+ AI B3 (Nervous System, hormones)

• The central nervous system consists of the brain and spinal cord.
• Sensory neurons are responsible for transmitting information about stimuli such as touch, temperature, pain, pressure, taste, smell, hearing, and vision to the CNS.
• Motor neurons transmit impulses from the CNS to muscles or glands, causing them to contract or secrete substances.
• Motor neurons transmit signals from the CNS to effectors (muscles or glands) that produce responses to stimuli.
• Reflexes involve rapid, automatic responses to specific stimuli without conscious thought.
• The nervous system is divided into the central nervous system (CNS) and peripheral nervous system (PNS).
• The CNS consists of the brain and spinal cord, while the PNS includes all other nerves.
• Neurons communicate through electrical and chemical signaling at synapses.
• Motor neurons carry messages out of the CNS to effectors such as muscles and glands.
• Sensory receptors detect changes in the environment and send information to the CNS via sensory neurons.
• Neurons communicate with one another through electrical and chemical signaling.
• What is the purpose of the hormone ethene?

  Ethene is produced by raging leaves. It stimulates cells that connect the leaf to the rest of the plant to expand- this breaks the cell walls and causes the leaf to fall off the plant. It also stimulates the enzymes that cause fruit to ripen.
• What is the purpose of the hormone gibberellin?


  Gibberellin stimulates seed germination, stem growth and flowering. It stimulates the stems of the plants to grow by stem elongation- this helps plants grow tall. Auxin and gibberellin can work together to have a really big effect on plant growth.
• What is seed germination?

  Seed germination is when a seed starts to grow into a plant.
• Plant growth responses experiment:

  
• What happens when a root is exposed to light?

  The roots are negatively phototropic and more auxin cumulates on the more shaded side. the auxin inhibits cell elongation on the shaded side, so the root bends downwards back into the ground.
• What happens when a root grows sideways?

  The roots are positively gravitropic as auxin is on its lower side; but in a root the extra auxin inhibits growth. This means the cells on top elongate faster, and the root bends downwards.
• What happens when shoot grows sideways?

  The shoots are negatively gravitropic and the gravity produces an unequal distribution of auxin in the tip, with more auxin on the lower side. This causes the lower side to grow faster, bending the shoot upwards.
• What happens when a shoot tip is exposed to light?

  The shoots are positively phototropic and they accumulate more auxin on the side that is in the shade than the side that is in the light. This makes the cells bro faster on the shaded side,so the shoot bends towards the light.
• What do auxins promote?

  Auxins promote growth in the shoot, but actually inhibits the growth in the root. It is also involved in the growth responses of plants to light (phototropism) and gravity (gravitropism).
• How is auxin produced?

  Auxin is produced in the tips and diffuses backwards to stimulate the cell elongation process which occurs in the cells just behind the tips.
• What are auxins and what is their function?

  Auxins are plant hormones which control growth at the tips of shoots and roots. They move through the plant in solution.
• What factors must you consider with both hormonal and non-hormonal methods of contraception?

  >Side effects (e.g hormonal causes acne, headaches).>Possibility of 'doing it wrong' (e.g withdrawal- need the right time and the patch- may not replace it at the right time).>Medical input (e.g prescription pills or one trip visit to the doctors).>Length of action- long lasting methods (e.g IUDs).>Sexually transmitted infections (STIs)- passed on from person to person- condoms are the only method that prevents these.
• What is sterilisation and how effective is it?

  >99% effective.>A surgical procedure to cut or tie tubes in the reproductive system. In women, the procedure means eggs are prevented from travelling from the ovaries to the uterus. In men, it prevents sperm from being ejaculated.
• What are 'natural' methods and how effective are they?

  >Least effective methods as they rely on timing.>Not having sex when the woman is most fertile or withdrawal (the man pulling out the penis before ejaculation.
• What is a intrauterine device (IUD) and how effective is it?


  >99% effective, can be kept in for up to 10 years.>T-shaped devices that contain copper. They are inserted into the uterus and prevent sperm from surviving. They also alter the lining of the womb so that fertilised eggs cannot implant.
• What is a diaphragm and how effective is it?

  >92-96% effective.>Fits over the cervix to stop sperm from meeting the egg. It has to be fitted by a GP/Nurse the first time its used and has to be used with a spermicide.
• How does a female condom prevent pregnancy and how effective is it?

  >95% effective.>Worn inside the vagina during intercourse.
• How does a condom prevent pregnancy and how effective is it?

  >98% effective.>Worn over the penis during intercourse to prevent sperm entering the vagina.
• What is a barrier method (in regards to contraception)?

  They try to stop the egg and sperm meeting.
• How does the patch prevent pregnancy and how effective is it?

  >Worn on the skin in a 4 week cycle- replaced once a week for 3 weeks then no patch worn for a week.>Progesterone and oestrogen involved- Prevents ovulation by inhibiting the production of FSH.>Overall, it is 99% effective.
• How does the combined pill prevent pregnancy and how effective is it?

  >Taken is a 21 day pill, 7 days no pill cycle.>Progesterone and oestrogen involved- Prevents ovulation by inhibiting the production of FSH.>Overall, it is 99% effective.
• How does the mini-pill prevent pregnancy and how effective is it?

  >Has to be taken everyday.>Overall, it is 99% effective.>Prevents ovulation by inhibiting the production of FSH and LH. However, this is not true for all types of mini-pill.
• How does the Intrauterine System (IUS) help to prevent pregnancy and how effective is it?

  >It is effective for 3-5 years.>A T-shaped piece of plastic that is inserted into the uterus. It thins the lining of the uterus to reduce the chance of fertilised egg implanting- uses progesterone
• How does the implant help to prevent pregnancy and how effective is it?

  >It is effective for 3 years.>It is inserted beneath the skin of the arm. Stimulates the production of thick cervical mucus by using progesterone- preventing the sperm from reaching the egg.Overall, it is 99% effective.
• How does the injection help to prevent pregnancy and how effective is it?

  >It is effective for up to 3 months.>Stimulates the production of thick cervical mucus by using progesterone- preventing the sperm from reaching the egg.>Overall, it is 99% effective.
• What happens once the embryos are grown in IVF?

  When they are tiny balls of cells, one or two of them are transferred to the woman's uterus to improve the chance of pregnancy.
• What is given to the women before egg collection in IVF?

  FSH and LH are given before egg collection to stimulate egg production.
• What is IVF?

  In vitro fertilisation is the process of collecting eggs from the woman's ovaries and fertilising them in a lab using the man's sperm. These are then grown into embryos.
• How are hormones uses to promote natural pregnancy?

  Some women have low levels of FSH which causes their eggs to mature, resulting in no ovulation and infertility. The hormones FSH and LH can be injected by these women to stimulate ovulation.