homeostasis 5.1

• homeostasis is the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes
• enzymes, pH and temperature all need to be controlled
• temperature needs to be approx 37 degrees to maintain optimum temperature for enzymes as they denature at too high temperatures and work too slowly at low temperatures
• pH levels need to be 7.4 in the blood because enzymes denature if pH is increased or decreased too far away from the optimum pH
• blood glucose concentration needs to be controlled because glucose is needed as the main substrate for respiration to provide energy for metabolic processes
• water levels of blood need to prevent water movement into or out of cells by osmosis, too high means the water moves into cells, causing them to lyse (burst), too low means the water moves into cells, causing them to plasmolyse
• ion concentrations of blood (Na+) need to be controlled because water will move into or out of cells by osmosis if this is incorrect, too high- water moves out of cells, causing them to plasmolyse, too low, water moves into cells causing them to burst
• concentration of waste materials (eg CO2, urea) are usually poisonous and need to be removed from the body before they build up to toxic levels and cause damaged cells
• CO2 is produced by cells during aerobic respiration
• when CO2 is dissolved, it forms an acidic solution, so it needs to be removed as it would affect the activity of enzymes
• CO2 diffuses into the blood at tissues and is removed from the body at the lungs
• inhaled air contains 0.04% CO2 and exhaled air contains 4% - so blowing out through a straw into limewater, will turn it milky/ cloudy
• urea is produced in the liver from the breakdown of excess amino acids, which cannot be stored or used for energy
• the amine group is removed and converted into urea, but this is poisonous and would damage cells if levels built up
• urea is filtered from the blood by the kidney and removed from the body in urine, along with excess salts and water
• organisms need to be constantly monitoring the internal and extrenal environment
• the two types of automatic systems are the nervous system (responses) and the hormonal system (chemical/enzyme)
• the two types of automatic systems are the nervous system (responses) and the hormonal system (chemical/enzyme)
• receptors detect changes in the internal/ external environment (called stimuli)
• coordination centres- receive and process the information from the receptors, and then coordinate the response - examples include the brain, spinal chord and organs
• effectors are the muscles or glands which bring about a response