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Questions and Answers
What is the primary cause of Horner's syndrome?
Which symptom is characterized by a constricted pupil?
Which symptom is associated with Horner's syndrome that involves inward displacement of the eye?
What facial symptom is caused by the absence of sweat secretion in Horner's syndrome?
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What results in redness or flushing of the face in Horner's syndrome?
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What primarily characterizes the sympathetic nervous system's preganglionic fibers?
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What is the primary function of adrenal ganglia?
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Which system is responsible for stimulating the 'fight or flight' response?
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What defines the transmission characteristics of the parasympathetic nervous system?
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Where are collateral ganglia primarily located?
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Study Notes
Types of Autonomic Ganglia
- Paravertebral Ganglia: Relay preganglionic sympathetic fibers
- Collateral Ganglia: Located near branches of the aorta, relay preganglionic sympathetic and parasympathetic fibers (mainly sympathetic).
- Terminal Ganglia: Found near or on effector organ walls, responsible for relaying preganglionic parasympathetic fibers.
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Adrenal Ganglia: Modified sympathetic ganglia receiving preganglionic sympathetic cholinergic fibers.
- This type releases catecholamines (norepinephrine and adrenaline) into the bloodstream in response to stimulation, enhancing and prolonging sympathetic effects on the body.
Comparison of Sympathetic and Parasympathetic Nervous Systems
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Sympathetic Nervous System (SNS):
- Preganglionic fibers synapse in either lateral or collateral ganglia.
- Short preganglionic fibers.
- Postganglionic effects mediated by norepinephrine.
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Parasympathetic Nervous System (PNS):
- Preganglionic fibers synapse in terminal ganglia.
- Long preganglionic fibers.
- Postganglionic effects mediated by acetylcholine.
Adrenal Medulla
- Supplied by preganglionic fibers, making it a modified sympathetic ganglion.
- Stimulation causes release of catecholamines (80% adrenaline, 20% norepinephrine) into the blood.
- Augments and potentiates sympathetic stimulation effects.
Functions of the SNS
- Emergency and Stress Response: "Fight-or-flight" reaction.
- Generalized Action: Acts as a single unit.
- Catabolic Action: Breaks down energy reserves.
- Delays Evacuation: Slows down the emptying of visceral content.
Divisions of the SNS
- Cervical Division: Supplies head and neck.
- Cardiopulmonary Division: Supplies thoracic viscera (heart and lungs).
- Splanchnic Division: Supplies abdomen and pelvis.
Horner's Syndrome
- Occurs due to injury or damage to the cervical sympathetic system, affecting head and neck innervation.
- Characterized by:
- Mitosis: Pupil constriction.
- Ptosis: Drooping of the upper eyelid.
- Endophthalmos: Inward displacement of the eye.
- Anhydrosis: Dryness of the face due to reduced sweat secretion.
- Facial Redness: Resulting from persistent vasodilatation.
Dual Innervation
- Almost all visceral organs receive both sympathetic and parasympathetic innervation.
- Both systems are stimulated simultaneously, but the dominant division depends on the body's needs at that time.
Structures Supplied Only By the SNS
- Skin (sweat glands, hair, and blood vessels).
- Dilator pupillae muscle.
- Blood vessels of skeletal muscles.
- Ventricles of the heart.
- Adrenal medulla.
- Spleen.
- Uterus.
Structures Supplied Only By the PNS
- Constrictor pupillae muscle.
- Gastric glands.
- Esophageal muscles.
Neurotransmitters
- Preganglionic fibers (sympathetic and parasympathetic): Release acetylcholine.
- Parasympathetic postganglionic fibers: Release acetylcholine.
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Most sympathetic postganglionic fibers: Release norepinephrine.
- Exceptions: Sweat glands and blood vessels of skeletal muscles.
- Cholinergic Fibers: All autonomic preganglionic fibers.
- Adrenergic Fibers: Most postganglionic sympathetic fibers.
Chemical Transmission at Autonomic Junctions
- Transmissions between pre- and postganglionic neurons, and between postganglionic neurons and effector organs, are chemically mediated by neurotransmitters.
- Key neurotransmitters involved: Acetylcholine and norepinephrine.
- Neurotransmitters act by binding to specific receptors on the target cell membrane.
Chemical Transmission in Autonomic Nervous Systems
- Parasympathetic (cholinergic): Postganglionic effects mediated primarily by acetylcholine.
- Sympathetic (adrenergic): Postganglionic effects mainly mediated by norepinephrine.
Synthesis of Acetylcholine
- Synthesized from choline and acetyl CoA by the enzyme choline acetyltransferase (CAT).
- Stored in synaptic vesicles for release.
- Released upon nerve impulse arrival, opening calcium channels.
- Binds to postsynaptic cholinergic receptors.
- Degraded by cholinesterase to choline and acetate.
- Choline recycled back into the neuron.
Fate of Acetylcholine:
- Degraded by cholinesterase enzyme into acetic acid and choline.
- Destruction of acetylcholine is faster than norepinephrine breakdown.
Autonomic Receptors
- Chemical structures primarily found on effector organ cell membranes.
- Respond to specific chemical interactions or drug influences.
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Two Main Groups:
- Cholinergic Receptors: Stimulated by acetylcholine.
- Adrenergic Receptors: Stimulated by norepinephrine (and epinephrine).
Cholinergic Receptors
- Can be stimulated by acetylcholine.
- Classified into two types, based on sensitivity to drugs:
- Nicotinic (N): Found in autonomic ganglia and adrenal medulla.
- Muscarinic (M): Found on effector organs innervated by postganglionic parasympathetic fibers.
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Description
Test your knowledge on the types of autonomic ganglia and their functions. This quiz covers the roles of paravertebral, collateral, terminal, and adrenal ganglia, as well as comparisons between the sympathetic and parasympathetic nervous systems. Challenge yourself to understand the intricate workings of the autonomic nervous system.
