, stimulation is not always excitatory For example: parasympathetic innervation of the heart slows heart rate No specialization of postsynaptic membrane (not motor end plate) 1. Efferent component of ANS involves two nerve cells in a chain a) Preganglionic - nerve cell body in the CNS b) Post ganglionic - nerve cell body outside the CNS (cell body housed in ganglion) B. Comparisons of the Somatic motor system with the Autonomic motor system Somatic Motor Autonomic Motor Effector Organs Skeletal Muscles Cardiac, smooth and glands Presence of ganglia None outside CNS Ganglia present Number of Neurons from CNS to effector One Two M Hopper 2006
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Type of Neuromuscular Junction Specialized Motor End Plate No specialization, receptors widespread Effect Excitatory only Either excitatory or inhibitory C. Structure of the ANS SYMPATHETIC Thoracolumbar cell bodies of the preganglionic fibers located in thoracic and lumbar regions of spinal cord Short preganglionic fibers that synapse with post ganglionic fibers just outside the spinal cord Pharmacologically defined as Adrenergic Most sympathetic nerve fibers (postganglionic) release norepinephrine at the region of the effector organ. Elicit fight or flight response. PARASYMPATHETIC Craniosacral Preganglionic fibers originate in the brain and the sacral levels of the spinal cord Long preganglionic fibers synapse with short postganglionic fibers near or within organ innervated. Cholinergic - all parasympathetic nerves (postganglionic fibers) release acetylcholine at the region of the effector organ. Often the action is in opposition to the sympathetic NS. D. Functions of the ANS Sympathetic and parasympathetic divisions of ANS affect visceral organs in different ways. Sympathetic - prepares body for intense physical activity (fight or flight). Increases heart rate, slows diges5tion and blood sent to skeletal muscles. Parasympathetic nerve stimulation in many ways opposes the effects of the sympathetic nerves. Decreases heart rate increased digestive activity, sends blood to the gut. Different responses due to the release of different neurotransmitter from
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Autonomic and Sensory NS - Biol 121 Anatomy &...

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