Question

how and by what mechanism is glomerular filtration rate (GFR) affected by

obstruction of the ureteropelvic junction by a stone?

stimulation of the splanchnic nerve?

a marathon run?

severing the post-glanglionic sympathetic fibers to the kidney

Answer 1

Ureteropelvic junction (UPJ) obstruction(stone) is a blockage in the renal pelvis of the kidney. The renal pelvis is located at the upper end of each ureter (tube that drains urine from the kidneys to the bladder). The renal pelvis, which is shaped like a funnel, collects urine.In UPJ obstruction, the flow of urine is slowed or stopped completely. GFR will decreased.This raises the risk of kidney damage. In most cases of UPJ obstruction, only one of the kidneys is affected.

Machanism-ureteropelvic obstruction there is a progressive fall in glomerular filtration rate (GFR) due to a reduction in single nephron glomerular filtration rate (SNGFR) and a reduced number of filtering nephrons. Renal plasma flow also declines after a transient, prostaglandin-dependent increase, due to afferent and efferent arteriolar vasoconstriction. The vasoactive hormones thromboxane A2 and angiotensin II are implicated in the pathogenesis of the vasoconstriction following ureteral obstruction and they also reduce the glomerular ultrafiltration coefficient by causing mesangial contraction. Ureteropelvic obstructiona also leads to profound changes in renal tubular cell function. These include altered sodium and water handling resulting in a post-obstructive diuresis and natriuresis and a failure to dilute or concentrate the urine. Potassium and divalent cation exchange is also affected, as is urinary acidification. Furthermore, the response of the tubule to hormones such as antidiuretic hormone and parathyroid hormone is impaired. The pathophysiology of these alterations in renal function is discussed.

Stimulation of the splanchinc nerve-​nerve- following normal Function are given it will be affected in marathon race).

The splanchnic nerves are paired, autonomic nerves that carry both visceral sympathetic and sensory fibers, except for the pelvic splanchnic nerves which carry parasympathetic fibers. There are five types of splanchnic nerves on both sides of the spinal vertebrae, including cardiopulmonary, thoracic splanchnic, lumbar splanchnic, sacral splanchnic, and pelvic splanchnic nerves. The splanchnic nerves arise from within the sympathetic thoracic trunk to innervate the abdomen. Their principal clinical significance is in splanchnicectomy, in which denervation of splanchnic nerves is mainly done to manage the intractable visceral pain. Therefore, comprehensive knowledge of anatomy and clinical variations of the splanchnic nerves is essential to achieve precision in splanchnicectomies.

Structure and Function

The splanchnic nerves have been structured to provide both sensory and motor fibers.They provide visceral efferent fibers to internal organs and visceral afferent fibers exiting these internal organs.The splanchnic nerves run down the entire body parallel to each other, innervating multiple different organs. The splanchnic nerves, as suggested, consist of five primary nerves, each one supplying a different region. All the splanchnic nerves carry preganglionic sympathetic fibers except for the pelvic splanchnic nerve, which carries preganglionic parasympathetic fibers.

Thoracic Splanchnic Nerves:

Structure

The thoracic splanchnic nerves arise from the medial branches of the lesser sympathetic ganglia.[3] These nerves are long, and they are broken down into the greater splanchnic nerves, the lesser splanchnic nerves, and the least splanchnic nerve. The greater splanchnic nerves receive branches from T5-T9 thoracic sympathetic ganglia, whereas the lesser splanchnic nerves arise from T10-T11 thoracic sympathetic ganglia.The least splanchnic nerve forms from branches of T12 sympathetic ganglia.All three portions of the splanchnic nerves travel through the diaphragm and then diverge and travel to their destination. The greater and lesser splanchnic nerves end at the celiac ganglion while the least splanchnic nerve ends by synapsing within the renal ganglion.[6]

The greater splanchnic nerve transverses the diaphragm via aortic hiatus and terminates in the superior preaortic ganglia, which is commonly called the celiac ganglia. The postsynaptic fibers then move toward to organs of the foregut as the celiac plexus.

The lesser splanchnic nerves are found lateral and inferior to the greater splanchnic nerve and synapse with either the superior mesenteric ganglia or the aorticorenal ganglia.

Function

The greater splanchnic nerve provides an inhibitory effect on the foregut, which causes inhibition of motility and secretions of the duodenum, stomach and distal esophagus, stimulation of gluconeogenesis, glycogenolysis and glucose release, inhibition of bile emptying and contraction of smooth muscle in the gallbladder, inhibits the secretion of pancreatic enzymes, stimulates glucagon release leading to inhibition of insulin release, secretion of catecholamines through stimulation of chromaffin cells, and lastly, innervates the spleens capsule to allow for transmission of splenic pain.

Lumbar Splanchnic Nerve:

Structure

The lumbar splanchnic nerve also consists of two nerves on each side of the body that form from branches of the L1 and L2 sympathetic chain. These nerves transverse down the body until reaching the aortic plexus where they then join and synapse in that ganglia and develop into postganglionic fibers to be sent to vessels in this region as well as smooth muscle and glands. Indirectly these splanchnic nerves are connected to the superior hypogastric plexus as the aortic plexus connects to it.

Function

The postganglionic sympathetic fibers vasoconstrict blood vessels, allow for secretions from sweat glands, and provide motor to arrector pili muscle. The fibers that reach skeletal muscle by following the motor nerves are vasodilators. Lastly, the fibers that reach the viscera regulate glandular secretions, allow for general vasoconstriction, and inhibit smooth muscle contraction of the gastrointestinal system.

Sacral Splanchnic Nerve:

Structure

The sacral splanchnic nerves are also a set of nerves that run parallel to one another on each side of the body. They allow the inferior hypogastric plexus to connect with the sacral portion of the sympathetic trunk. These pairs of splanchnic nerves travel up from the inferior hypogastric plexus to the superior hypogastric plexus and then transverse to the aortic plexus and the inferior mesenteric plexus to innervate the hindgut.Within the pelvic plexus, the sacral and pelvic splanchnic nerves are responsible for innervating the pelvic vessels as well as the pelvic organs that are present in that region.

Function

The sacral splanchnic nerve provides both motor and sensory information to the posterior leg, foot, lower leg, and the skin and muscles of the pelvis. The major branches of the sacral splanchnic nerve include the superior gluteal, inferior gluteal, sciatic, posterior cutaneous, and the pudendal. The pelvic splanchnic nerve carries the parasympathetic fibers and provides innervation to the distal one-third of the transverse colon through to the sigmoid and rectum, as well as the cervix, and upper canal opening.

Post-ganglionic sympathetic fiber-

Postganglionic fibers in the sympathetic division are adrenergic and use norepinephrine (also called noradrenalin) as a neurotransmitter. ... In the sympathetic nervous system, the postganglionic neurons of sweat glands release acetylcholine for the activation of muscarinic receptors.

The sympathetic nervous system influences the renal regulation of arterial pressure and body fluid composition. ... Therefore, the increased sympathetic nerve activity to the kidney and the renal afferent nerve activity to the CNS may contribute to the outcome of diseases, such as hypertension.