Homeostasis and Excretion

Question 1

What is Homeostasis?

Answer 1

Homeostasis is the regulation of conditions in the body to maintain a stable internal environment, in response to both internal and external conditions.

Question 2

1st Condition: Temperature

Answer 2

Low temperatures slow down metabolic reactions; and at high temperatures proteins (enzymes) are denatured.

Question 3

2nd Condition: Concentration of Glucose in the Blood

Answer 3

Glucose is needed for respiration, so lack of it causes respiration to slow or stop, depriving the cells of an energy source; too much glucose may cause water to move out of the cell by osmosis, again disturbing the metabolism of the cell

Question 4

3rd Condition: Water Potential of the Blood

Answer 4

If the water potential decreases, water may move out of cells by osmosis, causing metabolic reactions in the cell to slow or stop; if the water potential increases, water may enter the cell causing it to swell and maybe burst

Question 5

Metabolic Waste

Answer 5

Carbon dioxide and Urea

Question 6

Negative Feedback

Answer 6

A process in which a change in some parameter (e.g. blood glucose concentration) brings about processes which return it towards normal

Question 7

Excretion

Answer 7

It is the process by which animals rid themselves of waste products and of the nitrogenous by-products of metabolism.

Question 8

Excretory Organs

Answer 8

Lungs and Kidnyes

Question 9

Lungs

Answer 9

Carbon Dioxide

Question 10

Kidneys

Answer 10

Nitrogenous waste, water, salts, toxins, hormones, drugs

Question 11

Liver

Answer 11

The liver breaks down many subtrances in the blood, it recieves blood from two sources, the hepatic artery — delivers blood from the heart, and the hepatic portal vein — delivers blood from intestine. These two sources fill the liver with nuterients which are yet to be stored, processed and sorted.

The blood received from the intestines include carbohydrates, fats, along with other nutrients dissolved in it. They can be processed in different ways.
1. In the case of carbohydrates, the liver breaks them down and converts them into sugar which the body can use for energy.

Sometimes the liver has left over nutrients it doesnt immedietely require, so the liver holds them back and stores them for future cases in which it needs them.

The liver contains toxins and byproducts it does not need, so when it spots usless and toxic substances it either, converts them into something that cannot harm the body, or send them to the kidneys so they can be excreted.

The liver produces blood plasma which transports fatty acids, and helps form blood clots as well as cholestrol that help create hormones.

The livers most vital product is bile, the liver has hepatocytes which convert toxic substances and by products into a green liquid — bile. Bile helps with excreting toxic substances from the liver out from the body.

It is also the site of deamination

Question 12

What is deamination? How is urea formed

Answer 12

Deamination is the process in which, the nitrogen containing part of the amino acid (NH2) is removed and then converted into Ammonia (NH3) which is quite toxic and harmful to the body, so its then converted into urea which is sent to the kidneys for excretion.

Question 13

The role of the liver in the assimilation of amino acids by converting them into proteins

Answer 13

Amino Acids are obtained from the digestion of dietary proteins. After absorption, these amino acids are sent to the liver from the small intestine through hepatic portal vein.

The liver uses these amino acids to synthesize essential proteins such as enzymes, hormones and plasma proteins (fibrinogen).
These proteins are then used by the body for growth, repair, and maintaining homeostasis.
The liver stores temporarily and redistributes them if they were required.

The amino acids that are required assimilate back into the blood stream, while excess goes through the process of deamination.

Question 14

Main Function Of Kidney

Answer 14

It filters blood, and removes waste products, the main one being Urea. Which is made by the process of deamination.

It also Regulates levels of essential things such as water and ions.

It reabsorbs all glucose, some salts, and most water.

Removes Nitrogenous waste, as well as urea, excess salt, excess water, and toxins.

Question 15

Organ that stores urine

Answer 15

Bladder

Question 16

Tube that carries urine out of the kidney

Answer 16

Ureter

Question 17

Blood vessel with low concentration of urea

Answer 17

Renal vein

Question 18

Blood vessel with low concentration of CO2

Answer 18

Renal Artery

Question 19

Tube that carries urine out of the body

Answer 19

Urethra

Question 20

The Renal Artery

Answer 20

It is the blood vessel that controls blood flow into your kidney, it brings blood from the heart at high pressure.

Question 21

The Renal Cortex

Answer 21

It is the outer part of the kidney, where your nephrons begin

Question 22

The Renal Medulla

Answer 22

It is the inner part of the kidney, which contains most of the nephrons with their glomerulus and renal tubes except for the PCT and DCT

Question 23

The Renal Pelvis

Answer 23

It collects urine and passes it down through two ureters. Where it is collected in the bladder and stored.

Question 24

The nephron

Answer 24

They are the filtering units of the kidney. Each nephron contains a filter called the glomerulus, and a tubule. The glomerulus filters blood, and turns it into filtrate, while the tubules reabsorb substances from the filtrate.

Question 25

Golemerulus

Answer 25

Form: Its a ball of capillaries that are one cell thick and have pores. Its basically like a network of capillaries. Function: It provides blood at high pressure, and a large surface area with its extensive capillary network, increasing SA for filtration. High pressure forces small or soluble molecules like salt, urea, water, glucose, and amino acids out of the blood through the capillary walls into the bowman's capsule, forming a filtrate. Large or Insoluble molecules are kept in the blood in. the glomerulus.

Question 26

Proximal Convoluted Tubule

Answer 26

Its a cell line tubule with a high concentration of mitochondria, and a brush border of microvilli. It is the longest part of the renal tubule. It is responsible for reabsorption of almost all glucose and amino acids, some salts and most water. Reabsorption of substances from the filtrate in accordance with the needs of homeostasis.

Question 27

Loop Of Henle

Answer 27

It is a U shaped portion of the renal tubule. The descending unit of the loop is where reabsorption of water occurs by osmosis into the medulla. The ascending unit of the loop is where reabsorption of salts occurs by active transport into the medulla.

Question 28

How do tubules enable the excretion of salts?

Answer 28

The kidney tubules enable the excretion of salts by filtering blood in the glomerulus, where small molecules like salts pass through the pores in the capillary walls into the Bowman's capsule, while larger molecules like proteins and blood cells remain in the blood. Some of the filtered salt is reabsorbed back into the bloodstream in the tubules through active transport or diffusion, depending on the body's needs. Excess salt that is not reabsorbed remains in the filtrate and is eventually excreted in urine, ensuring the regulation of salt levels in the body.

Question 29

Explain why urine tests are a good indicator of how much salt has been consumed

Answer 29

The kidneys regulate the body's salt balance, when a lot of salt is consumed than needed, the excess is filtered out and removed from the body through urine. Some salt is reabsorbed back into the blood, but the remaining amount reflects dietary intake, making urine a good source for measuring salt intake.

Question 30

The cells that line the kidney tubules absorb many compounds from the filtrate, explain how the cells are adapted to absorption

Answer 30

Firstly, they have microvilli, which allows for a larger surface area which facilitates diffusion, allowing substances to move against the concentration gradient. There is also a large amount of mitochondria, to supply the amount of energy needed for active transport by aerobic respiration. Active transport is essential for moving substances against a concentration gradient, and this process is supported by carrier proteins in the cell membrane.

Question 30

Describe how salts are reabsorbed against a concentration gradient

Answer 30

Salts are reabsorbed against the concentration gradient by active transport. This process moves salts from an area of low concentration in the tubules, to an area of high concentration in the blood. This movement occurs in the cell membrane through channels. Active transport requires energy, which is used from respiration. This energy is important to facilitate the movement of salts against their concentration gradient ensuring salts are reabsorbed back into the blood stream.

Question 31

Explain the importance of excretion, limited to the toxicity of the urea.

Answer 31

Excretion is crucial for maintaining a bodys internal environment, if accumulated it could disrupt normal physiological factors. This process ensures that waset substances are effectively eliminated. Urea, if accumulated could significantly harm the body, so it is essential for the urea to be excreted to prevent toxic substance buildup, and to maintain a balanced amount of nitrogen in the blood