6.1 Digestion and absorption
The structure of the wall of the small intestine allows it to move, digest and absorb food.
Nature of science: Use models as representations of the real world dialysis tubing can be used to model absorption in the intestine.
Understandings:
-The contraction of circular and longitudinal muscle of the small intestine mixes the food with enzymes and moves it along the gut.
-The pancreas secretes enzymes into the lumen of the small intestine.
-Enzymes digest most macromolecules in food into monomers in the small intestine.
-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.
-Different methods of membrane transport are required to absorb different nutrients.
Stomach:
Applications and skills:
Application: Processes occurring in the small intestine that result in the digestion of starch and transport of the products of digestion to the liver.
Application: Use of dialysis tubing to model absorption of digested food in the intestine.
Skill: Production of an annotated diagram of the digestive system.
Skill: Identification of tissue layers in transverse sections of the small intestine viewed with a microscope or in a micrograph.
Utilization: Some hydrolytic enzymes have economic importance, for example amylase in production of sugars from starch and in the brewing of beer.
Nature of science: Use models as representations of the real world dialysis tubing can be used to model absorption in the intestine.
Understandings:
-The contraction of circular and longitudinal muscle of the small intestine mixes the food with enzymes and moves it along the gut.
-The pancreas secretes enzymes into the lumen of the small intestine.
-Enzymes digest most macromolecules in food into monomers in the small intestine.
-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.
-Different methods of membrane transport are required to absorb different nutrients.
Stomach:
- Secretes HCL which kills bacteria.
- HCL provides optimum pH for pepsin.
- Secretes pepsin for protein digestion.
- Intestinal wall secretes enzymes
- Receives enzymes from the pancreas.
- Has villi for absorption of food particles.
- Moves material that has not been digested along.
- Absorbes water.
- Produces faces.
- Many villi increase the surface area for absorption.
- Epithelium is only one cell layer thick and so food is quickly absorbed.
- Microvilli on the villi increase the surface area for absorption further.
- Protein channels and pumps are present in the microvilli for rapid absorption.
- The mitochondria in the epithelium provide ATP needed for active transport.
- Blood capillaries are very close to the epithelium so diffusion distance is small.
- The lacteal takes away fats after absorption.
Applications and skills:
Application: Processes occurring in the small intestine that result in the digestion of starch and transport of the products of digestion to the liver.
Application: Use of dialysis tubing to model absorption of digested food in the intestine.
Skill: Production of an annotated diagram of the digestive system.
Skill: Identification of tissue layers in transverse sections of the small intestine viewed with a microscope or in a micrograph.
Utilization: Some hydrolytic enzymes have economic importance, for example amylase in production of sugars from starch and in the brewing of beer.
6.2 The blood system
The blood system continuously transports substances to cells and simultaneously collects waste products.
Nature of science: Theories are regarded as uncertain William Harvey overturned theories developed by the ancient Greek philosopher Galen on movement of blood in the body.
Understandings:
-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.
-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.
-Valves in veins and the heart ensure circulation of blood by preventing backflow.
-There is a separate circulation for the lungs.
-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.
Arteries:
Blood is composed of plasma, erythrocytes, leucocytes (phagocytes and lymphocytes) and platelets.
Nutrients, oxygen, carbon dioxide, hormones, antibodies, urea and heat are all transported by the blood.
Applications and skills:
Application: William Harvey’s discovery of the circulation of the blood with the heart acting as the pump.
Application: Pressure changes in the left atrium, left ventricle and aorta during the cardiac cycle.
Application: Causes and consequences of occlusion of the coronary arteries.
Skill: Identification of blood vessels as arteries, capillaries or veins from the structure of their walls.
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.
Utilization: Understanding of the structure of the cardiovascular system has allowed the development of heart surgery.
Aims:
-A heart dissection is suggested as a means of studying heart structure.
-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?
In my opinion knowledge based on science and knowledge based on intuition are both equally valid. The arguments to this are newly found research that says that humans can anticipate near future events even without any evidence foretelling the event and apparently without realizing it. Some researchers even dictate that quantum behavior might be involved. This research states that this knowledge can be due to past experiences or expertise in the area, but since it is fully process by the subconscious, humans note this as intuition. Predicting the near future is common within humans because they notice patterns or clues of previous experiences without even noticing, and as a result learning new knowledge of how society works. These clues are mostly based on sensory clues that each individual has and mostly are determined as correct. Although knowledge based on science is definitely valuable, knowledge based on intuition should not be treated as inferior due to the positive correlation with factual knowledge and positive results.
Nature of science: Theories are regarded as uncertain William Harvey overturned theories developed by the ancient Greek philosopher Galen on movement of blood in the body.
Understandings:
-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.
-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.
-Valves in veins and the heart ensure circulation of blood by preventing backflow.
-There is a separate circulation for the lungs.
-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.
Arteries:
- Thick outer layer of longitudinal collagen and elastic fibres prevents leaks and bulges.
- Thick wall withstands high pressure.
- Thick layers of circular elastic fibres and muscle fibres to pump blood.
- Narrow lumen to maintain high pressure.
- Thin layer with few circular elastic fibres and muscle fibres as blood does not flow in pulses.
- Thin walls so that nearby muscles can help push blood towards the heart.
- Thin outer layer of longitudinal collagen and elastic fibers as pressure is low.
- Wide lumen to accomodate the slow flowing blood.
- Wall is one cell layer thick so distance for diffusion is small.
- Pores allow plasma to leak out and form tissue fluid. Phagocytes can also pass through pores.
- Very narrow lumen so that many can fit in a small space.
Blood is composed of plasma, erythrocytes, leucocytes (phagocytes and lymphocytes) and platelets.
Nutrients, oxygen, carbon dioxide, hormones, antibodies, urea and heat are all transported by the blood.
Applications and skills:
Application: William Harvey’s discovery of the circulation of the blood with the heart acting as the pump.
Application: Pressure changes in the left atrium, left ventricle and aorta during the cardiac cycle.
Application: Causes and consequences of occlusion of the coronary arteries.
Skill: Identification of blood vessels as arteries, capillaries or veins from the structure of their walls.
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.
Utilization: Understanding of the structure of the cardiovascular system has allowed the development of heart surgery.
Aims:
-A heart dissection is suggested as a means of studying heart structure.
-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?
In my opinion knowledge based on science and knowledge based on intuition are both equally valid. The arguments to this are newly found research that says that humans can anticipate near future events even without any evidence foretelling the event and apparently without realizing it. Some researchers even dictate that quantum behavior might be involved. This research states that this knowledge can be due to past experiences or expertise in the area, but since it is fully process by the subconscious, humans note this as intuition. Predicting the near future is common within humans because they notice patterns or clues of previous experiences without even noticing, and as a result learning new knowledge of how society works. These clues are mostly based on sensory clues that each individual has and mostly are determined as correct. Although knowledge based on science is definitely valuable, knowledge based on intuition should not be treated as inferior due to the positive correlation with factual knowledge and positive results.
6.3 Defense 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.
Understandings:
-The skin and mucous membranes form a primary defence against pathogens that cause infectious disease.
-Cuts in the skin are sealed by blood clotting.
-Clotting factors are released from platelets.
-The cascade results in the rapid conversion of fibrinogen to fibrin by thrombin.
-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.
-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.
Cause:
Applications and skills:
Application: Causes and consequences of blood clot formation in coronary arteries.
Application: Florey and Chain’s experiments to test penicillin on bacterial infections in mice.
Application: Effects of HIV on the immune system and methods of transmission.
Utilization: An understanding of immunity has led to the development of vaccinations.
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.
International-mindedness:
The spread and containment of diseases such as bird flu require international coordination and communication.
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.
Understandings:
-The skin and mucous membranes form a primary defence against pathogens that cause infectious disease.
-Cuts in the skin are sealed by blood clotting.
-Clotting factors are released from platelets.
-The cascade results in the rapid conversion of fibrinogen to fibrin by thrombin.
-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.
-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.
Cause:
- HIV causes AIDS.
- HIV destroys a type of lymphocyte vital for antibody production.
- Overtime there are less active lymphocytes.
- The body becomes very vulnerable to pathogens.
- Through vaginal and anal intercourse as well as oral sex if cuts or tears are present.
- Through hypodermic needles shared by drug users.
- Through placenta from mother to child.
- Through cuts during child birth or in milk during breast feeding.
- Through transfused blood.
- Through blood factors such as Factor VIII used to treat hemophiliacs.
- Grief suffered by relatives and friends.
- Families can get poorer.
- Can be hard to find a partner, employment and housing.
- Can reduce sexual activity in a population.
- Antibiotics block specific metabolic pathways in bacteria.
- Bacteria are very different to human cells so human cells are not affected.
- Viruses require host cell to carry metabolic processes for them and so antibiotics cannot be used to treat viruses.
- Harming the virus would harm the human cells.
Applications and skills:
Application: Causes and consequences of blood clot formation in coronary arteries.
Application: Florey and Chain’s experiments to test penicillin on bacterial infections in mice.
Application: Effects of HIV on the immune system and methods of transmission.
Utilization: An understanding of immunity has led to the development of vaccinations.
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.
International-mindedness:
The spread and containment of diseases such as bird flu require international coordination and communication.
6.4 Gas exchange
The lungs are actively ventilated to ensure that gas exchange can occur passively.
Nature of science:
Obtain evidence for theories epidemiological studies have contributed to our understanding of the causes of lung cancer.
Understandings:
-Ventilation maintains concentration gradients of oxygen and carbon dioxide between air in alveoli and blood flowing in adjacent capillaries.
-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.
-Different muscles are required for inspiration and expiration because muscles only do work when they contract.
Alveoli on Gas Exchange:
- The external intercostal muscles contract. This moves the ribcage up and out.
- The diaphragm contracts. As it does so it moves down and becomes relatively flat.
- Both of these muscle contractions result in an increase in the volume of the thorax which in turn results in a drop in pressure inside the thorax.
Exhalation:
- The internal intercostal muscles contract. This moves the ribcage down and in.
- The abdominal muscles contract. This pushes the diaphragm up, back into a dome shape.
- Both of these muscle contractions result in a decrease in the volume of the thorax.
- As a result of the decrease in volume, the pressure inside the thorax increases.
Applications and skills:
Application: Causes and consequences of lung cancer.
Application: Causes and consequences of emphysema.
Application: External and internal intercostal muscles, and diaphragm and abdominal muscles as examples of antagonistic muscle action.
Skill: Monitoring of ventilation in humans at rest and after mild and vigorous exercise.
Aims:
-The social consequences of lung cancer and emphysema could be discussed.
Nature of science:
Obtain evidence for theories epidemiological studies have contributed to our understanding of the causes of lung cancer.
Understandings:
-Ventilation maintains concentration gradients of oxygen and carbon dioxide between air in alveoli and blood flowing in adjacent capillaries.
-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.
-Different muscles are required for inspiration and expiration because muscles only do work when they contract.
Alveoli on Gas Exchange:
- Great numbers increase the surface area for gas exchange.
- Wall made up of single layer of cells and so are the walls of the capillaries so diffusion distance is small allowing rapid gas exchange.
- Covered by a dense network of capillaries which have low oxygen and high carbon dioxide concentrations. This allows oxygen to diffuse into the blood and carbon dioxide to diffuse out of the blood.
- Some cells in the walls secret fluid allowing gases to dissolve. Fluid also prevents the sides of alveoli from sticking together.
- The external intercostal muscles contract. This moves the ribcage up and out.
- The diaphragm contracts. As it does so it moves down and becomes relatively flat.
- Both of these muscle contractions result in an increase in the volume of the thorax which in turn results in a drop in pressure inside the thorax.
Exhalation:
- The internal intercostal muscles contract. This moves the ribcage down and in.
- The abdominal muscles contract. This pushes the diaphragm up, back into a dome shape.
- Both of these muscle contractions result in a decrease in the volume of the thorax.
- As a result of the decrease in volume, the pressure inside the thorax increases.
Applications and skills:
Application: Causes and consequences of lung cancer.
Application: Causes and consequences of emphysema.
Application: External and internal intercostal muscles, and diaphragm and abdominal muscles as examples of antagonistic muscle action.
Skill: Monitoring of ventilation in humans at rest and after mild and vigorous exercise.
Aims:
-The social consequences of lung cancer and emphysema could be discussed.
6.5 Neurons and synapses
Neurons transmit the message and synapses modulate the message.
Nature of science:
Cooperation and collaboration between groups of scientist biologists are contributing to research into memory and learning.
Understandings:
-Neurons transmit electrical impulses.
-The myelination of nerve fibres allows for saltatory conduction.
-Neurons pump sodium and potassium ions across their membranes to generate a resting potential.
-An action potential consists of depolarization and repolarization of the neuron.
-Nerve impulses are action potentials propagated along the axons of neurons.
-Propagation of nerve impulses is the result of local currents that cause each successive part of the axon to reach the threshold potential.
-Synapses are junctions between neurons and between neurons and receptor or effector cells.
-When presynaptic neurons are depolarized they release a neurotransmitter into the synapse.
-A nerve impulse is only initiated if the threshold potential is reached.
Resting potential: the electrical potential across the plasma membrane of a cell that is not conducting an impulse.
Action potential: the reversal and restoration of the electrical potential across the plasma membrane of a cell, as an electrical impulse passes along it (depolarization and repolarization).
How nerve impulses pass along non-myelinated neuron:
Applications and skills:
Application: Secretion and reabsorption of acetylcholine by neurons at synapses.
Application: Blocking of synaptic transmission at cholinergic synapses in insects by binding of neonicotinoid pesticides to acetylcholine receptors.
Skill: Analysis of oscilloscope traces showing resting potentials and action potentials.
Utilization: An understanding of the workings of neurotransmitters and synapses has led to the development of numerous pharmaceuticals for the treatment of mental disorders.
Aims:
-The social effects of the abuse of psychoactive drugs could be considered, as could the use of the neurotoxin Botox for cosmetic treatments.
Nature of science:
Cooperation and collaboration between groups of scientist biologists are contributing to research into memory and learning.
Understandings:
-Neurons transmit electrical impulses.
-The myelination of nerve fibres allows for saltatory conduction.
-Neurons pump sodium and potassium ions across their membranes to generate a resting potential.
-An action potential consists of depolarization and repolarization of the neuron.
-Nerve impulses are action potentials propagated along the axons of neurons.
-Propagation of nerve impulses is the result of local currents that cause each successive part of the axon to reach the threshold potential.
-Synapses are junctions between neurons and between neurons and receptor or effector cells.
-When presynaptic neurons are depolarized they release a neurotransmitter into the synapse.
-A nerve impulse is only initiated if the threshold potential is reached.
Resting potential: the electrical potential across the plasma membrane of a cell that is not conducting an impulse.
Action potential: the reversal and restoration of the electrical potential across the plasma membrane of a cell, as an electrical impulse passes along it (depolarization and repolarization).
How nerve impulses pass along non-myelinated neuron:
- Resting potential rises above threshold level.
- Voltage gated sodium channels open.
- Sodium ions flow into the cell, more sodium channels open.
- Inside of cell develops a net positive charge compared to the outside and results in depolarization.
- Voltage gated potassium channels open.
- Potassium ions flow out of the cell.
- Cell develops a net negative charge compared to the outside and results in repolarization.
- Concentration gradients restored by sodium-potassium pumps.
- Resting potential is restored.
Applications and skills:
Application: Secretion and reabsorption of acetylcholine by neurons at synapses.
Application: Blocking of synaptic transmission at cholinergic synapses in insects by binding of neonicotinoid pesticides to acetylcholine receptors.
Skill: Analysis of oscilloscope traces showing resting potentials and action potentials.
Utilization: An understanding of the workings of neurotransmitters and synapses has led to the development of numerous pharmaceuticals for the treatment of mental disorders.
Aims:
-The social effects of the abuse of psychoactive drugs could be considered, as could the use of the neurotoxin Botox for cosmetic treatments.
6.6 Hormones, hemostasis and reproduction
Hormones are used when signals need to be widely distributed.
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.
Understandings:
-β and α cells of the pancreas respectively to control blood glucose concentration secrete insulin and glucagon.
-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.
-Melatonin is secreted by the pineal gland to control circadian rhythms.
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.
Applications and skills:
Application: Causes and treatment of Type I and Type II diabetes.
Application: Testing of leptin on patients with clinical obesity and reasons for the failure to control the disease.
Application: Causes of jet lag and use of melatonin to alleviate it.
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.
Application: William Harvey’s investigation of sexual reproduction in deer.
Skill: Annotate diagrams of the male and female reproductive system to show names of structures and their functions.
Utilization: Hormones are used in a variety of therapies such as replacement therapies.
Aims:
-Scientists are aware that the drugs women take in fertility treatment pose potential risks to health. Should scientific knowledge override compassionate considerations in treating infertile couples?
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.
Understandings:
-β and α cells of the pancreas respectively to control blood glucose concentration secrete insulin and glucagon.
-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.
-Melatonin is secreted by the pineal gland to control circadian rhythms.
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.
Applications and skills:
Application: Causes and treatment of Type I and Type II diabetes.
Application: Testing of leptin on patients with clinical obesity and reasons for the failure to control the disease.
Application: Causes of jet lag and use of melatonin to alleviate it.
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.
Application: William Harvey’s investigation of sexual reproduction in deer.
Skill: Annotate diagrams of the male and female reproductive system to show names of structures and their functions.
Utilization: Hormones are used in a variety of therapies such as replacement therapies.
Aims:
-Scientists are aware that the drugs women take in fertility treatment pose potential risks to health. Should scientific knowledge override compassionate considerations in treating infertile couples?