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Questions and Answers
What is a primary function of the autonomic nervous system (ANS)?
Which neurotransmitter is released by preganglionic neurons in the ANS?
What characteristic differentiates the autonomic nervous system from the somatic nervous system?
What are postganglionic neurons responsible for in the autonomic ganglia?
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Where are the cell bodies of postganglionic neurons primarily located?
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Which system of the ANS typically facilitates the 'fight or flight' response?
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What is the primary function of varicosities in the autonomic nervous system?
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What type of neurons are categorized as general visceral efferent (GVE) neurons?
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What neurotransmitter is primarily released by the cholinergic neurons located in the thoracolumbar spinal cord?
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Which of the following statements accurately describes the action of muscarinic receptors in the body?
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Which type of ganglia are located anterior to the spinal column and contain the celiac ganglion?
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Which sympathetic nervous system effect is observed in the gastrointestinal tract?
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What effect does acetylcholine binding to nicotinic receptors primarily induce?
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Which type of G-protein is activated by M1, M3, and M5 muscarinic receptors?
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Which receptors are primarily affected by adrenergic neurons in the sympathetic nervous system?
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Which statement about acetylcholine degradation is correct?
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What is the primary function of chromaffin cells in the adrenal medulla?
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Which of the following locations would you find nicotinic receptors?
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In the sympathetic nervous system, which of the following responses would be expected during a stress response?
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During a sympathetic response, which outcome is likely to occur in the urinary system?
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Which section of the spinal cord primarily contains the preganglionic sympathetic neurons?
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What effect does the sympathetic nervous system have on heart rate during stress?
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What is the relationship between preganglionic and postganglionic neurons in the sympathetic nervous system?
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What type of receptors do postganglionic neurons use to communicate with target organs in the parasympathetic nervous system?
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Which statement accurately describes the location of preganglionic neurons in the parasympathetic nervous system?
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What is the primary neurotransmitter released by preganglionic neurons in the parasympathetic nervous system?
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Which effect is NOT associated with the activation of the parasympathetic nervous system?
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Where are postganglionic neurons typically located in the parasympathetic nervous system?
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Which of the following effects is mediated through muscarinic receptors in the parasympathetic nervous system?
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What is primarily influenced by the parasympathetic nervous system in the cardiovascular system?
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Which cranial nerve is associated with the ciliary ganglion in the parasympathetic nervous system?
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Which of these components is NOT typically classified as a function of the parasympathetic nervous system?
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What type of signaling mechanism do muscarinic receptors utilize?
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What is the primary effect of ɑ1 adrenergic receptors on blood vessels in the gastrointestinal tract?
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Which of the following pathways is primarily activated by β1 adrenergic receptors in the heart?
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What is the effect of catecholamines binding to ɑ2 adrenergic receptors?
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Which substance is produced from the degradation of norepinephrine by monoamine oxidase (MAO)?
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What effect does β2 adrenergic receptor activation have on the skeletal muscle blood vessels?
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Which adrenergic receptor subtype primarily leads to lipolysis and thermogenesis in adipose tissue?
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Which neurotransmitter is synthesized from L-dopa during catecholamine synthesis?
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What is the effect of adrenergic stimulation on salivary gland activity?
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What role does phenylethanolamine-N-methyltransferase (PNMT) play in catecholamine synthesis?
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Which of the following is NOT a function of the autonomic nervous system's adrenergic receptors?
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Study Notes
Autonomic Nervous System
- Part of the peripheral nervous system (PNS) that regulates basic visceral processes essential to homeostasis
- Affects visceral organs, glands, involuntary muscles.
- Regulates heart rate, respiration rate, digestion, urination, salivation, sexual arousal, etc.
- Its neurons are located in the central nervous system (CNS)
- Divided into two systems: sympathetic and parasympathetic
Sympathetic Nervous System
- Controls visceral functions that require a fast response (“fight or flight”).
- Ganglia close to the spinal cord (short preganglionic fibers, long postganglionic fibers)
- Preganglionic neurons are located in the thoracolumbar spinal cord’s intermediate horn (T1–L2)
- Postganglionic neurons: Located close to the spinal cord
- Paravertebral ganglia (cervical, thoracic, rostral lumbar, caudal lumbar, pelvic ganglia)
- Prevertebral ganglia (celiac, aorticorenal, superior mesenteric, inferior mesenteric ganglion)
- Chromaffin cells of the adrenal medulla (modified sympathetic ganglion)
- Preganglionic neurons are cholinergic (release ACh)
- Postganglionic neurons are either adrenergic (release norepinephrine/epinephrine) or cholinergic (release ACh)
- Effector organ receptors: α1, α2, β1, β2, β3
- Effects:
- Cardiovascular: ↑ heart rate, ↑ cardiac output, vasoconstriction
- Respiratory: bronchodilation
- Gastrointestinal: ↓ motility, ↓ secretions
- Genitourinary: ↓ bladder’s detrusor muscle activity, ejaculation
- Metabolic: ↑ gluconeogenesis
- Glands: ↓ salivation, ↑ sweating
- Pupils: mydriasis
Parasympathetic Nervous System
- Controls visceral functions that don’t require a fast response (“rest and digest”).
- Ganglia close to the target organ (long preganglionic fibers, short postganglionic fibers).
- Preganglionic neurons are located in the brainstem (nuclei of cranial nerves III, VII, IX, X), sacral spinal cord (S2–S4)
- Postganglionic neurons are localized near/inside the target organs
- Ciliary ganglion (cranial nerve III)
- Submandibular ganglion (cranial nerve VII)
- Otic ganglion (cranial nerve IX)
- Near/inside target organ (cranial nerve X, sacral nerves).
- Preganglionic neurons are cholinergic (release ACh)
- Mostly cholinergic, but some non-adrenergic, non-cholinergic (release neuropeptides)
- Effector organ receptors are muscarinic
- Effects:
- Cardiovascular: ↓ heart rate, ↓ cardiac output
- Respiratory: bronchoconstriction
- Gastrointestinal: ↑ motility, ↑ secretions
- Genitourinary: ↑ bladder’s detrusor muscle activity, erection
- Metabolic: ↓ glycogenesis
- Glands: ↑ salivation
- Pupils: miosis
Adrenergic Receptors
- Metabotropic receptors that respond to catecholamines (norepinephrine, epinephrine)
- Located on sympathetic effector organs → stimulated → sympathetic/sympathomimetic response
- Types: α, β adrenergic receptors (α1, α2, β1, β2, β3)
- α1: Stimulatory effect:
- Gastrointestinal tract blood vessels, skin blood vessels → vasoconstriction
- Bladder, gastrointestinal (GI) tract sphincters → contraction
- Radial (dilator) muscle of iris → contraction
- Pancreas → ↓ secretion
- Liver → ↑ glycogenolysis
- α2: Inhibitory effect:
- Presynaptic nerve terminals (autoreceptors) → presynaptic inhibition of neurotransmitter release
- Postganglionic parasympathetic nerve terminals in GI tract (heteroreceptors) → ↓ insulin secretion
- ↓ platelet aggregation
- β1: Stimulatory effect:
- Heart
- Sinoatrial (SA) node → ↑ heart rate (positive chronotropic effect)
- Atrioventricular (AV) node → ↑ conduction (positive dromotropic effect)
- Ventricular muscle → ↑ contractility (positive inotropic effect)
- Salivary glands → ↓ salivation
- Adipose tissue → lipolysis
- Kidney → ↑ renin secretion
- Heart
- β2: Stimulatory effect:
- Skeletal muscle blood vessels → vasodilation
- Bronchioles → relaxation
- Pancreas → ↑ secretion
- Liver → ↑ glycogenolysis, ↑ gluconeogenesis
- β3: Stimulatory effects:
- Adipose tissue → lipolysis, thermogenesis
- Detrusor muscle → relaxation
- α1: Stimulatory effect:
- Mechanism:
- Catecholamines binding → Gq (stimulatory) or Gi (inhibitory) protein activation → second messenger cascade → ↑ phospholipase C or ↓ adenylate cyclase → effect
- α1 adrenergic receptors: Gq protein activation → second messenger cascade → ↑ phospholipase C → ↑ IP3, DAG, Ca2+ → stimulatory effect
- α2 adrenergic receptors: Gi protein activation → ↓ adenylate cyclase → ↓ cAMP → inhibitory effect
- β1 adrenergic receptors: Gs protein activation → ↑ adenylate cyclase → ↑ cAMP → stimulatory effect
Catecholamines
- Neurotransmitters synthesized and released by adrenergic neurons
- Include epinephrine (adrenaline), norepinephrine (noradrenaline), dopamine
- Synthesis:
- Tyrosine → L-dopa (catalyzed by tyrosine hydroxylase).
- L-dopa → dopamine (catalyzed by dopa decarboxylase).
- Dopamine → norepinephrine (catalyzed by β hydroxylase).
- Norepinephrine → epinephrine (catalyzed by phenylethanolamine-N-methyltransferase (PNMT); only in adrenal medulla).
- Degradation:
- All catecholamines can be degraded by deamination by monoamine oxidase (MAO)/methylation by catechol-O-methyltransferase (COMT)/both.
- Norepinephrine:
- MAO: dihydroxymandelic acid
- COMT: normetanephrine
- Both: 3-methoxy-4-hydroxymandelic acid (VMA)
- Epinephrine:
- MAO: dihydroxymandelic acid
- COMT: metanephrine
- Both: 3-methoxy-4-hydroxymandelic acid (VMA)
- Dopamine:
- MAO: dihydroxyphenylacetic acid
- COMT: 3-methoxytyramine
- Both: homovanillic acid (HVA)
- Adrenergic transmission:
- Present in:
- Most postganglionic sympathetic neurons (norepinephrine)
- Adrenal medulla’s chromaffin cells (epinephrine)
- Ventral tegmental area, substantia nigra (dopamine)
- Present in:
Cholinergic Receptors
- Receptors that respond to the neurotransmitter acetylcholine
- Found in parasympathetic effector organs, CNS → stimulated → parasympathetic/parasympathomimetic response
- Types:
- Nicotinic:
- Ionotropic receptors
- Types: location
- Nm: neuromuscular junction (non-autonomic)
- Nn: autonomic ganglia and adrenal medulla
- Mechanism: Acetylcholine binding → Na+, K+ diffusion → depolarization → voltage Na+ channel activation → action potential → stimulatory effect
- Muscarinic:
- Metabotropic receptors (G-protein coupled receptors)
- Located in CNS, all parasympathetic effector organs, some sympathetic effector organs
- Types: location
- M1: autonomic ganglia, exocrine glands, CNS
- M2: heart, sweat glands, CNS
- M3: smooth muscle (blood vessels, lungs), glands, eyes, CNS
- M4: CNS, sweat glands
- M5: CNS
- Mechanism:
- Acetylcholine binding → Gq (stimulatory) or Gi (inhibitory) protein activation → second messenger cascade → ↑ phospholipase C/↓ adenylate cyclase → stimulatory/inhibitory effect
- M1, M3, M5 → Gq protein activation → ↑ phospholipase C → ↑ IP3, DAG, Ca2+ → stimulatory effect
- M4 → Gi protein activation → ↓ adenylate cyclase → ↓ cAMP → inhibitory effect
- M2 → Gi protein activation → K+ channel activation → inhibitory effect
- Nicotinic:
Acetylcholine (ACh)
- Neurotransmitter synthesized and released by cholinergic neurons
- Synthesis: Acetyl CoA + choline → acetylcholine (catalyzed by choline acetyltransferase)
- Degradation: Acetylcholine → acetylcholine CoA + choline (catalyzed by cholinesterase)
- Present in:
- Basal ganglia, hippocampus, cerebral cortex
- All neuromuscular junctions
- All preganglionic neurons (both parasympathetic, sympathetic neurons)
- All postganglionic parasympathetic neurons
- Some postganglionic sympathetic neurons (sweat glands)
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Description
Explore the essential functions of the autonomic nervous system, a crucial part of the peripheral nervous system that regulates visceral processes for homeostasis. This quiz delves into both the sympathetic and parasympathetic divisions, highlighting their roles in bodily functions like heart rate and digestion.
