Paper 2 AQA GCSE Biology

• What is homeostatsis?

  The maintenance of a constant internal environment.
• What is a stimulus?

  A change in your environment than requires a response. e.g Light, sound, touch, pressure, pain, chemical or temperature.
• What do the receptors do?

  Detect the stimulus or change in environment.
• What happens after the receptors?

  Receptors send messages to the CNS via the sensory neurone.
• What makes up the central nervous system?

  The brain or spinal cord

  
• What is an effector?

  Muscles or glands that bring about a response.

  
• What do the muscles and glands do in response to stimuli?

  Muscles contract and glands secrete chemical substances(hormones).
• What is a sensory neurone?


  A neurone that carry information from the receptors to the CNS.

  
• What is a relay neurone?


  Neurones that carry impulses from the sensory neurone to the motor neurone.
• What is a motor neurone?


  Neurones that carry information from the CNS to the effectors.

  
• What is the nervous system?

  It is a system that allows you to react to your surroundings.
• How do 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.

  
• What is a synapse?

  A gap between two neurones.

  
• What is the thermoregulatory centre of the brain?

  Near the hypothalamus, monitors the temperature of blood.

  
• Describe the stages in a reflex arc.

  Stimulus->Receptor->sensory neurone->CNS (relay neurone) -> motor neurone -> effector -> response

  
• Name responses that reduce body temperature.

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

  
• What happens during vasodilation?

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

  Hairs stand up, no sweat, shivering and blood vessels constrict(vasoconstriction)
• What happens during vasoconstriction?

  The blood vessels supplying the skin constrict to close off the skins blood supply.
• What is the body's core temp?

  37 degrees Celsius
• What are hormones?

  Chemical messengers that travel in the blood to target organs.

  
• Compare and Contrast the endocrine (hormone) system and the nervous system.


  Nervous is faster acting than the endocrine system.Hormones have longer lasting effects compared to electrical impulses. Nerves act on a very specific area whereas hormones act more general.
• What does the thyroid gland do?

  Produces thyroxine which is involved in regulating metabolism.

  
• What do the adrenal glands do?

  Produce adrenaline which is used to prepare the body for fight or flight.

  
• What is the role of the pancreas?

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

  
• Name the hormone that is released if blood sugar is too high.

  Insulin
• What does insulin do?

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

  
• Name the hormone that is released if blood sugar is too low.

  Glucagon
• What does glucagon do? HINT GLU-COSE-GONE

  It makes the liver convert glycogen to glucose. This causes the blood glucose level to increase.
• What is type I diabetes?

  When the pancreas produces little or no insulin.

  
• What is type II diabetes?

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

  
• How can type I diabetes be treated?

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

  It can be controlled by eating a carbohydrate controlled diet and getting regular exercise.

  
• What is the role of the kidneys.

  Kidneys make urine by taking unwanted waste products out of your blood. They are involved in selective reabsorption.

  
• Name three things that are re-absorbed by the kidneys into the blood.

  Glucose, water and ions.
• Name three things that are removed from the body in the urine.

  Urea, water and ions.
• What is 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.
• What is produced as a waste product of deamination?

  Ammonia is produced as a waste product. Ammonia is toxic so it is converted into urea in the liver.
• What hormone controls the amount of water absorbed by the kidneys?

  ADH
• What happens when the concentration of water in the blood is too low. I.e. the Blood is MORE concentrated.

  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.