kidney

Question 1

Homeostasis

Answer 1

it is the process by which the body adjusts to changes to keep essential internal conditions steady.e.g when body is too hot or too cold…

Question 2

How does homeostasis work?

Answer 2

Many of the body’s systems work best under specific chemical and physical condition. To keep things in a steady state, the body uses a system of receptors and effectors. The receptors detect the rise or fall in temperature of the skin. The effectors then brings about the changes in the opposite direction to restore the equilibrium. keeping the body’s internal temperature at 37’C is an example of homeostasis

Question 3

Negative feedback

Answer 3

Controlling water balance is an example of negative feedback, where one system is the reverse to another in order to maintain a steady state

Question 4

Give examples of homeostasis

Answer 4

body maintenance of water content, temperature and composition of blood are examples of homeostasis

Question 5

How does negative feedback mechanism work?

Answer 5

If a variable in the body becomes too low (e.g. pH, temperature) negative feedback mechanisms will rise to that variable and vice versa.

Question 6

How does kidneys control the water content of the body? Use negative feedback in your answer.

Answer 6

Receptors in brain measure water potential of blood. Changes in water potential alter the amount of ADH (Anti Diuretic Hormone) released. This hormone then controls the amount of water ‘saved’ by the kidney and so not lost in the urine. This demonstrates negative feedback, since a reduction in water intake eventually causes greater saving of water and so ‘cancels out’ the original change.

Question 7

When there is Too much Water in the Blood

Answer 7

• Receptors in your hypothalamus detect a decrease in salt concentration, no stimulus is sent to the pituitary gland.
• Less ADH is secreted into the blood.
• The collecting ducts of your kidneys become less permeable, so less water is reabsorbed.
• Your bladder fills with large quantity of dilute urine

Question 8

When there is NOT enough Water in the Blood

Answer 8

• Receptors in your hypothalamus detect an increase in salt concentration. A stimulus is sent to the pituitary gland. Thirst is stimulated to encourage drinking.
• More ADH is secreted into the blood.
• The collecting ducts of your kidey become more permeable, so more water is reabsorbed.
• Your bladder is filled with a small quantity of concentrated urine.

Question 9

Give two possible advantages of using a dialysis machine rather than having a kidney transplant.

Answer 9

It does not depend on the availability of a kidney for transplant/it should not challenge the patient’s immune system/drug treatment can go on through the
dialysis fluid entering the body

Question 10

Give two possible disadvantages of using a dialysis machine rather than having a kidney transplant.

Answer 10

it is inconvenient – the patient must spend long periods on the machine/long-term treatment is very expensive

Question 11

Explain why: protein molecules are not normally present in urine.

Answer 11

The protein molecules are too large to cross the filtration membrane and enter the urine

Question 12

Explain why glucose molecules are not normally present in urine.

Answer 12

glucose molecules can cross the filtration membrane, but it is possible for them to be selectively reabsorbed and returned to the blood

Question 13

Name organs for excretion

Answer 13

lungs, kidneys and skin

Question 14

Name two functions of kidney

Answer 14

It’s a homeostatic organ, controlling the water and salt (ion) concentration in the body as well as an excretory organ, concentrating nitrogenous waste in a form that can be eliminated.

Question 15

An athlete trained for two hours on a hot summer’s day. At the end of the training session, the athlete had a higher concentration of ADH in his blood than at the start of the training session. Explain why.

Answer 15

Training on a hot day means that much water will be lost in sweat/reduces the water potential of the blood/osmoreceptors in brain detect this change/more ADH is released to ‘instruct’ the kidney to recover more water from the urine.

Question 16

Define the term excretion.

Answer 16

Excretion is the removal of metabolic waste, including urea, carbon dioxide and water of metabolism

Question 17

Define the term egestion.

Answer 17

Egestion is the removal from the body of food materials that have not been digested and absorbed from the gut e.g dietary fiber.

Question 18

State where in the body urea is formed.

Answer 18

In the liver

Question 19

State when urea is formed from.

Answer 19

from excess amino acids (by the process
of deamination)

Question 20

Suggest why the concentration of the urea in the patient’s blood rises between dialysis treatments.

Answer 20

Urea is still being formed but it is not being excreted

Question 21

State two treatments which may help patient to prevent rejection of the transplanted kidney.

Answer 21

The patient may be treated with drugs which suppress the activity of their immune system, so that the body’s defences no longer attack the donor kidney/the donor kidney may be treated so that it has no antigens on its surface and so it is not recognized by the host defense.

Question 22

Renal artery

Answer 22

blood with high urea concentration

Question 23

Renal vein

Answer 23

blood with lowered urea concentration

Question 24

Urea

Answer 24

Urea is produced in the liver but excreted from the kidney. It’s is removed by ultra filtration of the blood in the kidney, and expelled from the body in the urine.

Question 25

Bladder

Answer 25

Storage of up to about 500cm3 of urine before expulsion from body

Question 26

Sphincter

Answer 26

ring of muscle that controls flow of urine from bladder to urethra

Question 27

Urethra

Answer 27

urine flow from bladder to outside

Question 28

Cortex

Answer 28

contains the Bowman's capsules in which ultra filtration of blood takes place

Question 29

Medulla

Answer 29

Medulla contains loops of Henle and collecting ducts.

Question 30

First coiled tubule (Proximal convoluted tubule)

Answer 30

here the useful solutes, glucose, amino acids and some minerals are selectively reabsorbed into the blood. Up to 90% of water is reabsorbed here.

Question 31

Urine

Answer 31

is mainly **water** with concentrated **urea** and excess **salts**

Question 32

Renal capsule

Answer 32

filtration of blood under **high pressure** to remove **toxic urea**. Unfortunately useful glucose, amino acids, salts and water also leave the blood.

Question 33

Collecting ducts

Answer 33

kidney can **reabsorb water** from here and return it to the blood according to the body's demand

Question 34

Anti-diuretic hormone (Anti Urine) - also known as vasopressin is a powerful vasoconstrictor

Answer 34

When the **hypothalamus** detects that the blood plasma has a **low water potential**, it stimulates the pituitary gland to release ADH. When ADH is released into the bloodstream, it causes **constrictuion** of blood vessels, raising blood pressure. It then reaches the kidneys causing more water to be **reabsorbed**. Therefore water is conserved and the water potential of blood is increased.

Question 35

Why is regulation of water potential important?

Answer 35

to prevent hydration or the bursting of cells

Question 36

How kidneys work?

Answer 36

The kidneys contain **millions of tiny filtering units** called **nephrons**. 3 stages took place: **ultra-filtration**, **selective reabsorption**, and **salt and water regulation**.

Question 37

Ultrafiltration

Answer 37

the blood from the **renal artery i**s forced into the glomerulus under **high pressure**. Most of the **water** is forced out of the **glomerulus** and into the **Bowman's capsule**, including all the small molecules like **urea**, **salts** and **glucose**. The liquid filtered into the Bowman's capsule is called **glomerular filtrate.** The cup shape of the Bowman's capsule allows the glomerulus to sit indide and allows high pressure to be maintained.

Question 38

Selective reabsorption

Answer 38

in the **Proximal convulted tubule** useful substance such as glucose are reabsorbed into the blood, which runs very close by. The coiled-up tubule is **long** and **folded** to **allow** **time** for the useful substances to pass back into the blood.

Question 39

Salt and water regulation

Answer 39

the **collecting duct** is where water is reabsorbed into the blood. The hairpin-shaped loop of Henle and collecting duct **extend** from the **cortext** to the **medulla**, allowing **plenty** of **time** for **reabsorption** of water and ions. Complex movements of ions and water across the loop result in the production of concentrated urine.

Question 40

Starting from glomerulus, **name** the **structures** that a urea modulecule passes through on its way from blood to the bladder

Answer 40

Glomerulus, Bowman's capsule, proximal convoluted tubule, loop of Henle, distal convoluted tubule, collecting duct, ureter, bladder

Question 41

Glucose is filtered out of the blood in the kidney. Why is glucose **not** found in the urine of the healthy people?

Answer 41

In a healthy kidney all the glucose that is **filtered out** of the **glomerulus** is **reabsorbed** in the **proximal convoluted** tubule.

Question 42

Name the hormone involved in the regulating water loss in the urine.

Answer 42

ADH (anti diuretic hormone)

Question 43

How does an **increase** in **ADH** affect the color, concentration, and volumne of urine?

Answer 43

small volumne of dark-coloured, concentrated urine produced

Question 44

Explain why blood **protein** is **not** normally found in urine.

Answer 44

Blood proteins are too **large** to **pass** out of the **glomerulus** into the Bowman's capsule.

Question 45

Explain why **glucose** is found is the **filtrate** but is not found in the urine.

Answer 45

glucose molecules can **cross** the **filtration** membrane, but it is possible for them to be **selectively reabsorbed** and returned to the blood by **diffusion** and **active transport**

Question 46

Describe how you could use **Benedict's Reagent t**o test a sample of urine for the presence of **glucose**.

Answer 46

Heat a urine sample with Benedict's Reagent; a **change** in colour to **red/orange** indicates that glucose is present

Question 47

Suggest why **protein** appears in the urine of people with **high blood pressure**.

Answer 47

The high pressure **damages** the **delicate glomerulus walls** and **allows large protein** molecules to be **forced** through.