Anatomy of the Autonomic Nervous System Flashcards
What is the role of the autonomic nervous system?
Motor innervation of smooth muscle, cardiac muscle (which make up viscera) and glands.
Revice signals via visceral afferent fibres and respond to stimuli via visceral efferent fibres.
What are the division of the nervous system?
Divides into the CNS (brain and spinal cord) and the PNS (cranial nerves and spinal nerves)
The PNS further splits into somatic (motor to skeletal muscle) and autonomic functions.
The autonomic then divides into the sympathetic and parasympathetic division.
What does the autonomic system respond to?
What does it control?
Responds to signals from the internal environment to control involuntary processes.
What is the function of the sympathetic nervous system?
Stress - fight of flight
Increase HR and BP
Decrease blood for to extremities and GIT through vasoconstriction
Increase blood flow to heart and muscles through vasodilation
Dilates the pupils
What is the role of the parasympathetic nervous system?
Rest and digest function
Decrease HR and force of contraction –> decrease BP
Increase blood flow to the extremities and GIT
Constrict the pupils.
How is homoestasis between the parsympathetic and sympathetic nervous system regulated?
By the hypothalamus
Controls the balance between sympathetic and parasympathetic tone.
Where do sympathetic neurons arise from?
Spinal nerve T1-L2
Thoracolumbar outflow
Where do parasympathetic nerves arise from?
Brain stem and spinal segments S2-4
Cranioscaral outflow
What is common in all pathways of autonomic nerves?
Consits of a pre-ganglionic and post-ganglionic fibre, that synapse in a ganglia
Describe how the adrenal gland medulla is innervated by the autonomic nervous system?
By preganglionic sympathetic neurons only
No post-ganglionic neuron
No parasympathetic innervation
Therefore innervation of the adrenal gland by ANS causes a widespread sympathetic response via hormone release
Describe the pathway of a sympathetic efferent.
Pre-ganglionic fibre originates from the lateral horn of grey matter in the T1-L2 spinal segments.
Travels through the ventral root and mixed spinal nerve
Into myelinated white ramus communicants
Synpase with post-ganglionic in the sympathetic ganglion, may travel up or down a few levels
Post-g exist via the grey rammus communicans (unmyelinated) and travels to target tissue via the ventral or dorsal ramus
What neurotransmitters are realised by the sympathetic nervous system?
Between pre and post ganglioninc - ACh
By post-g at target tissue NA
What are splanchnic nerves?
Autonomic fibres that target viscera
Can be sympathetic or parasympathetic
What provides most sympathetic innervation to viscera?
Splanchnic nerves
What provides most parasympathetic innervation to viscera?
Vagus nerve
What are the expceptions to the rule that splanchnic nerves supply most sympathetic innervation to the viscera?
The pulmonary plexus
The cardiac plexus
What is the pattern of travel of the pulmonary plexus?
Pre-g symphattic fibres innervating the lungs synapse in the sympathetic chain at level T1-T4
What is the pattern of travel of the cardiac plexus?
Pre-g sympathetic fibres innervating the heart synapse in the sympathetic chain at levels T1-4, as well as some contribution from cervical ganglia
What is the pattern of travel of sympathetic splanchnic nerves?
Have thoracolumbar outflow (lateral horn, ventral root, spinal nerve, white communicants, sympathetic ganglion, grey communicants)
Travel through but do not synapse within the sympathetic chain
Prevertebral ganglion lie on surface of blood vessel supplying specific organs
The post-ganglionic fibres are carried along the vessel to the target tissue
Describe the sympathetic and parasympathetic innervation of the GIT
Describe the pathway of a parasympathetic efferent from the sacral spinal cord?
The efferent neuron will run from the ventral horn of grey matter of the sacral spinal cord S2-S4.
Through the ventral root
Into the spinal nerve
Alonf the dorsal/ventral ramus
To synpases within a ganglion before reaching the target tissue.
Where are parasympathetic autonomic ganglia found?
On or near the lining of the target tissue or organ
What neurotransmitter is associated with the parasympathetic nervous system?
Aceylcholine is released in th ganglion (between pre and post)
Acetylcholine is released by post-ganglionic parasympathetic fibres.
What are the different parasympathetic nerves arising from the brainstem?
Oculomotor nerve (CN3)
Facial nerve (CN7)
Glassopharangeal nerve (CN9)
Vagus nerve (CN10)
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