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93 Cards in this Set
- Front
- Back
What is the major function of the autonomic nervous system?
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controls visceral function larely outside our awareness
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What do motor neurons in the central nervous system synapse with?
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visceral motor neurons in autonomic ganglia which control the visceral effectors
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Where is visceral motor nuclei stored in the CNS?
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the hypothalamus
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What are the visceral effectors involved in the ANS?
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smooth muscle, glands, cardiac muscle, adipocytes
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What are preganglionic neurons?
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visceeral moter neurons whos cell bodies lie in the brain stem and spinal cord
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What do preganglionic neurons activities represent?
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direct reflex responses rather than actual responses to commands from the hypothalamus
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What are autonomic ganglia?
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visceral motor neurons found in the peripheral ganglia. they innervate the visceral effectors
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Can a postganglionic neuron synapse with more than one preganglionic neuron?
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yes
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Are postganglionic neurons myelinated or unmyelinated?
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unmyelinated
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What are the three divisions of the ANS?
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sympathetic, parasympathetic and enteric
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Does the sympathetic or parasympathetic division of the ANS influence the enteric division?
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both
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When do the sympathetic and parasympathetic divisions work independently?
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when the structure is only innervated by one division
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Typically, when does the sympathetic division kick in?
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periods of exertion, stress, emergency
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When does the parasympathetic division dominate?
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under resting conditions
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Where do axons emerge from in the parasympathetic division?
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the brain stem and sacral segments of the spinal cord
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Where do axons emerege from in the sympathetic division?
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the thoracic and superior lumbar segments of the spinal cord
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What are the possible ganglionic neurons that preganglionic neurons in the spinal cord can synapse with?
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-sympathetic ganglia
-collateral ganglia -adrenal medulla |
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How do sympathtic chain and collateral ganglia exert their effects?
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innervate peripheral target organs with postganglionic fibers
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What are the target organs for sympathetic chain ganglia?
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visceral effectors in the thoracic cavity, head, body wall, limbs
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What are the target organs for collateral ganglia?
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visceral effectors in the abdominopelvic cavity
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How does the adrenal medula affect target organs throughout the body?
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the release of hormones into the general circulation
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Where are sympathetic chain ganglia located?
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either side of the vertebral column
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Where are the three collateral ganglia?
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anterior to the vertebral column close to the large abdominal arteries
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What are the three collateral ganglia?
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-celiac
-superior mesenteric -inferior mesenteric |
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Compare pre and post ganglionic fibers axons in teh sympathetic vs. parasympathetic division
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the sympathetic has short preganglionic axons and long postganglionic where the parasympathetic has long preganglionic and short postganglionic
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Where does the parasympathetic preganglionic fibers synapse?
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terminal or intramural ganglia
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Where are terminal ganglia located?
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close to the target organ (synapsing on or near)
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Wherer are intramural ganglia located?
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within the wall of the target organ
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What percentage of organs are innervated by the vagus nerve?
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75%
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What are the bundles that postganglionic fibers that innervate structures in the thoracic caviity called?
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sympathetic nerves
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What does the splanchnic bed innervate?
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the digestive system and excretory organs
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What is the sympathetic response of the cardiovascular system?
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increased heart rate and conduction velocity, vasoconstriction in the skin and splanchnic bed, blood flow to active muscles and heart
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What is the sympathetic response of the lung bronchioles?
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dialation for deeper breathing
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What is the sympathetic response of the skin?
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pale, sweat, hairs stand up
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What is the sympathetic response of the eyes?
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pupil dilation; lens flattens to see further
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What is the sympathetic response of the metabolism?
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speeds up; release stores from the liver; mobilization of energy reserves
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What is the sympathetic response of the GI tract?
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decreases motility, decreases secretions
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What are the purposes of the parasympathetic division?
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rest and digest, housekeeping functions of the body, conservation or restoration of energy, decreased overall metabolic activity
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What is the parasympathetic response of the heart?
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decreased heart rate and blood pressure
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What is the parasympathetic response of the GI system?
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increased motility, increased secretions, increased blood flow
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What is the parasympathetic response of excretory organs?
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allows urination and defecation
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What is the parasympathetic response of the exocrine glands?
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increased production of water saliva
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What is the parasympathetic response of the eye?
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contraction of pupillary muscles; narrows pupil
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What is dual innervation called?
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autonomic tone
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Where is dual innervation most evident?
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GI tract, heart, and lungs
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What is autonomic tone and what is it regulated by?
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it is a balancing act regulated by the hypothalamus
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What does "tone" indicate?
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both systems are always on
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What are neurouns that release acetylcholine called?
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cholinergic neurons
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What are neurons called that release norepinephrine?
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adrenergic
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What are the effects of sympathetic and parasympathetic stimulation mediated by?
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membrane receptors at target organs
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What type of neurons do neuross releasing norepinephrine have an effect on?
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most sympathetic postganglionic neurons except sweat glands
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What are the two classes of sympathetic adrenergic receptors?
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alpha receptors and beta receptors
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What do adrenergic receptors bind to?
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norepinephrine and epinephrine
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What releases norepinephrine and epinephrine to the blood?
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the suprarenal medulla
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What receptors are generally excited by NE/E?
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a1 and b1
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What receptors are generally inhibitied by NE/E?
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a2 and b2
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What receptor is the only receptor in adipose tisue and what do its effects cause?
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b3 and it causes lipolysis
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What are the two types of cholinergic receptors?
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nicotinic and muscarinic
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Where are nicotinic receptors located?
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dendrites and cell bodies of sympathetic and parasympathetic postganglionic neurons
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Where are muscarinic receptors located?
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plasma membranes of all effector cells innervated by the parasympathetic postganglionic axons and most sweat glands (sympathetic)
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What does exposure to ACh always cause in nicotinic receptors?
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excitation of the ganglionic neuron by opening chemically gated channes in the post synaptic membrane
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What is the response of muscarinic receptors to the exposure of ACh?
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either activates or inactivates specific enzymes; can be excitatory or inhibitory
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Is the parasympathetic or sympathetic division controlled and activated as a whole?
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sympathetic
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Why is the parasympathetic division called the anabolic system?
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its stimulation leads to a general increase in the nutrient content of the blood
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What is autonomic tone?
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a continuous level of spontaneous activity of autonomic motor neurons even in the abscence of stimuli
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How is it possible for both neurotransmitters to be released?
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autonomic tone
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Under resting conditions, which system dominates?
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parasympathetic
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What happens to the heart rate if there is parasympathetic inhibition or sympathetic stimulation?
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heart rate increases
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What is a visceral reflex?
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automatic response that can be modified or facilitated by higher centers
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Are visceral reflexes monosynaptic or polysynaptic?
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polysynaptic
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What does each visceral reflex arc consist of?
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-receptor
-sensory neuron -processing center (interneuron) -one or two visceral motor neurons |
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What are the two types of visceral reflexes?
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short and long
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Which type of reflex predominates in the enteric nervous system?
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short
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What type of motor responses do short reflexes control?
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simple, localized effects
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How do long reflexes work?
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visceral sensory neurons deliver info to teh CNS along dorsal roots of spinal nerves; interneurons process info in the CNS, ANS carries motor commands to appropriate visceral effectors
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Which type of reflex is responsible forr coordinated responses involving multiple organ systems
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long reflexes
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What is visceral sensory info collected by?
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interoceptors
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Where are interoceptors primarily located?
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thoracic and abdominopelvic cavities
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What is the function of autonomic motor neurons?
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regulates visceral activities
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Where are neurons controlling parasympathetic viscerall reflexes?
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sacral spinal cord s2-s4
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where are neurons controlling sympathetic visceral reflexes?
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spinal cord t1-l2
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What is the processing center for complex visceral reflexes?
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the medulla oblongata
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What is the visceral sensory neurons stimulated by?
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interoceptors and influence from somatic sensory and special sensory neurons
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How many motor neurons do most pathways have in a series?
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2 motor, 1 sensory
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Where do influences from the general somatic and special senses come from?
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the limbic system
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What is a receptor agonist?
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binds to and activates a receptor
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What is an adrenergic agonist?
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phenylephrine
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What happens with the adrenergic agonist phenylephrine?
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a1 receptors, contricts blood vesses, decreases secretions, and pupils dilate...the sympathetic nervous system is turning up
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What occurs with nicotinic receptor agonists?/
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stimulates receptors causing persistent depolarization; prolonged use causes desensitization/inhibition and dependence in users. BOTH SYSTEMS TURN ON
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What does a muscarinic antagonist do?
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blocks the neurotransmitter from exerting its effect
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What do adrenergic antagonists do?
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turn down the sympathetic nervous system; relaxes or decreases tension
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What are beta blockers used for?
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anxiety and congestive heart failure
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What are alpha blockers used for?
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to treat high blood pressure
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