Biology Paper 2

• Homeostasis is the maintenance of a constant internal environment.
• Homeostasis controls body temperature and blood glucose levels.
• Why is it important that the human body temperature remains constant at 37 degrees?

  To ensure that the enzymes within our body can work at their optimum.
• 3 ways water is lost from the body.

  Sweat (The skin), Exhaling (The lungs) , Urine (The Kidneys.)
• How can the body gain water?

  Eating , Drinking , Respiration
• What makes up the CNS?

  The brain and the spinal cord
• The Peripheral Nervous system PNS is nerves that carry information to or from the CNS.
• What does the nervous system allow us to do?

  React to our surroundings, Co-ordinate our behaviour.
• What is the main co-ordinator of the body?

  The Brain.
• What are the role of neurons (nerve cells)?

  Carry electrical impulses from one place to another.
• How have the nerve cells adapted for their function?

  They have long fibre (axon) which is insulated by a fatty Sheath.

  They have tiny branches (dendrons)
• what do receptors do?

  detect a change in the environment (Stimulus) and produce electrical impulses in response.
• what are examples of receptors?

  ears, eyes, skin
• what is an effector?

  A muscle or gland that carries out a response to a stimulus.
• what are the 3 different neurons?

  motor neuron, sensory neuron, relay neuron
• what is the role of a reflex action?

  way for the body to automatically and rapidly respond to a stimulus to minimise any further damage to the body.
• what is a synapse?

  A synapse is a junction between two nerve cells where chemical signals are transmitted rather than electrical impulses.
• what is reaction time?

  time between the presentation of a stimulus and the initiation of the muscular response.
• what factors can influence reaction time?

  age, gender, physical traits, fatigue, distraction, alcohol, diet
• what is a hormone?

  a chemical messenger secreted by a gland.
• where and why is testosterone produced in men?

  In the testes, to stimulate sperm production.
• Why and where is oestrogen produced in women?

  In the ovaries to stimulate the release of eggs.
• What 3 hormones control the menstrual cycle?

  FSH, LH, Oestrogen
• Where is FSH produced and what is it's role?

  In the pituitary gland and it's role is the maturation of an egg in the ovaries.
• Where is oestrogen produced and what is it's role?

  In the ovaries, and it's role is to stop the pituitary gland producing FSH and release the egg.
• Where is LH produced and what is it's role?

  Pituitary gland and it's role is to stimulate ovulation.
• Where is progesterone produced and what is it's role?

  Ovaries and it's role is to keep the uterus lining thick.
• What are pros of non hormonal contraception?

  Barrier methods prevent STIs, do not effect menstrual cycle or fertility, not affected by vomiting or other medications.
• What are cons of non hormonal contraception?

  Must be used correctly to be effective, barrier methods may break, male / female sterilisation can be irreversible.
• What are pros of hormonal contraception?

  Effective and reliable
• What are cons of hormonal contraception?

  Injection or implants involve a small medical procedure, pill only works if the user remembers to take it every day, can be affected by other medication, can have side effects, can't prevent STIs, do not provide immediate protection.
• What can cause infertility?

  Lifestlyle, genetics, age
• Describe the process of IVF.

  The woman is given FSH to stimulate maturation of the egg and LH to stimulate ovulation. Then, mature eggs are extracted from the woman and sperm from the father is set for fertilisation in a laboratory. After, one or two embryos are inserted into the mother's uterus. The fertilised eggs develop into embryos.
• What are pros of IVF?

  Infertile couples can have children
• What are the cons of IVF?

  In the UK 1/4 IVF treatments are successful, emotionally upsetting, physically unpleasant, embryos that could have become a life have been decarded / used as stem cells, can cause multiple births, unethical
• What is glucagon?

  A hormone released by the pancreas when blood sugar levels are too low.
• What does glucagon cause?

  Causes stored glucose (glycogen) in the liver and muscles to be converted back to glucose and released back into the blood.
• Negative feedback in the pancreas.

  Pancreas constantly monitors blood glucose concentration in the body. The pancreas will secrete insulin or glycogen depending when blood sugar levels rise or fall.
• If blood sugar levels are high, insulin is released into the blood stream. Glucose is then taken into cells and is used or stored as glycogen, creating the optimal blood sugar level. Furthermore, consuming sugary/starchy foods can cause high sugar levels.
• If blood sugar levels are low, the liver receives a message to release glucose into the blood. Furthermore, exercise (like riding a bike) or not eating enough can cause low blood sugar.