bio 2

• Homeostasis


  The maintenance of a constant internal environment
• Stimulus


  A change in your environment than requires a response. e.g Light, sound, touch, pressure, pain, chemical or temperature
• Receptors


  Detect the stimulus or change in environment
• After the receptors


  Receptors send messages to the CNS via the sensory neurone
• Central nervous system (CNS)


  The brain or spinal cord
• Effector


  Muscles or glands that bring about a response
• Muscles and glands in response to stimuli

  Muscles contract and glands secrete chemical substances(hormones)
• Sensory neurone


  A neurone that carry information from the receptors to the CNS
• Relay neurone


  Neurones that carry impulses from the sensory neurone to the motor neurone
• Motor neurone


  Neurones that carry information from the CNS to the effectors
• Nervous system


  It is a system that allows you to react to your surroundings
• How signals travel across a synapse


  The chemical or neurotransmitter diffuses across the synapse and binds to a complementary receptor on the neurone (postsynaptic). This causes an electrical impulse to travel down the next neurone
• Synapse


  A gap between two neurones
• Thermoregulatory centre of the brain


  Near the hypothalamus, monitors the temperature of blood
• Stages in a reflex arc

  Stimulus->Receptor->sensory neurone->CNS (relay neurone) -> motor neurone -> effector -> response
• Responses that reduce body temperature

  • Hairs lie flat, sweat and blood vessels get wider(vasodilation)
• Vasodilation


  The blood vessels supplying the skin dilate (widen). This helps to transfer energy to the environment
• Responses that increase body temperature

  • Hairs stand up, no sweat, shivering and blood vessels constrict(vasoconstriction)
• Vasoconstriction


  The blood vessels supplying the skin constrict to close off the skins blood supply
• The body's core temp is 37 degrees Celsius
• Hormones


  Chemical messengers that travel in the blood to target organs
• Thyroid gland


  Produces thyroxine which is involved in regulating metabolism
• Adrenal glands


  Produce adrenaline which is used to prepare the body for fight or flight
• Role of the pancreas

  Produces glucagon and insulin which are involved in regulating glucose levels in the blood
• Insulin


  The hormone released if blood sugar is too high
• What insulin does

  It makes the liver convert glucose into glycogen. This causes blood glucose levels to decrease
• Glucagon


  The hormone released if blood sugar is too low
• What glucagon does


  It makes the liver convert glycogen to glucose. This causes the blood glucose level to increase
• Type I diabetes


  When the pancreas produces little or no insulin
• Type II diabetes


  When a person becomes resistant to their own insulin. Being overweight can increase your chances of type II diabetes
• How type I diabetes can be treated

  Insulin injections, limiting intake of foods rich is simple carbohydrates e.g. sugars and regular exercise
• How type II diabetes can be treated

  It can be controlled by eating a carbohydrate controlled diet and getting regular exercise
• Role of the kidneys


  Kidneys make urine by taking unwanted waste products out of your blood. They are involved in selective reabsorption
• Things reabsorbed by the kidneys into the blood


  • Glucose, water and ions
• Deamination


  Proteins (excess amino acids) cannot be stored by the body. Excess amino acids are converted to fats and carbohydrates. This occurs in the liver
• Waste product of deamination

  Ammonia is produced as a waste product. Ammonia is toxic so it is converted into urea in the liver
• ADH


  The hormone that controls the amount of water absorbed by the kidneys
• When the concentration of water in the blood is too low


  Receptors in the hypothalamus detects the water content is too low. The coordinator in the brain receives the information and coordinates a response. The pituitary gland produces MORE (Anti-diuretic hormone) ADH, which makes the kidney tubule MORE permeable. This means that MORE water is reabsorbed into the bloodstream. The kidneys produce a small volume of concentrated urine
• When the concentration of water in the blood is too high


  Receptors in the hypothalamus detects the water content is too high. The coordinator in the brain receives the information and coordinates a response. The pituitary gland produced LESS ADH, which makes the kidney tubule LESS permeable. This means that LESS water is reabsorbed into the bloodstream. The kidneys produce a large volume of dilute urine
• How a dialysis machine works


  In a dialysis machine the patients blood flows between a partially permeable membrane surrounded by dialysis fluid. The dialysis fluid contains the same concentration of dissolved ions and glucose as healthy blood. This means they won't be lost from the blood during dialysis. Only wastes such as urea and excess ions and waters diffuse across the barrier