Paper 2

• Homeostasis


  An organism's ability to regulate internal conditions even when external conditions change
• Importance of homeostasis


  • Allows crucial chemical reactions involving enzymes to happen at an Optimum rate
  • Regulates blood glucose concentration, temperature, and water levels
• Nervous system regulation of homeostasis

  1. Receptor detects change due to stimulus

  2. Electrical signal travels to spine through sensory and relay neurons

  3. Signal travels across synapse by neurotransmitter

  4. Signal goes to brain for conscious decision

  5. Signal goes back to effector via relay and motor neurons
• Reflex


  Signal bypasses the brain and goes straight through the spine to the effector
• Effectors


  Glands that produce specific chemicals the body needs
• Investigating reaction time


  1. Hold ruler between finger and thumb, drop without warning

  2. Measure distance fallen before caught

  3. Repeat multiple times, take mean average
• Parts of the brain

  • Cerebral cortex - higher level functions
  • Cerebellum - motor skills, movement, balance, coordination
  • Medulla oblongata - controls unconscious actions
• MRI scans


  Magnetic resonance imaging to see brain activity safely
• Accommodation in the eye

  1. For far objects: Ciliary muscles relax, suspensory ligaments tighten, lens becomes thin

  2. For near objects: Ciliary muscles contract, suspensory ligaments slacken, lens becomes fatter
• Pupil


  Hole in the iris that can change size depending on light intensity
• Retina


  Contains rods (detect light intensity) and cones (detect colour)
• Thermoregulation


  1. Brain senses blood temperature

  2. Sends nervous and hormonal signals to effectors

  3. Effectors cause body to lose or retain heat
• Endocrine system


  System of glands that produce hormones that travel in the blood
• Pituitary gland


  Main or master gland that produces hormones in response to stimuli
• Pancreas


  Produces insulin to regulate blood glucose levels
• Type 1 diabetes


  Pancreas can't produce enough insulin
• Type 2 diabetes


  Cells don't absorb glucose properly
• Water and nitrogen balance

  1. Body loses water through exhaling, sweating, urinating

  2. Kidneys remove excess water and mix with urea

  3. Antidiuretic hormone regulates water reabsorption
• Dialysis


  Process that does the job of non-functioning kidneys
• Menstrual cycle


  1. FSH causes egg maturation and estrogen production

  2. LH causes egg release

  3. Progesterone maintains uterus lining
• IVF


  In vitro fertilization - eggs fertilized in lab, embryos inserted into uterus
• Adrenaline


  Hormone that increases heart and breathing rate in stress
• Thyroxin


  Hormone that controls metabolic rate
• Plant hormones


  Gibberellins, ethylene, auxins
• Meiosis


  Chromosomes copied, paired up, genes swapped, cell divides twice to make haploid gametes
• Asexual reproduction


  Daughter cells genetically identical to parent
• Genome


  All the genetic material in an organism
• Gene


  Section of DNA that codes for a specific protein
• Genotype


  Genetic code stored in DNA
• Phenotype


  How the genetic code is expressed in characteristics
• Nucleotides are the monomers between the two DNA strands
• Asexual reproduction


  Only one parent is needed, e.g. a plant on its own can still reproduce to ensure species survival
• Parasite that causes malaria

  Can reproduce both sexually and asexually
• Genome


  The term given to all the genetic material in an organism
• DNA


  A two-stranded polymer in a double helix shape that stores the genetic code
• Gene


  A section of DNA that codes for a specific protein
• The Human Genome Project completed its initial goal in 2003 when scientists mapped out what every gene is responsible for coding
• Genotype


  The code stored in your DNA specifically
• Phenotype


  How the genotype is expressed in your characteristics and physiology
• Nucleotides


  The monomers between the two DNA strands, made from a sugar and phosphate group, of which there are four types: A, T, C, and G