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Transcript of Option H
H1 Hormonal Control
H.1.1 State that hormones are chemical messengers secreted by endocrine glands into the blood and transported to specific target cells.
H.1.2 State that hormones can be steroids, proteins and tyrosine derivatives, with one example of each.
H.1.3 Distinguish between the mode of action of steroid hormones and protein hormones.
H.1.4 Outline the relationship between the hypothalamus and the pituitary gland.
H.1.5 Explain the control of ADH (vasopressin) secretion by negative feedback.
H.2.1 State that digestive juices are secreted into the alimentary canal by glands, including salivary glands, gastric glands in the stomach wall, the pancreas and the wall of the small intestine.
H.2.2 Explain the structural features of exocrine gland cells.
H.2.3 Compare the composition of saliva, gastric juice and pancreatic juice.
H.2.4 Outline the control of digestive juice secretion by nerves and hormones, using the example of secretion of gastric juice.
H.2.5 Outline the role of membrane-bound enzymes on the surface of epithelial cells in the small intestine in digestion.
H.2.6 Outline the reasons for cellulose not being digested in the alimentary canal.
H.2.7 Explain why pepsin and trypsin are initially synthesized as inactive precursors and how they are subsequently activated.
H.2.8 Discuss the roles of gastric acid and Helicobacter pylori in the development of stomach ulcers and stomach cancers.
H.2.9 Explain the problem of lipid digestion in a hydrophilic medium and the role of bile in overcoming this.
H.3.1 Draw and label a diagram showing a transverse section of the ileum as seen under a light microscope.
H.3.2 Explain the structural features of an epithelial cell of a villus as seen in electron micrographs, including
microvilli, mitochondria, pinocytotic vesicles and tight junctions.
H.3.3 Explain the mechanisms used by the ileum to absorb and transport food, including facilitated diffusion, active transport and endocytosis.
H.3.4 List the materials that are not absorbed and are egested. Limit this to cellulose, lignin, bile pigments, bacteria and intestinal cells.
H.4.1 Outline the circulation of blood through liver tissue, including the hepatic artery, hepatic portal vein, sinusoids and hepatic vein.
H.4.2 Explain the role of the liver in regulating levels of nutrients in the blood.
H.4.3 Outline the role of the liver in the storage of nutrients, including carbohydrate, iron, vitamin A and vitamin D.
H.4.4 State that the liver synthesizes plasma proteins and cholesterol.
H.4.5 State that the liver has a role in detoxification.
H.4.6 Describe the process of erythrocyte and hemoglobin breakdown in the liver, including phagocytosis, digestion of globin and bile pigment formation.
H.4.7 Explain the liver damage caused by excessive alcohol consumption.
H.5.1 Explain the events of the cardiac cycle, including atrial and ventricular systole and diastole, and heart sounds.
H.5.2 Analyse data showing pressure and volume changes in the left atrium, left ventricle and the aorta, during the cardiac cycle.
H.5.3 Outline the mechanisms that control the heartbeat, including the roles of the SA (sinoatrial) node,
AV (atrioventricular) node and conducting fibres in the ventricular walls.
H.5.4 Outline atherosclerosis and the causes of coronary thrombosis.
H.5.5 Discuss factors that affect the incidence of coronary heart disease.
H.6.1 Define partial pressure.
H.6.2 Explain the oxygen dissociation curves of adult hemoglobin, fetal hemoglobin and myoglobin.
H.6.3 Describe how carbon dioxide is carried by the blood, including the action of carbonic anhydrase, the chloride shift and buffering by plasma proteins.
H.6.4 Explain the role of the Bohr shift in the supply of oxygen to respiring tissues.
H.6.5 Explain how and why ventilation rate varies with exercise.
H.6.6 Outline the possible causes of asthma and its effects on the gas exchange system.
H.6.7 Explain the problem of gas exchange at high altitudes and the way the body acclimatizes.
Steroid Hormones Are Derivatives of Cholesterol: Prednisone, Testosterone, Estrogen
Peptide hormones are short chains of amino acids:
Human Growth Hormone, Anti-Diuretic Hormone, FSH, Glucagon, Insulin, Oxytocin
Tyrosine Derivative Hormones are variations of the amino acid tyrosine.
Thyroxine: An iodine-containing hormone that is produced by the thyroid gland, increases the rate of cell metabolism, regulates growth, and is made synthetically for treatment of thyroid disorders.
Epinephrine/Adrenaline: Fight or flight
Neurosecretory cells in the hypothalamus synthesise and transport ADH to the posterior pituitary gland where it is stored
Osmoreceptors in the hypothalamus detect an increase in blood solute concentration when levels of water in the blood drop
This may be caused by excessive sweating, too little water intake or too much salt intake
In response to this nervous activation, ADH is released from the posterior pituitary and travels in the blood to the kidneys
ADH makes the epithelium of the collecting ducts more permeable to water by upregulating the expression of aquaporins
This increases the amount of water reabsorption by the kidneys, causing blood solute concentration to drop
With a drop in blood solute concentration, ADH secretion is inhibited (negative feedback)
If blood solute concentration is low (due to excessive water intake), the collecting duct remains impermeable to water and urine is dilute
Food entering the stomach causes distension (stretching), which is detected by stretch receptors in the stomach lining
Impulses are sent to the brain, which triggers the secretion of gastrin from the pits lining the stomach wall
Gastrin causes the sustained release of gastric juice, particularly its acid component
When the pH drops too low, gastrin secretion is inhibited by hormones (secretin and somatostatin)
Some digestive enzymes are immobilized on the plasma membrane of the epithelial cells of the small intestine, serving two main benefits:
1. The enzyme is fixed in place and does not pass through the digestive system, meaning it can be reused
2. The enzyme can be linked to secondary functions (e.g. membrane transport)
Maltase is immobilised on the epithelial lining with its active site facing towards the intestinal lumen
Maltase digests the disaccharide maltose into two glucose monomers, which are then absorbed by localised transporters
The sight and smell of food triggers a reflex response in which gastric juice is secreted from gastric pits in the stomach wall
This ensures that gastric juice is in the stomach by the time the food is consumed