Autonomic Nervous System Flashcards
Preganglionic sympathetic neurones are located exclusively in
the thoracic and upper two or three lumbar segments of the spinal cord
Preganglionic sympathetic neurones lie in
the lateral horn of the spinal grey matter
Preganglionic sympathetic axons leave the cord in
the ventral nerve roots and join the spinal nerve
Postganglionic sympathetic neurones have their cell bodies in
the sympathetic chain of ganglia lying alongside the vertebral column or the plexuses that surround the main branches of the abdominal aorta e.g. superior mesenteric etc.
Preganglionic sympathetic axons in the spinal nerve enter
the sympathetic chain
Ganglia of the sympathetic chain are linked to the spinal nerves which contain sympathetic outflow by
the rami communicantes (two small nerves)
Preganglionic sympathetic fibres pass into the chain via
the which ramus communicantes
Preganglionic parasympathetic neurones are located in
the brainstem and spinal cord
Within the brainstem, parasympathetic neurones lie in
cranial nerve nuclei associated with the oculomotor, facial, glossopharyngeal and vagus nerves
Within the brainstem, parasympathetic neurones provide innervation for structures of
the head, thorax and abdomen
Within the spinal cord, preganglionic parasympathetic neurones lie in
the second, third and fourth sacral segments
Preganglionic parasympathetic neurones within the spinal cord innervate
pelvic viscera
The cell bodies of postganglionic parasympathetic neurones lie in ganglia that are located close to
the structure that they innervate
Within the alimentary canal, postganglionic parasympathetic neurones contribute to what plexuses?
Myenteric and submucosal
Neurotransmitter released by preganglionic sympathetic neurones
acetylcholine
Transmitter released by postganglionic sympathetic neurones
noradrenaline
The adrenal medulla is innervated directly by
preganglionic sympathetic neurones
The neurotransmitter released by preganglionic and postganglionic parasympathetic neurones is
acetylcholine
The effects of the sympathetic system are most apparent under conditions of
stress, excitement, fear
“fight or flight” response
Effect of the sympathetic system of blood pressure and heart rate
BP and HR are increased
Effect of sympathetic system on bronchi
Dilated to increase airflow to and from the lungs
Effect of sympathetic system on blood vessels
Vasodilation in skeletal muscles
Vasoconstriction in GI tract
Effect of sympathetic system on blood glucose levels and sweating
Blood glucose levels increase
Sweating occurs to increase heat loss
Effect of the parasympathetic system on cardiac output, heart rate and blood pressure
All decreased
What is syncope?
Loss of consciousness and posture (fainting)
Syncope most commonly occurs when blood pressure is
low (hypotensive)
