B5

• Temperature and glucose levels fluctuate but only within small bounds
• Low temperature detected

  Receptors send signals to coordination centers, which then send signals to effectors like muscles for responses such as shivering
• Endocrine system is generally slower, longer-lasting, and more generalized than the nervous system
• Components of automatic control systems

  • Receptors
  • Coordination centers
  • Effectors
• Negative feedback


  Opposite response to changes in levels to maintain stability
• Automatic control systems

  Recognize changes from optimal conditions and send signals to reverse the change
• Automatic control systems maintain stable internal environment through negative feedback loop
• Homeostasis

  Maintaining a stable internal environment by regulating conditions inside the body in response to changes in both internal and external conditions
• Endocrine system relies on hormones released into the bloodstream to affect specific cells with the right receptors
• Automatic control systems

  • Receptors detect changes, coordination centers interpret changes and decide on actions, effectors carry out changes
• Negative feedback mechanism decreases levels when too high and increases levels when too low to maintain normal levels
• High temperature detected

  Receptors send signals to coordination centers, which then send signals to effectors for responses such as sweating
• Nervous system sends fast and precise electrical impulses through nerves for quick responses
• Homeostasis relies on a system of negative feedback, meaning whenever the levels of something get too high they're brought back down, and whenever the levels of something get too low, they're brought back up.
• Balance needed to keep blood glucose concentration not too high or too low
• Blood glucose concentration

  The amount of sugar in the bloodstream
• High blood glucose concentration can damage tissues
• Control of blood glucose concentration

  Controlled by the hormones insulin and glucagon in a negative feedback loop
• Response to high blood glucose levels


  Release of insulin by the pancreas, insulin binds to receptors on cells, cells take in glucose, liver and muscle cells combine glucose to form glycogen, blood glucose concentration decreases
• Response to low blood glucose levels


  Release of glucagon by the pancreas, glucagon binds to liver cells, liver breaks down glycogen into glucose molecules, glucose released into the blood, blood glucose concentration increases
• Insulin and glucagon ensure that blood glucose concentration is maintained around the right levels
• Insulin decreases blood glucose levels, while glucagon increases blood glucose levels
• Cells need a constant supply of glucose for respiration
• Insulin and glucagon

  Create a negative feedback loop to regulate blood glucose levels
• Breakdown of carbohydrates in intestines

  Carbohydrates broken down into glucose molecules, absorbed into the bloodstream, causing blood glucose concentration to increase
• Blood glucose concentration constantly changes due to the release of insulin and glucagon
• When blood glucose levels get too high, insulin is released from the pancreas into the bloodstream. This causes organs such as the liver and muscles to absorb glucose from the blood, and convert it into glycogen.
• People with type 1 diabetes have to inject insulin after meals because they don't produce it themselves. They also have to monitor their diets (for example not have too much sugary food), and also exercise regularly. 
• The menstrual cycle is a series of steps that prepares the uterus for the implantation of a fertilised egg.

  If there is no fertilised egg, then the cycle repeats.

  But if there is a fertilised egg, then the cycle will stop and the egg will implant into the uterus lining, where it can develop into a foetus. 
• menstrual cycle - stage 1

  Period of bleeding as the uterus lining breaks down
• menstrual cycle - stage 2

  Building up of the uterus lining 
• menstrual cycle - stage 3

  Release of the egg from the ovaries
• menstrual cycle - stage 4


  Maintenance of uterus lining 
• Which hormone stimulates the uterus lining to develop

  Oestrogen 
• stimulates the egg to be released during ovulation

  Luteinising hormone (LH)
• stimulates the egg follicle to mature

  Follicle stimulating hormone (FSH)
• Motor neurons

  • Carry impulses from the central nervous system to effectors (muscles or glands) to contract or release hormones
• Central nervous system

  • Made up of the brain and spinal cord, where thinking takes place, processes sensory information, and sends out orders to the body
• Nerve cell

  • Adapted to carry electrical impulses from one point to another, long, thin, with branch connections at either end
• Nervous system communication in large multicellular organisms like humans

  Requires two different organ systems: the nervous system and the endocrine system