6.1 Digestion and absorption:
Nature of science: Use models as representations of the real world—dialysis tubing to model absorption in the intestine.
β - Skill: Production of an annotated diagram of the digestive system.
Check out the Inner Body website to see where everything fits into your body. You can also use this site the fill in the boxes above.
∑ - The contraction of circular and longitudinal muscle of the small intestine mixes the food with enzymes and moves it along the gut.
Video showing peristalsis https://www.youtube.com/watch?v=o18UycWRsaA (turn off the music as it is terrible)
Smooth muscle function https://www.youtube.com/watch?v=yzQAgfivX74
∑ - The pancreas secretes enzymes (amylase, lipase and an endopeptidase) into the lumen of the small intestine.
∑ - Enzymes digest most macromolecules in food into monomers in the small intestine (starch, glycogen, lipids and nucleic acids are digested into monomers and that cellulose remains undigested). Some hydrolytic enzymes have economic importance, for example, amylase in the production of sugars from starch and in the brewing of beer.
|Enzyme||Source||Breaks Down (substrate)||Products Formed (products)||pH |
|Amylase||Salivary glands and pancreas||STARCH||MALTOSE||Neutral to slightly basic|
|Maltase||Walls of the epithelial cells of the SI||MALTOSE||GLUCOSE||Slightly Basic|
|Lactase||Walls of the epithelial cells of the SI||LACTOSE||GLUCOSE AND GALACTOSE||Slightly Basic|
|Sucrase||Walls of the epithelial cells of the SI||SUCROSE||GLUCOSE AND FRUCTOSE||Slightly Basic|
|Lipase||Pancreas||LIPIDS||FATTY ACIDS AND GLYCEROL||Slightly Basic|
|Phospholipase||Pancreas||PHOSPHOLIPIDS||FATTY ACIDS, GLYCEROL AND PHOSPHATE||Slightly Basic|
Such as Trypsin
|POLYPEPTIDES||SHORTER PEPTIDES OR DIPEPTIDES||Slightly Basic|
|Dipeptidases||Walls of the epithelial cells of the SI||DIPEPTIDES||AMINO ACIDS||Slightly Basic|
|Nucleases||Walls of the epithelial cells of the SI||NUCLEIC ACIDS SUCH AS DNA AND RNA||NUCLEOTIDES||Slightly Basic|
Hydrolytic enzymes such as amylase are used in the brewing of beer to breakdown the starchy endosperm of barley seeds to produce maltose (malt sugar) thus having a great economic importance
Here is a video on the process https://www.youtube.com/watch?v=OWX7a6waHX8 (just watch the first few minutes)
∑ - Villi increase the surface area of epithelium over which absorption is carried out.
∑ - Villi absorb monomers formed by digestion as well as mineral ions and vitamins.
Absorption – process where small molecules and nutrients pass into the blood vessels (capillary beds) in the wall of the intestine.
Assimilation – products of digestion that are absorbed into the blood are transported to the various tissues. These molecules are used to build up larger molecules that become part of the structure of the tissue or body.
These products include the following monomers:
∑ - Tissue layers should include longitudinal and circular muscles, mucosa and epithelium.
The epithelial layer is the inner tissue layer, that is in contact with the lumen
The next layer is the mucosa layer; in between the epithelial cells near the lumen and the sub-mucosa layer
Circular muscle is on the inside of the longitudinal muscle towards the lumen of the small intestine. The longitudinal muscles are at a right angle to the circular muscles.
β - Skill: Identification of tissue layers in transverse sections of the small intestine viewed with a microscope or in a micrograph.
Here are some examples of micrographs with transverse sections of the small intestine
∑ - Different methods of membrane transport are required to absorb different nutrients.
These modes of transport will be outlined using two products of digestion.
Since glucose has many hydroxyl groups it is a polar molecule and cannot pass through the cell membrane by simple diffusion and therefore relies on different types of facilitated diffusion in order to move into and out of the epithelial cells of the villi. (The numbers 1-4 here, match with numbers on the two diagrams above and below).
1) As seen above Na+ is pumped out of the cytoplasm of the epithelial cells into the interstitial space inside the interstitial by sodium/potassium pumps.
- This creates a concentration gradient between the lumen and the cytoplasm of the epithetical cells.
- This means Na+ ions want to diffuse into the epithelial cells.
- Co-transport proteins in the membrane of the microvilli, allow a sodium ion and a glucose molecule to be transported together into the epithelial cell.
This type of facilitated diffusion is passive, but requires active transport of the Na+ ions out of the cell to create the concentration gradient.
2) Specific glucose channels allow glucose to diffuse from the epithelial cells into the blood cells of the capillaries
3) Fatty acids, glycerol and monoglycerides, which are products of lipid digestion can diffuse into epithelial cells from the lumen by passive diffusion
4) Inside the epithelial cells, fatty acids and monoglycerides reform into triglycerides, and therefore can’t move back out into the lumen because of their size. These lipids combine together with proteins and phospholipids to form lipoproteins. The lipoproteins are then excreted by exocytosis, enter the lacteal and are carried away by the lymph
Applications and skills:
β - Application: Processes occurring in the small intestine that result in the digestion of starch and transport of the products of digestion to the liver.
β - Application: Use of dialysis tubing to model absorption of digested food in the intestine.
See handout on Manage Bac
Build a body https://www.brainpop.com/games/buildabodydigestivesystem/
Click on the above link and drag and drop digestive system parts to build a body for review. After this is complete, click on the game quiz and do the multiple choice quiz.
Crash Course on Biology. https://www.youtube.com/watch?v=s06XzaKqELk
Cartoon on digestion https://www.youtube.com/watch?v=VwrsL-lCZYo
6.6 Hormones, homeostasis and reproduction
Hormones are used when signals need to be widely distributed.
∑ - Insulin and glucagon are secreted by β and α cells of the pancreas respectively to control blood glucose concentration.
Type II diabetes
***Do the data based questions on page 331***
∑ - Thyroxin is secreted by the thyroid gland to regulate the metabolic rate and help control body temperature.
∑ - Leptin is secreted by cells in adipose tissue and acts on the hypothalamus of the brain to inhibit appetite.
Journal article on Leptin and regulation of body weight in mammals http://www.nature.com/nature/journal/v395/n6704/full/395763a0.html
β - Application: Testing of leptin on patients with clinical obesity and reasons for the failure to control the disease.
Leptin and obesity: https://www.youtube.com/watch?v=oN3woHJ7ZDY
Shorter version http://www.hhmi.org/biointeractive/leptin-feedback-control-system
∑ - Melatonin is secreted by the pineal gland to control circadian rhythms.
β - Application: Causes of jet lag and use of melatonin to alleviate it.
Skill: Annotate diagrams of the male and female reproductive system to show names of structures and their functions.
∑ - A gene on the Y chromosome causes embryonic gonads to develop as testes and secrete testosterone.
∑ - Testosterone causes pre-natal development of male genitalia and both sperm production and development of male secondary sexual characteristics during puberty.
∑ - Estrogen and progesterone cause pre-natal development of female reproductive organs and female secondary sexual characteristics during puberty.
∑ - The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones. The roles of FSH, LH, estrogen and progesterone in the menstrual cycle are expected.
FSH (Follicle stimulating hormone)
LH (luteinizing hormone)
**Do data-based questions on page 338**
β - Application: The use in IVF of drugs to suspend the normal secretion of hormones, followed by the use of artificial doses of hormones to induce superovulation and establish a pregnancy.
Pregnancy test is given after about 2 weeks.
IVF - https://www.youtube.com/watch?v=GeigYib39Rs
Nature of science: Developments in scientific research follow improvements in apparatus—William Harvey was hampered in his observational research into reproduction by lack of equipment. The microscope was invented 17 years after his death.
β - Application: William Harvey’s investigation of sexual reproduction in deer.
Interesting video on Harvey - http://www.smithsonianmag.com/science-nature/meet-william-harvey-misunderstood-genius-human-anatomy-180953682/?no-ist
Utilization: Hormones are used in a variety of therapies such as replacement therapies.
Aims: Scientists are aware that the drugs women take infertility treatment pose potential risks to health. Should scientific knowledge override compassionate considerations in treating infertile couples?
6.5 Neurons and synapses:
Neurons transmit the message, synapses modulate the message.
Nature of science: Cooperation and collaboration between groups of scientists—biologists are contributing to research into memory and learning.
∑ - Neurons transmit electrical impulses.
∑ - The myelination of nerve fibres allows for saltatory conduction.
MS effect on neuron - http://nebraskamedical.staywellsolutionsonline.com/MultimediaRoom/VideoLibrary/?e=0#player:138,v1013
∑ - Neurons pump sodium and potassium ions across their membranes to generate a resting potential.
Sodium/potassium pump video - https://www.youtube.com/watch?v=fHRC8SlLcH0
∑ - An action potential consists of depolarization and repolarization of the neuron.
Action potential -http://highered.mheducation.com/sites/0072943696/student_view0/chapter8/animation__voltage-gated_channels_and_the_action_potential__quiz_1_.html
∑ - Nerve impulses are action potentials propagated along the axons of neurons.
Propagation - https://www.youtube.com/watch?v=pbg5E9GCNVE
∑ - Propagation of nerve impulses is the result of local currents that cause each successive part of the axon to reach the threshold potential.
Good video - https://www.youtube.com/watch?v=Sa1wM750Rvs
β - Skill: Analysis of oscilloscope traces showing resting potentials and action potentials.
***Do data based questions on page 324***
∑ - Synapses are junctions between neuron; between neurons and receptor; effector cells.
∑ - When presynaptic neurons are depolarized they release a neurotransmitter into the synapse.
Crash course - https://www.youtube.com/watch?v=x4PPZCLnVkA
***Data based questions page 325***
∑ - A nerve impulse is only initiated if the threshold potential is reached.
β - Application: Secretion and reabsorption of acetylcholine by neurons atsynapses.
Two videos on Acetylcholine –
β - Application: Blocking of synaptic transmission at cholinergic synapses in insects by binding of neonicotinoid pesticides to acetylcholine receptors.
β - Application: The social effects of the abuse of psychoactive drugs could be considered, as could the use of the neurotoxin Botox for cosmetic treatments.
Utilization: An understanding of the workings of neurotransmitters and synapses has led to the development of numerous pharmaceuticals for the treatment of mental disorders.
6.2 The blood system: The blood system continuously transports substances to cells and simultaneously collects waste products.
β - Applications and skills:
∑ - Arteries convey blood at high pressure from the ventricles to the tissues of the body.
∑ - Arteries have muscle cells and elastic fibres in their walls.
Tunica externa – outer layer made from connective tissue
Tunica media– thick layer containing smooth muscle and elastin fibres
Tunica intima– endothelium layer that lines the inside of the artery
Video on structure https://www.youtube.com/watch?v=VMwa6yC3r-s
∑ - The muscle and elastic fibres assist in maintaining blood pressure between pump cycles.
∑ - Blood flows through tissues in capillaries. Capillaries have permeable walls that allow exchange of materials between cells in the tissue and the blood in the capillary.
∑ - Veins collect blood at low pressure from the tissues of the body and return it to the atria of the heart.
β - Skill: Identification of blood vessels as arteries, capillaries or veins from the structure of their walls. (Make sure you look at the pictures above as well)
|Size (diameter)||Larger than 10µm||Variable but much larger than 10µm||Approx.. 10µm|
|Thickness of the wall and diameter of the lumen|
|Fairly thin walls, large lumen diameter||Very thin walls, one cell thick|
|Layers of the walls||3 (tunica externa, media and intema)|
3 (tunica externa, media and intema)
Thinner than arteries
|One layer – tunica intima|
|Muscle and Elastic Fibres||Large amounts of these fibres||Small amounts of these fibres||none|
∑ - Valves in veins and the heart ensure circulation of blood by preventing backflow.
∑ - There is a separate circulation for the lungs.
Below is a more in-depth description of the circulation of blood in humans
Nature of science: Theories are regarded as uncertain—William Harvey overturned theories developed by the ancient Greek philosopher Galen on the movement of blood in the body.
β - Application: William Harvey’s discovery of the circulation of the blood with the heart acting as the pump.
Interesting video on Harvey - http://www.smithsonianmag.com/science-nature/meet-william-harvey-misunderstood-genius-human-anatomy-180953682/?no-ist
For further details please read this article online
β - Application: Pressure changes in the left atrium, left ventricle and aorta during the cardiac cycle.
Atrial Systole (0 to 0.1 s)
Ventricular Systole (approx. 0.1 – 0.5 s)
Atrial and Ventricular Diastole (approx. 0.5 to 0.8)
***Do Data-based questions on page 301***
∑ - The heartbeat is initiated by a group of specialized muscle cells in the right atrium called the sinoatrial node.
∑ - The sinoatrial node acts as a pacemaker.
∑ - The sinoatrial node sends out an electrical signal that stimulates contraction as it is propagated through the walls of the atria and then the walls of the ventricles.
∑ - The heart rate can be increased or decreased by impulses brought to the heart through two nerves from the medulla of the brain.
∑ - Epinephrine increases the heart rate to prepare for vigorous physical activity.
β - Skill: Recognition of the chambers and valves of the heart and the blood vessels connected to it in dissected hearts or in diagrams of heart structure. A heart dissection will be carried out in class. The instructions are uploaded to Manage Bac.
How the heart works https://www.youtube.com/watch?v=H04d3rJCLCE
Crash Course – Circulatory – Respiratory https://www.youtube.com/watch?v=9fxm85Fy4sQ
β - Application: Causes and consequences of occlusion of the coronary arteries. The social implications of coronary heart disease could be discussed.
Theory of knowledge: Our current understanding is that emotions are the product of activity in the brain rather than the heart. Is knowledge based on science more valid than knowledge based on intuition?
6.4 Gas exchange: The lungs are actively ventilated to ensure that gas exchange can occur passively.
∑ - Ventilation maintains concentration gradients of oxygen and carbon dioxide between air in alveoli and blood flowing in adjacent capillaries.
***Do data based questions on page 312***
β - Draw a diagram to show the structure of an alveolus and an adjacent capillary.
∑ - Type I pneumocytes are extremely thin alveolar cells that are adapted to carry out gas exchange.
∑ - Type II pneumocytes secrete a solution containing surfactant that creates a moist surface inside the alveoli to prevent the sides of the alveolus adhering to each other by reducing surface tension.
∑ - Air is carried to the lungs in the trachea and bronchi and then to the alveoli in bronchioles.
∑ - Muscle contractions cause the pressure changes inside the thorax that force air in and out of the lungs to ventilate them.
β -Application: External and internal intercostal muscles, and diaphragm andabdominal muscles as examples of antagonistic muscle action
Ventilation consists of inhalation (inspiration) and exhalation (expiration)
|contracts and flattens out||diaphragm||relaxes and returns to domed shape|
|relax||abdominal muscles||contracts – pressure formed in abdomen pushes organs up and helps push diaphragm into a dome shape|
|Contract moving ribcage up and out||external intercostal muscles||relax|
|relax||internal intercostal muscles||contract, moving ribcage down and in|
|increases||volume of the thoracic cavity and lungs||decreases|
|Decreases to below atmospheric pressure and therefore air flows in||pressure of the thoracic cavity and lungs||Increases to above atmospheric pressure and therefore air flows out|
∑ - Different muscles are required for inspiration and expiration because muscles only do work when they contract.
Short video on antagonistic pairs https://www.youtube.com/watch?v=NoFxgMrjR_U
Applications and skills:
Nature of science: Obtain evidence for theories—epidemiological studies have contributed to our understanding of the causes of lung cancer.
Answer the following questions on epidemiological studies and lung cancer.
1) What is epidemiology and why are these studies generally observational and not experimental?
2) If you had to carry out an epidemiological study, how would you test the theory that smoking is a major cause of lung cancer?
3) What are confounding factors, why are they a problem with epidemiological studies and how can you compensate for these factors?
β - Application: Possible Causes and consequences of lung cancer and emphysema.
Construction sites, factories and mines can have dust particles in the air. If steps aren’t taken to properly protect the workers, lung cancers can develop.
Lung cancer is a very serious disease and the consequences can be severe, especially if the cancer is not recognized early on.
β - Application: The social consequences of lung cancer and emphysema could be discussed.
Some interesting videos to discuss in class.
Social smoking campaign funny commercials https://www.youtube.com/watch?v=C8JoQ7_aYPw
Nine year old chain smoker from Indonesia https://www.youtube.com/watch?v=woVcHfnhBqI
Do e-cigarettes cause the same chronic lung problems?http://www.dailymail.co.uk/health/article-3073502/E-cigarettes-lead-chronic-lung-conditions-Vapour-gadgets-disrupts-cells-way-tobacco-smoke.html
Are all these things true? http://www.dailyrx.com/smoking-goes-beyond-lungs-affect-body-head-toe
The Doctors talk about smoking https://www.youtube.com/watch?v=JC5yWEyw7bs
Good anti-smoking commercial https://www.youtube.com/watch?v=2oHkTR4fXhE
Top 40 scary anti-smoking https://www.youtube.com/watch?v=9kKN8_aa38A
6.3 Defence against infectious disease: The human body has structures and processes that resist the continuous threat of invasion by pathogens.
Nature of science: Risks associated with scientific research—Florey and Chain’s tests on the safety of penicillin would not be compliant with current protocol on testing.
Aims: The social as well as the economic benefits of the control of bacterial diseases around the world should be stressed. Science has limited means in the fight against pathogens, as shown by the spread of new diseases and antibiotic-resistant bacteria.
Good Introduction to the Immune System:
∑ - The skin and mucous membranes form a primary defence against pathogens that cause infectious disease.
Video on non-specific immune https://www.youtube.com/watch?v=Non4MkYQpYA
∑ - Cuts in the skin are sealed by blood clotting.
∑ - Clotting factors are released from platelets.
The platelets and the damaged tissue release chemical factors called clotting factors.
∑ - The cascade results in the rapid conversion of fibrinogen to fibrin by thrombin.
Diagram of Blood Clotting (to the right)
∑ - Application: Causes and consequences of blood clot formation in coronary arteries.
∑ - Ingestion of pathogens by phagocytic white blood cells gives non-specific immunity to diseases.
∑ - Production of antibodies by lymphocytes in response to particular pathogens gives specific immunity.
∑ - Some lymphocytes act as memory cells and can quickly reproduce to form a clone of plasma cells if a pathogen carrying a specific antigen is re-encountered.
The Cell Secret Immune System https://www.youtube.com/watch?v=v1MnNO4I9aU
Immune System Game
∑ - Antibiotics block processes that occur in prokaryotic cells but not in eukaryotic cells.
∑ - Viruses lack a metabolism and cannot, therefore, be treated with antibiotics. Some strains of bacteria have evolved with genes that confer resistance to antibiotics and some strains of bacteria have multiple resistance.
Since viruses lack their own metabolism, they have to use the chemical processes of a cell from a host that they infect
They are unable to reproduce on their own and cannot perform protein synthesis, transcription and other metabolic functions
Antibiotics work by blocking these vital processes in bacteria, killing the bacteria, or stopping them from multiplying
Since viruses do not perform their own metabolic reactions antibiotics such as penicillin and streptomycin, are ineffective in treating viral infections
Therefore treating viruses with antibiotics is not only useless and ineffective, but it can also create antibiotic resistance in bacterial strains eg. Methicillin-resistant Staphylococcus aureus
Video on Staph Infections: http://www.webmd.com/a-to-z-guides/video/truth-about-mrsa
Video on Antibiotic Resistance - Last line of Defence Breached in China
Applications and skills:
∑ - Application: Florey and Chain’s experiments to test penicillin on bacterial infections in mice.
Video on Penicillin discovery https://www.youtube.com/watch?v=7qeZLLhx5kU
Another video https://www.youtube.com/watch?v=5RGs-2eNnjM
∑ - Application: An understanding of immunity has led to the development of vaccinations.
Meningitis - http://www.scidev.net/sub-saharan-africa/children/news/vaccine-blow-meningitis-africa-path.html
Graph of a Primary and Secondary Immune Response Resulting from Exposure to an Antigen
Measles Immunity: http://fred.publichealth.pitt.edu/measles/
Herd Immunity: http://www.software3d.com/Home/Vax/Immunity.php
Another Simulation: http://www.theguardian.com/society/ng-interactive/2015/feb/05/-sp-watch-how-measles-outbreak-spreads-when-kids-get-vaccinated
∑ - Application: Effects of HIV on the immune system (a reduction in the number of active lymphocytes and a loss of the ability to produce antibodies, leading to the development of AIDS) and methods of transmission.
Virus Evolution - https://www.youtube.com/watch?v=3Ms04x6MvMY
International-mindedness: The spread and containment of diseases such as bird flu require international coordination and communication.
Aims: The social, as well as the economic benefits of the control of bacterial diseases around the world, should be stressed. Science has limited means in the fight against pathogens, as shown by the spread of new diseases and antibiotic-resistant bacteria.
Crash course Immunity: https://www.youtube.com/watch?v=CeVtPDjJBPU
IB Biology - Curriculum Notes