Autonomic Nervous System II
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Questions and Answers

Which of the following receptors are responsible for mediating the effects of acetylcholine in the sympathetic ganglia?

  • Alpha-1 receptors
  • Nicotinic receptors (correct)
  • Muscarinic receptors
  • Beta-2 receptors

    • Which of the following substances acts as an antagonist to muscarinic receptors?

  • Hexamethonium
  • Atropine (correct)
  • Nicotine
  • Tubocurarine

    • What is the primary mode of action for nicotinic receptors?

  • Ligand-gated ion channel activation (correct)
  • Second messenger cascades
  • Direct activation of adenylate cyclase
  • G-protein coupled signaling

    • Which of the following is NOT a characteristic of the parasympathetic nervous system?

    <p>Prepares the body for 'fight or flight' responses (D)</p> Signup and view all the answers

    Which of the following correctly describes the effect of activating Beta-1 receptors?

    <p>Increased heart rate and strength (C)</p> Signup and view all the answers

    Which of the following subtypes of nicotinic receptors is located at the neuromuscular junction?

    <p>Nm (D)</p> Signup and view all the answers

    Which neurotransmitter(s) are involved in adrenergic transmission?

    <p>Epinephrine and Norepinephrine (B)</p> Signup and view all the answers

    What is the primary mechanism by which muscarinic receptors mediate their effects?

    <p>Activation of G-protein coupled signaling (C)</p> Signup and view all the answers

    Which of the following is NOT a symptom of Horner syndrome?

    <p>Dilated pupil (mydriasis) (A)</p> Signup and view all the answers

    What is the primary function of the enzyme acetylcholine esterase (AChE)?

    <p>Break down acetylcholine (B)</p> Signup and view all the answers

    Which of the following accurately describes the effects of activating Alpha-1 receptors?

    <p>Smooth muscle contraction and vasoconstriction (A)</p> Signup and view all the answers

    Where are the majority of sympathetic postganglionic neurons located?

    <p>In the peripheral nervous system (B)</p> Signup and view all the answers

    Which of the following drugs would be most effective in blocking the effects of acetylcholine at the neuromuscular junction?

    <p>Tubocurarine (C)</p> Signup and view all the answers

    Which enzyme is involved in the breakdown of norepinephrine in the nerve endings?

    <p>Monoamine oxidase (MAO) (C)</p> Signup and view all the answers

    Which of the following is TRUE about the synthesis of epinephrine and norepinephrine?

    <p>Both epinephrine and norepinephrine are synthesized from tyrosine through a series of steps (D)</p> Signup and view all the answers

    What is the role of sympathetic postganglionic neurons that innervate sweat glands?

    <p>Stimulate sweat production (D)</p> Signup and view all the answers

    Study Notes

    Autonomic Nervous System II

    • Objectives:
      • Compare parasympathetic and sympathetic nervous system functions.
      • Identify neurotransmitters and receptor types involved in autonomic nervous system neurotransmission and target organs.

    Functions of the Parasympathetic Nervous System (PNS)

    • Dominates during normal physiological conditions.
    • Primary function: "Rest and Digest".
    • Note: The parasympathetic system is always active in the gastrointestinal (GIT) and urinary systems.

    Functions of the Sympathetic Nervous System (SNS)

    • Prepares the organism to handle environmental stresses.
    • Primary function: "Fight or Flight".

    Parasympathetic and Sympathetic Divisions

    • Diagram (Page 5): Shows the pathways (cranial, thoracic, lumbar, sacral nerves) for each system, illustrating the effects on different organs (eg., pupils, heart, breathing, digestion, etc.). Sympathetic division increases activity during stress, while parasympathetic division works to return the body to a resting state.

    Horner Syndrome

    • Rare disorder caused by interruption of preganglionic/postganglionic sympathetic innervation to the face.
    • Possible causes include injury to nerves, carotid artery injury, stroke, brain stem lesions, or tumors.
    • Typically unilateral (one side).
    • Hallmark triad:
      • Anhidrosis (reduced sweating).
      • Ptosis (drooping eyelid).
      • Miosis (constricted pupil).
    • Additional symptoms may include: Enophthalmos (sunken eyeball), and vasodilation.

    Chemical Transmission at Autonomic Junctions

    • Cholinergic transmission: Primarily uses Acetylcholine (ACh).
    • Adrenergic transmission: Primarily uses Epinephrine (E) / adrenaline, and Norepinephrine (NE) / noradrenaline.

    Cholinergic Autonomic Neurons

    • All preganglionic neurons release ACh.
    • All parasympathetic postganglionic neurons release ACh.
    • Some sympathetic postganglionic neurons release ACh (e.g., sweat glands, some blood vessels).

    Adrenergic Neurons

    • Most sympathetic postganglionic neurons release norepinephrine (NE).
    • Exceptions: Sweat glands and some blood vessels.
    • Adrenal glands.

    ACh Synthesis and Degradation

    • ACh is synthesized from acetyl CoA and choline.
    • Stored in vesicles in nerve endings.
    • After action, ACh is broken down by acetylcholinesterase (AChE).
    • Choline is recycled.
    • Some ACh diffuses away into the surrounding fluids, where pseudocholinesterase breaks it down.

    NE Synthesis and Degradation

    • NE is synthesized from tyrosine, dopamine, and norepinephrine.
    • Stored in synaptic vesicles.
    • After action, NE is broken down by monoamine oxidase (MAO) in nerve endings, and catechol-O-methyltransferase (COMT) in other tissues.

    Autonomic Receptors

    • Cholinergic:
      • Muscarinic
      • Nicotinic
    • Adrenergic:
      • Alpha
      • Beta

    Nicotinic Receptors

    • Respond to ACh and nicotine.
    • Do not respond to muscarine.
    • Act through ligand-gated ion channels.
    • Blocked by tubocurarine (neuromuscular blocker).
    • Activation results in rapid increases in sodium (Na+) and calcium (Ca2+) conductance, depolarization, and excitation.
    • Two subtypes:
      • Nm (neuromuscular end plate, skeletal muscle)
      • Nn (autonomic ganglia).

    Muscarinic Receptors

    • Respond to ACh, muscarine, and carbachol.
    • Blocked by atropine.
    • Coupled via G-proteins, activating second messengers (e.g., cAMP).
    • Multiple subtypes (M1, M2, M3).

    Adrenergic Receptors (Alpha and Beta)

    • Alpha 1, Alpha 2 (located in various tissues).

    • Beta 1, Beta 2, Beta 3 (located in various tissues).

    • Different subtypes have different effects (e.g., on heart rate, blood vessels, etc.)

    • Detailed receptor locations and effects of binding on various tissues (Page 21)

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    Autonomic Nervous System II PDF

    Description

    Explore the intricate functions of the autonomic nervous system with a focus on the parasympathetic and sympathetic divisions. This quiz covers their roles in physiological responses, neurotransmitters involved, and the effects on target organs. Test your understanding and compare the functions of these two crucial systems.

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