Paper 2

• Homeostasis


  The term given to an organism's ability to regulate internal conditions even when external conditions change
• Importance of homeostasis

  • Crucial chemical reactions involving enzymes can happen at an optimum rate
• Ways our body achieves homeostasis

  • Regulating blood glucose concentration, temperature, and water levels
• Nervous system

  Consists of the CNS (central nervous system - brain and spinal cord) and the PNS (peripheral nervous system - nerves that go through the rest of the body)
• Nervous system response

  Receptor detects change, electrical signal travels to spine through sensory and relay neurons, signal travels to brain, decision made, signal goes back to affector via relay and motor neurons
• Reflex arc

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

  • Glands can be effectors which produce specific chemicals needed by the body depending on the situation
• Investigating reaction times

  • Measure distance ruler falls before caught, introduce independent variables like stimulants or depressants to see effects on reaction time
• MRI scans are a way of seeing the activity in your brain safely
• Parts of the brain

  • Cerebral cortex (higher level functions), cerebellum (motor skills), medulla oblongata (controls unconscious actions)
• Accommodation in the eye

  • Ability to change the shape of the lens to focus light from objects at different distances
• Eye structure

  • Pupil changes size depending on light intensity, cornea is the transparent outer layer, retina at the back consists of Rod and Cone cells
• Function of Rod and Cone cells

  • Rods detect light intensity, Cones detect specific wavelengths of light (green, blue, red)
• Light focusing on the retina

  Light is focused on the retina at the back of the eye which consists of Rod and Cone cells which respond to light. Rods detect light intensity while cones detect green, blue, or red wavelengths of light, a mix of which produces the colors we perceive. The signal reaches the brain via the optic nerve
• Myopia


  Medical term for shortsightedness where one can't focus on far objects
• Hyperopia


  Long-sightedness where glasses or contact lenses are used to mitigate by slightly converging or diverging light before it enters the eye. Laser eye surgery aims to change the shape of the cornea to achieve the same effect
• Thermo regulation

  Your body controlling its internal temperature by the brain sensing blood temperature then sending nervous and hormonal signals to various effectors around your body to regulate heat loss to surroundings
• If too hot

  Sweat glands in the skin cause water to cover the surface, blood vessels dilate (vaso dilation) to increase blood flow to the skin for heat loss
• If too cold

  Vaso constriction occurs, causing paleness, and shivering to produce more heat
• Endocrine system


  A system of glands that produce or secrete hormones affecting various body functions via the blood. Slower than the nervous system
• Pituitary gland


  Main or Master gland producing hormones in response to stimuli that travel to other glands in the body
• Examples of glands and their functions

  • Pancreas produces insulin
  • Thyroid controls growth, heart muscle, and digestive function
  • Adrenal glands produce adrenaline
  • Ovaries and testes release eggs or produce sperm
• Pancreas function

  Regulating blood glucose levels by secreting insulin to move glucose into cells for energy, converting excess glucose into glycogen, and producing glucagon to convert glycogen back into glucose when levels are low
• Type one diabetes
• Type two diabetes
• Water and nitrogen balance are triple science topics
• Reproduction is for everyone
• Menstruation in females


  Occurs after puberty, eggs mature due to FSH causing an egg to mature in the ovary, ovaries produce estrogen which thickens the uterus lining, and LH is produced for ovulation
• Ovulation

  Causes an egg to mature in the ovary, ovaries to produce estrogen, uterus lining to thicken, inhibits or stops the production of FSH, causes the pituitary gland to produce LH, and releases the egg to travel towards the uterus via the UCT over several days
• Progesterone


  Produced by the ovaries to maintain the uterus lining
• Contraception options include pills that inhibit FSH production, progesterone injections that stop egg release, implants that release progesterone slowly, condoms, diaphragms, IUDs, avoiding sex after egg release, clamping the UCT, having tubes tied or cutting sperm ducts
• Infertility can be due to issues like not enough FSH or LH, which can be fixed with injections. IVF (in vitro fertilization) is the most expensive solution for bigger issues
• IVF (in vitro fertilization)

  Eggs are harvested, fertilized in the lab with sperm, and inserted back into the uterus for potential pregnancy
• Adrenaline increases heart and breathing rate in stressful situations for fight or flight response
• Thyroxin

  Secreted by the thyroid to control metabolic rate
• Gibberellins cause seed germination, promote flowering, increase fruit size, and induce ripening
• Orins


  Control shoot and root growth, causing phototropism in shoots and geotropism in roots
• Orins can be used as weed killers, rooting powders, and for promoting growth in tissue cultures
• Geotropism is proven by observing root bending in response to gravity
• Meiosis

  Occurs in the testes to make sperm, involves copying chromosomes, pairing up similar chromosomes, swapping genes, and dividing to make four haploid cells ready to fuse with an egg