chapter 15 science

• 1. heart = pump

  • pump that pushes blood along in the blood vessels
  • consists mainly of muscles

  2. blood = medium

  • red blood cells -> transport oxygen from lungs to all parts of body
  • plasma -> transports water, other dissolved substances around body eg. digested nutrients from small intestine, waste products (CO2) from tissue cells to lungs
  • white blood cells -> protect aginst disease-causing microorganisms
  • platelets -> required for formation of blood clots to reduce blood loss in injuries

  3. blood vessels = network of pipes around body
• circulation of blood around body

  • lungs -> left atrium -> left ventricle -> body -> right arium -> right ventricle

  
• arteries

  • carry blood AWAY from heart
  • blood rich in oxygen
  • digested nutrients from small intestine to other tissue cells
• veins

  • carry blood toward heart
  • blood poor in oxygen, rich in waste products (CO2)
• capillaries

  • transport blood from arteries to veins (UNIDIRECTIONAL)
  • oxygen, digested nutrients in blood to cells
  • waste products from cells to organs that remove them eg. CO2 to lungs
  • capillary walls are one-cell thick (very thin!) -> quick exchange of substances between blood and tissue cells
• in capillaries

  1. blood with high oxygen, D.N, low waste products move from arteries to capillaries
  2. oxygen, D.N diffuse out of capillaries into tissue cells ——— waste products (CO2) diffuse from tissue cells into capillaries
  3. as blood moves along capillaries, concentration of oxygen, D.N decreases ——— concentration of waste products increases
  4. blood now contains low concentration of oxygen, D.N ——— high concentration of waste products -> carried to veins (transported back to heart)
• xylem - unidirectional (one-way)

  1. plant takes in water molecules, mineral salts through roots via absorption
  2. water molecules, mineral salts transported up stem through xylem vessels
  3. reach leaves, flowers -> water used for photosynthesis, other chemical reactions
• phloem - bidirectional (two-ways)

  1. glucose made in leaves during photosynthesis
  2. sugars transported from leaves to other parts by phloem vessels — also transport to shoot tips to provide energy for growth
  3. some sugars transported to root tips : stored in roots as starch/ provide energy for growth
• diffusion

  : net movement of particles from a region of higher concentration to a region of lower concentration

  • rate of diffusion affected by 1) temperature of substance and 2) size of molecule

  in human circulatory system:

  • allows for substances to be exchanged between blood and tissue cells

  in plants

  • CO2 diffuses from surrounding air into air spaces in leaves via stomata -> diffuses to plant cells for photosynthesis
  • oxygen and water vapour diffuse from air spaces inside leaves to surrounding air via stomata
• diffusion

  • roots help to absorb water and mineral salts from soil
  • dissolved mineral salts diffuse from soil solution (dissolved M.S in water) into root hair cells
  • M.S diffuse from root hair cells into inner root cells until it reaches xylem in roots
  • M.S tranported by xylem to rest of plant
  • xylem continuously transports M.S from roots to rest of plant
  • root hair cells have lower concentration of M.S than soil solution, allowing it to continuously absorb mineral salts by diffusion
• osmosis

  : net movement of water molecules from a solution of higher water potential to a solution of lower water potential, through a partially permeable membrane

  (used to describe movement of WATER in LIQUID state only)

  • water potential = tendency for water molecules to move away
  • water potential in decreasing order: 1. pure water, 2. dilute solution (higher W.P), 3. concentrated solution (lower W.P)
• osmosis

  in plants:

  • in soil, M.S dissolve to form soil solution (higher W.P)
  • water moves from S.S to root hair cells (lower W.P) via osmosis
  • water moves by osmosis from root hair cells into inner root cells, until it reaches xylem in roots
• drug abuse

  • medicinal drugs -> prescribed by doctors in appropriate doses to treat illnesses
  • smoking/ drug abuse -> disrupts human circulatory system

  1. nervous system

  • poor coordination and balance
  • slower reaction
  • insomnia
  • anxiety
  • irritability
  • hallucination
  • memory loss

  2. circulatory system

  • irregular heartbeat
  • increased heart rate, blood pressure
  • increased risk of heart attack, stroke
  • narrowed arteries causing reduced blood flow to limbs
• drug abuse

  3. respiratory system

  • lung cancer
  • emphysema (collapse of walls of tubes in lungs)

  4. digestive system

  • nausea
  • increased risk of mouth and throat cancer
  • severe tooth decay
  • stomach ulcer
  • liver damage

  5. sexual reproductive system

  • infertility
• organ transplant - to replace a damaged tissue

  1. respect for persons

  • if donor is able to make decision willingly
  • if donor has been given full info to decide

  2. minimal harm, maximised benefits

  • decisions that increase patient’s survival
  • if there are alternative treatments available

  3. justice

  • to what extent patient‘s quality of life be enhanced to
  • if age is a consideration

  Singapore‘s Human Organ Transplant Act

  • increase supply of organs, save more lives
  • allowed to opt out : eg. religious reasons