Parasympathetic Nervous System Quiz
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Questions and Answers

What distinguishes prevertebral ganglions from other ganglions?

  • They are located within the walls of innervated organs.
  • They are found primarily outside of the innervated organs. (correct)
  • They are formed from postganglionic fibers.
  • They mainly produce epinephrine as a hormone.

    • Which neurotransmitter is primarily released by adrenergic nerves?

  • Dopamine
  • Acetylcholine
  • Epinephrine
  • Norepinephrine (correct)

    • Which enzyme is primarily responsible for the degradation of norepinephrine in neuronal tissue?

  • Acetylcholinesterase
  • Phenylethanolamine-N-methyltransferase
  • Catechol-O-methyltransferase (COMT)
  • Monoamine oxidase (MAO) (correct)

    • In the autonomic nervous system, what type of receptor is activated by acetylcholine in ganglia?

    <p>Nicotinic receptor</p> Signup and view all the answers

    Which statement correctly describes the effect of the parasympathetic nervous system compared to the sympathetic nervous system?

    <p>The parasympathetic system effects are more localized due to preganglionic fibers activating fewer postganglionic fibers.</p> Signup and view all the answers

    What is the primary effect of β1 adrenergic receptors in the heart?

    <p>Increase force of contraction</p> Signup and view all the answers

    Which receptor favors the stimulation of aggregation in platelets?

    <p>α1 receptor</p> Signup and view all the answers

    What is the effect of norepinephrine on blood vessels?

    <p>Constriction of blood vessels</p> Signup and view all the answers

    How does epinephrine primarily affect the cardiovascular system?

    <p>Increases peripheral resistance</p> Signup and view all the answers

    What is the physiological role of β2 adrenergic receptors?

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

    The activation of β1 adrenergic receptors in the kidneys leads to the secretion of which hormone?

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

    Which of the following effects is NOT associated with β3 adrenergic receptors?

    <p>Increases heart rate</p> Signup and view all the answers

    What effect does the constriction of blood vessels have on peripheral resistance?

    <p>Increases peripheral resistance</p> Signup and view all the answers

    What function do calcium ions serve in muscle contraction?

    <p>They bind to troponin, facilitating myosin binding to actin.</p> Signup and view all the answers

    What role do the sodium ions play during cardiac muscle cell excitation?

    <p>They flow into the cell, causing depolarization.</p> Signup and view all the answers

    How does the sarcomere regain its initial length?

    <p>Due to the elastic forces of titin-like filaments.</p> Signup and view all the answers

    What is the role of electrodes in electrocardiography?

    <p>To pick up electrical potential differences from the skin.</p> Signup and view all the answers

    Which of the following describes the composition of a typical electrocardiogram setup?

    <p>It employs four electrodes to record electrical activity.</p> Signup and view all the answers

    What is the primary function of ganglioblockers in the autonomic nervous system?

    <p>Blocking effect of acetylcholine</p> Signup and view all the answers

    Which drug is primarily categorized as a muscarinic cholinoblocker?

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

    What physiological response primarily occurs when light enters the pupil?

    <p>Contraction of the constrictive pupil muscle</p> Signup and view all the answers

    Which type of pupillary reflex is directly activated by light entering the eyeball?

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

    What can disrupt the pupillary reflex pathways?

    <p>Traumatic events or skull fractures</p> Signup and view all the answers

    What is a potential therapeutic use of ganglioblockers?

    <p>To treat high blood pressure</p> Signup and view all the answers

    Which statement correctly describes the mechanism of the indirect pupillary light reflex?

    <p>It causes the constriction of the opposite pupil.</p> Signup and view all the answers

    What effect does atropine have on the body?

    <p>Blocks parasympathetic functions</p> Signup and view all the answers

    What effect does norepinephrine have on heart function?

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

    How does epinephrine influence peripheral resistance?

    <p>It leads to a decrease in peripheral resistance.</p> Signup and view all the answers

    Which adrenergic receptors are primarily stimulated by epinephrine in blood vessels?

    <p>β2-receptors.</p> Signup and view all the answers

    What is the primary outcome when β2-receptors are activated in the synaptic cleft?

    <p>Stimulation of norepinephrine release.</p> Signup and view all the answers

    Which factor signals the brain to inhibit heart function in response to blood pressure changes?

    <p>An increase in blood pressure in big arteries.</p> Signup and view all the answers

    Which neurotransmitter is synthesized first in the adrenergic synapse from tyrosine?

    <p>Dopamine.</p> Signup and view all the answers

    How does an increase in blood volume in the arteries affect the release of norepinephrine?

    <p>It inhibits norepinephrine release.</p> Signup and view all the answers

    What is the primary source of epinephrine in the bloodstream?

    <p>Adrenal medulla.</p> Signup and view all the answers

    Study Notes

    Parasympathetic Nervous System

    • Certain ganglions of the parasympathetic nervous system are prevertebral, meaning they are located on the outside of the innervated organ.
    • Preganglionic fibers of the parasympathetic nervous system are longer than postganglionic fibers.
    • The neurotransmitter and receptor at the synapse in ganglia are the same: Acetylcholine → nicotinic receptor
    • At the synapse with the effector organ, the neurotransmitter and receptor are also the same: Acetylcholine → muscarinic receptor
    • In the parasympathetic nervous system, one preganglionic fiber often activates just one or two postganglionic fibers, resulting in a less widespread effect compared to the sympathetic nervous system.
    • The parasympathetic nervous system does not have any gland that can produce acetylcholine as a hormone to release into the bloodstream.
    • This lack of a circulating hormone means the parasympathetic nervous system does not exert its effects in all parts of the body.

    Synthesis and Degradation of Norepinephrine and Epinephrine

    • Epinephrine and norepinephrine are synthesized from tyrosine.
    • Tyrosine is converted to norepinephrine, and then norepinephrine is further converted to epinephrine with the help of phenylethanolamine-N-methyltransferase.
    • Phenylethanolamine-N-methyltransferase activity and concentration in presynaptic varicosities of adrenergic nerves is minimal.
    • The predominant neurotransmitter released from adrenergic nerve terminals is norepinephrine.
    • The adrenal medulla is an exception – it contains high concentrations of phenylethanolamine-N-methyltransferase, leading to the predominant release of epinephrine.

    Degradation of Norepinephrine and Epinephrine

    • Two primary enzymes degrade norepinephrine and epinephrine:
      • Monoamine oxidase (MAO) is present in neuronal tissues, including varicosities in the autonomic nervous system and the presynaptic terminal in the brain.
      • Catechol-O-methyltransferase (COMT) is located in non-neuronal tissues and the circulatory system.
    • COMT receptors are found in:
      • Smooth muscle cells (in blood vessels), where activation leads to contraction
      • Presynaptic terminals, where activation inhibits norepinephrine release
      • Platelets, where activation stimulates aggregation.

    Adrenergic Receptors

    • Adrenergic receptors are classified into beta (β) subtypes:
      • β1 receptors:
        • Increased cAMP in the heart, leading to:
          • Increased heart rate
          • Increased force of contraction
          • Increased excitability and impulse conduction speed
          • Increased relaxation rate
        • Activation in juxtaglomerular cells of the kidneys leads to renin secretion, which stimulates the production of the vasoconstrictor angiotensin
      • β2 receptors:
        • Increased cAMP in smooth muscle cells causing relaxation
        • Increased cAMP in adipose tissues, triggering lipolysis (fat breakdown)
      • β3 receptors:
        • Increased cAMP in adipose tissues, triggering lipolysis (fat breakdown)

    Epinephrine and Norepinephrine Actions

    • Epinephrine preferentially activates β1 and β2 receptors.
    • In high concentrations, epinephrine can also activate α1 and α2 receptors.
    • Norepinephrine preferentially activates α1 and α2 receptors.
    • Norepinephrine can also activate β1 receptors.

    Cardiovascular Effects of Epinephrine and Norepinephrine

    • Norepinephrine:
      • Peripheral resistance: Increases due to α1 receptor-mediated vasoconstriction.
      • Blood pressure: Increases in big arteries due to the increased peripheral resistance.
      • Heart rate: Decreases, as the brain detects high blood pressure in the arteries and inhibits heart function.
    • Epinephrine:
      • Peripheral resistance: Decreases because β2 receptors on blood vessels in skeletal muscles, the coronary circulation, and the small circuit (pulmonary circulation) cause vasodilation.
      • Blood pressure: Increases slightly, as the decrease in peripheral resistance allows more blood to flow to the periphery.
      • Heart rate: Increases, as the slight increase in blood pressure does not trigger the negative feedback mechanism that inhibits heart function, allowing epinephrine to act on β1 receptors.

    Adrenergic Synapse

    • Tyrosine is transported from the extracellular space into the varicosity/nerve terminal.
    • Tyrosine is converted to dopamine within the varicosity/nerve terminal.
    • Dopamine is transported into a vesicle by a monoamine transporter.
    • Dopamine is further converted to norepinephrine within the vesicle.
    • Upon stimulation, norepinephrine is released into the synaptic cleft, where it binds to different adrenergic receptors.
    • When norepinephrine accumulates in the synaptic cleft, it can bind to α2 receptors on the presynaptic terminal, inhibiting further neurotransmitter release.
    • β2 receptors also exist on the presynaptic terminal. Activation of these receptors stimulates neurotransmitter release, but norepinephrine does not strongly bind to these receptors.
    • A small amount of epinephrine is produced in the presynaptic terminal, but most of it comes from the bloodstream, produced by the adrenal medulla.
    • Epinephrine from the bloodstream can enter the synaptic cleft and activate β2 receptors, stimulating further norepinephrine release.

    Cholinergic Blockers

    • Nicotinic cholinergic blockers (ganglioblockers):
      • Prevent acetylcholine from acting on effector cells at nicotinic receptors in autonomic ganglia.
      • Examples: Hexamethonium
      • Used to treat high blood pressure by blocking sympathetic effects predominantly.
    • Muscarinic cholinergic blockers:
      • Block acetylcholine from acting on effector cells at muscarinic receptors.
      • Examples: Atropine
      • Block mostly parasympathetic functions in the body.
      • Used in ophthalmology to dilate pupils.
      • Can decrease gastrointestinal juice secretion, motility, and sweating intensity.

    Pupillary Light Reflex

    • Pathway:
      • Light enters the pupil.
      • The optic pathway is activated.
      • Impulses travel to the pretectal nucleus in the midbrain.
      • Impulses are relayed to the Edinger-Westphal nucleus.
      • The third cranial nerve carries impulses to the ciliary ganglion.
      • The ciliary ganglion transmits impulses to the constrictor pupillae muscle, causing constriction of the iris and a smaller pupil.

    Pupillary Reflex Types

    • Direct reflex: Light entering one eye causes constriction of that same eye's pupil. Uncrossed lateral optic nerve fibers activate the pretectal nucleus on the same side of the midbrain, leading to contraction of the constrictor pupillae muscle on that side.
    • Indirect reflex: Impulses travel through crossed optic nerve fibers to the pretectal nucleus on the opposite side of the midbrain, causing constriction of the opposite pupil.

    Pupillary Reflex Applications

    • Pupillary light reflexes are checked clinically to assess the health of these pathways.
    • Traumatic events or skull fractures can disrupt the optic pathway.

    Calcium Pump and Na+/Ca2+ Exchanger

    • Calcium ions are removed from the cytoplasm through the calcium pump or the Na+/Ca2+ exchanger.

    Muscle Relaxation

    • Troponin releases calcium, regaining its initial conformation.
    • Tropomyosin is repositioned back onto the active sites of actin.
    • The myosin head detaches from the actin molecule.
    • The elastic forces of titin filaments return the sarcomere to its original length.

    Electrocardiography

    • Principle:
      • When cardiac muscle cells are excited, sodium ions enter the cell, depolarizing it.
      • The extracellular fluid surrounding the excited region becomes more electronegative compared to non-excited areas.
      • These charge differences create circular currents that propagate through the interstitial space and reach the skin.
      • Electrodes placed on the skin pick up potential differences between regions, which are amplified and recorded by an electrocardiogram as a curve.

    Electrocardiography Leads

    • A typical electrocardiogram uses four electrodes.
    • The ECG leads record electrical activity from different parts of the heart.
    • These recordings are used to diagnose various heart conditions.

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    Description

    Test your knowledge on the parasympathetic nervous system with this quiz. Explore key concepts including ganglions, neurotransmitters, and the differences between preganglionic and postganglionic fibers. See how this system's functions compare with the sympathetic nervous system.

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