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How Are The Activities Of The Kidneys Controlled

Conditions Of Sodium Imbalance

How do your kidneys work? – Emma Bryce

    Hypernatremia is usually associated with dehydration, and instead of having too much sodium, there is too little water. This water loss can occur from illnesses with vomiting or diarrhea, excessive sweating from exercise or fever, or from drinking fluid that has too high concentrations of salt.

    Hyponatremia is caused by water intoxication or by a syndrome of inappropriate anti-diuretic hormone secretion . SIADH can be associated with illnesses like pneumonia, brain diseases, cancer, thyroid problems, and some medications.

    Actions Of The Parathyroid Glands

    Like the thyroid’s calcitonin, the parathyroid’s parathyroid hormone also regulates the levels of calcium in the blood. However, its stimulus and effect are just the opposite. Thus, calcitonin and PTH are antagonistic: they work against each other to maintain the normal levels of calcium in the bloodstream.

    The parathyroids secrete PTH when blood calcium levels are low. Like calcitonin, PTH targets the bones and the kidneys. In the bones, PTH stimulates the bone-dissolving cells to break down bone, thus releasing calcium into the bloodstream. In the kidneys, PTH decreases the amount of calcium that is excreted in the urine. Both of these actions raise the levels of calcium in the blood. When those levels have returned to normal, the parathyroids stop secreting PTH.

    Measurement Of Renal Function

    A simple means of estimating renal function is to measure pH, blood urea nitrogen, creatinine, and basic electrolytes . As the kidney is the most important organ in controlling these values, any derangement in these values could suggest renal impairment.

    There are several more formal tests and ratios involved in estimating renal function:

    Measurement

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    Where Are The Kidneys And How Do They Function

    There are two kidneys, each about the size of a fist, located on either side of the spine at the lowest level of the rib cage. Each kidney contains up to a million functioning units called nephrons. A nephron consists of a filtering unit of tiny blood vessels called a glomerulus attached to a tubule. When blood enters the glomerulus, it is filtered and the remaining fluid then passes along the tubule. In the tubule, chemicals and water are either added to or removed from this filtered fluid according to the body’s needs, the final product being the urine we excrete.

    The kidneys perform their life-sustaining job of filtering and returning to the bloodstream about 200 quarts of fluid every 24 hours. About two quarts are removed from the body in the form of urine, and about 198 quarts are recovered. The urine we excrete has been stored in the bladder for anywhere from 1 to 8 hours.

    How Do Kidneys Regulate Ions

    Renal Denervation, Hypertension, and Kidney Disease

    The cells of the kidney contain many specialized ion channels and transporters, which act in concert to regulate volume and ionic concentration by absorption or secretion of ions into the urine. Each region of the kidney involved in filtration and concentration of ions expresses a particular subset of ion channels.

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    Actions Of The Thymus

    The thymus and its collective hormones, thymosins, play an important role in helping the body develop immunity . In a fetus and infant, immature or not fully developed lymphocytes are produced in the bone marrow, the spongylike material that fills the cavities inside most bones. A certain group of these lymphocytes then travel to the thymus. There, thymosins changed them into T lymphocytes or T cells . While maturing, dividing, and multiplying in the thymus, T cells are “programmed” to recognize the difference between cells that belong to the body and those that are foreign or abnormal. Once they are fully mature, T cells leave the thymus and enter the bloodstream. They circulate to the spleen, lymph nodes, and other lymphatic tissue where they await the call to defend the body.

    Questions On Artificial Kidney Dialysis

    • Why is a salt solution, rather than pure water, used as the external solution for artificial kidney dialysis?
    • Are the pores formed by the cellulose fibers best suited for allowing the passage of polar or nonpolar molecules? Briefly, explain your answer in terms of the functional groups of the cellulose polymer.

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    What Could Go Wrong With The Kidneys

    When the kidneys are not working correctly, waste products and excess fluid can build up and the levels of sodium, potassium, phosphate and calcium are not regulated correctly. When these substances gather together, this causes the symptoms of kidney disease, which can include high blood pressure, excessive tiredness, fluid retention and possibly lower back pain.

    Kidney damage can occur for a number of reasons diabetes, high blood pressure, infections and a group of diseases that affect the glomerulus.;The kidneys also need an adequate supply of blood, so if there is something wrong with the blood vessels to the kidney, such as a narrowing, this will prevent the kidneys from working efficiently.;

    Afferent Signals From The Kidney To The Cns

    Hormones in body fluid homestasis (ADH/vasopressin, Aldosterone and Natriuretic peptides)

    In addition to the abundant renal efferent sympathetic innervation, afferent sensory fibres are also present in the kidney. Viral tracing studies revealed that the cell bodies of the afferent fibres are located in the dorsal root ganglion from T10 to L1 of the spinal cord . Moreover, there is evidence that 8% of the sensory fibres project monosynaptically to the brainstem . A combination of functional and immunostaining techniques showed that electrical stimulation of the renal afferents increased the labelling of the neuronal activity marker Fos in many cardiovascular brain regions, such as the organum vasculosum of the lamina terminalis, the subfornical organ, the median preoptic nucleus and the PVN in the forebrain and the nucleus tractus solitarii, RVLM and A5 noradrenergic cell group in the brainstem . Supporting the existence of these anatomical projections of renal afferents, a study showed that electrical stimulation of renal afferents increased neuronal activity in the hypothalamus and brainstem .

    Figure 1. Schematic representation of the potential integration of renal afferent and efferent fibres in the CNS and kidneys

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    Can You Ever Get Off Metformin

    Its available in tablet form or a clear liquid you take by mouth with meals. If youre taking metformin for the treatment of type 2 diabetes, it may be possible to stop. You may be able to manage your condition by making certain lifestyle changes, such as maintaining a healthy weight and getting more exercise.

    Measuring How Your Kidneys Work

    It is difficult to calculate the exact rate at which your kidneys work. The best measure of kidney function is called the glomerular filtration rate . The GFR can be estimated using a mathematical formula. This formula uses the level of creatinine in your blood to estimate how well your kidneys are filtering waste from your blood. It can indicate if there is any kidney damage.

    The higher the filtration rate, the better the kidneys are working. A GFR of 100 mL/min/1.73 m2 is in the normal range. This is about equal to 100 per cent kidney function. Based on this measurement system, a GFR of 50 mL/min/1.73 m2 could be called 50 per cent kidney function and a GFR of 30 mL/min/1.73 m2 could be called 30 per cent kidney function.

    If your doctor orders a blood test to learn more about your kidney function, an eGFR result is provided automatically, along with your creatinine results.;

    Your doctor may also test for other signs and conditions that may indicate you have chronic kidney disease. These may include tests for:

    • protein in your urine
    • blood in your urine
    • high blood pressure;
    • diabetes.

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    Kidneys: The Main Osmoregulatory Organ

    The kidneys, illustrated in Figure 22.4, are a pair of bean-shaped structures that are located just below and posterior to the liver in the peritoneal cavity. The adrenal glands sit on top of each kidney and are also called the suprarenal glands. Kidneys filter blood and purify it. All the blood in the human body is filtered many times a day by the kidneys; these organs use up almost 25 percent of the oxygen absorbed through the lungs to perform this function. Oxygen allows the kidney cells to efficiently manufacture chemical energy in the form of ATP through aerobic respiration. The filtrate coming out of the kidneys is called urine.

    Renal Nerve Activation In Renovascular Hypertension

    Figure 3 from Modulation of renal sympathetic innervation ...

    Experimental studies have demonstrated that surgical renal denervation delays or prevents the increase in blood pressure in several models of hypertension . A plausible mechanism for this decrease in blood pressure is the disruption of renal efferent sympathetic fibres. Nevertheless, the interference of renal afferent sensory fibres is also likely to be involved. In the normal state, renal afferent sensory activity leads to a reflex decrease in sympathetic outflow, which is known as an inhibitory renorenal reflex . The renorenal reflex is impaired in hypertension, and an increase in renal afferent activity augments the sympathoexcitation to the kidney and aggravates hypertension .

    Renal ischaemia and injury are conditions that may cause afferent sensory activation. Selective denervation of renal afferents prevented the increase in noradrenaline secretion from the posterior hypothalamus and prevented the increase in blood pressure following phenol-induced renal injury in rats . Renal artery occlusion-induced renal ischaemia increased the firing rate and Fos labelling in neurons in the RVLM of normal rats . These data suggest that intrarenal changes are sensed by renal afferents, and this information appears to be integrated in the brain such that in pathological states, this information contributes to sympathoexcitation.

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    Adh And Control Of The Water Balance

    What is a hormone?

    Hormones are special chemicals which coordinate many processes in your body. Hormones are made in glands which then release them into your bloodstream. They are carried around the body in your blood to their target organs. Hormones regulate the functions of many of your organs and cells, including the amount of water which is reabsorbed by your kidneys. You can read more about hormones here.

    ADH and the water balance of the body

    The amount of water in the blood must be kept more or less the same all the time to avoid cell damage as a result of osmosis . There has to be a balance between the amount of water gained and the amount of water lost by the body .

    This is achieved by the action of the hormone ADH . How does it work?

    Perhaps you have not drunk anything for a while or you have been sweating a lot. Part of the brain, the hypothalamus, detects that there is not enough water in the blood. The hypothalamus sends a message to the pituitary gland which releases ADH. This travels in the blood to your kidneys and affects the tubules so more water is reabsorbed into your blood. As a result you make a smaller volume of more concentrated urine. The level of water in your blood increases until it is back to normal.

    This is an example of negative feedback. As the level of water in the blood falls, negative feedback ensures that the amount of ADH rises. As the level of water in the blood rises negative feedback ensures that the amount of ADH falls.

    Questions On Membranes And Concentrationgradients In The Kidneys

    • Suppose that the sodium concentration in your body is neither unusually high nor unusually low, and you drink a large quantity of pure water.
  • Based on the changes in the concentrations of sodium and water in the blood that would result from drinking so much water, predict what will happen to the levels of aldosterone and ADH in the body. Briefly, explain your answer.
  • What effect will these hormonal changes have on sodium and water reabsorption ?
    • Briefly, explain why drugs consisting of nonpolar molecules are more difficult for the kidneys to remove from the body than drugs consisting of polar molecules.

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    Actions Of The Testes

    Puberty in boys usually occurs between the ages of twelve and sixteen. At this time, the anterior pituitary gland releases luteinizing hormone, which stimulates the testes to produce testosterone. This hormone produces many growth changes in an adolescent boy: growth of all the reproductive organs, growth of facial and body hair, growth of the larynx , and growth of the skeletal muscles. Follicle-stimulating hormone, also secreted from the anterior pituitary, initiates the production of sperm in the testes. Testosterone then helps the sperm mature. This process, begun at puberty, continues throughout life.

    Actions Of The Adrenal Glands

    Skin Kidneys and Bladder Parsley drink

    The small adrenal glands, capping the kidneys, control numerous activities in the body. The hormones they secrete aid in cell metabolism, adjust the water balance, and increase cardiovascular and respiratory activity.

    CORTISOL. In times of physical stress , the hypothalamus secretes a releasing hormone that causes the anterior pituitary to release adrenocorticotropic hormone . ACTH, in turn, targets the adrenal cortex, stimulating it to secrete cortisol. Like insulin, cortisol stimulates most body cells to increase their energy production. Unlike insulin, cortisol causes the cells to increase energy output by using fats and amino acids instead of glucose. In stressful situations, this is extremely important because glucose is conserved for use by the brain .

    Cortisol also has an anti-inflammatory effect, suppressing the activities of white blood cells and other components in the body’s defense line. Inflammation is an important first step in tissue repair, but if left unchecked, will lead to excessive tissue destruction. Cortisol limits the inflammation process to what is necessary for immediate tissue repair by blocking the effects of histamine .

    By 1950, Scharrer’s research and theories on neurosecretion had become accepted as fact by the scientific community. For her pioneering scientific work, Scharrer received many honors. Included among these was the naming of a cockroach species, scharrerae , in her honor.

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    P2 Receptor Activation In Renal Tubular Segments

    Sodium balance and regulation of ECFV is controlled by regulating sodium transport along the nephron. An increase in systemic blood pressure increases renal perfusion pressure to the kidney. While autoregulation is efficient, it is not perfect, leading to a subtle increase in glomerular capillary pressure and a small increase in glomerular filtration rate which can increase tubular fluid flow rate, stimulate ATP release from tubular epithelium where it can activate P2 receptors and reduce epithelial sodium transport. Therefore, regulation of ECFV occurs in part by P2-receptor-mediated regulation of salt and water reabsorption by the nephron .

    Conditions Of Calcium Imbalance

      Hypercalcemia is associated with “moans, stones, abdominal groans”; symptoms include kidney stones, abdominal pain, and depression. Also, too much calcium can be associated with heart rhythm disturbances. Causes of hypercalcemia include parathyroid tumors, other tumors including breast cancer, excess amounts of Vitamin A or D, Paget’s disease, and kidney failure.

      Hypocalcemia is usually associated with eating disorders or lack of parathyroid hormone. Symptoms include weakness, muscle spasms, and heart rhythm disturbance.

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      Tubular Reabsorption And Secretion

      Tubular reabsorption occurs in the PCT part of the renal tubule. Almost all nutrients are reabsorbed, and this occurs either by passive or active transport. Reabsorption of water and some key electrolytes are regulated and can be influenced by hormones. Sodium is the most abundant ion and most of it is reabsorbed by active transport and then transported to the peritubular capillaries. Because Na+ is actively transported out of the tubule, water follows it to even out the osmotic pressure. Water is also independently reabsorbed into the peritubular capillaries due to the presence of aquaporins, or water channels, in the PCT. This occurs due to the low blood pressure and high osmotic pressure in the peritubular capillaries. However, every solute has a transport maximum and the excess is not reabsorbed.

      In the loop of Henle, the permeability of the membrane changes. The descending limb is permeable to water, not solutes; the opposite is true for the ascending limb. Additionally, the loop of Henle invades the renal medulla, which is naturally high in salt concentration and tends to absorb water from the renal tubule and concentrate the filtrate. The osmotic gradient increases as it moves deeper into the medulla. Because two sides of the loop of Henle perform opposing functions, as illustrated in Figure 22.8, it acts as a countercurrent multiplier. The vasa recta around it acts as the countercurrent exchanger.

      Nephron Segment Metabolism And Physiology

      Sympathetic regulation of renal function; glomerular ...

      Each nephron segment has distinct physiological characteristics, and substrate utilization and metabolic pathway activities vary substantially between nephron segments and are generally consistent with oxygen availability . In regions where PO2 is high, nephrons use primarily oxidative phosphorylation to produce ATP, whereas segments where PO2 is low rely mainly on glycolysis. However, the current understanding of nephron segmental metabolism is mainly based on studies that measured specific substrate utilization, ATP production, and abundance or activities of a small number of metabolic enzymes in nephron segments isolated from rats, mice, and other animal models,,,. One should be cautious with extrapolating these findings to nephron segmental metabolism in vivo because metabolism is highly dynamic and dependent on the cellular milieu and anatomical context.

      The thick ascending limb of the loop of Henle reabsorbs 2025% of the filtered NaCl without reabsorbing water. Glucose may be the primary energy source in thick ascending limb, even though lactate, fatty acids, and ketone bodies may also contribute. Glycolytic capabilities are present in the thick ascending limb and subsequent nephron segments and largely absent in the proximal tubule,,,. The thin descending and ascending limbs of the loop of Henle do not have significant active transport.

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