1. Visceral motor system
Domina Petric, MD

2. Visceral motor system overview
Maintains the internal environment of the body and regulates the activity of visceral organs, glands and blood vessels.
Governs circulation, respiration, digestion, metabolism, bodily secretions, thermal regulation and reproduction.
Elements of visceral system (together with components of the somatic motor system) are involved in the experience and expression of emotional behavior (and other aspects of cognition).
July 22, 2012
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3. Sympathetic division: energy mobilization.
Functional divisions
Sympathetic division: energy mobilization.
Parasympathetic division: energy conservation.
Enteric division: coordinates digestive reflexes.
July 22, 2012
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4. Visceral motor system main functions
HOMEOSTASIS (constancy of the internal environment)
ALLOSTASIS (change of the internal environment)
July 22, 2012
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5. Enteric division
Network of neurons that are found in the lining of the gut.
Myenteric (Auerbach) plexus: coordination of rhythmical contractions of longitudinal gut muscles.
Submucous (Meissner) plexus: coordination of secretions of various glands within the gastrointestinal system.
Enteric division plays in semi-autonomus way.
July 22, 2012
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6. CNS systems for visceral motor control
Higher brain centers in:
LIMBIC FOREBRAIN (CINGULATE GYRUS, ORBITAL MEDIAL PREFRONTAL CORTEX, AMYGDALA)
HYPOTHALAMUS
BRAINSTEM (PERIACQUEDUCTAL GRAY, RETICULAR FORMATION)
Descending projections to lower motor neuronal pools in brainstem and spinal cord.
Interneurons and preganglionic neurons in the brainstem and spinal cord that communicate indirectly with effector organs.
July 22, 2012
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7. Visceral motor efferents
Sympathetic division
Parasympathetic division
Intermediolateral cell column in thoracal and lumbar spinal cord (T1-L3): preganglionic neuron.
Sympathetic ganglia that run along the lateral side of vertebral bodies: ganglionic neuron.
Preparing the body for ACTION!
First neuron (preganglionic neuron) can be found in brainstem and in sacral segments of the spinal cord.
Preganglionic axons are much longer than in sympathetic division.
Second neuron (ganglionic neuron) is close to or embedded in the visceral organ.
Postganglionic axon is much shorter than in sympathetic division.
July 22, 2012
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8. Visceral motor efferents
Sympathetic division
Parasympathetic division
Neurotransmitter of the preganglionic neuron is ACETYLCHOLINE.
Receptors for acetylcholine are muscarinic receptors (G-protein coupled receptors).
Neurotransmitter of the postganglionic (ganglionic) neuron is NOREPINEPHRINE.
Receptors are alfa and beta adrenergic receptors for norepinephrine (G- protein coupled receptors).
Neurotransmitter of the preganglionic neuron is ACETYLCHOLINE.
Postganglionic neurotransmitter is ACETYLCHOLINE.
July 22, 2012
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9. Autonomus nervous system divisions
Parasympathetic
Sympathetic
Autonomus nervous system divisions
July 22, 2012
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10. Parasympathetic nuclei in the brainstem
Edinger-Westphal nucleus of the third cranial nerve: pupil constriction.
Salivatory nuclei (superior and inferior): tear glands and salivatory glands.
Dorsal motor nucleus of vagus: visceral targets, activity of the heart.
Nucleus ambiguus: activity of the heart (slowing the heart beat).
July 22, 2012
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11. Sacral parasympathetic nucleus
July 22, 2012
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12. Coordination of visceral motor function
Sympathetic division mobilizes resources for action: FIGHT or FLIGHT.
Parasympathetic division restores resources: REST and DIGEST.
Functions are complementary and coordinated.
There is always some tonic activity in both divisions.
Not all-or-none action, rather local, for each organ: for example, we can cry (parasympathetic activity) and at the same time have high heart rate (sympathetic activity).
July 22, 2012
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13. Integration of visceral motor signals
Nucleus of the solitary tract is important level of visceral motor integration.
Important level of visceral motor integration of abdominal organs is in the spinal cord.
July 22, 2012
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14. Nucleus of the solitary tract
Rostral division: GUSTATION.
Caudal division: VISCERAL SENSORY division.
July 22, 2012
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15. Visceral afferents can be:
mechano-sensory
nociceptive
chemo-sensory
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16. Central autonomic network
Signals from spinal visceral sensory neurons, IX. and X. cranial nerves are distributed first to the NUCLEUS SOLITARIUS and then up to AUTONOMIC CENTERS IN BRAINSTEM RETICULAR FORMATION and PARABRACHIAL NUCLEUS.
Parabrachial nucleus sends signals to the medial parts of the THALAMUS, to HYPOTHALAMUS and AMYGDALA.
Final station is medial and ventral aspects of the prefrontal cortex.
Amygdala is also connected with INSULAR CORTEX.
Insular cortex is connected with orbital medial parts of the prefrontal cortex.
Insular cortex is sensory cortex for the viscera.
July 22, 2012
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17. Central autonomic network
Medial prefrontal cortex is the principal coordinator of the visceral motor output.
Hypothalamus is important mediator for the visceral motor output.
July 22, 2012
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18. Literature
Leonard E. White, PhD, Duke University
July 22, 2012
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