2.75 - Urine

- Role of brain influencing the kidneys 

- Filtration of blood in the kidneys 

- Resulting in the waste going into the bladder and coming out as urine 

Urine contains - Salt, H2O and Urea

- Salt and H2O affected the composition of the tissue fluid - Osmoregulation 

- Removal of urea - part of the process of excretion of metabolic waste

- composition of Urine varies - depends on the condition of which the person is operating

2.74 - ADH.

ADH - Anti Diuretic Hormone 

Produced in the Hypothalamus (a part in the brain) - flows through the blood stream to it's target (the kidney)

- ADH - controls and alter the composition of water in blood - more or less concentrated

- Tissue is isotonic with the cytoplasm of the cell

ADH - targets the collecting duct (more accurate then kidney) 

- It allows more water to come out of the collecting duct 

- Collecting Duct - where water is selectively reabsorbed into the blood 

- possible to increase the amount of water going into the blood by adding the hormone, ADH

- It makes the collecting duct walls more porous - so that more water can escape from the collecting duct - this water goes back into the blood 

- consequence of ADH secretion - Urine coming out will be more concentrated and will have a lower volume 

- ADH response to a hot day 

- ADH response to a cold day 

- ADH response to dehydration

2.73 - Glucose re-absorption

Selective re-absorbtion means the molecule is selected (glucose) and re-absorbtion means it will go from the glomereule filtrate back into the blood

- filtration occurs in Bowmans capsule - contains glucose (in the plasma, along with H2O, Salt and urea) 

- end of nephron is where the Urine comes out - does not contain glucose 

- If you have glucose in your urine - it means you have diabetes

- Proximal Convoluted Tubule - glucose is removed and taken back into the blood 

2.72 - Water re-absorption

- In the Bowmans capsule - Ultrafiltration takes place 

- When filtration occurs, it filters out too much water

- As filtrate passes along the tube and reaches Collecting Duct 

- As it passes through the Collecting Duct - water is removes from the filtrate. 

- It goes back into the blood stream 

- Water has been selected and reabsorbed into the blood - Selected reabsorption 

2.71 - Ultrafiltration

Nephron of the kidney (shown) - carries out filtration of blood 

two things : Filtered blood (clean blood) and waste blood, Urine

Urine emerges from bottom of tubule - Composed of H2O, Salts and Urea(nitrogen waste) - goes into pelvic region

Bowmans capsule - where filtration begins - Ultrafiltration 

Filtration begins when blood comes in the Afferent arteriole (high pressure - wide) 

- starts to branch into twists and coils - Glomerulus 

- Blood vessel coming out - Efferent arteiole (smaller diameter) - develops high pressure 

- High pressure forces the liquid in blood (Plasma) out of the blood vessel into the inside of the Bowmans capsule

Plasma - H2O - Salts - Amino Acids - Glucose - Urea

When it is the bowmans capsule it is called Glomerula filtrate (contains plasma) 

Blood has been filtered by pressure due to the smaller diameter arteriole, generating a high pressure in the glomerulus, forcing the liquid into the tube

2.70 - Nephron Structure

Branch of Aorta taking blood into the kidney is called the Renal Artery 

Kidney filters the blood

Contents which are removed are called Urine (through Ureter) - collects in Bladder

Filtered blood goes through the Renal Vein 

Out region - Cortex

Inner region - Medulla

The Space - Pelvic region - where the urine collects and drains down the ureter

Different colour because the kidney is made up of millions of tubes

Tube starts on the edge of the medulla and goes out into the cortex, then winds and then drops down to the medulla again, then winds and comes to a dead end. 

The dead end is called the Bowman's capsule. 

The tube structure is called a Nephron

Above the dotted line - Cortex 

Below the dotted line - Medulla

Twisted sections - Convoluted tubules 

The dip - loop of Henlé 

Dead end cup shape structure - Bowman's Capsule 

Tight knot of blood vessels - Glomeruloui

First twisted section - Proximal convoluted tubules (PCT) 

Second twisted section - Distal convoluted tubules (DCT)

This nephron structure is what gives the different colours - millions of them

2.69 - Urinary system

- 2 kidneys (left and right) - both have separate blood supply - carry out excretion, filtration and osmoregulation

- from each kidney there is a tub from the kidney to the bladder - the Ureter

Ureter carries urine from the kidney to the bladder

- common bladder  for both ureters - urine is conducted to the outside of the body through the urethra down through the vagina or through the penis 

2.68b - Osmoregulation

osmo - osmosis
regulation - to control
osmoregulation - control of blood composition


cells in the tissue fluid are isotonic with the cytoplasm of the cells - means water going in and out of cells is equal (maintain size and function)


danger to tissue - blood circulating into the tissue would be concentrated causing a hypertonic tissue fluid (remove to much water) or a hypotonic tissue fluid (add to much water)


need to control - achieved by controlling the composition of the blood
kidney controls the composition
excess salts and water is excreted in the kidney so this controls the blood


this maintains the cells functions

2.68a - Excretion

excretion of Urea - Nitrogen is toxic to the body so it cannot be stored and must be excreted

original form of nitrogen in blood stream is amino acids

amino acids are usually used for growth but if there is extra (excess) they must be removed - rule of both liver and kidneys

- blood circulates to the liver and amino acids are converted into Urea

- it then re-enters the body and circulates to the kidneys.

- Kidneys then filter the Urea from the blood and the Urea is then added to water to form Urine which then travels down the Ureter

- Then collected in the bladder (form of Urine) - filtered blood then goes back to veins with toxic Urea removed

2.67b - Human organs of excretion

1. Lungs - metabolic waste is carbon dioxide - from respiration

2.  Kidneys - excretion of excess water, molecule Urea (nitrogen waste from amino acids) and Salts

3. Skin - excretion of water and salts as sweat and very small amounts of Urea

2.67a - Excretion in plants

Photosynthesis - leaf absorbs light energy and in this process it combines CO2 with water to form glucose and oxygen (given off as waste molecules)

CO2 + H2O ---> C6H12oO6 + O2 -> excretion

Respiration - glucose and oxygen (aerobic resp.) through enzyme reactions the glucose is broken down and forms ATP , water and carbon dioxide (as waste)

- Carbon dioxide is a metabolic waste - excretion

C6H12oO6 + O2 ---> ATP + CO2 + H2O

3.31 - Evolution

- Evolution : change in the form of organisms or change in the frequency (how many) of alleles

- Natural selection is the mechanism of evolution - Charles Darwin 

- S.A.- causes infections of the lung and skin infections 

 - Evolving S.A. 

the normal form of S.A is suceetable to being killed my methecilline (Anti-biotic)

- represented in first graph - MSSA 

- random mutation to the geno of S.A - characteristic of 'breaking down methecilline' - no longer killed by the anti-biotic - resistant form 

- represented in second graph - MRSA 

- 2 forms of the bacteria - different forms is definiton of evolution 

- when antibiotics applied to the population, MSSA is decreased and MRSA is increased (common) 

- increase in the frequency of the allele for resistance (evolution)

2 features: 

- Random mutation - MRSA

- non-random selection - antibiotic - MRSA to survive and MSSA to be selected and killed

- These are Natural selection - a process and not a thing

3.33 - Antibiotic Resistance

- bacterial population = staphlococcus aureus - causes skin infections and lung infections 

- when infected, can be treated with Methecilline (antibiotic) - kills the S.A.

- Type of S.A that is killed my Methecilline is the Susceptable form 

- Methecilline Susceptable Staphlococcus Aureus (MSSA) = called 

- random mutation to the geno of S.A. so when the methecilline was applied, the bacteria did not die. = resistant form 

- Methecilline Resistant Staphlococcus Aureus (MRSA) 

- increasingly survives -> becomes more common -> serious problem in hospitals because the antibiotic no longer works

3.32 - Type of Mutation

- Gene ---mutation---> new alleles 

- new alleles are responsible for the phenotype - could be beneficial or harmful or no effect (neutral) 

- Beneficial - improve efficiency of enzymes 

- Harmful - leads to the formation of an enzyme that doesn't work (non-functional) 

- Neutral - may not last forever and with environmental change it can become beneficial or harmful

3.30 - Mutation

- Gene - Allele

- certain processes can cause a change in the base sequence 

- change creates a new version of the allele 

- possible for second allele to create a different protein and have a different effect on the phenotype 

- Allele A and Allele a - exist because of the process mutation 

- mutation changes the base sequence of the gene

3.29 - Species Variation

Variation = difference in the phenotypes of individuals. 

- you can measure the difference and show them in graphic form 

- individual has a phenotype = because of genotype + environment

- variation in a population is the variation in all individuals 

- Vpop. = variation in genotype and variation in environment 

- surviving and living in different environments 

1.

- different classes or groups 

first graph shows variation in population = variation in genotypes (no environment playing a role) - example: Blood groups A, AB, O, B 

2.

second graph shows variation in population/species  = variation in the genotype + modified by environment (third graph) - example: height in humans...one might inherit genes for a height but it would be modified by quality of diet etc. 

- continuous variation

3.

- variation in a population/species = entirely environmental variation 

- genes have no role to play in the differences we see in a population 

- example: home language 

- cannot be inherited