Podcast
Questions and Answers
In a scenario where the vagus nerve exhibits exceptionally strong parasympathetic stimulation, what physiological outcome is most probable?
In a scenario where the vagus nerve exhibits exceptionally strong parasympathetic stimulation, what physiological outcome is most probable?
- A pronounced increase in the rate and depth of respiration, possibly leading to hyperventilation.
- A brief cessation of cardiac activity potentially leading to temporary loss of arterial pressure. (correct)
- An immediate and sustained increase in gastrointestinal motility, causing severe diarrhea.
- A transient yet substantial elevation in arterial pressure due to robust peripheral vasoconstriction.
If the stellate ganglion is surgically removed, immediately followed by the administration of norepinephrine, what vascular response would be expected, considering denervation supersensitivity?
If the stellate ganglion is surgically removed, immediately followed by the administration of norepinephrine, what vascular response would be expected, considering denervation supersensitivity?
- Reduced vasoconstriction relative to pre-sympathectomy due to damaged adrenergic nerve endings.
- An equivalent vasoconstrictive response due to direct agonistic action on vascular smooth muscle.
- Exaggerated vasoconstriction compared to pre-sympathectomy, indicative of postsynaptic upregulation. (correct)
- Augmented vasodilation because of unopposed beta-adrenergic receptor stimulation.
Suppose a novel pharmaceutical agent selectively targets and ablates sympathetic preganglionic neurons. Which compensatory mechanism would least likely mitigate the resultant homeostatic imbalances?
Suppose a novel pharmaceutical agent selectively targets and ablates sympathetic preganglionic neurons. Which compensatory mechanism would least likely mitigate the resultant homeostatic imbalances?
- Increased synthesis and release of acetylcholine from somatic motor neurons. (correct)
- Upregulation of adrenergic receptors on post-synaptic effector cells.
- Augmentation of parasympathetic nervous system activity.
- Enhanced sensitivity of target tissues to circulating catecholamines.
Consider a patient exhibiting symptoms of both hyperhidrosis and elevated basal metabolic rate, refractory to conventional treatments. Which potential autonomic imbalance is most likely implicated?
Consider a patient exhibiting symptoms of both hyperhidrosis and elevated basal metabolic rate, refractory to conventional treatments. Which potential autonomic imbalance is most likely implicated?
Upon administration of a quaternary ammonium compound with known ganglionic blocking activity to a patient, what is the most probable immediate effect on cardiovascular parameters?
Upon administration of a quaternary ammonium compound with known ganglionic blocking activity to a patient, what is the most probable immediate effect on cardiovascular parameters?
Following complete transection of the spinal cord at the mid-thoracic level, what long-term adaptive change would least likely contribute to the return of partial autonomic function below the lesion?
Following complete transection of the spinal cord at the mid-thoracic level, what long-term adaptive change would least likely contribute to the return of partial autonomic function below the lesion?
If a researcher aims to selectively inhibit the parasympathetic postganglionic neurons innervating the sinoatrial node while sparing other muscarinic receptors, which pharmacological agent is most suitable?
If a researcher aims to selectively inhibit the parasympathetic postganglionic neurons innervating the sinoatrial node while sparing other muscarinic receptors, which pharmacological agent is most suitable?
In elucidating the effects of targeted gene knockout on adrenal medullary function, ablation of which enzyme would most directly impair the conversion of norepinephrine to epinephrine?
In elucidating the effects of targeted gene knockout on adrenal medullary function, ablation of which enzyme would most directly impair the conversion of norepinephrine to epinephrine?
If a subject is administered a bolus of isoproterenol, subsequent to complete autonomic blockade, what cardiovascular change would least likely be observed?
If a subject is administered a bolus of isoproterenol, subsequent to complete autonomic blockade, what cardiovascular change would least likely be observed?
Following a traumatic brain injury, a patient manifests chronic orthostatic hypotension, gastrointestinal dysmotility and anhydrosis. Which specific brain region is most likely compromised?
Following a traumatic brain injury, a patient manifests chronic orthostatic hypotension, gastrointestinal dysmotility and anhydrosis. Which specific brain region is most likely compromised?
In a patient diagnosed with pheochromocytoma, hypersecretion of adrenal catecholamines leads to persistent hypertension. Which adrenoreceptor antagonist regimen would most effectively counteract the diverse effects of circulating catecholamines?
In a patient diagnosed with pheochromocytoma, hypersecretion of adrenal catecholamines leads to persistent hypertension. Which adrenoreceptor antagonist regimen would most effectively counteract the diverse effects of circulating catecholamines?
When comparing the effects of norepinephrine and epinephrine released during the 'alarm' response, which physiological outcome is preferentially mediated by epinephrine due to its receptor affinity profile?
When comparing the effects of norepinephrine and epinephrine released during the 'alarm' response, which physiological outcome is preferentially mediated by epinephrine due to its receptor affinity profile?
Consider a scenario where a patient exhibits excessive salivation coupled with bradycardia. Which pharmacological intervention would most effectively mitigate these parasympathetic excess symptoms?
Consider a scenario where a patient exhibits excessive salivation coupled with bradycardia. Which pharmacological intervention would most effectively mitigate these parasympathetic excess symptoms?
What would be the least probable physiological response following selective lesioning of the intermediolateral cell column at the T1-L2 spinal cord levels?
What would be the least probable physiological response following selective lesioning of the intermediolateral cell column at the T1-L2 spinal cord levels?
In the context of autonomic reflex arcs, which component is primarily responsible for modulating the effector response based on homeostatic feedback?
In the context of autonomic reflex arcs, which component is primarily responsible for modulating the effector response based on homeostatic feedback?
What best describes the interaction between circulating catecholamines and direct sympathetic innervation in regulating vascular tone during exercise?
What best describes the interaction between circulating catecholamines and direct sympathetic innervation in regulating vascular tone during exercise?
A researcher investigates the effects of chronic stress on autonomic balance. Which ratio would be most indicative of heightened sympathetic tone relative to parasympathetic activity?
A researcher investigates the effects of chronic stress on autonomic balance. Which ratio would be most indicative of heightened sympathetic tone relative to parasympathetic activity?
A patient presents with idiopathic hyperhidrosis localized to the palms and soles. What pharmacological approach is most appropriate given the atypical sympathetic innervation of sweat glands?
A patient presents with idiopathic hyperhidrosis localized to the palms and soles. What pharmacological approach is most appropriate given the atypical sympathetic innervation of sweat glands?
Select the neuroanatomical configuration that enables coordinated cardiovascular and respiratory adaptations observed during the mammalian diving reflex:
Select the neuroanatomical configuration that enables coordinated cardiovascular and respiratory adaptations observed during the mammalian diving reflex:
In comparison to the parasympathetic system, what factors make the sympathetic nervous system more amenable to mass discharge phenomena?
In comparison to the parasympathetic system, what factors make the sympathetic nervous system more amenable to mass discharge phenomena?
What is the best example of an autonomic function that is not directly subject to reciprocal control by both sympathetic and parasympathetic innervation?
What is the best example of an autonomic function that is not directly subject to reciprocal control by both sympathetic and parasympathetic innervation?
A patient undergoing prolonged bed rest exhibits signs of orthostatic intolerance. What compensatory mechanism would least likely mitigate these effects?
A patient undergoing prolonged bed rest exhibits signs of orthostatic intolerance. What compensatory mechanism would least likely mitigate these effects?
If a researcher is investigating the role of specific brain regions in autonomic control using optogenetics, stimulation of which area of the brainstem would lead to most pronounced increase in sympathetic nerve activity?
If a researcher is investigating the role of specific brain regions in autonomic control using optogenetics, stimulation of which area of the brainstem would lead to most pronounced increase in sympathetic nerve activity?
Following a spinal cord injury above T1, a patient develops autonomic dysreflexia in response to bladder distention. Which intervention would least likely improve the hypertensive crisis?
Following a spinal cord injury above T1, a patient develops autonomic dysreflexia in response to bladder distention. Which intervention would least likely improve the hypertensive crisis?
Which physiological response is least likely mediated by alpha-2 adrenergic receptors located on presynaptic sympathetic nerve terminals?
Which physiological response is least likely mediated by alpha-2 adrenergic receptors located on presynaptic sympathetic nerve terminals?
What best describes the difference of postganglionic sympathetic actions of norepinephrine and epinephrine on cardiac muscle?
What best describes the difference of postganglionic sympathetic actions of norepinephrine and epinephrine on cardiac muscle?
What has the opposite effect to both sympathetic and parasympathetic stimulation?
What has the opposite effect to both sympathetic and parasympathetic stimulation?
Which of the following is NOT an organ that vagus nerves (cranial nerve X), supply parasympathetic nerves.
Which of the following is NOT an organ that vagus nerves (cranial nerve X), supply parasympathetic nerves.
During the Alarm and Stress Response, which of the following is NOT a listed sympathetic event.
During the Alarm and Stress Response, which of the following is NOT a listed sympathetic event.
What best describes stimulation to Kidney.
What best describes stimulation to Kidney.
In the following, where are the sympathetic postganglionic neurons?
In the following, where are the sympathetic postganglionic neurons?
What best describes the Sympathetic nerve fibers?
What best describes the Sympathetic nerve fibers?
Most systemic blood vessels, sympathetic stimulation, What is the Para stimulation.
Most systemic blood vessels, sympathetic stimulation, What is the Para stimulation.
What function does the apocrine glands NOT perform.
What function does the apocrine glands NOT perform.
Where is the parasympathetic postganglionic neurons?
Where is the parasympathetic postganglionic neurons?
Where do Norepinephrine synthesis basic steps?
Where do Norepinephrine synthesis basic steps?
In the context of long-term compensatory mechanisms following autonomic denervation, what cellular adaptation is least likely to contribute to the restoration of basal function in a visceral organ?
In the context of long-term compensatory mechanisms following autonomic denervation, what cellular adaptation is least likely to contribute to the restoration of basal function in a visceral organ?
If a researcher selectively ablates the neural crest cells destined to become sympathetic ganglia, what compensatory mechanism would be least likely to occur in order to maintain homeostatic blood pressure control?
If a researcher selectively ablates the neural crest cells destined to become sympathetic ganglia, what compensatory mechanism would be least likely to occur in order to maintain homeostatic blood pressure control?
In a scenario involving a patient with complete sympathetic blockade, which of the following physiological responses would be least likely to be observed during moderate exercise?
In a scenario involving a patient with complete sympathetic blockade, which of the following physiological responses would be least likely to be observed during moderate exercise?
Following a traumatic injury leading to selective damage to postganglionic sympathetic neurons innervating cutaneous blood vessels, which long-term effect is least probable?
Following a traumatic injury leading to selective damage to postganglionic sympathetic neurons innervating cutaneous blood vessels, which long-term effect is least probable?
Consider an experiment where the vagus nerve is chronically stimulated at a high frequency, leading to persistent activation of muscarinic receptors in the heart. Which of the following cellular adaptations is least likely to occur?
Consider an experiment where the vagus nerve is chronically stimulated at a high frequency, leading to persistent activation of muscarinic receptors in the heart. Which of the following cellular adaptations is least likely to occur?
A patient presents with a rare genetic mutation causing a complete absence of preganglionic sympathetic neurons, yet exhibits paradoxical hypertension during periods of stress. What mechanism least likely contributes to this phenomenon?
A patient presents with a rare genetic mutation causing a complete absence of preganglionic sympathetic neurons, yet exhibits paradoxical hypertension during periods of stress. What mechanism least likely contributes to this phenomenon?
If a novel compound selectively inhibits the reuptake of norepinephrine into postganglionic sympathetic neurons while simultaneously blocking the enzymatic degradation by monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT), what cardiovascular effect would least likely be observed?
If a novel compound selectively inhibits the reuptake of norepinephrine into postganglionic sympathetic neurons while simultaneously blocking the enzymatic degradation by monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT), what cardiovascular effect would least likely be observed?
In a genetically modified mouse model lacking functional alpha-2 adrenergic autoreceptors on sympathetic nerve terminals, what cardiovascular response would be least likely to occur under conditions of high sympathetic nerve activity?
In a genetically modified mouse model lacking functional alpha-2 adrenergic autoreceptors on sympathetic nerve terminals, what cardiovascular response would be least likely to occur under conditions of high sympathetic nerve activity?
What best describes the mechanism by which stimulation of the sympathetic nervous system increases blood glucose levels during the alarm response?
What best describes the mechanism by which stimulation of the sympathetic nervous system increases blood glucose levels during the alarm response?
A researcher aims to study the effects of selective parasympathetic denervation on gastrointestinal motility. Ablation of which cranial nerve would least directly impact gastric emptying?
A researcher aims to study the effects of selective parasympathetic denervation on gastrointestinal motility. Ablation of which cranial nerve would least directly impact gastric emptying?
Suppose a toxin selectively targets and destroys cholinergic neurons solely within autonomic ganglia. What physiological change would least likely result?
Suppose a toxin selectively targets and destroys cholinergic neurons solely within autonomic ganglia. What physiological change would least likely result?
A patient with a spinal cord injury at C7 exhibits signs of autonomic dysreflexia. Which intervention would least likely prevent the triggering of this response?
A patient with a spinal cord injury at C7 exhibits signs of autonomic dysreflexia. Which intervention would least likely prevent the triggering of this response?
In an experiment designed to assess the relative contributions of sympathetic and parasympathetic nervous systems to heart rate variability (HRV), which manipulation would least likely reduce HRV?
In an experiment designed to assess the relative contributions of sympathetic and parasympathetic nervous systems to heart rate variability (HRV), which manipulation would least likely reduce HRV?
What is the most probable effect on vascular resistance following selective activation of beta-2 adrenergic receptors in skeletal muscle vasculature?
What is the most probable effect on vascular resistance following selective activation of beta-2 adrenergic receptors in skeletal muscle vasculature?
Consider a patient with a tumor secreting excessive amounts of norepinephrine. Blocking which receptor type would least effectively mitigate the resulting hypertension?
Consider a patient with a tumor secreting excessive amounts of norepinephrine. Blocking which receptor type would least effectively mitigate the resulting hypertension?
If researchers selectively lesion the intermediolateral cell column (IML) at the T1-L2 levels of the spinal cord, what is the least probable long-term effect?
If researchers selectively lesion the intermediolateral cell column (IML) at the T1-L2 levels of the spinal cord, what is the least probable long-term effect?
Following damage to the stellate ganglion, what change to the sinoatrial node is least likely to occur?
Following damage to the stellate ganglion, what change to the sinoatrial node is least likely to occur?
How would homeostasis be affected following administration of a drug to a patient that targets the neurons leaving cranial nerve IX.
How would homeostasis be affected following administration of a drug to a patient that targets the neurons leaving cranial nerve IX.
During activation of the parasympathetic component of the autonomic nervous system, which event relating to nitric oxide (NO) is least likely to occur?
During activation of the parasympathetic component of the autonomic nervous system, which event relating to nitric oxide (NO) is least likely to occur?
What paracrine mechanism contributes least to localized vasodilation during vigorous exercise?
What paracrine mechanism contributes least to localized vasodilation during vigorous exercise?
The autonomic nervous system controls visceral functions, including gastrointestinal motility, but not body temperature.
The autonomic nervous system controls visceral functions, including gastrointestinal motility, but not body temperature.
The autonomic nervous system can only decrease, but not increase, the heart rate.
The autonomic nervous system can only decrease, but not increase, the heart rate.
The cerebral cortex, especially the limbic cortex, cannot influence autonomic control.
The cerebral cortex, especially the limbic cortex, cannot influence autonomic control.
Subconscious sensory signals from visceral organs do not play a role in autonomic reflexes.
Subconscious sensory signals from visceral organs do not play a role in autonomic reflexes.
The sympathetic and parasympathetic nervous systems are the efferent divisions through which autonomic signals are transmitted.
The sympathetic and parasympathetic nervous systems are the efferent divisions through which autonomic signals are transmitted.
Sympathetic nerve fibers originate from the spinal cord between segments C1 and L2.
Sympathetic nerve fibers originate from the spinal cord between segments C1 and L2.
Each sympathetic pathway from the spinal cord to the stimulated tissue is composed of three neurons.
Each sympathetic pathway from the spinal cord to the stimulated tissue is composed of three neurons.
Preganglionic sympathetic fibers synapse with postganglionic neurons exclusively within the ganglion that they enter.
Preganglionic sympathetic fibers synapse with postganglionic neurons exclusively within the ganglion that they enter.
Approximately 30% of the fibers in the average skeletal nerve are sympathetic fibers.
Approximately 30% of the fibers in the average skeletal nerve are sympathetic fibers.
Sympathetic nerve fibers from cord segment T1 primarily terminate in the legs.
Sympathetic nerve fibers from cord segment T1 primarily terminate in the legs.
The distribution of sympathetic nerves to each organ is solely random and not related to embryonic origin.
The distribution of sympathetic nerves to each organ is solely random and not related to embryonic origin.
Preganglionic sympathetic nerve fibers directly innervate the adrenal medulla.
Preganglionic sympathetic nerve fibers directly innervate the adrenal medulla.
The parasympathetic nervous system uses cranial nerves III, VII, IX, and XII, in addition to sacral spinal nerves.
The parasympathetic nervous system uses cranial nerves III, VII, IX, and XII, in addition to sacral spinal nerves.
In the parasympathetic nervous system, postganglionic neurons are located in the discrete ganglia in the abdomen.
In the parasympathetic nervous system, postganglionic neurons are located in the discrete ganglia in the abdomen.
Adrenergic fibers secrete acetylcholine.
Adrenergic fibers secrete acetylcholine.
All of the postganglionic neurons of the parasympathetic system are adrenergic.
All of the postganglionic neurons of the parasympathetic system are adrenergic.
Acetylcholinesterase catalyzes the split of acetylcholine into an acetate ion and choline.
Acetylcholinesterase catalyzes the split of acetylcholine into an acetate ion and choline.
Muscarinic receptors are ligand-gated ion channels.
Muscarinic receptors are ligand-gated ion channels.
The beta receptors are divided into beta₁, beta₂, and beta₃ receptors all of which are linked to different G proteins.
The beta receptors are divided into beta₁, beta₂, and beta₃ receptors all of which are linked to different G proteins.
If sympathetic stimulation excites a particular organ, parasympathetic stimulation always excites it too.
If sympathetic stimulation excites a particular organ, parasympathetic stimulation always excites it too.
Match the examples to whether they are controlled almost entirely, or only partially, by the autonomic nervous system:
Match the examples to whether they are controlled almost entirely, or only partially, by the autonomic nervous system:
Match the location of the autonomic nervous system's activation centers:
Match the location of the autonomic nervous system's activation centers:
Match the division, to the origin of the sympathetic nerve fibers:
Match the division, to the origin of the sympathetic nerve fibers:
Match the terms related to sympathetic neurons:
Match the terms related to sympathetic neurons:
Match the function to the segment of the spinal cord, the sympathetic fibers originate from:
Match the function to the segment of the spinal cord, the sympathetic fibers originate from:
Match the effect, to the vagus nerves:
Match the effect, to the vagus nerves:
Match the term to the fiber type, from the sympathetic and parasympathetic nervous system:
Match the term to the fiber type, from the sympathetic and parasympathetic nervous system:
Match the description to the type of acetylcholine resceptors:
Match the description to the type of acetylcholine resceptors:
Match the receptor type to the effect of stimulating it:
Match the receptor type to the effect of stimulating it:
Match activity to the response, from the parasympathetic system:
Match activity to the response, from the parasympathetic system:
Flashcards
Autonomic Nervous System
Autonomic Nervous System
Controls visceral functions like arterial pressure, GI motility, bladder emptying, sweating and temperature.
Autonomic System Speed
Autonomic System Speed
Can drastically alter visceral functions rapidly, like heart rate or blood pressure changes in seconds.
Autonomic Activation
Autonomic Activation
Activated by centers in the spinal cord, brain stem, and hypothalamus; cerebral cortex can also influence it.
Visceral Reflexes
Visceral Reflexes
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Efferent Autonomic Signals
Efferent Autonomic Signals
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Sympathetic Nerve Fiber Origin
Sympathetic Nerve Fiber Origin
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Sympathetic Neurons Anatomy
Sympathetic Neurons Anatomy
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Preganglionic Neuron Location
Preganglionic Neuron Location
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Preganglionic Fiber Paths
Preganglionic Fiber Paths
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Postganglionic Neuron Origin
Postganglionic Neuron Origin
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Sympathetic Fibers in Skeletal Nerves
Sympathetic Fibers in Skeletal Nerves
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Segmental Distribution
Segmental Distribution
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Organ Sympathetic Innervation
Organ Sympathetic Innervation
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Adrenal Medullae Innervation
Adrenal Medullae Innervation
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Adrenal Medullae Secretory Cells
Adrenal Medullae Secretory Cells
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Parasympathetic Fiber Origin Nerves
Parasympathetic Fiber Origin Nerves
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Vagus Nerve (X)
Vagus Nerve (X)
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Sacral Parasympathetic Fibers
Sacral Parasympathetic Fibers
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Parasympathetic Ganglia Location
Parasympathetic Ganglia Location
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Cholinergic Fibers
Cholinergic Fibers
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Adrenergic Fibers
Adrenergic Fibers
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Preganglionic Transmitter
Preganglionic Transmitter
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Adrenergic Postganglionic
Adrenergic Postganglionic
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Parasympathetic Transmitter
Parasympathetic Transmitter
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Neurotransmitter Action
Neurotransmitter Action
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Varicosities
Varicosities
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Transmitter Secretion
Transmitter Secretion
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Acetylcholine Synthesis
Acetylcholine Synthesis
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Acetylcholine Duration
Acetylcholine Duration
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Norepinephrine Synthesis
Norepinephrine Synthesis
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Norepinephrine Removal
Norepinephrine Removal
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Receptor Binding Outcomes
Receptor Binding Outcomes
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Effector Cell Permeability
Effector Cell Permeability
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Second Messenger Enzymes
Second Messenger Enzymes
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Acetylcholine Receptors
Acetylcholine Receptors
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Muscarinic Receptor
Muscarinic Receptor
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Nicotinic Receptors
Nicotinic Receptors
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Adrenergic Receptors
Adrenergic Receptors
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Sympathetic Stimulation Effect on Heart
Sympathetic Stimulation Effect on Heart
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Parasympathetic Stimulation Effect on Heart
Parasympathetic Stimulation Effect on Heart
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Alpha Receptor Effects
Alpha Receptor Effects
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Beta Receptor Effects
Beta Receptor Effects
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Epinephrine vs. Norepinephrine
Epinephrine vs. Norepinephrine
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Sympathomimetic Drugs
Sympathomimetic Drugs
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Autonomic Effector Activation Rate
Autonomic Effector Activation Rate
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Sympathetic and Parasympathetic Tone
Sympathetic and Parasympathetic Tone
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Epinephrine/Norepinephrine Basal Secretion
Epinephrine/Norepinephrine Basal Secretion
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Denervation Supersensitivity
Denervation Supersensitivity
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Mass Sympathetic Discharge
Mass Sympathetic Discharge
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Sympathetic Stress Response Effect
Sympathetic Stress Response Effect
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Value of Tone
Value of Tone
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Parasympathetic Postganglionic Neurons
Parasympathetic Postganglionic Neurons
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Parasympathetic Gland Stimulation
Parasympathetic Gland Stimulation
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Sympathetic Gland Stimulation
Sympathetic Gland Stimulation
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Sympathetic Heart Effects
Sympathetic Heart Effects
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Parasympathetic Heart Effects
Parasympathetic Heart Effects
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Sympathetic vs. Parasympathetic hearts
Sympathetic vs. Parasympathetic hearts
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Sympathetic effect on Blood Vessels
Sympathetic effect on Blood Vessels
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Sympathetic Stimulation, Gastrointestinal Tract
Sympathetic Stimulation, Gastrointestinal Tract
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Arterial Pressure Determinants
Arterial Pressure Determinants
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Sympathetic Impact on Blood Pressure
Sympathetic Impact on Blood Pressure
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Parasympathetic Impact on Blood Pressure
Parasympathetic Impact on Blood Pressure
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Sympathetic Stim and Adrenal Medullae Release
Sympathetic Stim and Adrenal Medullae Release
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Methods of Sympathetic Stimulation
Methods of Sympathetic Stimulation
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Parasympathetic System Effect
Parasympathetic System Effect
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Special Difference
Special Difference
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Mass Sympathetic Discharge Effect
Mass Sympathetic Discharge Effect
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Brain Stem Autonomic Centers
Brain Stem Autonomic Centers
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Sympathomimetic Definition
Sympathomimetic Definition
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Nicotine Effects
Nicotine Effects
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Norepinephrine effect
Norepinephrine effect
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Epinephrine Effects
Epinephrine Effects
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Epinephrine Circulatory Impact
Epinephrine Circulatory Impact
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Adrenal Medullae Value
Adrenal Medullae Value
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Sympathetic Activation Examples
Sympathetic Activation Examples
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Alarm Response Increases
Alarm Response Increases
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The Sympathetic Alarm Reaction
The Sympathetic Alarm Reaction
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Brain Control Centers
Brain Control Centers
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Brain Stem as Relays
Brain Stem as Relays
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Ephedrine, tyramine, amphetamine
Ephedrine, tyramine, amphetamine
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Study Notes
- The autonomic nervous system controls most visceral functions, like arterial pressure, gastrointestinal activity, bladder function, sweating, and temperature.
- It can rapidly and intensely alter visceral functions, such as doubling heart rate in 3 to 5 seconds or causing fainting in 10 to 15 Seconds.
- It's activated by centers in the spinal cord, brain stem, and hypothalamus.
- The cerebral cortex, especially the limbic cortex, can also influence autonomic control by transmitting signals to lower centers.
- Visceral reflexes allow subconscious responses to control activities based on sensory signals from visceral organs.
- Efferent autonomic signals are transmitted through the sympathetic and parasympathetic nervous systems.
Sympathetic Nervous System
- Sympathetic nerve fibers originate with spinal nerves from T1 to L2.
- These fibers connect to paravertebral sympathetic chains of ganglia alongside the vertebral column.
- They also connect to prevertebral ganglia like the celiac, superior mesenteric, aorticorenal, inferior mesenteric, and hypogastric.
- Each sympathetic pathway consists of a preganglionic neuron and a postganglionic neuron.
- The preganglionic neuron's cell body is in the spinal cord's intermediolateral horn; its fiber passes through a ventral root.
- Immediately after leaving the spinal canal, preganglionic sympathetic fibers leave the spinal nerve and enter the sympathetic chain via the white ramus.
- Fibers can (1) synapse with postganglionic neurons in the ganglion they enter, (2) travel up or down the chain to synapse in another ganglion, or, (3) pass through the chain and synapse in a peripheral sympathetic ganglion.
- Postganglionic fibers travel from either the sympathetic chain ganglia or peripheral ganglia to their destinations in various organs.
- Some postganglionic fibers return to the spinal nerves via gray rami at all levels of the cord and extend to the body through skeletal nerves to control blood vessels, sweat glands, and piloerector muscles. These fibers are very small type C fibers, and account for about 8% of all the fibers in the average skeletal nerve.
- Sympathetic fibers from T1 ascend in the sympathetic chain to the head.
- T2 fibers go to the neck; T3-T6 to the thorax; T7-T11 to the abdomen; T12, L1, and L2 to the legs, though there's overlap and is an approximate distribution.
- An organ's sympathetic nerve distribution is determined by its origin in the embryo.
- Preganglionic sympathetic nerve fibers pass without synapsing; through the sympathetic chains and splanchnic nerves, then to the adrenal medullae to end directly on hormone-secreting hormone producing cells.
- These modified neuronal cells secrete epinephrine and norepinephrine into the bloodstream. They are derived from nervous tissue and have rudimentary nerve fibers.
Parasympathetic Nervous System
- Parasympathetic fibers exit the central nervous system through cranial nerves III, VII, IX, and X, and sacral spinal nerves S2-S4 (occasionally S1 and S4).
- About 75% of parasympathetic fibers are in the vagus nerves, serving thoracic and abdominal organs.
- Fibers in the third cranial nerve go to the pupillary sphincter and ciliary muscle of the eye.
- Fibers from the seventh cranial nerve serve the lacrimal, nasal, and submandibular glands; fibers from the ninth cranial nerve serve the parotid gland.
- Sacral parasympathetic fibers in the pelvic nerves serve the descending colon, rectum, bladder, lower ureters, and external genitalia, and cause erection in the external genitalia.
- Preganglionic fibers pass uninterrupted to the organ to be controlled, except in some cranial parasympathetic nerves.
- Postganglionic neurons are in the organ wall; postganglionic fibers are very short, and range from a fraction of a millimeter to centimeters in length.
Sympathetic vs Parasympathetic
- Cholinergic fibers secrete acetylcholine; adrenergic fibers secrete norepinephrine.
- All preganglionic neurons are cholinergic in both systems so acetylcholine excites both sympathetic and parasympathetic postganglionic neurons.
- Most postganglionic sympathetic neurons are adrenergic, but those to sweat glands and a few blood vessels are cholinergic.
- Parasympathetic system terminal nerve endings all secrete acetylcholine.
- Neurotransmitters act on organs to cause parasympathetic or sympathetic effects; acetylcholine is a parasympathetic transmitter, norepinephrine is a sympathetic transmitter.
- Transmitter substances are secreted from bulbous enlargements called varicosities where filaments may touch or pass near cells to be stimulated.
- Action potentials increase membrane permeability to calcium ions that cause contents to empty to the exterior releasing the transmitter substance.
- Acetylcholine is synthesized in cholinergic nerve fiber terminals and varicosities and stored in vesicles.
- After secretion, acetylcholine persists briefly and is split into an acetate ion and choline by acetylcholinesterase.
- Choline is transported back into the terminal for resynthesis of acetylcholine.
- Norepinephrine synthesis begins in the axoplasm of adrenergic nerve endings and completes inside secretory vesicles.
- After secretion, norepinephrine is removed via (1) reuptake into adrenergic nerve endings, (2) diffusion into body fluids and blood, and (3) destruction by tissue enzymes like monoamine oxidase and catechol-O-methyl transferase.
- Norepinephrine's action is short, but adrenal medullae hormones remain active longer in the blood.
- Neurotransmitters bind with receptors, causing a conformational change, to excite or inhibit cells by changing membrane permeability or activating intracellular enzymes.
- Changing membrane permeability opens/closes ion channels, affecting cell polarization and activity.
- Receptors can activate enzymes inside the cell like adenylyl cyclase, which then forms cyclic adenosine monophosphate cAMP.
- Acetylcholine activates muscarinic and nicotinic receptors.
- Muscarinic receptors, act via G proteins, are on all effector cells stimulated by postganglionic cholinergic neurons.
- Nicotinic receptors, which are ligand-gated ion channels, are at synapses between pre- and postganglionic neurons in both systems
- Alpha (α) and beta (β) adrenergic receptors exist. There are alpha1 and alpha2 receptors; beta receptors are further divided into subtypes beta1, beta2, and beta3.
- Norepinephrine excites alpha receptors, epinephrine excites alpha receptors mainly, and epinephrine excites both types approximately equally.
Actions of Sympathetic and Parasympathetic Stimulation on Specific Organs
- The pupillary opening is controlled by the autonomic nervous system.
- Sympathetic stimulation dilates via contraction of the iris's meridonal fibers.
- Parasympathetic stimulation constricts via the circular muscle.
- Focus is controlled by lens via the parasympathetic nervous system: excitation contracts the ciliary muscle allowing the lens to become more convex.
- Nasal, lacrimal, salivary, and gastrointestinal glands are strongly stimulated by the parasympathetic nervous system, usually resulting in copious watery secretions.
- Glands of the alimentary tract most affected in their secretion processes, are stomach and mouth.
- Intestinal glands are controlled by local factors and the intestinal enteric nervous system.
- Sympathetic stimulation causes a concentrated secretion with more enzymes and mucus but can reduce secretion due to vasoconstriction.
- Sweat glands secrete large quantities of sweat when the sympathetic nerves are stimulated; these fibers are cholinergic but a few adrenergic fibers go to the palms and soles of hands/feet.
- Apocrine glands secrete a thick odoriferous secretion via sympathetic stimulation but not by parasympathetic, to assist with sliding motion within the shoulder joint.
- Sympathetic stimulation increases heart rate and force; parasympathetic stimulation decreases heart rate and force.
- Sympathetic stimulation dilates the bronchi; parasympathetic stimulation constricts it.
- In general, sympathetic stimulation decreases peristalsis and increases sphincter tone in the gut, slowing propulsion.
- Sympathetic stimulation decreases urine output and increases renin secretion; parasympathetic stimulation has no effect.
- In general, entodermal structures (e.g., liver ducts, gallbladder, ureter, urinary bladder, bronchi) are inhibited by sympathetic stimulation but excited by parasympathetic stimulation.
- Sympathetic stimulation also results in glucose release, increased blood glucose concentration, increased rate of glycogenolysis, increased skeletal muscle strength, increased basal metabolic rate and increased mental activity.
Sympathetic/"Mass Discharge"
- Occurs when nearly all the sympathetic portions in the nervous system discharges, and occur when the hypothalamus is activated by severe pain or fright.
- Also known as the "alarm" or "stress" response, and results in widespread reaction through the body
- During this process epinephrine and norepinephrine are released into the circulating blood, causing increased ability of the body to perform vigorous muscle activity. These hormones have the same effects on the different organs as the direct sympathetic stimulation except that they last longer, about 5-10 times longer, and are slowly removed after 2 to 4 minutes.
- Has the following effects:
- Increased arterial pressure
- Increased blood flow to active muscles and decreased flow to kidneys/gastrointestinal tract
- Increased cellular metabolism rates through the body
- Increased blood glucose concentration and glycolysis
- Increased mental and muscle strength
- Increased blood coagulation
- This process is activated in many emotional states, and is also known as the "fight-or-flight" reaction
Arterial Pressure
- Arterial pressure is determined by heart propulsion and peripheral blood vessel resistance.
- Sympathetic stimulation can significantly increase both propulsion and resistance. Moderate parasympathetic stimulation, via the vagal nerves, decreases pumping by the heart but has virtually no effect on vascular peripheral resistance, which slightly decreases arterial pressure. Very strong vagal parasympathetic stimulation can stop the heart entirely for a few seconds, causing temporary loss of arterial pressure.
Sympathetic and Parasympathetic Effects
- Because of the importance of the control systems, it can be discussed during multiple systems with relation to multiple body functions. Metabolic effects such as the release of glucose from the liver, increase in blood glucose concentration, glycogenolysis in the muscle/liver and the increased mental state
- It can cause high concentrations of the Sympathetic systems; where a low frequency is required when full activation of the autonomic effectors can be achieved. There can be activation when nerve fibers discharge from 10 times/sec and in comparison to the skeletal nervous system at 50-500 or greater.
Sympathetic and Parasympathetic Actions
- Sweating could be called a parasympathetic function, even though it is controlled by nerve fibers that anatomically are distributed through the sympathetic nervous system.
- Intramural Plexus / Intestinal Enteric Nervous System, can affect activity by decreasing and increasing specific action. Increases in sympathetic stimulation are associated with normal motor functions in order to affect secretions.
- Normal motility functions of the gastrointestinal tract are not dependent on sympathetic stimulation, but strong reactions increase tone of the sphincters.
- Heart rates are stimulated to increase by the sympathetic effects, where blood is released at a greater efficiency
- Blood vessels that stem, are controlled by the sympathetic system, for the most dominance over Beta which is a lesser effect.
- The arterial can be controlled by the vagal nerves to increase arterial pressure, or have almost no affect on vascular pressure and also prevent its modulation to prevent the arterial system from continuing.
- To maintain homeostasis by stabilizing structures and organs. Such as stimulation increasing and decreasing the blood glucose and rates throughout different areas and stimulation
- It can cause high stimulation from low frequency that can achieve autonomic effectors. Where it can affect activation from 10 times and compared to more due to skeletal/high activity
Adrenal Medullae
- This stimulation or sympathetic nerves, causes a quantity of epinephrine to release with multiple hormones to be carried. On Average 20 percent of the secretion or NE, where over the physiological period.
- Norepinephrine also has blood vessels over the body and increasing activity,
- Where these effects last for 5-10 times due to its ability to affect.
- There is resistance where the hormone does not increase by the arterial body or increase the caridac output or more.
Supersensitivity' to Norepinephrine and Acetylcholine After Denervation
- During this time as sympathetic or sympathetic and denervation increases sensitivity such as to be injected. Affect vascular with a lot higher to 2 to 4 or greater This Occurs with in more organs to a for greater to more
Autonomic Reflexes
- Heart rates are increased and regulated to the brain from the sympathetic impulse.
- Gastrointestinal functions and tracts.
Selective and Stimulation
- the parasympathetic is a specific function, and cardio affects do not always transfer, and the other processes does have
- When mass discharge from the SNS system increasing the ability of the vigorous activity such as increasing a pressure and or resistance.
- The parasympathetic system will cause highly specific responses, where effects on various organs from the digestive system may be small. These will create an increase of ability to perform multiple activities as well as emotions and responses.
- The parasympathetic will continue and provide responses from activities such as digestion or bladder contraction, The Medulla which consists of the Autonomic Nervous System, maintains functions and system and cardiovascular system.
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