biology

• Homeostasis


  The regulation of a constant internal environment. The conditions are maintained to ensure optimum conditions for metabolism and changes in response to both internal and external fluctuations.
• Homeostasis regulates


  • Blood glucose (sugar) levels
  • Body temperature
  • CO₂ levels
  • Water levels
• Homeostasis control systems


  • Nervous responses (coordinated by the nervous system)
  • Chemical responses (coordinated by the endocrine system)
• Stimulus


  Information about the environment detected by a receptor
• Homeostasis process


  1. Stimulus detected by receptor

  2. Information processed by central coordination system

  3. Response initiated by effector
• Synapse


  The gap where the ends of two neurons meet
• Neurotransmitters


  Chemical messengers that transmit information across the synapse
• Synapse process


  1. Electrical impulse arrives at neuron terminal

  2. Neurotransmitters released into synapse

  3. Neurotransmitters bind to receptor sites on next neuron

  4. Nerve impulse created in second neuron
• Nervous pathway


  • Stimulus received by receptor
  • Electrical impulse along sensory neuron to CNS
  • CNS coordinates response
  • Electrical impulse along motor neuron to effector
  • Effector carries out response
• Receptors


  • Rod and cone cells in eye
  • Cells in skin responding to pressure or temperature
• Effectors


  • Muscles
  • Glands
• Endocrine System


  System of glands that produce and secrete hormones into the bloodstream
• Major glands of the endocrine system

  • Pituitary
  • Thyroid
  • Parathyroid
  • Adrenal
  • Pancreas
  • Ovaries
  • Testes
• Hormones


  Chemical messengers transported in the bloodstream to an effector where they can activate a response
• Hormones


  Similar job to neurons of the nervous system but with differences
• Hormones


  • Released from glands around the body which make up the endocrine system
  • Travel in the blood plasma to their target cells and affect only those certain cells
  • Act on organs or cells where constant adjustments are made to maintain a stable state
• Hormones produced by the pituitary gland

  • FSH
  • LH
• Pituitary gland


  Acts as a master gland because many of the hormones it releases control and coordinate the release of other hormones from other glands in the body
• Type 1 diabetes


  Disorder affecting the pancreas where it does not produce enough insulin to control the blood sugar level
• Type 2 diabetes


  Disorder of effector cells which no longer respond to the hormones released from the pancreas
• Risk of developing type 2 diabetes

  Higher in people who are obese (have a BMI >30)
• Oestrogen


  Main reproductive hormone in females, produced in the ovaries, increases during puberty and stimulates an egg to be released from an ovary each month (ovulation)
• Testosterone


  Main reproductive hormone in males, produced in the testes, stimulates the production of sperm
• Reflex arc


  Begins with a stimulus, detected by receptor cells, transmits an electrical impulse along the sensory neuron, passed through relay neurons in the spinal cord or brain, response coordinated automatically and sent along the motor neuron to the effector cells
• Reflex


  Fast and automatic response to a particular stimulus which may be harmful to the organism, no conscious thought or process to deliver the response (involuntary action)