Biology Paper 2

• Homeostasis maintains the optimum conditions for an enzyme.
• The human nervous system contain the central nervous system (CNS) and the peripheral nervous system (PNS).
• The CNS contains the brain and the spinal cord.
• The perirhinal contains nerves that carry's information to the CNS.
• Receptors detect stimuli (changes in the environment).
• the co ordation centre, such as the Brain and spine, receives and processes information from the receptors.
• Effectors bring about a response, which is the response of the body to the stimulus.
• Nerve cells are called neurons. there are 3 main types of nerve cell, sensory, motor and relay.
• stimulus -- receptor -- sensory neuron --CNS-- motor neuron --effector -- response.
• The receptors are groups of cells which detect change in the environment.
• Effectors include muscles and glands. that produce a response to the environment.
• The small gap where two neurons meet is called a synapse.
• testosterone is the main male sex hormone and is produced in the testes.
• oestrogen is the main female sex hormone and is produced by the ovaries.
• At Puberty, eggs begin to mature and one is released every 28 days. This is ovulation.
• FHS is produced in the pituitary gland and causes the egg to mature in the ovary, also stimulates the ovaries to release oestrogen.
• Oestrogen is produced in the ovaries. It stops FSH from being released and repairs thickens and maintains the uterus lining.
• LH is produced in the pituitary gland and stimulates the release of an egg from the ovaries.
• Progesterone is produced in the ovaries. It maintains the lining Of the uterus during the menstrual cycle and pregnancy.
• Days 1-12 of the menstrual cycle, oestrogen increases and peaks by day 12. LH and FSH stay at the same level until day 12 when they gradually increase.

  FSH and LH peak during days 14. They drop at 15 and stay constant till 28.

  oestrogen drops on days 13 and 14, progesterone increases till day 21 when it begins to decrease again.
• The oral contraceptive pill Contains oestrogen and Progesterone, with stops eggs from maturing.
• in vitro fertalisation (test tube kids), FH and LSH are given to a mother to mature an egg, These eggs are the collected and fertilised with sperm. The eggs develop into embryos. They are then implanted into the mother's uterus.