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BIO 354 - Neurobiology 2 1
Lecture 11 and 12 – Autonomic nervous system
Raghav Rajan
Bio 354 – Neurobiology 2
February 11
th
Material for lecture is from the following links
http://www.ib.cnea.gov.ar/~redneu/2013/BOOKS/Principles%20of%20Neural%20Science%20-%20Kan
del/gateway.ut.ovid.com/gw2/ovidweb.cgisidnjhkoalgmeho00dbookimagebookdb_7c_2fc~57.htm
2) Links provided at the bottom of the slide
BIO 354 - Neurobiology 2 2
Divisions of the nervous system
http://serendip.brynmawr.edu/exchange/brains/structures
BIO 354 - Neurobiology 2 4
Somatic
and
Autonomic
reflexes
● Differ in the
involvement
of CNS
● Differ in the
targets
BIO 354 - Neurobiology 2 5
Autonomic nervous system had 3 sub-divisions
● Sympathetic - “Fight or Flight”
(Walter Cannon)
● Parasympathetic - “Rest and
digest” (Walter Cannon)
● “Homeostasis” - main function to
maintain constant internal
environment (negative feedback
regulation)
● Hypothalamus is the “boss”
● Enteric – related to the gut and
mediates digestive reflexes
– More independent than the other
two
– Very few connections to the rest
of the nervous system
http://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/bio%20102/bio%20102%20lectures/nervous%20system/nervous1.htm
BIO 354 - Neurobiology 2 7
Differences between somatic and autonomic motor
systems : 1) location of motor neuron
Motor neurons of autonomic
nervous system are outside
CNS
– Preganglionic fiber from CNS
– Postganglionic fiber to
target
One extra synapse in the
path from CNS to peripheral
target – autonomous nervous
system
BIO 354 - Neurobiology 2 8
Differences between somatic and autonomic motor
systems : 2) synaptic terminals
● Nerve endings that don't have pre-synaptic boutons
● Rather, presence of multiple varicosities along the length – mutliple release sites
● Small number of fibers providing diffuse innervation – longer range effect than
normal neurotransmitters
BIO 354 - Neurobiology 2 10
Organisation of
projections to
sympathetic
system
3 major types
Depends on
origin and
target or
projection
https://voer.edu.vn/m/divisions-of-the- autonomic-nervous-system/1121e1d0#tbl- ch15_
BIO 354 - Neurobiology 2 11
Organisation of
parasympathetic nervous
system
Craniosacral system
Cranial and spinal nerves
– origins or preganglionic
fibers
Ganglia are close to
targets or within targets
Preganglionic fibers – long
Postganglionic fibers -
short
https://voer.edu.vn/m/divisions-of-the- autonomic-nervous-system/1121e1d0#tbl- ch15_
BIO 354 - Neurobiology 2 13
Circuit that controls changes in pupil size
Only one part
of the circuit
http://neuroscience.uth.tmc.edu/s3/chapter07.html
BIO 354 - Neurobiology 2 14
Separate sympathetic and
parasympathetic control
https://voer.edu.vn/m/autonomic-reflexes-and-homeostasis/0058b
BIO 354 - Neurobiology 2 16
How do you get different responses in the targets?
Otto Loewi – Nobel prize in 1934 – for the discovery of
chemical neurotransmission – ACh (Vagusstoff)
His experiments were done in 1921 – at a time when it
was not clear if neurotransmission was chemical or
electrical
http://en.wikipedia.org/wiki/Otto_Loewi
BIO 354 - Neurobiology 2 17
Interesting history pertaining to his discovery
On mature consideration, in the cold light of the morning, I would not have done it.
After all, it was an unlikely enough assumption that the vagus should secrete an
inhibitory substance; it was still more unlikely that a chemical substance that was
supposed to be effective at very close range between nerve terminal and muscle be
secreted in such large amounts that it would spill over and, after being diluted by the
perfusion fluid, still be able to inhibit another heart. (Loewi 1921)
While it remains unclear how much of Loewi's account is true, Loewi was fortunate
in his choice of experimental preparation. In the species of frog used (Rana esculenta
), the vagus contains both inhibitory and stimulatory fibers. In the winter, inhibitory
fibers predominate, so Loewi was also fortunate to have performed his experiments
in February or March. Additionally,acetylcholinesterase activity (the enzyme that
degrades acetylcholine) is low, particularly in an unheated laboratory, allowing the
neurotransmitter to remain long enough to be collected and applied to a second heart.
Thanks to this confluence of events, Loewi was able to describe the existence
of vagusstoff and prove the existence of chemical synaptic transmission
http://en.wikipedia.org/wiki/Vagusstoff
BIO 354 - Neurobiology 2 19
Neurotransmitters typically used by both systems
BIO 354 - Neurobiology 2 20
Other neuropeptides also used
