Human Body Systems PDF

Cell Differentiation in Multicellular Organism - Cell differentiation is caused by changes in gene expression. This occurs when different signalling molecules in the environment activate or repress different transcription factors that are necessary to express certain genes in the DNA....

Cell Differentiation in Multicellular Organism - Cell differentiation is caused by changes in gene expression. This occurs when different signalling molecules in the environment activate or repress different transcription factors that are necessary to express certain genes in the DNA. Organisation of Life - Atom, molecule/compound, organelle, cell, tissue, organ, organ system, organism Exchange Surfaces in the Body - Very Thin -- keeps the diffusion distance small -- decreases time take to diffuse - Layer of Moisture -- allows for substances such as carbon dioxide to dissolve and diffuse easily. - Increased Surface Area -- allows for more particles to be diffused across the membrane. Homeostasis and Negative Feedback - Homeostasis is the maintenance of a stable environment. - Stimulus, receptor, control centre, effector, response, negative feedback. - Stimulus: any detectable change in the environment - Receptor: specialised parts of the nervous system able to sense change in the environment - Control Centre compares the current conditions to the set point and facilitates the response via the effector. - Effector: causes changes to compensate for the deviation - Response: what actually occurs in response from the control centre. - Feeback: the response reverses the deviation Excretory System: - Renal artery, kidney, urethra, bladder, ureter. - Glomerulus, Bowmans Capsule, proximal tubule, loop of Henle, distal tubule, collecting duct. - Function of Kidneys: Excretion of waste, controlling ion levels, maintenance of water balance. - Filtration: soluble materials are forced through capillary walls into the nephron - Reabsorption: useful materials are absorbed back into the blood. - Control of Ion levels: substances dissolved in the kidneys have a threshold level. If the concentration level exceeds, the kidney ensures that the excess is excreted in the urine. - Maintenance of Water Balance: water is used to dilate waste products and transport them to the bladder. Any water not needed for this will be reabsorbed into the blood via the nephron. - Filtration occurs in the glomerulus in the bowman's capsule. - Collecting ducts: are permeable to water, waters pass from collecting ducts to kidney tissue, resulting in higher concentration of urine, the level of permeability of collecting ducts to water, is controlled by antidiuretic hormone. - More ADH means the urine is more concentrated. Digestive System - Mouth, epiglottis, oesophagus, stomach, small intestine, large intestine, rectum, anus. Liver, gallbladder, appendix. - Hindgut: digest the cellulose after the large intestine, often eat faeces. - Foregut: rumen is before the small intestine and cellulose is broken down and absorbed in the small intestine. Respiratory System - Trachea, bronchi, bronchioles, alveoli - CO2 and Oxygen - They are exchanged via diffusion, concentration gradient, and are transported around the body and are exchanged in the tissues. - Counter current: Equilibrium is not reached, so there is always a difference in concentration, so that gas exchange is continuous. Equilibrium is not reached. - Haemoglobin: increases carrying capacity of blood by 70 times. Maintains concentration gradient between blood and alveoli. Cardiovascular System - Oxygen and other important nutrients need to be transported around the whole body, and waste products need to be removed. - Oxygen, Nutrients, Hormones - Capillary Exchange: At the arterial end of the capillary, the blood pressure is higher than that on the outside, therefore substances are forced out of the capillary due to diffusion. In the middle, equilibrium is reached and there is no exchange of substances. At the vein end, substances enter in as the blood pressure is lower than that of pressure outside, forcing the particle back in. - What is in the blood?: Red Blood Cells, Digested food, white blood cells, waste, oxygen, carbon dioxide, plasma, hormones, platelets. - Plasma is a straw-coloured liquid that carries cells and platelets. - Platelets are fragments of other cells, made in the bone marrow. Don't have a nucleus and they create e net that traps blood cells, forming a blood clot. - Arteries take blood away fro9m the heart. The walls of an artery are made up of think muscle walls and elastic fibres. Veins carry blood to the heart and have valves. The capillaries link arteries and vain and have one cell think wall. Blood is made up of four things, plasma, the liquid part of the blood; red blood cells to carry oxygen; white blood cells to protect the body from disease and platelets to blood clot when necessary. - Superior vena cava, right atrium, atrioventricular valve, right ventricle, semi -- lunar valve, pulmonary artery, lungs, pulmonary veins, left atrium, atrioventricular valve, left ventricle, semi-lunar valve, aorta, rest of the body.