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 Literature: https://www.coursera.org/learn/medical-neuroscience2
3. Functional divisions
Sympathetic division: energy mobilization.
Parasympathetic division: energy
conservation.
Enteric division: coordinates digestive
reflexes.
July 22, 2012 Literature: https://www.coursera.org/learn/medical-neuroscience3
4. Visceral motor system main functions
HOMEOSTASIS (constancy
of the internal environment)
ALLOSTASIS (change of the
internal environment)
July 22, 2012 Literature: https://www.coursera.org/learn/medical-neuroscience4
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 Literature: https://www.coursera.org/learn/medical-neuroscience5
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 Literature: https://www.coursera.org/learn/medical-neuroscience6
7. Visceral motor efferents
Sympathetic 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!
Parasympathetic division
• 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 Literature: https://www.coursera.org/learn/medical-neuroscience7
8. Visceral motor efferents
Sympathetic 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).
Parasympathetic division
•Neurotransmitter of
the preganglionic
neuron is
ACETYLCHOLINE.
•Postganglionic
neurotransmitter is
ACETYLCHOLINE.
July 22, 2012 Literature: https://www.coursera.org/learn/medical-neuroscience8
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 Literature: https://www.coursera.org/learn/medical-neuroscience10
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 Literature: https://www.coursera.org/learn/medical-neuroscience12
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 Literature: https://www.coursera.org/learn/medical-neuroscience13
14. Nucleus of the solitary tract
Rostral division:
GUSTATION.
Caudal division:VISCERAL
SENSORY division.
July 22, 2012 Literature: https://www.coursera.org/learn/medical-neuroscience14
15. Visceral afferents can be:
mechano-
sensory
nociceptive
chemo-
sensory
July 22, 2012 Literature: https://www.coursera.org/learn/medical-neuroscience15
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 Literature: https://www.coursera.org/learn/medical-neuroscience16
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 Literature: https://www.coursera.org/learn/medical-neuroscience17
