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BIO - Chapter 10-13 - Respiration, Excretion, Homeostasis, The Nervous System
Chapter 10: RespirationRespiration is the oxidation of food substances with the release of energy in living cells.Aerobic respiration is the oxidation of food substances in the presence of oxygen with the release of alarge amount of energy.Word equation: glucose + oxygen carbon dioxide + water + energyChem equation: C6H12O6 + 6O2 6CO2 + 6H2O + energyAnaerobic respiration is the breakdown of food substances in the absence of oxygen with the release of alot less energy.In muscle cells,Word equation: glucose lactic acid + energyChem equation*: C6H12O6 2C3H6O3 + energyDuring vigorous muscular contractions during exercise, your muscles first respire aerobically. Pantingmay follow to take in more oxygen and remove more carbon dioxide. However due to the limit to the rateof breathing and heartbeat, the muscles have to respire anaerobically to provide the extra needed energyto support the muscle contractions. As a result, lactic acid is formed.Since there is insufficient oxygen to meet the demands of vigorous muscular contractions, the muscles aresaid to incur an oxygen debt. When lactic acid concentrations get too high, it causes fatigue and muscularpains and this forces the person to stop exercise and recover. However during rest, the breathing ratecontinues to be high so that sufficient oxygen is absorbed to repay the oxygen debt as well as to oxidisethe lactic acid to produce energy. When the lactic acid is used up, the oxygen debt has been repaid.
In yeast,Word equation: glucose ethanol + carbon dioxide + energyChem equation*: C6H12O6 2C2H5OH + 2CO2 Part Form and function Air enters the lungs through 2 external nostrils whose walls bear a fringe of hairs and also lined with a moist mucous membrane. This allows the air breathed in to be: cleaner since dust Nose and foreign particles are trapped in the hairs and mucus, warmer and moist since the air passes through the warm nasal passages and safer as harmful chemicals are detected by small sensory cells in the mucous membrane. The thinner walls of trachea and bronchi are lined by epithelium bearing cilia. Gland cells inTrachea the epithelium secrete mucus to trap dust particles and bacteria. Cilia help sweep these particles up into the pharynx to be swallowed into the oesophagus. Each lung lies in the pleural cavity, withing which the lungs expands. Two pleural membranes line each pleural cavity. A thin layer of lubricating fluid between the pleura Lungs allow membranes to glide over each other easily. Alveoli are well-supplied with capillaries for efficient gaseous exchange. Thousands of alveoli are present to increase surface area to volume ratio for rapid diffusion of gases. Inspiration (inhalation) Expiration (exhalation)Diaphragm contracts and flattens. Diaphragm relaxes and arches upwards.External intercostal muscles contract. External intercostal muscles relax.Internal intercostal muscles relax. Internal intercostal muscles contract.Ribs move upwards and outwards. Ribs moves downwards and inwards.Sternum also moves up and forward. Sternum also moves down to original position.Volume of thoracic cavity increases. Volume of thoracic cavity decreases.Air pressure in your lungs causes them to expand to Air pressure in your lungs causes them tofill up the enlarged space in the thorax. compress.Air pressure in the lungs decrease. Air pressure in the lungs increase.Atmospheric pressure is higher than in lungs hence Atmospheric pressure is lower than in lungs henceair rushes in. air rushes out.
How is carbon dioxide removed? How is oxygen absorbed?Since the concentration of carbon dioxide in the Since the concentration of oxygen in the venousvenous blood is higher than in the alveolar cavity, blood is lower than in the alveolar cavity, oxygencarbon dioxide diffuses from the blood vessels diffuses from the alveoli into the thin film ofthrough the alveolar wall and into the thin film of moisture and diffuses through the blood vessel wallmoisture on the inner alveolar wall after which it where it combines with the haemoglobin in RBCsdiffuses into the air and escapes. to form oxyhaemoglobin and it is transported. How is gaseous exchange optimised?1. A continuous blood flow ensures that the concentration gradient in the blood vessels are maintained.2. Breathing in and out ensures that the concentration gradient in the alveoli are maintained.Due to carbon dioxide’s insolubility with water, there isanother method how carbon dioxide is transported in theblood.1. CO2 + H2O ⇌ H2CO3 (via carbonic anhydrase) carbon dioxide + water ⇌ carbonic acid2. H2CO3 ⇌ H+ + HCO3- carbonic acid ⇌ hydrogen + hydrogencarbonate ionsStimulus for breathing: High concentration of carbondioxide in blood, and not low concentration of oxygen inair.Long exposure to irritants (eg. formaldehyde) cannot be coped by our defence mechanisms. It will causeus to cough excessively leading to lung damage. As such they should wear protective masks.
Chemical in Properties of chemicals Effects on the body tobacco smoke Addictive drug Increased heartbeat and blood pressure Nicotine Causes release of adrenaline Increased risk of blood clotting in BVs Makes blood clot easily Combines with haemoglobin to form carboxyhaemoglobin Death if CO concentration > 1% that reduces transportCarbon monoxide Increased risk of coronary heart disease efficiency of RBCs Increases atherosclerosis Increased risk of blood clotting Damages lining of BVs Contains carcinogenic Blockage in air sacs and reduction in chemicals that induce Tar gaseous exchange efficiency uncontrolled cell division Dust particles trapped cannot be removed Paralyses cilia lining Irritants Increased risk of chronic bronchitis and Paralyses cilia lining(eg. formaldehyde) emphysemaChronic bronchitis:The epithelium lining becomes inflamed. Excessive mucus is secreted by the epithelium. The cilia on theepithelium are paralysed hence dust and foreign particles cannot be removed. The airways are blockedand hence the person has to frequently cough violently to expel their dust. This increases the risk of lunginfections.Emphysema:Persistent coughing breaks the partition walls between the air sacs. This decreases the surface area forgaseous exchange. Hence the lungs get inflated with air and lose their elasticity. As such breathingbecomes difficult. The person wheezes and suffers sever breathlessness.
Chapter 11: ExcretionExcretion – Process by which toxic materials and metabolic wastes are removed from the body of anorganism. Egestion – removal of undigested material from the alimentary canal = NOT EXCRETION.Accumulation of nitrogenous and other compounds in an organism is harmful to the organism.Excretory organs – Skin, kidney and lungs URINE FORMATION1. Ultrafiltration – mechanical filtration of different solutes (waste, nutrients) in the blood plasma, except red and white blood cells that takes place due to a high hydrostatic blood pressure produced by the difference in diameter between the afferent and efferent arteriole, in each glomerulus, through a selectively permeable membrane. For ultrafiltration to occur, there must be a high hydrostatic blood pressure formed because the afferent arteriole has a larger diameter than the efferent arteriole. A partially permeable membrane (aka. basement membrane) must be present as it acts as a filter and only allows small molecules to pass through.
2. Selective reabsorption – process whereby useful materials are taken back into the blood stream by osmosis (water), diffusion and active transport (glucose, amino acids) Region Processes - Most of the mineral salts and all of the glucose and amino acids reabsorbed by First convoluted tubule diffusion and active transport. - Most of the water is reabsorbed by osmosis. Loop of Henle - Remaining water is reabsorbed by osmosis. - Remaining water is reabsorbed by osmosis. Second convoluted tubule - Mineral salts (eg. Na+) is reabsorbed by diffusion and active transport. Collecting duct - Remaining water is reabsorbed by osmosis.Excess water, excess salts and metabolic waste products (eg. urea, uric acid and creatinine) pass out ofthe collecting duct into renal pelvis as a mixture called urine. OSMOREGULATION WITH ANTI-DIURETIC HORMONE (ADH)
Dialysis1. Kidney failure is fatal as the body is not able to remove waste materials such as urea and other toxic chemicals.2. Patients suffering from kidney failure can use a kidney dialysis machine to remove urea as well as balance their salt concentration.3. Blood is drawn from an artery in the patient’s arm and flows through a narrow tubing throught the dialysis machine and is soon returned to a vein in the patient’s arm. Characteristic of dialysis How it helps? Allows only small solutes such as urea, excess salts and Partially permeable water to diffuse out from the blood while RBCs and tubing WBCs remain in the blood. Increases surface area to volume ratio to increase the Long, narrow and coiled rate of diffusion. tubing Ensures that these substances do not diffuse into the dialysis fluid when the blood plasma has a higher Same concentration of concentration of these substances. essential substances as normal blood plasma Allows these substances to diffuse into the blood when the blood plasma has a lower concentration of these substances. Ensures a steep concentration gradient which increases No metabolic waste in the rate of diffusion of waste products to be diffused supplied dialysis fluid out into the dialysis fluid. Direction of blood flow is opposite to direction of Maintains the concentration gradient at all sections of flow of dialysis fluid the dialysis machine to increase rate of diffusion. Treatment is 2-3 times a Allows sufficient time for the waste products to be week for a few hours removed from the blood.
Chapter 12: HomeostasisHomeostasis is the maintenance of a constant internal environment.4 basic principles of homeostasis:1. Stimulus – change in the internal environment2. Receptor – detects the stimulus3. Corrective mechanism – reverses effects of stimulus4. Negative feedback – provides information to receptor to stop corrective mechanis, Structure of mammalian skin REGULATING HEAT IN THE BODY
Chapter 13: Nervous System1. Central nervous system (CNS) consists of brain and spinal cord, Peripheral nervous system (PNS) consists of cranial nerves and spinal nerves.2. CNS does not come in direct contact with external environment. PNS comes in direct contact with external environment. direction of nerve impulse direction of nerve impulse Neurone part Form and function Contains nucleus and much of cytoplasm; most Cell body of the metabolic activity of the cell occurs here Axon Transmits impulses away from the cell body Dendrons Transmits impulses towards the cell body Dendrites Terminal branches on axons and dendrons Layer of fatty substance that encloses the nerve Myelin sheath fibre and insulates axon Neurilemma Thin membrane surrounding myelin sheath Motor end plate (applicable to motor neuron) Junction between dendrite and muscle fibre Regions where myelin sheath is absent allow Nodes of Ranvier nerve impulses to jump from node to node, increasing the speed of nerve transmission
Path of a nerve impulseSTIMULUS causes RECEPTOR to create impulse…Step 1: Sensory neuron at receptor Step 2: Sensory neurons in nerves Step 3: Sensory neuron at dorsal root ganglion Step 4: SAME sensory neuron in dorsal root Step 5: SYNAPSE with relay neuron in grey matter in spinal cord (neurotransmitters released) Step 6: Brain (processes information) Step 7: Relay neuron in grey matter in spinal cord Step 8: Motor neuron in ventral root Step 9: Motor neuron in nerves Step 10: Effector…EFFECTOR causes RESPONSE3. The nervous system serves to coordinate and regulate bodily functions.4. A reflex is an immediate response to a specific stimulus without conscious control.5. A reflex arc is the shortest pathway by which nerve impulses travel from the receptor to the effector in a reflex action.6. Receptor and effectors – i. Knee jerk reflex: Sensory receptor in patellar tendon, upper thigh muscle ii. Hand on hot object reflex: Thermoreceptors, biceps