Sympathetic Nervous System Functions
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Questions and Answers

What is the primary purpose of the sympathetic nervous system's fight-or-flight response?

  • To enhance cognitive functions during stress
  • To initiate sleep and recovery processes
  • To promote relaxation and digestion
  • To prepare the body for life-threatening situations (correct)

    • Which of the following responses is NOT typically associated with the sympathetic nervous system during a fight-or-flight reaction?

  • Increased blood glucose levels
  • Increased heart rate
  • Bronchial dilation
  • Decreased blood pressure (correct)

    • What happens to parasympathetic output during the sympathetic nervous system's fight-or-flight response?

  • It fluctuates continuously
  • It remains unchanged
  • It ceases (correct)
  • It increases to balance sympathetic activity

    • Which of the following best describes the nature of sympathetic output during the fight-or-flight response?

    <p>Coordinated and massive across the body</p> Signup and view all the answers

    What is meant by the term 'chemical coding' in the context of sympathetic neurons?

    <p>The distribution of various neurotransmitters among sympathetic neurons</p> Signup and view all the answers

    What neurotransmitters are released by guinea pig postganglionic sympathetic neurons during depolarization?

    <p>Norepinephrine, ATP, and neuropeptide Y</p> Signup and view all the answers

    In Walter Cannon’s proposal about sympathetic division activity, what is stated about its effects on target organs?

    <p>It produces uniform effects on all target organs.</p> Signup and view all the answers

    Which physiological change occurs as a result of sympathetic nervous system activation?

    <p>Sweating and piloerection</p> Signup and view all the answers

    Which brain region is primarily responsible for coordinating autonomic output?

    <p>Hypothalamus</p> Signup and view all the answers

    What role does the forebrain have regarding the brainstem in autonomic regulation?

    <p>It modulates and coordinates activities of the brainstem.</p> Signup and view all the answers

    Which of the following structures is NOT involved in maintaining autonomic homeostasis?

    <p>Cerebellum</p> Signup and view all the answers

    Which feature distinguishes forebrain regions in relation to autonomic control?

    <p>They have direct connections to brainstem nuclei for autonomic control.</p> Signup and view all the answers

    What is one of the primary functions of the hypothalamus concerning autonomic output?

    <p>It initiates and coordinates integrated responses.</p> Signup and view all the answers

    Which physiological processes does the hypothalamus integrate with autonomic function?

    <p>Circadian rhythms, thermoregulation, and feeding.</p> Signup and view all the answers

    Which brain region primarily initiates the fight-or-flight response?

    <p>Hypothalamus</p> Signup and view all the answers

    Which component is responsible for influencing autonomic output alongside the hypothalamus?

    <p>All of the above</p> Signup and view all the answers

    What is the primary function of feedback loops in the ANS?

    <p>To maintain physiological parameters within an optimal range</p> Signup and view all the answers

    How do the sympathetic and parasympathetic divisions of the ANS typically function?

    <p>They usually act in opposite ways to make physiological adjustments</p> Signup and view all the answers

    What is an example of a visceral feedback loop mentioned in the content?

    <p>Blood pressure control</p> Signup and view all the answers

    What happens to sympathetic output when blood pressure increases?

    <p>It decreases</p> Signup and view all the answers

    How does the ANS respond when a person begins to exercise?

    <p>Sympathetic output increases before metabolic need arises</p> Signup and view all the answers

    What effect does anticipatory sympathetic output have on blood levels of CO2 at the onset of exercise?

    <p>It leads to a decrease in CO2 levels</p> Signup and view all the answers

    What type of feedback does the ANS primarily rely on for maintaining homeostasis?

    <p>Negative feedback</p> Signup and view all the answers

    Which organ system is primarily adjusted by the CNS during blood pressure feedback?

    <p>Cardiovascular system</p> Signup and view all the answers

    What type of fibers does the vagus nerve contain that contributes to its effect on cortical function?

    <p>Parasympathetic preganglionic motor and sensory fibers</p> Signup and view all the answers

    What is the primary action of the vagus nerve stimulator used in epilepsy treatment?

    <p>To electrically stimulate the vagus nerve for 30 seconds every 5 minutes</p> Signup and view all the answers

    What effect can visceral input have on cortical neurons?

    <p>It can sometimes overwhelm cortical function</p> Signup and view all the answers

    What is a significant side effect of vagus nerve stimulation?

    <p>Hoarseness, coughing, and breathlessness</p> Signup and view all the answers

    How much does the vagus nerve stimulation typically reduce the number of seizures?

    <p>By about one in four patients can achieve a 50% reduction</p> Signup and view all the answers

    What remains uncertain regarding the vagal afferent input and its effects on seizures?

    <p>The specific pathways that produce the anticonvulsant effect</p> Signup and view all the answers

    In what instance can patients manually activate the vagus nerve stimulator?

    <p>When experiencing a seizure aura</p> Signup and view all the answers

    Why is the impact of visceral input on cortical function significant?

    <p>It highlights the interconnectedness of body signals and brain activity</p> Signup and view all the answers

    What role do postganglionic sympathetic neurons in the inferior mesenteric ganglion primarily play?

    <p>They control gut motility and secretion.</p> Signup and view all the answers

    Which statement accurately describes the function of parasympathetic neurons?

    <p>They function in a discrete, organ-specific, and reflexive manner.</p> Signup and view all the answers

    Which reflex is mediated by preganglionic parasympathetic neurons in the dorsal motor nucleus of the vagus?

    <p>Baroreceptor reflex</p> Signup and view all the answers

    Which of the following reflexes is NOT associated with the parasympathetic nervous system?

    <p>Increased heart rate during exercise</p> Signup and view all the answers

    What is a key feature of sympathetic neurons compared to parasympathetic neurons?

    <p>They adapt to support long-lasting effects in organs.</p> Signup and view all the answers

    Which of the following is an example of an involuntary parasympathetic reflex?

    <p>Pupillary light reflex</p> Signup and view all the answers

    In sympathetic control, what effect does depolarization of neurons induce?

    <p>Vasoconstriction and release of neuromodulators.</p> Signup and view all the answers

    How do sympathetic neurons differ in their effects on targets compared to parasympathetic neurons?

    <p>They produce different effects based on the target's function.</p> Signup and view all the answers

    What primary role do autonomic ganglia play in the nervous system?

    <p>They integrate autonomic activity at peripheral sites.</p> Signup and view all the answers

    Which part of the brain is critical for coordinating visceral control and is vital for survival?

    <p>Medulla</p> Signup and view all the answers

    What occurs in individuals with transection of the low cervical spinal cord?

    <p>They are capable of autonomic hyper-reflexia.</p> Signup and view all the answers

    What is the significance of the spinal cord in the context of chordate evolution?

    <p>It coordinates activities across different root levels.</p> Signup and view all the answers

    Which structure would lead to instant death if destroyed, assuming no life support is provided?

    <p>Medulla</p> Signup and view all the answers

    What is NOT a characteristic of autonomic ganglia?

    <p>They strictly function in one-way signal transmission.</p> Signup and view all the answers

    How do the spinal cord and lower autonomic ganglia contribute to homeostasis in humans?

    <p>They assist in maintaining homeostasis even without cranial nerve involvement.</p> Signup and view all the answers

    What neurotransmitter action primarily influences the integration of autonomic activity at peripheral sites?

    <p>Release from interneurons in autonomic ganglia.</p> Signup and view all the answers

    Study Notes

    Sympathetic Output

    • Walter Cannon proposed (1915) that the entire sympathetic division is activated uniformly for fight-or-flight responses.
    • This massive, coordinated output prepares the body for life-threatening situations.
    • Parasympathetic output ceases during these situations.
    • Responses include increased heart rate, cardiac contractility, blood pressure, and lung ventilation; bronchial dilation; sweating; piloerection; glucose release; insulin inhibition; faster blood clotting; and blood cell mobilization.
    • The fight-or-flight response is a survival mechanism; panic attacks can be triggered spontaneously or with minimal provocation.

    Sympathetic Output (Specificity)

    • The sympathetic division can also be discrete and organ-specific under normal conditions.
    • Different postganglionic sympathetic neurons have varying electrophysiological properties.
    • They release different neurotransmitters, besides norepinephrine—this is chemical coding.
    • Example: Depolarization in guinea pig lumbar sympathetic chain neurons causes a brief action potential burst (95%) with norepinephrine and ATP & neuropeptide Y release, potentially inducing vasoconstriction.
    • Other neurons (inferior mesenteric ganglion) sustain firing (80%) and release norepinephrine and somatostatin, potentially controlling gut motility and secretion.
    • This variability allows different effects on specific organs based on their function.

    Parasympathetic Neurons

    • Unlike sympathetic neurons, parasympathetic neurons function in discrete, organ-specific, and reflexive manners.
    • They're involved in simple reflexes like urination (bladder distension), salivation (food sight/smell), vagovagal reflexes (e.g., colon contraction due to stomach food), and bronchoconstriction (lung receptor activation).
    • The pupillary light reflex is a bedside testable parasympathetic reflex.

    Brainstem Nuclei

    • Various brainstem nuclei (nucleus tractus solitarii, area postrema, ventrolateral medulla, medullary raphe, reticular formation, locus coeruleus, and parabrachial nucleus) control visceral function .
    • Some nuclei play specific roles (e.g., rostral ventrolateral medulla increases sympathetic output to the cardiovascular system).
    • Others modulate general autonomic tone.
    • The nucleus tractus solitarii (NTS) is a crucial medulla structure receiving input from peripheral chemoreceptors, baroreceptors, and afferent nerves, ultimately integrating visceral information.

    Forebrain Influence on ANS

    • The hypothalamus, including the paraventricular nucleus, substantially coordinates autonomic output, initiating and coordinating responses to body needs & modulating autonomic output, pituitary, feeding, thermoregulation, etc.
    • Forebrain regions interact with brainstem nuclei for autonomic control, although the neocortex has limited direct control.
    • Emotional states, stress, fear, etc. strongly modulate autonomic responses mediated through the ANS.
    • Specific forebrain regions can't control all aspects of autonomic functions; the ANS has its own feedback loops.

    Descending Cortical Control

    • Fear, panic attacks, emotional stress, painful stimuli, seizures, chronic stress, and sleep deprivation can influence autonomic function.
    • These stimuli trigger activation of the sympathetic division, leading to increased breathing, vasodilation (potentially hypotension), and stress responses.

    Visceral Afferent's Influence

    • Visceral afferents can powerfully influence the cortex; their lack of viscerotopic representation limits precise localization.
    • Overwhelming visceral input can block processing of other information.

    Vagus Nerve Stimulation

    • The vagus nerve plays a significant role in ANS function and is involved in seizures treatment via a vagus nerve stimulator.
    • It significantly influences cortical function in several ways and could be helpful in anticonvulsive treatments.

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    Central Nervous System Control of the Viscera PDF

    Description

    Explore the complexities of the sympathetic division of the autonomic nervous system and its fight-or-flight responses. Understand how it prepares the body for stress and the nuances of its function, including organ-specific outputs and neurotransmitter releases. This quiz covers both historical concepts and specific physiological mechanisms.

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