the glomerular filtration rate is regulated by three major principles renal autoregulation neural regulation and hormonal regulation the renal autoregulation happens when something disrupts homeostasis by increasing the glomerular filtration rate the cells there at the jga the macula densa and the adjustable murler cells detect increased delivery of sodium chloride and water that's going to send cause these guys to decrease secretion of nitric oxide okay nitric oxide is a vasodilator if they decrease secretion of nitric oxide then the afferent arterial is going to constrict if it constricts then it's going to have a smaller diameter and so even though the efferent arterial has a smaller diameter it's going to decrease the amount of pressure so in other words if the pressure the glomerular filtration rate pressure is too high there's going to be too much water in that distal convoluted tubule in the macula densa and there's going to be too much salt chloride and water because they're not going to be reabsorbed properly and then this happens to slow it down the decreased secretion of nitric oxide so we're removing a vasodilator which causes this constrict there isn't as much pressure because these are closer in size and not as much fluid is going to be filtered so that you have a decrease in the glomerular filtration rate all right the renal autoregulation the other mechanism is a myogenic mechanism so we talked about the tubular glomerular feedback in the last slide the myogenic happens when you have increases in blood pressure and it stretches that afrin arterial and with this you would have um too much pressure and the filtration rate would be too high and you would lose a lot of valuable nutrients and water so the smooth muscle then is going to contract to reduce the diameter of the arterial and return the glomerular filtration rate back neural regulation um is strictly sympathetic remember the kidney is the one organ that only has sympathetic stimulation it doesn't it doesn't have dual innervation and it's kind of odd that it's only sympathetic because you think of the acronym slud salivation lacrimation urination defecation and digestion as parasympathetic but this only has the sympathetic input so you will filter the amount of blood that you filter is going to be dependent upon how much sympathetic stimulation you have if you have a lot of it you're in fight or flight you're exercising you're doing something one of those e situations and the sympathetic stimulation is high you're going to decrease filtration if the sympathetic stimulation is low you're just sitting and resting you're going to increase filtration so because we we don't want a lot of blood flowing to be filtered flowing to the kidneys to be filtered if we need to go to the skeletal muscle for fight or flight with this the stimulation so what happens is at rest the renal blood vessels are maximally dilated because there's not a lot of sympathetic activity and so it's mainly going to be auto regulated through renal autoregulation if you have a little bit of sympathetic stimulation both the afferent nephron arterioles constrict equally so that decreases the glomerular filtration rate if you have extreme sympathetic stimulation you're going to have vasoconstriction of the afrin arterioles and that is going to significantly reduce your filtration rate and that'll lower urine output and permit the blood to go to other tissues we have a number of different hormones that we're going to have to discuss in chapters in chapters 26 and 27. um atrial natural peptide is one if you look at the name atria atrial refers to the atria of the heart natrium is sodium erratic urine okay now um and we'll talk about the sodium part of it later but this acts it's going to act in secretion of sodium into the urine but it's also going to act here at the messenger cells so these are the little cells that you find in between the capillaries and when the atrial natural peptide is released it's released because the atria stretch because the blood volume is too high so if we think about a negative feedback loop the action of this hormone is going to be to decrease blood volume uh yeah to decrease blood volume by increasing urine output so the way that you would increase urine output is one way is to increase the filtration rate so more blood is filtered and the other effect that this is going to have is having less of it less of the the fluid reabsorbed back into the blood so when the atria stretch this is released and the one effect it's going to have is to relax those mesengel cells when they relax it increases the surface area and that increases the glomerular filtration rate when they're constricted or contracted that is going to decrease the surface area and decrease the filtration rate the other one that's going to act here is angiotensin angiotensin ii and angiotensin ii is going to reduce the glomerular filtration rate this is a very strong vasoconstrictor so it's going to narrow both the afferent and efferent arterioles and that reduces the overall glomerular filtration rate the goals for this lecture are to list the three processes involved in forming urine and identify where each occurs which features of the renal corpuscle enhanced filtration describe the three filters the glomerulus and list the substances each of them blocks from entering the filtrate the three forces of nfp are the glomerular blood hydrostatic pressure the capsular hydrostatic pressure and the blood colloidal osmotic pressure identify what causes each of these pressures and which direction each will try to force the blood to go into the filtrate or out of the filtrate state the formula for net filtration pressure and the normal values for each pressure how will a decrease in plasma proteins from kidney disease or liver disease affect the net filtration pressure what is the glomerular filtration rate what happens if it is too high or too low list and describe the three mechanisms of glomerular filtration rate regulation which two hormones directly affect the rate of glomerular filtration rate and define filtration fraction