(I)GCSE 2.77 c) Osmoregulation

- Regulation of body water content = Homeostasis

 - Homeostasis is maintaining constant conditions

- Regulation is of body water content, largely making up Plasma and Tissue Fluids

- Homeostasis of water body content = OSMOREGULATION

- Major receptor in water body content = hypothalamus of the brain

- Stimulus to Hypothalamus = blood

- Effector = kidney

- Output of kidney = filtered blood

(I)GCSE 2.77 b) Thermoregulation

- Negative feedback loop = control and maintaining constant conditions

- Co-ordinator = body temp of 37 - 38 d.c.

- Receptor of body temperature = Hypothalamus of the brain

- Hypothalamus responds to temperature of the body/ blood

- Change in temperature brought about by receptor = skin

- Response = increase/ decrease in body temperature

(I)GCSE 2.76 Sensitivity

- Organisms are able to respond to changes in the environment. 

- MRS. NERG S = Sensitivity

- Sensitivity = characteristic when organisms respond to changes in the environment.

Types of changes in the environment: 

: light level 

: temperature 

: pressure level 

:chemicals 

- Organisms are required to have receptors in order to detect the changes.

- Organisms have effecters such as muscles or glands to respond.

- Response show that organisms are able to survive the changes in the environment. 

(I)GCSE 2.69 Urinary System

- Each kidney (left and right) would have its own blood supply carrying out the process of excretion and flitration. 

- Ureter = tube carrying the urine from the kidney to the bladder.

- Urine is excreted through the Urethra down through the vagina or penis. 

(I)GCSE 2.68 b) Osmoregulation

How the kidney carries out its roles of Osmoregulation

- The tissue layers surrounding each cell must be isotonic with the cytoplasm of the cells. This means that the amount of water going into and out of the cell is equal and the cells will remain the same size shape and function. 

- The danger to the tissue is the blood circulating into the tissue would be concentrated - causing a hypertonic tissue fluid. 

- It could also be very dilute causing a hypotonic tissue fluid.

- Both hypertonic and hypotonic tissue fluids are undesirable - Hypertonic removes too much water

                                                                                         - Hypotonic adds too much water

- The tissue fluid is Isotonic to the cell cytoplasm by controlling the composition of blood - blood controls the tissue fluid. 

- It is the job of the kidney to control the composition of our blood.

By controlling the content of water and salts in the blood, the kidney can keep the blood and therefore the tissue fluid Isotonic with the cells cytoplasm, maintaining the function of the cells. 

(I)GCSE 2.68 a) Excretion

How kidneys carry out its roles of excretion and osmoregulation.

- Urea contains Nitrogen which is toxic to the body and cannot be stored. 

- The original form of Nitrogen circulating in our blood stream are the Amino Acids.

- Amino acids are normally used for growth but extra amino acids must be removed - TOXIC this is the rule of both the liver and the kidneys. 

1. Blood circulates to the liver and the amino acid is broken down into molecules called the Urea. 

2. It then circulates to both of the kidneys. 

3. The kidneys will then filter the Urea from the bottom and the Urea will be added with water to form Urine. 

4. Urine will drain down the orators to collect down in the bladder.

5. Urea is now in the bladder in the form of Urine - it is removed from the body.

6. The filtered blood returns to the circulation with the toxic amino acids and urea removed. 

This is an example of excretion.  

(I)GCSE 2.67 b) Human Organs of Excretion

- Lungs, kidneys, and skin are organs of excretion. 

- Lungs excrete Carbon-dioxide

- Kidneys excrete Excess Water; Molecule Urea - hydrogen waste from amino acids; Salts 

- Skin excretes Water and Salts through sweat; Urea