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Questions and Answers
What is the function of the white rami communicantes?
What is the function of the white rami communicantes?
Where do some preganglionic axons terminate in the sympathetic trunk?
Where do some preganglionic axons terminate in the sympathetic trunk?
What are the nerves formed by the preganglionic axons that pass through the sympathetic trunk without terminating in it?
What are the nerves formed by the preganglionic axons that pass through the sympathetic trunk without terminating in it?
Why do only the thoracic and first two or three lumbar nerves have white rami communicantes?
Why do only the thoracic and first two or three lumbar nerves have white rami communicantes?
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Where are sympathetic ganglia formed by neural crest cells migrating toward?
Where are sympathetic ganglia formed by neural crest cells migrating toward?
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How many postganglionic neurons can a single sympathetic preganglionic fiber synapse with?
How many postganglionic neurons can a single sympathetic preganglionic fiber synapse with?
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Where are the postganglionic neuron cell bodies located?
Where are the postganglionic neuron cell bodies located?
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How many groups of sympathetic ganglia are there?
How many groups of sympathetic ganglia are there?
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Where do sympathetic trunk ganglia lie in the body?
Where do sympathetic trunk ganglia lie in the body?
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How many cervical sympathetic trunk ganglia are typically present?
How many cervical sympathetic trunk ganglia are typically present?
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Where do postganglionic neurons from sympathetic trunk ganglia return via gray communicating rami to?
Where do postganglionic neurons from sympathetic trunk ganglia return via gray communicating rami to?
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Which ganglion serves the head and heart primarily?
Which ganglion serves the head and heart primarily?
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What do postganglionic neurons leaving the middle and inferior cervical ganglia innervate?
What do postganglionic neurons leaving the middle and inferior cervical ganglia innervate?
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What do the thoracic portion of each sympathetic trunk ganglion primarily innervate?
What do the thoracic portion of each sympathetic trunk ganglion primarily innervate?
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Where does the lumbar portion of each sympathetic trunk ganglion primarily innervate?
Where does the lumbar portion of each sympathetic trunk ganglion primarily innervate?
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What do the gray rami communicantes contain?
What do the gray rami communicantes contain?
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Where do sympathetic preganglionic neurons also extend to?
Where do sympathetic preganglionic neurons also extend to?
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Which ganglia lie close to major abdominal arteries?
Which ganglia lie close to major abdominal arteries?
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Where do splanchnic nerves from thoracic area synapse with postganglionic cell bodies?
Where do splanchnic nerves from thoracic area synapse with postganglionic cell bodies?
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Which ganglion does the lesser splanchnic nerve pass through to innervate blood vessels of small intestine and proximal colon?
Which ganglion does the lesser splanchnic nerve pass through to innervate blood vessels of small intestine and proximal colon?
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Which ganglion does the lumbar splanchnic nerve terminate in, supplying blood vessels of distal colon and rectum, urinary bladder, and genital organs?
Which ganglion does the lumbar splanchnic nerve terminate in, supplying blood vessels of distal colon and rectum, urinary bladder, and genital organs?
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From where are adrenal medullae and sympathetic ganglia derived?
From where are adrenal medullae and sympathetic ganglia derived?
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What hormones are released by adrenal medullae, intensifying responses elicited by sympathetic postganglionic neurons?
What hormones are released by adrenal medullae, intensifying responses elicited by sympathetic postganglionic neurons?
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Where are parasympathetic preganglionic neurons located?
Where are parasympathetic preganglionic neurons located?
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What is the parasympathetic division known as?
What is the parasympathetic division known as?
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Where does the cranial parasympathetic outflow consist of preganglionic axons?
Where does the cranial parasympathetic outflow consist of preganglionic axons?
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What do vagal axons extend to in the thorax and abdomen?
What do vagal axons extend to in the thorax and abdomen?
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Where are nicotinic receptors present in the ANS?
Where are nicotinic receptors present in the ANS?
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What is the function of the enteric division of the Autonomic Nervous System?
What is the function of the enteric division of the Autonomic Nervous System?
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What is the neurotransmitter released by cholinergic neurons in the ANS?
What is the neurotransmitter released by cholinergic neurons in the ANS?
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What is the main cause of autonomic dysreflexia?
What is the main cause of autonomic dysreflexia?
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Where do most nerve fibers innervating digestive organs arise from within the enteric system?
Where do most nerve fibers innervating digestive organs arise from within the enteric system?
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What are muscarinic receptors present in the plasma membranes of?
What are muscarinic receptors present in the plasma membranes of?
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Where are autonomic neurons classified based on the neurotransmitter they release?
Where are autonomic neurons classified based on the neurotransmitter they release?
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What is the exaggerated response of the sympathetic division that occurs in about 85% of individuals with spinal cord injury at or above the level of T6 called?
What is the exaggerated response of the sympathetic division that occurs in about 85% of individuals with spinal cord injury at or above the level of T6 called?
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What is the role of interneurons in the enteric division?
What is the role of interneurons in the enteric division?
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What is the function of cholinergic receptors in the ANS?
What is the function of cholinergic receptors in the ANS?
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What is the function of the myenteric plexus and submucosal plexus within the enteric system?
What is the function of the myenteric plexus and submucosal plexus within the enteric system?
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Study Notes
Structure and Function of Sympathetic and Parasympathetic Divisions
- Gray rami communicantes outnumber white rami and carry sympathetic output to smooth muscle and glands
- Prevertebral ganglia, including celiac, superior mesenteric, inferior mesenteric, and aorticorenal ganglia, lie close to major abdominal arteries
- Splanchnic nerves from thoracic area synapse with postganglionic cell bodies in celiac ganglion, innervating blood vessels to stomach, spleen, liver, kidneys, and small intestine
- Lesser splanchnic nerve passes through celiac plexus to enter aorticorenal ganglion and superior mesenteric ganglion, innervating blood vessels of small intestine and proximal colon
- Lumbar splanchnic nerve terminates in inferior mesenteric ganglion, supplying blood vessels of distal colon and rectum, urinary bladder, and genital organs
- Sympathetic preganglionic neurons also extend to adrenal medullae, releasing hormones into the blood upon stimulation
- Adrenal medullae and sympathetic ganglia are derived from the same tissue, the neural crest
- Adrenal medullae release a mixture of hormones, including epinephrine and norepinephrine, intensifying responses elicited by sympathetic postganglionic neurons
- Parasympathetic preganglionic neurons are located in the nuclei of cranial nerves in the brain stem and in the lateral gray horns of the second through fourth sacral segments of the spinal cord
- Parasympathetic division is known as the craniosacral division, and its axons are referred to as the craniosacral outflow
- Cranial parasympathetic outflow consists of preganglionic axons in four cranial nerves, while sacral parasympathetic outflow consists of preganglionic axons in anterior roots of the second through fourth sacral nerves
- Cranial outflow has four pairs of ganglia and plexuses associated with the vagus nerve, with vagal axons extending to terminal ganglia in the thorax and abdomen
Enteric Division of the Autonomic Nervous System
- The enteric division is a specialized network of nerves and ganglia within the gastrointestinal tract, pancreas, and gallbladder.
- It contains around 100 million neurons, equivalent to the number in the spinal cord, and can function independently.
- The network includes sensory neurons monitoring intestinal wall tension and content composition, which relay signals to interneurons in the enteric ganglia.
- Interneurons process incoming signals and generate output signals to motor neurons, regulating motility, secretory activities, and blood supply of the digestive organs.
- Most nerve fibers innervating digestive organs arise from the myenteric plexus and the submucosal plexus within the enteric system.
- Autonomic dysreflexia is an exaggerated response of the sympathetic division that occurs in about 85% of individuals with spinal cord injury at or above the level of T6.
- Autonomic dysreflexia results from the interruption of ANS control by higher centers and causes severe vasoconstriction, elevated blood pressure, and emergency symptoms.
- Autonomic neurons are classified based on the neurotransmitter they release, with cholinergic neurons releasing acetylcholine (ACh) in the ANS.
- ACh is stored in synaptic vesicles and binds with specific cholinergic receptors, including nicotinic receptors and muscarinic receptors.
- Nicotinic receptors are present in the plasma membranes of dendrites and cell bodies of sympathetic and parasympathetic postganglionic neurons, and in the motor end plate at the neuromuscular junction.
- Muscarinic receptors are present in the plasma membranes of all effectors innervated by parasympathetic postganglionic axons, including smooth muscle, cardiac muscle, and glands.
- Cholinergic and adrenergic receptors are integral membrane proteins located in the plasma membrane of a postsynaptic neuron or an effector cell.
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Description
Test your knowledge of the autonomic nervous system with this quiz on the structure and function of the sympathetic and parasympathetic divisions, as well as the enteric division. Explore the pathways, ganglia, neurotransmitters, and specific functions of each division.
