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?

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

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

Acetylcholine (A) Signup and view all the answers

What neurotransmitter is primarily involved in the parasympathetic nervous system?

Acetylcholine (B) Signup and view all the answers

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

Enzymatic breakdown by acetylcholinesterase (D) 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?

Nicotinic receptors (C) Signup and view all the answers

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

Increased salivation (C) Signup and view all the answers

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

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

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

They are short and myelinated. (A) Signup and view all the answers

Which neurotransmitter is released by postganglionic sympathetic neurons?

Norepinephrine (B) Signup and view all the answers

Which type of receptors do parasympathetic target tissues primarily have?

Muscarinic receptors (C) Signup and view all the answers

What is the central nervous system origin for parasympathetic neurons?

Cranio-sacral (C) Signup and view all the answers

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

Sympathetic has high divergence. (D) Signup and view all the answers

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

They are unmyelinated and short. (A) Signup and view all the answers

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

In sweat gland activation. (C) Signup and view all the answers

What type of neurotransmitter is released by parasympathetic postganglionic neurons?

Acetylcholine (D) Signup and view all the answers

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

Regulate internal processes to maintain homeostasis (D) Signup and view all the answers

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

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

Which neurotransmitter is commonly associated with the parasympathetic nervous system?

Acetylcholine (B) Signup and view all the answers

Where do sympathetic neurons originate in the spinal cord?

Thoracic and lumbar regions (A) Signup and view all the answers

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

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

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

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

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

They cooperate to fine-tune physiological functions. (C) 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?

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

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

Contraction of the bladder wall (C) Signup and view all the answers

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

Glossopharyngeal nerve (CN IX) (C) Signup and view all the answers

What happens to the gall bladder during parasympathetic stimulation?

Contraction of the gall bladder wall (D) Signup and view all the answers

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

Precipitation of asthma (C) Signup and view all the answers

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

Relaxation of the internal anal sphincter (C) Signup and view all the answers

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

Causes contraction of the gall bladder wall (D) Signup and view all the answers

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

Regulation of vision and pupil size (B) Signup and view all the answers

What effect does parasympathetic stimulation have on erectile tissue?

Dilation of blood vessels (D) Signup and view all the answers

What neurotransmitter is primarily released by postganglionic sympathetic neurons?

Norepinephrine (C) Signup and view all the answers

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

α1 (C) Signup and view all the answers

What is the effect of norepinephrine on the sinoatrial node?

Increases depolarization rate (C) Signup and view all the answers

Which statement about the action of norepinephrine is true?

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

How does norepinephrine affect smooth muscle in arteries and arterioles?

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

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

Relaxes the muscle and decreases voiding. (B) Signup and view all the answers

Which enzyme is responsible for metabolizing norepinephrine to inactive intermediates?

Both B and C (D) Signup and view all the answers

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

They inhibit norepinephrine release. (C) Signup and view all the answers

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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Description

Test your knowledge on the autonomic nervous system, including the locations of neuron cell bodies and neurotransmitter actions in both the sympathetic and parasympathetic pathways. This quiz covers key concepts such as neurotransmission mechanisms and receptor activation.