brain control of urination

The filtering action of the kidneys is controlled by the pituitary gland. The pituitary gland is about the size of a pea and is found below the brain ( Figure 1.3). The pituitary gland releases hormones that help the kidneys to filter water from the blood. The movement of water back into blood is controlled by a hormone called antidiuretic hormone (ADH). ADH is one of the hormones released from the pituitary gland in the brain. One of the most important roles of ADH is to control the bodys ability to hold onto water. If a person does not drink enough water, ADH is released. It causes the blood to reabsorb water from the kidneys. If the kidneys remove less water from the blood, what will the urine look like? It will look darker, because there is less water in it. When a person drinks a lot of water, then there will be a lot of water in the blood. The pituitary gland will then release a lower amount of ADH into the blood. This means less water will be reabsorbed by the blood. The kidneys then produce a large volume of urine. What color will this urine be?

formation of urine

The process of urine formation is as follows: 1. Blood flows into the kidney through the renal artery. The renal artery connects to capillaries inside the kidney. Capillaries and nephrons lie very close to each other in the kidney. 2. The blood pressure within the capillaries causes water, salts, sugars, and urea to leave the capillaries and move into the nephron. 3. The water and salts move along through the tube-shaped nephron to a lower part of the nephron. 4. The fluid that remains in the nephron at this point is called urine. 5. The blood that leaves the kidney in the renal vein has much less waste than the blood that entered the kidney. 6. The urine is collected in the ureters and is moved to the urinary bladder, where it is stored. Nephrons filter about 14 cup of body fluid per minute. In a 24-hour period, nephrons filter 180 liters of fluid, and 1.5 liters of the fluid is released as urine. Urine enters the bladder through the ureters. Similar to a balloon, the walls of the bladder are stretchy. The stretchy walls allow the bladder to hold a large amount of urine. The bladder can hold about 1 12 to 2 21 cups of urine but may also hold more if the urine cannot be released immediately. How do you know when you have to urinate? Urination is the process of releasing urine from the body. Urine leaves the body through the urethra. Nerves in the bladder tell you when it is time to urinate. As the bladder first fills with urine, you may notice a feeling that you need to urinate. The urge to urinate becomes stronger as the bladder continues to fill up. The location of nephrons in the kidney. The fluid collects in the nephron tubules and moves to the bladder through the ureter.


the kidneys

The kidneys ( Figure 1.1) are important organs in maintaining homeostasis, the ability of the body to maintain a stable internal environment despite a changing environment. Kidneys perform a number of homeostatic functions. They maintain the volume of body fluids. They maintain the balance of salt ions in body fluids. They excrete harmful nitrogen-containing molecules, such as urea, ammonia, and uric acid. There are many blood vessels in the kidneys ( Figure 1.1). The kidneys remove urea and other wastes from the blood through tiny filtering units called nephrons. Nephrons ( Figure 1.2) are tiny, tube-shaped structures found inside each kidney. Each kidney has up to a million nephrons. Each nephron collects a small amount of fluid and waste from a small group of capillaries. Structures of the kidney; fluid leaks from the capillaries and into the nephrons where the fluid forms urine then moves to the ureter and on to the bladder. Nitrogen-containing wastes, together with water and other wastes, form the urine as it passes through the nephrons and the kidney. The fluid within nephrons is carried out into a larger tube in the kidney called a ureter, which carries it to the bladder ( Figure 1.2). The kidneys never stop filtering waste products from the blood, so they are always producing urine. The amount of urine your kidneys produce is dependent on the amount of fluid in your body. Your body loses water through sweating, breathing, and urination. The water and other fluids you drink every day help to replace the lost water. This water ends up circulating in the blood because blood plasma is mostly water.


instructional diagrams

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each kidney has up to 1,000 individual filtering units.

a. true

-->  b. false

the kidneys only work when you are awake.

a. true

-->  b. false

what is the first step in urine formation?

a) blood flows into the kidney through the urethra.

b) blood flows into the kidney through the renal vein.

-->  c) blood flows into the kidney through the renal artery.

d) blood flows into the kidney through the nephron.

what is the functional unit of the kidney?

a) the urethra

-->  b) the nephron

c) the renal gland

d) the kidney gland

which best describes the blood that leaves the kidney?

-->  a) the blood that leaves the kidney has much less waste than the blood that

b) the blood that leaves the kidney has much less oxygen than the blood that entered the kidney.

c) the blood that leaves the kidney has much less carbon dioxide than the blood that entered the kidney.

d) all of the above

what leaves the capillaries during the filtration process?

a) blood

b) oxygen

-->  c) water, salts, sugars, and urea

d) all of the above

each day, how much fluid is filtered by the kidneys?

a) 18 liters

b) 180 liters

-->  c) 1,800 liters

d) 180,000 liters

diagram questions

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