hi let's discuss renal autonomics in this video we'll discuss the
extrinsic control of renal function as well as the autonomic innervation of the kidneys
now control of renal function may either be intrinsic from within the kidneys which
is the most significant form of control of renal regulation or it may be extrinsic through either
hormonal control such as antidiuretic hormone aka vasopressin anp parathyroid hormone etc
all of these things can impact the physiology of the cells of the renal tubule or it may be
through neural control neural control of renal function is accomplished through the renal plexus
the renal plexus is an autonomic plexus so there are sympathetic fibers there
are parasympathetic fibers there are visceral afferent fibers and these are
going to follow the vasculature specifically the arteries into the parenchyma of the kidney
the greatest level of effect that the renal plexus may have upon renal function will be through the
sympathetic fibers sympathetic fibers can do two major things to affect renal function the first
and this is pretty typical of a sympathetic response is through vasoconstriction now by
vasoconstricting the vessels that lead to the nephrons especially at the levels of
the afferent arterioles by constricting those afferent arterioles you lower the blood flow
into the glomeruli and as a result you can decrease
glomerular filtration pressure
so you're making less filtrate and this kind of makes sense because during a sympathetic response
you probably don't want to be sacrificing blood volume to make urine the second thing that a
sympathetic response can do is to stimulate the juxtaglomerular apparatus the juxtaglomerular
apparatus in particular drugstore cells will secrete renin renin is the beginning
of the raa pathway or the renin angiotensin aldosterone pathway whose ultimate impact
is to increase blood pressure so this again is going to be consistent with a sympathetic response
now the renal plexus is going to be served by the abdominal
autonomics now to understand the the autonomics here is going to take a little bit of effort
on our part but it's not insurmountable so we need to think about the two sources of
efferents into an autonomic plexus and these are going to be sympathetic and parasympathetic
now sympathetic inputs are going to come by means of the sympathetic chains or trunks so
these are collections of para vertebral ganglia and the connections between them that are going to
ride alongside of the vertebral bodies from the level of the base of the skull so the
superior cervical ganglion all the way down to the coccyx at the ganglion empire
so these sympathetic chains run the the length of the spinal cord and even beyond
and so coming from these sympathetic chains are going to be various sympathetic fibers
so in particular descending down from the thoracic sympathetic chain are thoracic
splanchnic nerves these thoracic splanchnic nerves represent preganglionic sympathetic fibers
that enter the sympathetic chains and pass through without synapsing because they don't synapse in
paravertebral ganglia which comprise the chain they're going to synapse in pre-vertebral ganglia
so we can see some of the examples of pre-vertebral ganglia here i'm putting tiny
little x's over them so these thoracic splanchnic nerves consist of the greater the lesser and the
least splanchnic nerves now there are also lumbar splenic nerves so we can see a lumbar splenic
nerve arising from the first lumbar ganglion we can also see another one from the second lumbar
ganglion there as you can see these are going to contribute fibers to various autonomic plexuses
about and we'll get into the details of those shortly we can also see that there are
parasympathetic fibers entering the abdominal plexuses the majority of these are coming from
the posterior vagal trunk as we can see coming down here so the the vagus nerves
on the esophagus form trunks there's an anterior and a posterior vagal trunk in terms
of abdominal autonomics the majority of these are supplied by the posterior basal vagal trunk so
we have a couple of various autonomic ganglia and plexuses to discuss here and you can see that a
lot of these are associated with large visceral arterial branches so for instance there is our
celiac trunk and associated with the celiac trunk are the celiac ganglia and there are
portions of fibers that enmesh themselves about the the celiac trunk that are of the
celiac plexus so we have ganglia and plexuses now the sympathetic fibers
are going to synapse in these ganglia the parasympathetic fibers are going to pass
through these ganglia without synapsing they're going to synapse closer to their targets
in addition to the the celiac ganglia and let's just add that there's also a superior mesenteric
ganglion associated with the sma there there are aorticorenal ganglia and then there is an inferior
mesenteric ganglion and plexus now between the superior mesenteric
plexus in the inferior mesenteric plexus there's a region called the intermesenteric plexus
this is just a continuation of the aortic plexus which would be all of these fibers
so we just give this region a a specific name the inter mesenteric plexus so just for your own
simplicity here everything that you see in yellow or orange represents something that is purely
sympathetic everything that you see in blue is purely parasympathetic everything in green is
going to be mixed so it will be both sympathetic and parasympathetic now when we look let me erase
some of this here when we look around the kidneys we can see that there is a healthy amount of
mixed autonomic activity associated with those renal arteries that mixed autonomic activity
on each are the renal plexuses so this is going to be the the innervation of the kidneys and
let's take a look at the specific sources of this renal plexus so the renal plexus again we
can see that it's green therefore we know that it is a mixed plexus it's consisting of both
sympathetic and parasympathetic and visceral afferent fibers there aren't grossly visible
ganglia here to be witnessed but there are very tiny ganglia associated with the renal plexus
and the the largest of them are actually found posterior to the origins of the renal arteries
so we can see them just in there behind the renal arteries if we can see them at all now as
as i discussed earlier the renal plexus its greatest impact or its greatest known impact
has to do with the the sympathetic component of the plexus and a sympathetic response is going
to lead to vasoconstriction vasoconstriction is going to decrease the glomerular filtration rate
and a sympathetic response can also lead to the secretion of renin
which leads to the activation of the raa pathway so we're decreasing the formation of urine
and we're also increasing blood pressure as the result of a sympathetic stimulus to the uh the
renal tissue now the particular inputs to the renal plexus include everything from the celiac
ganglia and plexuses so these will get their inputs through the greater and the lesser
splanchnic nerves from the thorax there's also the posterior vagal trunk that's going
to be the parasympathetic through there we also have aorticorenal
aorticorenal gets its input from largely the lesser splanchnic nerves
and the least splanchnic nerve when it's present innervates the renal plexus directly
there's also direct innervation from the first lumbar splanchnic nerve
so that will be purely sympathetic
as well as innervation from the inter mesenteric or aortic plexus
so that leads us to our assessment question for the video and that is when present
which thoracic splenic nerve provides direct sympathetic innervation to the renal
plexus is it the first lumbar splenic nerve well a lumbar splenic nerve is not a thoracic
splenic nerve so we can eliminate that same logic holds true for the second lumbar splenic nerve
the greater thoracic splenic nerve that predominantly goes to the celiac
the least thoracic splenic nerve sounds pretty good to me that directly does go
to the renal plexus and the lesser thoracic splanchnic nerve that goes to the aorticorenal
ganglion and plexus so it's probably important to note that both c and e or
greater and lesser thoracic splenic nerves are going to contribute sympathetic fibers
to the renal plexus but it's only the least thoracic splanchnic nerve that is going to
directly supply sympathetic fibers from the thoracic region thank you very much for your time