Autonomic Nervous System Quiz

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Questions and Answers

Where is the cell body of the preganglionic neuron located in the sympathetic nervous system?

  • In the lateral grey horns of the sacral region
  • In the lateral grey horns of the thoraco-lumbar region (correct)
  • In various nuclei of the brain stem
  • In the brain's cortical layers

What type of neurotransmitter is released by the postganglionic neuron in the sympathetic pathway?

  • GABA
  • Norepinephrine (correct)
  • Dopamine
  • Acetylcholine

In which location do the cell bodies of the preganglionic neurons in the parasympathetic nervous system predominantly reside?

  • Dorsal root ganglia
  • Anterior horn cells of the spinal cord
  • Nuclei in the brain stem and lateral grey horns of the sacral region (correct)
  • Lateral grey horns of the thoraco-lumbar region

What is the role of the postganglionic neuron in the autonomic nervous system?

<p>It sends impulses to a target organ from an autonomic ganglion (C)</p> Signup and view all the answers

Which neurotransmitter is specifically released at the target organ by the postganglionic neuron in the parasympathetic pathway?

<p>Acetylcholine (A)</p> Signup and view all the answers

What neurotransmitter is primarily involved in the parasympathetic nervous system?

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

What is the mechanism by which acetylcholine is terminated in the synaptic cleft in the parasympathetic nervous system?

<p>Enzymatic breakdown by acetylcholinesterase (D)</p> Signup and view all the answers

During neurotransmission in the ganglia of the parasympathetic nervous system, what receptors do preganglionic fibers activate on postganglionic dendrites?

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

What biological effect results from the activation of muscarinic receptors in the parasympathetic nervous system?

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

Both sympathetic and parasympathetic nervous systems share which of the following characteristics?

<p>Use two neurons that synapse in a peripheral ganglion (C)</p> Signup and view all the answers

What is the primary characteristic of preganglionic neurons in the sympathetic nervous system?

<p>They are short and myelinated. (A)</p> Signup and view all the answers

Which neurotransmitter is released by postganglionic sympathetic neurons?

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

Which type of receptors do parasympathetic target tissues primarily have?

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

What is the central nervous system origin for parasympathetic neurons?

<p>Cranio-sacral (C)</p> Signup and view all the answers

How does the divergence of the sympathetic nervous system compare to that of the parasympathetic nervous system?

<p>Sympathetic has high divergence. (D)</p> Signup and view all the answers

Which characteristic correctly describes postganglionic neurons in the parasympathetic nervous system?

<p>They are unmyelinated and short. (A)</p> Signup and view all the answers

In which situation would you expect cholinergic transmission from sympathetic neurons?

<p>In sweat gland activation. (C)</p> Signup and view all the answers

What type of neurotransmitter is released by parasympathetic postganglionic neurons?

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

What is the primary function of the autonomic nervous system (ANS)?

<p>Regulate internal processes to maintain homeostasis (D)</p> Signup and view all the answers

Which of the following is true about the sympathetic nervous system?

<p>It prepares the body for intense physical activity. (D)</p> Signup and view all the answers

Which neurotransmitter is commonly associated with the parasympathetic nervous system?

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

Where do sympathetic neurons originate in the spinal cord?

<p>Thoracic and lumbar regions (A)</p> Signup and view all the answers

Which of the following correctly describes the anatomical difference between sympathetic and parasympathetic nervous systems?

<p>Sympathetic neurons are found in the lateral horn of the spinal cord. (C)</p> Signup and view all the answers

What is the role of the hypothalamus in relation to the autonomic nervous system?

<p>It helps maintain homeostasis by regulating the ANS. (D)</p> Signup and view all the answers

How do the sympathetic and parasympathetic systems generally work in relation to each other?

<p>They cooperate to fine-tune physiological functions. (C)</p> Signup and view all the answers

Which of the following best describes the effect of the autonomic nervous system on the stomach's smooth muscle?

<p>Delays emptying until the intestine is ready. (C)</p> Signup and view all the answers

What is the effect of parasympathetic stimulation on the urinary bladder?

<p>Contraction of the bladder wall (C)</p> Signup and view all the answers

Which cranial nerve is responsible for the secretion of saliva from the parotid glands?

<p>Glossopharyngeal nerve (CN IX) (C)</p> Signup and view all the answers

What happens to the gall bladder during parasympathetic stimulation?

<p>Contraction of the gall bladder wall (D)</p> Signup and view all the answers

What is the overall effect of bronchoconstriction as a result of parasympathetic stimulation?

<p>Precipitation of asthma (C)</p> Signup and view all the answers

Which of the following effects occurs due to the parasympathetic sacral outflow?

<p>Relaxation of the internal anal sphincter (C)</p> Signup and view all the answers

How does the vagus nerve contribute to the function of the gall bladder?

<p>Causes contraction of the gall bladder wall (D)</p> Signup and view all the answers

What is the primary role of the oculomotor nerve in parasympathetic functions?

<p>Regulation of vision and pupil size (B)</p> Signup and view all the answers

What effect does parasympathetic stimulation have on erectile tissue?

<p>Dilation of blood vessels (D)</p> Signup and view all the answers

What neurotransmitter is primarily released by postganglionic sympathetic neurons?

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

Which receptor subtype is associated with the contraction of the radial muscle in the eye?

<p>α1 (C)</p> Signup and view all the answers

What is the effect of norepinephrine on the sinoatrial node?

<p>Increases depolarization rate (C)</p> Signup and view all the answers

Which statement about the action of norepinephrine is true?

<p>It can produce different responses depending on the receptor subtype. (A)</p> Signup and view all the answers

How does norepinephrine affect smooth muscle in arteries and arterioles?

<p>It causes contraction through α1 and α2 receptors. (B)</p> Signup and view all the answers

What effect does norepinephrine have on the detrusor muscle of the urinary bladder?

<p>Relaxes the muscle and decreases voiding. (B)</p> Signup and view all the answers

Which enzyme is responsible for metabolizing norepinephrine to inactive intermediates?

<p>Both B and C (D)</p> Signup and view all the answers

What is the effect of α2-adrenergic receptors on the release of norepinephrine?

<p>They inhibit norepinephrine release. (C)</p> Signup and view all the answers

Flashcards

Autonomic Nervous System (ANS)

The part of the nervous system responsible for involuntary, subconscious functions, such as heart rate, digestion, and breathing.

Sympathetic Nervous System

The branch of the ANS that activates the "fight-or-flight" response, preparing the body for intense physical activity. It increases heart rate, breathing, and blood flow to muscles.

Parasympathetic Nervous System

The branch of the ANS that activates the "rest-and-digest" response, promoting relaxation and energy conservation. It slows heart rate, promotes digestion, and constricts pupils.

Homeostasis

The state of balance or equilibrium in the internal environment of the body, maintained by the ANS.

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Preganglionic Neuron

The first neuron in the ANS pathway, originating from the CNS.

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Postganglionic Neuron

The second neuron in the ANS pathway, located outside the CNS in an autonomic ganglion.

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Neurotransmitters

The chemicals released by neurons to transmit signals across synapses.

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Receptors

Proteins on the surface of cells that bind to neurotransmitters, triggering a specific response.

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Sympathetic Preganglionic Neuron

The type of neuron that originates in the thoracolumbar region of the spinal cord and is part of the sympathetic nervous system. Its cell body is in the lateral grey horns.

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Norepinephrine

A neurotransmitter that is released by postganglionic neurons in the sympathetic nervous system.

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Acetylcholine

The neurotransmitter released by postganglionic neurons in the parasympathetic nervous system, also used by preganglionic neurons in the sympathetic nervous system.

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What is the sympathetic nervous system?

The portion of the ANS responsible for the "fight-or-flight" response. It prepares the body for action by increasing heart rate, breathing, and blood flow.

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What is the parasympathetic nervous system?

The portion of the ANS responsible for the "rest-and-digest" response. It promotes relaxation and energy conservation by slowing heart rate, promoting digestion, and constricting pupils.

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What is a preganglionic neuron?

The first neuron in the autonomic nervous system, located in the central nervous system.

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What is a cholinergic neuron?

A type of neuron that uses acetylcholine (ACh) as its neurotransmitter. Note: The preganglionic neuron of both sympathetic and parasympathetic systems are cholinergic releases ACh.

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What is a postganglionic neuron?

The second neuron in the autonomic nervous system, located outside the CNS.

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What is an adrenergic neuron?

A type of neuron that uses norepinephrine (NE) as its neurotransmitter. Note: The postganglionic neuron of the sympathetic system is adrenergic and release NE.

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What is divergence?

The release of neurotransmitters by preganglionic neurons towards postganglionic neurons is an example of this.

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What are nicotinic receptors?

The receptors on postganglionic neurons that bind to acetylcholine (ACh).

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What does the parasympathetic nervous system do?

The parasympathetic nervous system is responsible for "rest and digest" functions. It slows heart rate, promotes digestion, and constricts pupils.

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What does the sympathetic nervous system do?

The sympathetic nervous system is responsible for "fight or flight" responses. It increases heart rate, breathing, and blood flow to muscles. It also dilates pupils.

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What neurotransmitter is used in preganglionic neurons of both sympathetic and parasympathetic nervous systems?

Both the sympathetic and parasympathetic nervous systems utilize acetylcholine (ACh) as their neurotransmitter in preganglionic neurons.

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What neurotransmitter is used in postganglionic neurons of the parasympathetic nervous system?

The parasympathetic nervous system uses acetylcholine (ACh) as its neurotransmitter in postganglionic neurons as well.

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What neurotransmitter is usually used in postganglionic neurons of the sympathetic nervous system?

The sympathetic nervous system usually uses norepinephrine (NE) as its neurotransmitter in postganglionic neurons.

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Parasympathetic stimulation on gall bladder

Parasympathetic nerve stimulation leads to contraction of the gall bladder's wall and relaxation of its sphincter, resulting in the expulsion of bile into the duodenum.

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Parasympathetic effect on heart rate

The parasympathetic system, acting through the vagus nerve, slows down the heart rate.

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Parasympathetic effect on lungs

Parasympathetic stimulation leads to bronchoconstriction, increased bronchial secretions, and vasodilation of pulmonary blood vessels. These responses can contribute to asthma.

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Parasympathetic effect on bladder

Parasympathetic stimulation causes bladder wall contraction, relaxing the sphincter, leading to urination.

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Parasympathetic effect on rectum

Parasympathetic stimulation causes contraction of the rectal wall and relaxation of the internal anal sphincter, leading to defecation.

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Parasympathetic effect on male reproductive organs

Parasympathetic stimulation leads to the secretion of fluids from the seminal vesicles and prostate, contributing to ejaculation.

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Parasympathetic effect on erectile tissue

Parasympathetic stimulation causes vasodilation of erectile tissue, leading to erection

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Parasympathetic origin

Parasympathetic nerve fibers originate from cranial nerve nuclei in the brainstem and from sacral segments of the spinal cord.

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Sympathetic Nervous System (SNS)

The sympathetic nervous system (SNS) is responsible for the "fight-or-flight" response, preparing the body for intense physical activity and stress. It increases heart rate, respiration, and blood flow to muscles while diverting resources from less essential functions.

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Parasympathetic Nervous System (PNS)

The parasympathetic nervous system (PNS) is responsible for the "rest-and-digest" response, promoting relaxation, energy conservation, and digestion. It slows heart rate, constricts pupils, and stimulates digestive processes.

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Study Notes

Autonomic Nervous System (ANS)

  • Definition: A system for involuntary, subconscious functions, controlling internal environment for homeostasis.
  • Involuntary branch of the peripheral efferent division.
  • Innervates various tissues and organs.
  • Two-neuron system: Preganglionic neuron from CNS to autonomic ganglion outside CNS & postganglionic neuron to target.
  • Works in opposition to maintain homeostasis.
  • Regulated by brain (hypothalamus, pons, and medulla), as well as spinal reflexes. No higher order input is needed.
  • Often involves two branches (rest-and-digest/parasympathetic and fight-or-flight/sympathetic)

Learning Objectives

  • Explain functions of sympathetic and parasympathetic systems.
  • Explain physiological effects of ANS on body functions.
  • Explain neurotransmitters and receptors within the ANS.
  • Explain tissues innervated exclusively or jointly by these systems.

Anatomical Distribution of ANS

  • Sympathetic neurons originate from lateral horns of thoracic and lumbar spinal cord portions.
  • Parasympathetic neurons originate in midbrain, medulla oblongata, and sacral spinal cord.
  • These pathways are distributed throughout the body, connecting to targeted organs and tissues.

Two Motor Neurons (Preganglionic and Postganglionic)

  • Preganglionic neuron: Cell body located in brain or spinal cord (sympathetic in thoracolumbar region, parasympathetic in various brain stem or sacral regions).
  • Postganglionic neuron: Cell body in autonomic ganglion. Postganglionic fibers connect the ganglion to target organs.
  • Target organ effects are dependent on neurotransmitter type and receptor specificity.

Preganglionic vs Postganglionic Neurons

  • Sympathetic: Short preganglionic, long postganglionic neurons; mainly myelinated preganglion; noradrenergic postganglion.
  • Parasympathetic: Long preganglionic, short postganglionic neurons; preganglion unmyelinated; cholinergic postganglion.
  • Divergence: High in sympathetic; low in parasympathetic.
  • Neurotransmitters: Sympathetic uses norepinephrine; parasympathetic uses acetylcholine.

Parasympathetic Nervous System

  • Preganglionic and postganglionic neurotransmitters: Acetylcholine (ACh).
  • Effect of ACh on postsynaptic tissue is terminated by rapid action of acetylcholinesterase (AChE).
  • Transmission in ganglia achieved by preganglionic fibers releasing ACh, activating nicotinic (N) receptors on postganglionic neurons.
  • Depolarization of postganglionic cholinergic nerve releases stores of ACh in innervated tissue, activating muscarinic (M) receptors for biological effects.
  • Choline is taken into nerve terminal and conjugated to acetate by choline acetyltransferase (ChAT) to produce ACh.
  • Synthesized ACh is subsequently transported into synaptic vesicles.

Parasympathetic Nervous System (Cont'd)

  • Effectors/organs: Eye, heart (SA node, AV node, atria, ventricles), coronary arteries, lungs (bronchi, bronchial glands), GIT (smooth muscle walls, sphincters), urinary bladder (detrusor muscle, trigone & sphincter muscle), salivary glands, erectile tissue.

Sympathetic Nervous System

  • Secretion of Norepinephrine (NE) is important in the action at distant target cells, while the effect of epinephrine is systemic (on many organs).
  • Pathways of sympathetic nervous system effects: medulla (via adrenal medulla) which secretes epinephrine (mostly) and norepinephrine (some), and pathways directly from sympathetic nerves (via axons).
  • Norepinephrine is released into the synapse and binds to adrenergic receptors on target cells.
  • Norepinephrine is cleared from the synapse via reuptake and metabolism by monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT).

Sympathetic vs Parasympathetic

  • Similarities: Efferent (motor) systems; regulation of internal environment (outside conscious control); two-neuron pathways.
  • Differences: Origin (location of preganglionic nuclei), neurotransmitters (NE vs ACh), receptor subtypes (α and β vs muscarinic).

Sympathetic - Cervical Division (T1-T4)

  • Eye: Pupil dilatation, widening of palpebral fissure, exophthalmos; vasoconstriction of eyeball vessels, relaxation of ciliary muscle
  • Salivary glands: Salivary gland trophic secretion and vasoconstriction of blood vessels.
  • Lacrimal gland: Trophic secretion and vasoconstriction.
  • Sweat glands: Copious secretion.
  • Face skin blood vessels: Vasoconstriction (pale skin).
  • Hair: Erection due to contraction of erector pilae muscles.
  • Cerebral vessels: Weak vasoconstriction

Sympathetic - Cardiopulmonary Division (T1-T6)

  • Heart: Increase all properties of cardiac muscle.
  • Bronchi: Bronchodilation, decreased bronchial secretion, vasoconstriction of pulmonary blood vessels.
  • Coronary vessels: First vasoconstriction, then vasodilation due to accumulation of metabolites.
  • Hair: Erection due to contraction of erector pilae muscles.

Sympathetic - Splanchnic Division (T5-L2)

  • Stomach & intestine: Sphincter contraction and food retention
  • Liver: Glycogenolysis leading to increased blood glucose.
  • Urinary bladder: Relaxation of the bladder wall & contraction of internal urethral sphincter.
  • Genital organs: Vasoconstriction of blood vessels; shrinkage of penis and clitoris.
  • Spleen: Blood is evacuated from the spleen due to contraction of its capsule.
  • Rectum: Relaxation of the distal part of large intestine and contraction of the internal anal sphincter.

Sympathetic - Somatic Division (upper spinal cord levels)

  • Skin: Vasoconstriction, leading to pale skin color; stimulation of sweat glands leading to secretion (copious from eccrine; thick from apocrine)
  • Skeletal muscle: Blood vessels dilate due to cholinergic effects, vasoconstriction due to adrenergic effects; muscle stimulation causing delayed fatigue and early recovery.
  • Adrenal medulla: Secretes large quantities of Epinephrine and some Norepinephrine, stimulated by preganglionic sympathetic nerve fibres.

Parasympathetic - Sacral outflow (pelvic nerve)

  • Urinary bladder: Contraction of bladder wall, relaxation of sphincter, leading to micturition.
  • Seminal vesicles & prostate: Secretion of seminal vesicle fluid and prostatic fluid.
  • Rectum & descending colon: Contraction of wall and relaxation of internal anal sphincter, leading to defecation.
  • Erectile tissue: Vasodilation, leading to arousal.

Additional Notes

  • Pheochromocytoma: Rare tumor of the adrenal medulla or similar cells outside; 10% are malignant.
  • Common symptoms: Palpitations, headache, sweating, pallor.
  • Important to note that these points are largely based on text provided, not fully developed to contain all necessary detail to use for formal study.

Effects of ANS Activity

  • Bradycardia: Slow heart rate
  • Tachycardia: Increased heart rate
  • Faintness
  • Dizziness
  • Shortness of breath
  • Lightheadedness

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