homeostasis

• Homeostasis is the regulation of internal conditions of a cell or organism to maintain optimum conditions for function in response to internal or external changes
• homeostasis consists of automatic control systems that make sure the internal conditions stay as constant as possible
• receptor cells detect changes in the environment ( internal or external )
• A change in the environment is called a stimulus
• the receptor cells pass information to the coordination centre
• Coordination centre - brain , spinal cord , pancreas
• coordination centre recieves and processes information sent by receptor cells and they decide appropriate response
• effectors carry out the response
• Coordination centre send instructions to the effectors to carry out the response.
• central nervous system is brain and spinal cord
• Response is normally muscle contracting or a gland that secretes hormones
• The chemical released from synapse triggers a response in motor neurone which passes impulses to an effector
• reflexes are not controlled by the brain
• Endocrine system uses chemicals called hormones which are carried in the blood
• endocrine system has a slower longer lasting effect
• pancreas release's hormones that control glucose levels
• ovaries and testes release reproductive and puberty hormones
• thyroid gland regulates basal metabolic rate and growth
• adrenal glands release adrenaline when the body is under stress
• pituitary gland releases a number of different hormones into the blood depending on conditions
• pituitary glands act on other glands
• if blood glucose levels rise this is detected by the pancreas
• the pancreas releases insulin which is a hormone
• insulin triggers body cells to take up all the glucose
• insulin triggers muscles and the liver to store glucose as glycogen
• glucagon triggers cells to turn glycogen back into glucose
• if the blood water concentration is too high the kidneys remove the excess water
• urea and excess ions are also removed in urine
• we lose water through sweating peeing and exhaling
• blood enters the kidneys through the arteries
• the kidneys removes urea excess ions and water from the blood that enters through the artery
• the excess waste leaves the kidneys as urine and is stored in the bladder
• the urea free blood leaves the kidney through a vein
• blood passes through capillaries and small molecules are filtered out of the blood. After the blood passes through a tube and reabsorbs all of the glucose and some of the water and ions. This is selective absorbtion
• liver breaks down excess amino acids into ammonia and this is called deamination
• urea is less toxic than ammonia so it can be safely removed from the body
• urea is made of amino acids that are stored as fats and carbs
• kidneys regulate amount of water and ions
• in kidneys there are nephrons
• as blood passes through the kidneys the tubules will absorb anything small