B2 revison

• Conscious response


  Signal goes from receptor through sensory neuron to relay neurons up the spinal cord to the brain, decision is made to act, signal goes back via relay and motor neurons to an effector
• Reflex arc


  Signal goes straight through the spinal cord to the motor neurons, bypassing the brain, action occurs before realizing what happened
• Stimulants


  Decrease reaction time or improve reactions, increase rate of neurotransmitter release across synapses
• Depressants


  Impair reactions, reduce amount of neurotransmitters crossing synapses
• Accommodation (focusing on distant objects)

  Ciliary muscles relax, suspensory ligaments tighten, lens becomes thinner, light refracts less, focuses on retina
• Thermoregulation


  • Body's ability to control internal temperature, an example of homeostasis
• Body response to heat

  Sweat glands produce sweat, blood vessels dilate to increase blood flow and heat loss
• Body response to cold

  Vasoconstriction - blood vessels constrict to reduce blood flow and heat loss, hairs stand on end to trap insulating air
• Glands


  Part of endocrine system, secrete hormones that affect other parts of the body
• Pituitary gland


  Master gland, responds to changes and secretes hormones that cause other glands to do the same
• Body response to high blood glucose

  Pancreas secretes insulin, causes glucose to enter cells for respiration, excess converted to glycogen
• Body response to low blood glucose

  Pancreas secretes glucagon, causes liver and muscles to convert glycogen back to glucose
• Kidneys


  Remove excess water from blood, mix with urea to form urine, filter out glucose and mineral ions
• ADH (anti-diuretic hormone)


  Causes kidneys to reabsorb water into bloodstream if water levels are too high
• Thyroxin


  Controls metabolic rate, secreted by thyroid gland
• Adrenaline


  Increases blood flow and breathing rate, secreted by adrenal glands
• Hormones in menstrual cycle

  • FSH (follicle stimulating hormone)
  • Estrogen
  • LH (luteinizing hormone)
  • Progesterone
• FSH


  Causes egg maturation, causes ovaries to produce estrogen
• Estrogen


  Causes uterus lining to thicken, inhibits FSH
• LH


  Causes egg release
• Progesterone


  Maintains uterus lining
• Gibberellins


  Induce germination, promote flowering, increase fruit size
• Ethylene


  Promotes fruit ripening
• Auxins


  Growth hormones in plants, promote growth and elongation of shoots, cause phototropism
• Meiosis


  Chromosomes copied, homologous chromosomes pair up and genes swapped, cell divides twice to produce 4 genetically different haploid cells (gametes)
• DNA


  Double helix polymer, A-T and C-G base pairs, 3 bases code for 1 amino acid, sequence determines proteins synthesized
• Sexual reproduction


  • Offspring can be better adapted to environment
• Asexual reproduction


  • Produces clones
• Homozygous


  Two identical alleles for a gene
• Heterozygous


  Two different alleles for a gene
• Cloning animals


  Take nucleus from cell, insert into egg cell of same species, insert into surrogate mother
• Estimating population size


  Use quadrats to sample 10% of area, count organisms, calculate average per square meter, multiply by total area
• Food chains and food webs

  Show direction of energy/biomass transfer between trophic levels
• Humans impact biodiversity through deforestation, peat extraction, and land use changes
• Homeostasis


  An organism's ability to regulate internal conditions even when external conditions change
• Pyramids of biomass get smaller going up trophic levels due to energy and biomass losses at each level
• 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 stimulus

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

  3. Signal travels across synapse by neurotransmitter

  4. Signal goes to brain

  5. Conscious decision to act

  6. Signal goes 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