Read my full disclosure statement.
Sodium in biologyTubuloglomerular feedbackand Sodium-calcium exchanger The homeostatic mechanism which controls the plasma sodium concentration is rather more complex than most of the other homeostatic mechanisms described on this page. The sensor is situated in the juxtaglomerular apparatus of kidneys, which senses the plasma sodium concentration in a surprisingly indirect manner.
Instead of measuring it directly in the blood flowing past the juxtaglomerular cellsthese cells respond to the sodium concentration in the renal tubular fluid after it has already undergone a certain amount of modification in the proximal convoluted tubule and loop of Henle. In response to a lowering of the plasma sodium concentration, or to a fall in the arterial blood pressure, the juxtaglomerular cells release renin into the blood.
This decapeptide is known as angiotensin I. However, when the blood circulates through the lungs a pulmonary capillary endothelial enzyme called angiotensin-converting enzyme ACE cleaves a further two amino acids from angiotensin I to form an octapeptide known as angiotensin II.
Angiotensin II is a hormone which acts on the adrenal cortexcausing the release into the blood of the steroid hormonealdosterone. Angiotensin II also acts on the smooth muscle in the walls of the arterioles causing these small diameter vessels to constrict, thereby restricting the outflow of blood from the arterial tree, causing the arterial blood pressure to rise.
This, therefore, reinforces the measures described above under the heading of "Arterial blood pressure"which defend the arterial blood pressure against changes, especially hypotension. The angiotensin II-stimulated aldosterone released from the zona glomerulosa of the adrenal glands has an effect on particularly the epithelial cells of the distal convoluted tubules and collecting ducts of the kidneys.
Here it causes the reabsorption of sodium ions from the renal tubular fluidin exchange for potassium ions which are secreted from the blood plasma into the tubular fluid to exit the body via the urine.
The hyponatremia can only be corrected by the consumption of salt in the diet. However, it is not certain whether a "salt hunger" can be initiated by hyponatremia, or by what mechanism this might come about. When the plasma sodium ion concentration is higher than normal hypernatremiathe release of renin from the juxtaglomerular apparatus is halted, ceasing the production of angiotensin II, and its consequent aldosterone-release into the blood.
The kidneys respond by excreting sodium ions into the urine, thereby normalizing the plasma sodium ion concentration. The low angiotensin II levels in the blood lower the arterial blood pressure as an inevitable concomitant response. The reabsorption of sodium ions from the tubular fluid as a result of high aldosterone levels in the blood does not, of itself, cause renal tubular water to be returned to the blood from the distal convoluted tubules or collecting ducts.
This is because sodium is reabsorbed in exchange for potassium and therefore causes only a modest change in the osmotic gradient between the blood and the tubular fluid. Furthermore, the epithelium of the distal convoluted tubules and collecting ducts is impermeable to water in the absence of antidiuretic hormone ADH in the blood.
ADH is part of the control of fluid balance. Its levels in the blood vary with the osmolality of the plasma, which is measured in the hypothalamus of the brain. Aldosterone's action on the kidney tubules prevents sodium loss to the extracellular fluid ECF.THE HUMAN BRAIN AND THE UNIVERSE.
Some time ago I shared with you a strange but beautiful comparison between the human brain and the universe. This post contains affiliate links to products I recommend. Read my full disclosure statement. Kids LOVE learning about the human body.
It’s so fascinating!
Videos are a great way for them to learn about different body systems and organs. The human body is the entire structure of a human caninariojana.com is composed of many different types of cells that together create tissues and subsequently organ caninariojana.com ensure homeostasis and the viability of the human body..
It comprises a head, neck, trunk (which includes the thorax and abdomen), arms and hands, legs and feet. The study of the human body . Biological systems like those of your body are constantly being pushed away from their balance points.
For instance, when you exercise, your muscles increase heat production, nudging your body . Homeostasis is the state of steady internal conditions maintained by living things. This dynamic state of equilibrium is the condition of optimal functioning for the organism and includes many variables, such as body temperature and fluid balance, being kept within certain pre-set limits (homeostatic range).Other variables include the pH of extracellular fluid, the concentrations of sodium.
caninariojana.com is an amazing human body resource for young learners. The site has videos, articles, and activities about the body. This muscular system video is one of their many videos.
It’s a great intro to muscles and how they work.