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Lecture 5 Autonomic Nervous System Overview
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Lecture 5 Autonomic Nervous System Overview

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Questions and Answers

What is the main role of preganglionic fibers that extend to the adrenal medulla?

  • Stimulate secretion of epinephrine and norepinephrine (correct)
  • Control muscle contractions in the abdomen
  • Supply blood to the adrenal glands
  • Inhibit secretion of hormones

    • Which cranial nerve is primarily responsible for supplying parasympathetic fibers to the body?

  • Cranial nerve V
  • Cranial nerve X (correct)
  • Cranial nerve VII
  • Cranial nerve III

    • What type of receptor binds acetylcholine in target organs of the parasympathetic system?

  • Muscarinic receptors (correct)
  • Adrenergic receptors
  • G-protein coupled receptors
  • Nicotinic receptors

    • Which of the following effects does the sympathetic system have on the urinary bladder?

    <p>Relaxes muscle tone</p> Signup and view all the answers

    Which adrenergic receptor type is primarily associated with increasing the heart's contraction strength and rate?

    <p>β1-adrenergic</p> Signup and view all the answers

    What is the effect of the parasympathetic system on intestinal mobility?

    <p>Stimulation of movement</p> Signup and view all the answers

    Which medication is known as a β-adrenergic antagonist and is used to decrease heart rate?

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

    What is the primary action of muscarinic receptor blockers like atropine in the eye?

    <p>Dilates the pupil</p> Signup and view all the answers

    How do β2-adrenergic agonists like salbutamol function in treating asthma?

    <p>Induce bronchodilation</p> Signup and view all the answers

    What distinguishes the ganglia of the parasympathetic system from those of the sympathetic system?

    <p>Parasympathetic ganglia are adjacent to target organs</p> Signup and view all the answers

    What is the primary function of the autonomic nervous system?

    <p>Manages body functions without conscious thought</p> Signup and view all the answers

    Which division of the autonomic nervous system is primarily involved during stress?

    <p>Sympathetic division</p> Signup and view all the answers

    The process of autonomic reflexes involves which of the following components?

    <p>Sensory cells, integration center, and effectors</p> Signup and view all the answers

    What differentiates motor nerve fibers in the autonomic nervous system from those in the somatic motor system?

    <p>They include two peripheral nerves in the circuit</p> Signup and view all the answers

    Where do preganglionic neurons of the sympathetic division originate?

    <p>Thoracic and lumbar regions of the spinal cord</p> Signup and view all the answers

    Which structure serves as the primary control center for autonomic functions?

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

    In autonomic reflexes, what happens when the sensory input differs from the set reference?

    <p>Frequency on the motor fiber is altered</p> Signup and view all the answers

    Which type of muscle is controlled by the autonomic nervous system?

    <p>Cardiac and smooth muscle</p> Signup and view all the answers

    What characterizes the postganglionic fibers in the sympathetic nervous system?

    <p>They are very long and innervate distant organs</p> Signup and view all the answers

    Which neurotransmitter is commonly associated with the autonomic nervous system?

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

    What is the primary role of the autonomic nervous system?

    <p>To regulate body functions automatically and involuntarily.</p> Signup and view all the answers

    Which structure serves as the 'master command' for autonomic functions?

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

    During which type of activities is the sympathetic division primarily activated?

    <p>Stressful and demanding situations</p> Signup and view all the answers

    What distinguishes the preganglionic neurons of the sympathetic and parasympathetic systems?

    <p>Sympathetic preganglionic neurons arise from the thoracic or lumbar spinal cord.</p> Signup and view all the answers

    How many neurons are typically involved in the peripheral circuit of the autonomic nervous system?

    <p>Two neurons</p> Signup and view all the answers

    What type of muscle is controlled by the autonomic nervous system?

    <p>Smooth muscle and cardiac muscle</p> Signup and view all the answers

    Which part of the spinal cord is primarily associated with the sympathetic nervous system's outflow?

    <p>Thoracic region</p> Signup and view all the answers

    In autonomic reflexes, the integration center can be found in which structure?

    <p>Spinal cord</p> Signup and view all the answers

    Which fiber type is typically longer in the sympathetic nervous system compared to the parasympathetic nervous system?

    <p>Postganglionic fibers</p> Signup and view all the answers

    Which system is integrated with the parasympathetic division of the autonomic nervous system?

    <p>Enteric nervous system</p> Signup and view all the answers

    What is the primary effect of the sympathetic system on the blood vessels?

    <p>Constriction in most cases</p> Signup and view all the answers

    What characterizes the postganglionic fibers in the parasympathetic system?

    <p>They are short and connect directly with specific organs</p> Signup and view all the answers

    Which of the following is a function of α2-adrenergic receptors?

    <p>Decrease cAMP levels</p> Signup and view all the answers

    In what way do the adrenal medulla's secretions affect the autonomic nervous system?

    <p>They enhance the actions of the sympathetic system by releasing epinephrine and norepinephrine.</p> Signup and view all the answers

    Which cranial nerves supply parasympathetic fibers to the body's organs?

    <p>III, VII, IX, and X</p> Signup and view all the answers

    What is one of the effects of sympathetic stimulation on the eye?

    <p>Pupil dilation</p> Signup and view all the answers

    How do muscarinic receptors influence target organs in the parasympathetic system?

    <p>They require intracellular second messengers for action.</p> Signup and view all the answers

    What is the role of a β2-adrenergic agonist in treating asthma?

    <p>It induces bronchodilation.</p> Signup and view all the answers

    Which of the following actions is primarily associated with the parasympathetic system?

    <p>Increased intestinal mobility</p> Signup and view all the answers

    What impact does atropine have on muscarinic receptors?

    <p>It blocks muscarinic receptors, causing dilation of pupils.</p> Signup and view all the answers

    Study Notes

    Autonomic Nervous System (ANS)

    • Controls body functions automatically and involuntarily
    • Maintains homeostasis through reflexes
    • Controls smooth muscle, cardiac muscle, and glands
    • Influences various bodily functions including respiration, heart rate, blood pressure, digestion, sleep, arousal, and body temperature

    Structure and Function of ANS

    • Sensory cells: Specialized receptors for specific stimuli (e.g., baroreceptors for pressure, thermosensors for temperature)
    • Sensory nerve fibers: Similar to somatic nervous system
    • Control centers:
      • Hypothalamus: Master command center
      • Brain stem: Specific control functions (e.g., respiratory center)
      • Spinal cord: Local integration in thoracic and sacral segments
    • Motor nerve fibers:
      • Differ from somatic motor system, target organ (smooth muscle, cardiac muscle, glands)
      • Two neurons involved in peripheral circuit:
        • Preganglionic neuron: Cell body in CNS, axon innervates postganglionic neuron
        • Postganglionic neuron: Cell Body in ganglion, axon innervates effector organ

    Major Divisions of the ANS

    • Sympathetic (thoracolumbar): Activated during stress, preganglionic neurons originate in thoracic or lumbar spinal area
    • Parasympathetic (cranio-sacral): Most active during rest, preganglionic neurons originate in brain or sacral spinal cord
    • Enteric Nervous System: Associated with parasympathetic

    Sympathetic System

    • Preganglionic axons enter the paravertebral sympathetic ganglion chain
    • Postganglionic fibers are long, innervate hollow organs, blood vessels, etc.
    • Some preganglionic fibers extend to the adrenal medulla, stimulating secretion of epinephrine and norepinephrine into the blood

    Parasympathetic System

    • Long preganglionic fibers: Cranial nerves III, VII, IX, and X supply parasympathetic fibers to glands and organs, Vagus nerve being a major supplier
    • Ganglia located in the wall or adjacent to target organs, no interconnection
    • Short postganglionic fibers, direct connection with specific organs, no enhancement by hormones

    Communication Within ANS

    • Neurotransmitters:
      • Acetylcholine: Released by preganglionic neurons of both sympathetic and parasympathetic divisions
      • Norepinephrine: Released by postganglionic neurons of the sympathetic division
      • Epinephrine: Released by adrenal medulla (sympathetic)

    Receptors to ANS Neurotransmitters

    • Acetylcholine receptors:
      • Nicotinic: Located at preganglionic synapses, ionotropic
      • Muscarinic: Located in target organs of parasympathetic, metabotropic
    • (Nor)epinephrine receptors (adrenergic): Metabotropic
      • Alpha-adrenergic:
        • Alpha 1: Increases intracellular calcium, usually smooth muscle constriction
        • Alpha 2: Decreases cAMP, usually smooth muscle constriction
      • Beta-adrenergic:
        • Beta 1 and Beta 2: Increases cAMP, main form in heart, relaxation of smooth muscles

    Pharmacological Significance

    • Agonists: Drugs that activate neurotransmitter receptors
    • Antagonists: Drugs that block neurotransmitter receptors
    • Hypertension treatment: Beta-adrenergic blockers (Propranolol) reduce heart rate
    • Asthma treatment: Beta-adrenergic agonists (salbutamol) dilate bronchioles
    • Atropine: Muscarinic receptor antagonist, dilates pupils, inhibits contraction of lower GI tract, reduces mucus production in the respiratory tract

    Reciprocal Effects of Sympathetic and Parasympathetic Systems

    • Effectors:
      • Eye: Sympathetic dilation, Parasympathetic constriction
      • Salivary gland: Sympathetic stimulation, Parasympathetic inhibition
      • Heart rate: Sympathetic increased, Parasympathetic decreased
      • Blood vessels: Sympathetic constriction (most), Parasympathetic dilation (few)
      • Lungs (bronchiole): Sympathetic dilation, Parasympathetic constriction
      • Intestinal mobility: Sympathetic inhibition, Parasympathetic stimulation
      • Sphincters: Sympathetic closing, Parasympathetic opening
      • Urinary bladder: Sympathetic relaxation, Parasympathetic contraction
      • Penis: Sympathetic ejaculation, Parasympathetic erection

    ### Autonomic Nervous System

    • Controls bodily functions without conscious thought (automatically, involuntarily), a key role in homeostasis
    • Achieved via reflexes - autonomic reflexes
    • Works on smooth muscle, cardiac muscle, and glands
    • Responsible for respiration, heart rate, blood pressure, digestion, rumination, sleep, arousal, and body temperature

    Autonomic Reflexes

    • Sensory cells (baroreceptors, cold and warm receptors, etc...) - dependent on the system
    • Sensory nerve fibers: similar to somatic arc reflexes
    • Control centers: hypothalamus, brain stem, spinal cord
      • Hypothalamus: master command
      • Brain stem: special control function (respiratory center)
      • Spinal cord: local integration
    • Receive continuous information from sensory nerves and compare it to a set reference, if different, alter frequency on the motor fiber.

    Motor Nerve Fibers

    • Differ from somatic motor systems:
      • Target organ (Smooth muscle, cardiac muscle, glands)
      • Number of neurons in its peripheral circuit: two peripheral nerves (vs. 1 in somatic arc reflex)
        • Preganglionic neuron: cell body in CNS, axon innervates second neuron (postganglionic neuron)
        • Postganglionic neuron: cell body in a ganglion

    Major Divisions of the ANS

    • Sympathetic (thoraco-lumbar): activated during stress, preganglionic neurons originate in thoracic or lumbar spinal area
    • Parasympathetic (cranio-sacral): most active during rest, preganglionic neurons originate in the brain or sacral part of the spinal cord
    • Enteric Nervous System: associated with the parasympathetic

    Sympathetic System

    • Outflow from thoracolumbar spinal cord, preganglionic axons enter the paravertebral sympathetic ganglion chain
    • Postganglionic fibers are very long, innervate hollow organs, blood vessels, etc.
    • Some preganglionic fibers extend to the adrenal medulla, stimulating the secretion of epinephrine and norepinephrine into the bloodstream

    Parasympathetic System

    • Very long preganglionic fibers, cranial nerves III, VII, IX, and X supply parasympathetic fibers, X (vagus nerve) is the major supplier
    • Ganglia: located in the wall or adjacent to target organs, no interconnection between ganglia
    • Postganglionic fibers: short axons, direct connection with specific organs with no branching off or enhancement by hormones

    Receptors to ANS Neurotransmitters

    • Acetylcholine:

      • Nicotinic: preganglionic synapses, ionotropic, part of an ion channel (here: Na+)
      • Muscarinic: in target organs of parasympathetic, separate from ion channel, requires intracellular second messengers, slower, and more prolonged effect than nicotinic

    • (Nor)Adrenalin (Adrenergic): separate receptors associated with G-proteins, activate intracellular second messengers

      • α-adrenergic:
        • α1 = ï‚­ Ca2+
        • α2 =  cAMP
        • Usually constriction of smooth muscles (vascular)
      • β-adrenergic:
        • β1 and β2 = ï‚­cAMP
        • Main form in the heart  ï‚­ contraction strength & rate
        • Relaxation of smooth muscles (GI tract, uterus, bronchioles)

    Pharmacological Significance

    • Use of agonists and antagonists to selectively activate or block receptors
    • Hypertension:
      • β-adrenergic blocker (Propranolol) =  heart rate
    • Asthma:
      • β2-adrenergic agonist (salbutamol) = bronchodilation
    • Atropine:
      • Muscarinic receptor blocker
      • Drop in eye = dilation of pupils
      • Inhibits contraction of lower GI tract
      • Reduces mucus production in respiratory tract

    Reciprocal Effects

    • Effectors:
      • Eye:
        • Sympathetic: Pupil dilation
        • Parasympathetic: Pupil constriction
      • Salivary gland:
        • Sympathetic: Stimulation
        • Parasympathetic: Inhibition
      • Heart Rate:
        • Sympathetic: Increased
        • Parasympathetic: Decreased
      • Blood Vessels:
        • Sympathetic: Constriction (most)
        • Parasympathetic: Dilation (few)
      • Lungs (Bronchiole):
        • Sympathetic: Dilation
        • Parasympathetic: Constriction
      • Intestinal Mobility:
        • Sympathetic: Inhibition
        • Parasympathetic: Stimulation
      • Sphincters:
        • Sympathetic: Stimulate closing
        • Parasympathetic: Inhibit closing
      • Urinary Bladder:
        • Sympathetic: Muscle tone relaxed
        • Parasympathetic: Contraction
      • Penis:
        • Sympathetic: Ejaculation
        • Parasympathetic: Erection

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    Explore the intricacies of the Autonomic Nervous System (ANS) that automatically regulates bodily functions and maintains homeostasis. This quiz covers its structure, function, and control centers including the hypothalamus and brain stem. Test your knowledge on how the ANS influences respiration, heart rate, and more.

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