Homeostasis and Excretion

• Homeostasis


  It maintaining a constant internal environment
• Osmoregulation


  The proces of maintaining water and salt concentrations across membranes within the body
• Thermoregulation


  Maintaining the optimum temperature (36 degrees Celsius)
• Excretion


  removal of metabolic waste
• What is urea?

  Nitrogen waste
• Where is urea excreted?

  Kidney where it is filter out to produce urine and Skin through sweat
• Where is CO2 excreted?

  Lungs when breathing out
• What is urine made up of?

  Water, urea and salts(sodium ions and chloride ions)
• structure of kidney

  
• cortex


  outer layer of the kidney which contains capillaries that branch from the renal artery and microscopic filtering units called nephrons
• renal pelvis


  Collects urine from nephrons passes to the ureter
• Medulla


  Area contains collecting ducts leading from nephrons
• renal artery

  brings blood to the kidney
• renal vein


  takes blood away from the kidney
• Ureter


  takes urine from kidney to bladder
• Structure of nephron

  
• How nephrons work

  -Blood arrives from renal artery and enters the glomerulus (ball of capillaries)

  -Small molecules leave the glomerulus and enter the Bowman's capsule by ULTRAFILTRATION

  -The filtrate moves down the nephron

  -After this the process of SELECTIVE REABSORPTION occurs

  -This is when specific molecules glucose, water and sodium and chloride ions are absorbed

  -Glucose is absorbed in the first convoluted tube and is done by active transport because its useful for respiration

  -Water is reabsorbed via osmosis in the first convoluted tube, collecting duct and loop of Henle as it helps maintain a constant water content of the blood

  -Protein molecules are not absorbed as they are too big to be filtered so just remain in blood at all times

  The amount of water reabsorbed depends on how much water the body needs.
• What is ADH?

  antidiuretic hormone which controls the concentration of urine
• What happens in the process of ADH?

  -The hypothalamus (receptor in the brain) detects the conc of the blood

  -The pituitary gland in the brain release more ADH if the blood is too concentrated and vice versa

  -The ADH travels in the blood to the kidneys and cause the collecting ducts to become more permeable

  -If the blood is too concentrated then more water is reabsorbed into the blood from the nephron so urine becomes more concentrated

  -The brain will release less ADH if the blood becomes too dilute. This is an example of NEGATIVE FEEDBACK

  -Because of ADH, the level of water in the internal environment is kept constant
• negative feedback


  The response that reverses or cause the opposite effect of the original stimulus
• Homeotherm


  an animal with a constant body temperature
• Why is the constant internal body temp important for enzyme activity

  If too cold that enzyme won't work fast enough but if too hot enzyme will departure
• How does the body monitor body temp?

  -The thermoregulatory part of the hypothalamus sense the temp of the blood flowing through it

  -Temperature impulses send the hypothalamus info via electrical impulses

  -If body temp starts to change then the hypothalamus triggers a response which brings it back to 36.9 degrees C

  -First response is to change our behaviour but if that doesn't work that it can be regulated by physiological means
• vasoconstriction

  -If blood temp is to low than the body will stop producing sweat

  -less heat lost due to evaporation

  -Blood vessels close to skins surface because they become narrower to reduce heat lost to radiation
• vasodilation

  -If body is too hot, the heat sensitive receptors in the hypothalamus detect this via blood temp

  -To lose heat the body produces sweat which takes heat energy away from the body when it evaporates

  -Blood vessel widen on the surface of the skin to allow more heat to radiate from the body
• What does your body do in a hot environment?

  -Produces sweat via the pores

  -Hairs lie flat

  -Blood vessel near the surface of the skin get wider
• What does your body do in a cold environment?

  -Hairs stand on end

  -Our muscles shiver/ metabolism speeds up

  -Blood vessel get narrower
• skin diagram

  
• What is the endocrine system?

  The endocrine system is the collection of the glans in the body produces hormones
• What is hormones?

  They are chemical messengers secrets from the glands
• What do hormones do?

  Hormones travel in the blood to a target organ and cause a response. They also control many aspects of life processes
• What hormones does the Pituarity Gland release and what are their roles

  -ADH - controls the amount of water in the blood

  -Luteinising Hormone - Stimulates egg release in females/testosterone production in males

  -Follicle Stimulating Hormone - Stimulates egg development/sperm production
• What hormones does the Thyroid Gland release and what are their roles

  -Thyroxine- controls the body's metabolic rate
• What hormones does the Pancreas release and what are their roles

  -Insulin - lowers blood glucose levels

  -Glucagon - Raises blood glucose levels
• What hormones does the Adrends Gland release and what are their roles

  -Adrenaline - prepress the body for physical activity
• What hormones does the Testes Gland release and what are their roles

  -Testosterone - Control development of secondary sexual characteristics in males
• What hormones does the Ovaries Gland release and what are their roles

  -Oestrogen - Controls development of female secondary characteristics

  -Progesterone - Regulates the menstrual cycle
• What happens when your glucose level rises (eat food)

  Insulin is produced by the pancreas causes liver to change glucose to glycogen
• What happens when your Glucose level falls (excretion)

  Glucagon produced by the pancreas is released which causes the liver to convert glycogen back to glucose
• What is diabetes?


  A long life condition where the pancreas docents produce enough or any insulin or the insulin doesn't work properly. Increased amounts of glucose in the blood