The Autonomic Nervous System Flashcards
What are the key features of the autonomic nervous system?
Has two motoneurons.
Secretes acetylcholine or noradrenaline.
What are the different spinal segments from the lateral horn?
Sympathetic - T1-L2 (thoracolumbar).
Parasympathetic - S2-S4 (sacral).
How is the body innervated below L2?
Differential growth of the vertebral column.
How are sympathetic fibres spread?
Bilateral sympathetic chains.
Runs paravertebrally from C1 to Cc1.
Allows for mass distribution.
What are the white rami?
Myelinated, preganglionic.
From spinal nerve to spinal cord.
Synapses in the spinal cord.
Sends signals to the grey rami.
What are the grey rami?
Unmyelinated, postganglionic.
From spinal cord back to the spinal nerve.
What fibres do spinal nerves contain?
Sensory, motor and sympathetic.
Contains ventral and dorsal rami.
How do all parts of the body receive sympathetic supply?
Some preganglionic fibres travel up or down the sympathetic chain without synapsing there.
Synapses at a sympathetic ganglion and enters the spinal nerve at that level.
What are splanchnic nerves?
Sympathetic fibres emerge from the lateral horn and pass through the spinal cord without synapsing.
Synapses in an autonomic ganglion in the abdomen lying outside the spinal cord.
Only abdominal organs.
How do sympathetic fibres innervate the head and face?
Synapses in cervical ganglia and ‘climbs up’ the blood vessels.
What is Horner’s syndrome?
Damage of sympathetic fibres of the face.
Partial ptosis - drooping of the upper eyelid.
Miosis - pupil constriction.
Anhydrosis - decreased sweating.
What pathways does the ANS use?
Sympathetic and parasympathetic.
Sympathetic sensory fibres go from organs to the spinal cord via the dorsal root.
Mainly sympathetic afferent fibres.
Parasympathetic afferent fibres are in the pelvis.
What is the difference between somatic and visceral sensation?
Somatic - well localised and conscious.
Visceral - poorly localised and often unconscious.
What are pelvic splanchnic nerves?
S2-S4 spinal nerves carrying parasympathetic fibres to pelvic organs.
Cell bodies - lateral horn, in L2-L3.
How do pelvic splanchnic nerves innervate the target organ?
Preganglionic axons synapse in parasympathetic ganglions close to or within the pelvic target organ.
