Topic 6

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  1. Where is food absorbed in the gut?
    In the small intestine.
  2. Name the 5 stages from taking in food - to getting rid of the waste.
    • 1. INGESTION
    • 2. DIGESTION
    • 5. EGESTION (different from excretion)
  3. Image Upload 1
    Label the villus
    Image Upload 2
  4. Give 2 reasons why we need to digest food?
    • 1. Often food is made of substances that are not suitable for human tissues, and so needs to be broken down and reassembled.
    • 2. Food is too large to be absorbed and so needs to be broken down first.
  5. Why do we need enzymes in digestion?
    Enzymes are biological catalysts and speed up processes of digestion. The need for increasing the rate of digestion at body temperature should be emphasized.
  6. How is villus structure related to its function?
    (7 reasons)
    • 1.Villi to increase surface area
    • 2. Microvilli increase it even more
    • 3. Epithelium layer of villus = 1 cell thick
    • 4.Protein channels in microvilli - for facilitated diffusion and pump to allow rapid absoprtion
    • 5.Mitochondria - provide ATP for active transport
    • 6.Blood supply very close - so diffusion distance is very small.
    • 7. Lacteal carries away fats after absorption
  7. What is absorption and assimilation?
    • Absorption = When food molecules pass through the layer of cells of intestine into body's tissues
    • Assimilation = it now gets made up into new molecules and becomes party of the tissues of the body.
  8. Name an amylase, say what it does, where is it secreted from and what pH it works at.
    • salivary amylase
    • Breaks starch to maltose
    • released from salivary glands
    • pH 7.0
  9. Name an lipase, say what it does, where is it secreted from and what pH it works at.
    • Pancreatic lipase
    • Released from pancreas
    • Breaks triglycerides (fats and oils) into fatty acids & glycerol
    • pH 7.0
  10. Name an protease in stomach, what it does and pH it works at.
    Pepsin - from Chief cells in wall of stomach. Breaks proteins into polypeptides.  pH 1.5
  11. What does myogenic cardiac muscle mean?
    Myogenic means it can contract on its own without being stimulated by a nerve.
  12. What is the name of the area of heart responsible for starting each heart contraction?
  13. Properties of arteries
    • Thick outer layer of collagen and elastic fibers
    • Thick layers of circular elastic and muscle fibers (help pump blood further on after each heart beat)
    • Narrow lumen (hole) to keep high pressure
  14. Properties of veins
    • Thin layers of circular elastic and muscle fibers.
    • Wide lumen
    • Valves to prevent back flow
  15. Properties of capillaries
    • Very thin (single layer of cells)
    • Gaps between cells so some of plasma can leak out
    • Very narrow lumen (hole) 10um diameter
  16. What is the composition of blood?
    • Erythrocytes (red blood cells)
    • Leukocytes (white blood cells)
    • Plasma
    • Platelets
  17. What does blood plasma transport?
    • nutrients
    • carbon dioxide
    • hormones
    • antibodies
    • urea
    • heat
  18. What is an antibody?
    Image Upload 3
    • Proteins that recognize and bind to specific antigens.
    • Image Upload 4
  19. What do coronary arteries do?
    Feed the heart itself with oxygenated blood and nutrients.
  20. Outline the control of the heart beat.
    • 1. Sino Atrial (SA) node sends signal to both atria to contract (atrial systole)
    • 2. Message goes down to Atrio-Ventricular (AV) node which causes both ventricles to contract (ventricular systole)
    • 3. Ventricles contract from bottom up (squeezing blood UP)
    • 4. Heart relaxes and so heart re-fills (diastole)
  21. What does systole mean?
    Heart is contracted.
  22. What does diastole mean?
    Heart is relaxed (think diarrhea ...when... ahem...everything relaxes)
  23. What is a pathogen?
    Any organism (or virus) that causes disease (eg. parasite, bacterium)
  24. Why are antibiotics effective against bacteria but NOT viruses?
    Antibiotics block specific metabolic pathwaysfound in bacteria. Viruses reproduce using the hostcell’s metabolic pathways, which are not affectedby antibiotics.
  25. What is your BEST defense from disease?
    Your skin
  26. What is the role of the skin and mucous membranes in defense against pathogens?
    • Waterproof and impermeable to most pathogens
    • Multilayered. Outer layers of skin are a tough barrier. The skin is also slightly acidic (pH 3-5) – preventing growth of most bacteria
    • Mucous membranes found in   -nose  -trachea  -vagina  -urethra
  27. Outline phagocytosis ('eating' of a pathogen by a phagocyte)
    • 1. Pathogen ingested.
    • 2. Forms a phagosome
    • 3. Binds with a lysosome (organelle containing digestive enzymes)
    • 4. Forms a phagolysosome
    • 5. The pathogen is digested
    • 6. Microbial debris is released from cell
  28. Outline antibody production
    • 1. Lymphocytes make antibodies Humans are born with about 10 000 different antibodies so that they can respond to almost any antigen that enters the body.
    • 2. Each type of lymphocyte cell recognizes only one antigen. The lymphocyte with a surface epitope complementary to the antigen is selected.
    • 3. When a pathogen enters body, the corresponding lymphocyte responds
    • 4. That lymphocyte forms many clones of itself so that a large number of that particular antibody can be produced to neutralize that particular antigen
    • 5. Some cloned cells remain as memory cells – ready for subsequent invasions.  This is what we call immunity.
  29. Outline the effects of HIV on immune system.
    • The virus is a virus that affects certain lymphocytes (T helper cells – CD4 cells). 
    • Over a period of years, these lymphocytes are destroyed.  The body is then vulnerable to pathogens that would normally be easily controlled.
  30. Discuss cause of AIDS (acquired immune deficiency syndrome).
    Infection with HIV.
  31. Discuss the transmission of AIDS.
    • HIV doesn’t live long outside the body
    • Cannot easily pass through skin
    • Transfer must involve body fluids from infected person to uninfected person
    • Small cuts or tears in vagina, penis, mouth, intestine during vaginal, anal or oral sex
    • Traces of blood on hypodermic needle
    • Across placenta from mother to baby, cuts during childbirth or in milk during breast feedingTransfused blood products (such as Factor VIII used to treat haemophiliacs)
  32. What are the social implications of AIDS?
    • Families and friends suffer grief
    • Families become poorer if sufferer was wage earner
    • Sufferer may become stigmatized – may be denied life insurance, partners, housing, employment
  33. What is ventilation?
    • Movement of air into and out of lungs. Inspiration/inhalation (air moving in)
    • Expiration/exhalation (air moving out)
  34. What is gas exchange?
    Just what it says. The exchange (diffusion) of oxygen and carbon dioxide into and out of blood at the alveoli.
  35. Why are alveoli (in lungs) so awesome at doing their job?
    • They have a huge surface area!
    • There are:-
    • Millions of them
    • Each has own blood supply
    • Membranes are very thin (of alveoli and capillary) and so diffusion is short
    • Surfaces are kept moist (gases can dissolve)
  36. Image Upload 5Label the diagram
    • a= trachea
    • b= bronchi
    • c= bronchioles
    • d= alveoli
    • e= diaphragm
  37. What happens when you breathe in?
    • Inspiration
    • External intercostal muscles contract
    • Diaphragm contracts and drops
    • Rib cage moves up and out
    • Chest volume increases
    • Pressure drops
    • Air rushes in
  38. What happens when you breathe out?
    • Expiration
    • External intercostal muscles relax
    • Diaphragm relaxes and returns to dome shape
    • Rib cage drops down and in
    • Chest volume decreases
    • Pressure goes up
    • Air rushes out
  39. What two parts make up the Nervous System?
    • Central nervous system (brain and spinal cord)
    • Peripheral nervous system
  40. What is the name for a nerve cell?
  41. What kind of nerve cells go from the CNS to an effector (muscle or gland)?
    Motor neuron
  42. Wht kind of nerve cells go from receptors to CNS?
    Sensory neurons
  43. What kind of nerve cells go across the spinal cord?
    Relay (or inter-) neurons
  44. Label the motor neuron
    Image Upload 6
    • A = Dendrites
    • B = Nucleus (within the cell body)
    • C = Axon
    • D = Myelin sheath
    • E = Node of Ranvier
    • F = Motor end plates
  45. What is the resting potential?
    The electrical potential across a plasma cell membrane (that is not transmitting an electrical impulse).
  46. How is an action potential maintained?
    • To start with...lots of K+ inside, and lots of Na+ outside.
    • Na+ leak out
    • K+ leak in
    • To put them back, a Na/K pump pumps out 3 Na+ for every 2 K+.
    • This results in inside of membrane being relatively negative with respect to the outside.
    • Image Upload 7
  47. What happens at REpolarization of the neuron?
    Potassium ions leaving the axon (makes it more negative)
  48. How many mV is the inside of the axon?
  49. Define action potential.
    This is the reversal (depolarization) and restoration (repolarization)of the electrical potential across a plasma membrane as a nerve impulse passesalong a neuron
  50. What happens in an action potential? (10 steps)
    • 1.Now voltage gated ion channels are used.
    • 2.When a stimulus disturbs the membrane, Na+ channels open and Na+ rushes inside the cell.
    • 3. If sufficient Na+ open, then the threshold value (about
    • -50mV) is reached, then an action potential occurs.  This is a complete reversal of the electrical charge, and the interior becomes positively charged relativeto outside. (+35mV) - depolarisation
    • 4. Now the Na+ channel closes, and the K+ channel opens.
    • 5. Now K+ leaves the cell….this makes the cell negative again - repolarization.
    • 6. However, the K+ channels take a long time to close, and so too many leave. The cell hyperpolarizes.
    • 7. The electrical potential drops below the resting level to about -80mV.
    • 8. Finally, when all the K+ channels are closed, the electrical potential comes back to normal (-70mV)
    • 9. For a brief period, after the action potential, the nerve fibre is completely inexcitable = absolute refractory period.
    • 10. For another brief period, only a stimulus above the normal threshold will produce another action potential = relative refractory period.
  51. How do neurons 'talk' to each other?
    Using synapses
  52. How does an impulse pass from one cell to another? (7 steps)
    Image Upload 8
    • 1.Nerve impulse reaches presynaptic terminal
    • 2.Depolarisation causes voltage gated Ca2+ channels to open in response to action potential
    • 3.Synaptic vesicles release a neurotransmitter (eg. Acetylcholine)
    • 4.These go across the synaptic cleft to the post synaptic terminal and bind to receptor sites on Na+ channels
    • 5.Na+ is released into the post-synaptic cell
    • 6.Na+ diffuses into the cell making it more positive. If a threshold level is reached, then an action potential results.
    • 7.Enzymes in synaptic cleft then break down the neurotransmitter and the products are taken up by active transport (lots of mitochondria in presynaptic terminal).
  53. Hormones are RELEASED from....
  54. What is homeostasis?
    Maintaining the internal environment (of blood and tissue fluids) of the body within safe limits
  55. What things need to be maintained by homeostasis in humans?
    • oxygen levels
    • blood pH
    • temperature (thermoregulation)
    • glucose (glucoregulation)
    • water balance (osmoregulation)
  56. What is a negative feedback loop?
    A process that allows levels to be raised/lowered to bring it back to a desired level. It has a stabilizing effect.
  57. What happens when you are too hot?
    • Hairs lie flat
    • Vasodilation (capillaries open up)
    • Sweat glands produce sweat
    • Sweat forms (takes heat away from body by latent heat of evaporation)
  58. Image Upload 9
    Which hormones match which colours?
    • Red = oestrogen
    • Dotted blue = Lutenizing hormone
    • Orange = Follicle Stimulating Hormone
    • Green = Progesterone
  59. How many days (approx) after the peak of LH does a menstrual bleed occur?
    14 days later
  60. On what day does ovulation occur?
    Day 14
  61. Which hormone makes ovulation occur?
  62. What does SRY stand for?
    Sex related Y gene
  63. How does an embryo turn into a male?
    SRY gene on Y chromosome switches on other genes that result in testis development.
  64. Why does an antibiotic not work against viruses?
    • Antibiotics disrupt metabolic reactions in bacteria.
    • The enzymes of bacteria are inhibited by enzymes.
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Topic 6
2013-04-03 18:13:16
IB DP Biol Topic

IB DP bio
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