Homeostasis is the process by which organisms maintain a stable internal environment-
- Blood temperature should be around 37oC and blood pH around 7.38-7.42, blood sugar should remain around 90mg/ 100mL of blood.
- Homeostasis is the process, which organisms use to maintain their optimum temperature even when affected by limits caused by changes in external environment, behaviour. They adjust this through changing their psychological process.
- Homeostasis- 'staying similar' or 'unchanging'. Refers to the 'steady state' of an organism.
- Homeostasis can occur in living and non-living things, but is more common in vertebrates.
- Homeostasis is called a self-regulation in non-living things, and homeostasis in living things.
- Receptors are constantly monitoring
- Control centre compares stimulus with the set point.
- Effectors carry the message
- Homeostasis first begun by Claude Bernard in 1859. Though he didn't call it this, a man named Walter Cannon did in 1929.
- They may be self regulating- e.g. a thermostat, which has certain vital parts:
o A system where a set value must be maintained
o A detector device, which sends feedback
o A control centre, which responds to the feedback
o A regulator, which corrects any deviations from the set value.
- Living things need to control their-
• Body temp and metabolic rate.
• Concentrations of dissolved salts and minerals
• Concentration of nutrients, e.g. glucose in blood.
• Input and output of water
• Amount of nitrogenous wastes
• O2 and CO2 concentrations.
• Removal of malfunctioning cells or foreign substances.
- These systems monitor all the activities of cells, their requirements and the wastes produced- to maintain health.
- The internal environment of cells are kept within the certain limits of the coordinating systems of the body
o Non-Living: refrigerator or lab bath: required temperature set on a thermostat. It is switched on, a sensitive thermometer (detection system) gives feedback to control centre. Activates/ turns off heater to cool and heat to get to ideal temp.
• Needs: set value, detector device (which sends feedback), control centre and a regulator.
o Living: needs a receptor, a control centre and an effector to carry out homeostatic levels. Receptor plays roll of the detector and monitors changes. Responding is done by the effector. This takes place in two stages: detection and responding.
Coordination in animals is controlled by two different systems-
- The nervous system
- The endocrine system (hormonal system)
In plants it is run by the hormone system-
- In plants the hormone system brings about coordinated functioning of organ systems.
- The feedback mechanisms are self-regulating systems that maintain a balance or homeostasis. It is any circular process where information is fed back to the central control region. E.g. the human body uses feedback mechanisms to deal with changes in body temperature.
Stage 1- Detecting changes from the stable state:
- Receptor detects changes- stimulus
- Body needs to remain in 'stable state' in order to function properly
- The changes/deviations to the stable state are a result of changes to the external and internal environment.
- These changes provoke a response called a stimulus.
- Receptors detect stimuli, to which the organism then reacts to the change.
- Internal Stimuli- Light, day length, sound, temperature, odours
- External Stimuli- levels of CO2, oxygen levels, water, wastes, etc. inside the body.
- Receptors can range from a patch of sensitive cells (e.g. tongue) to complex organs such as eyes and ears.
- If human body temp rises, the brain is stimulated by the rise in blood (using the anterior hypothalamus)
- Also when a mammal is exposed to the cold the skin receptors increase their activity sending nerve impulses to the posterior hypothalamus.
- Plants can detect gravity, light intensity and direction and the length of a period of darkness.
Stage 2- Counteracting changes from the stable state:
- Effectors control change.
- After the receptors detect change the organism then reacts to the change.
- The response will counteract the change in the stable state so that it is once again maintained.
- Effectors- They bring about responses to the stimuli
- Effectors can be muscles or glands- Muscles bring about change by movement, glands bring about change by secreting chemical substances.
- After detecting the rise in body temp. The hypothalamus them stimulates heat loss by increasing the blood circulation through the skin, increasing sweat and decreasing metabolic activity and muscular activity. Thus lowering body temperature.
- After detecting the drop in temperature, activity in the posterior hypothalamus stimulates the sympathetic nervous system to activate mechanisms that conserve heat.
- Plants after detecting and increase in concentration of fluids, release abscisic acid from chloroplasts so that there is a closing of stomates and an increase in the production of watertight resins.
1. What are the current technologies?
- ABG (arterial blood gas) analysis
o Measures the amount of oxygen and CO2 in blood.
o It evaluates how efficiently the lungs and delivering oxygen and getting rid of carbon dioxide.
o It measures the partial pressure of oxygen and carbon dioxide, oxygen content and saturation, bicarbonate content and blood pH.
o Oxygen saturation is the amount of oxygen actually combined with the haemoglobin compared to the total amount of oxygen it is actually able to combine with.
o Arterial blood is collected for this type of analysis.
o Uses electrochemical methods
− A pulse oximeter is used for monitoring oxygen saturation (oxygen levels).
− It is attached to a finger and uses the transition of light through the tissues to measure oxygen saturation.
− This method has its advantages because it is painless, easy to apply, quickly to give results and non-invasive and provides continuous monitoring for patients undergoing anaesthesia or medical ventilation.
− Can also be used as a general check-up procedure to analyse O2 levels
− This is gained due to the large difference in red light absorbed by the haemoglobin compared to oxyhaemoglobin.
2. The conditions under which the technologies are used-
− To assess respiratory diseases and other conditions affecting/or may affect the lungs. E.g. pneumonia and silicosis.
− It is used to manage patients receiving oxygen therapy, mechanical ventilation, and anaesthesia, in intestine care, in accident and emergency facilities or for premature babies.
− Test of blood pH also provide information on how well the kidneys and lungs are maintaining blood pH.
− As a response to signs of low oxygen or high carbon dioxide levels.
− For diagnoses and monitoring of patients
− Also used during surgeries, to monitor patients under anaesthesia.
− And used to monitor premature babies that are in neo-natal wards.
− Used in many conditions - this is because it is painless, easy to apply and quick to give results.
− Can also be used as a general check-up procedure to analyse O2 levels.
Chemical Composition of the blood as it moves around the body Tissues in which these changes occur-
− Blood receives oxygen and carbon dioxide is released.
− Blood enters via the right atrium of the heart via the vena cava (major vein)
− Blood which enters is high in carbon dioxide
− Blood is low in glucose and other nutrients; it is also high in urea, other nitrogenous wastes and various poisons.
− As the heart beats, the right ventricle pumps the blood through the pulmonary artery, to the lungs
− Where the blood gains oxygen, and loses carbon dioxide.
− The blood then enters the left atrium via the pulmonary vein. Lung tissue
− Blood receives carbon dioxide and released oxygen
− The left ventricle pumps oxygenated blood to the body through the aorta.
− The blood loses oxygen and gains carbon dioxide in all body cells, as respiration occurs. Glucose levels also drop. General body tissue e.g. Skin tissue
− Water diffuses into the blood. Some substances e.g. alcohol pass into the stomach tissue from the blood through the walls of the stomach Stomach tissue
− Digested food, amino acids, glucose- diffuse into the blood and go to the liver. Fatty acids go to the lymph. Small intestine tissue
− Glucose is regulated (added or removed) and some poisonous/unwanted substances are removed. Excess vitamins, ions, lipids are removed. Excess amino acids are removed and converted into ammonia, and then into urea, which is added to the blood.
− Poisons are also reduced, as the liver changes them to less toxic forms Liver tissue
− Water/salts/vitamins absorbed in large intestine and passed into blood. Large intestinal tissue
− Urea, excess water, salts removed from blood excreted. Kidney tissue
− Hormones are secreted directly into the blood stream. Endocrine tissue
o PULMONARY CIRCUIT (Lungs):
• Blood enters the right atrium of the heart via the vena cava (major vein):
• The blood is deoxygenated, and high in carbon dioxide
• It is low in glucose and other nutrients; it is also high in urea, other nitrogenous wastes and various poisons.
• As the heart beats, the right ventricle pumps the blood through the pulmonary artery, to the lungs:
• Here the blood gains oxygen, and loses its carbon dioxide.
• The blood then enters the left atrium via the pulmonary vein.
o SYSTEMIC CIRCUIT (Body):
• The left ventricle pumps oxygenated blood to the body through the aorta.
• In the body, various changes occur to the blood.
• The blood loses oxygen and gains carbon dioxide in all body cells, as respiration occurs. Glucose levels also drop.
• In the LIVER:
• Levels of glucose are regulated - excess glucose is changed to glycogen, or glycogen stores are changed to glucose (if needed)
• Excess amino acids are changed to ammonia, and then to urea
• Poisons are also reduced, as the liver changes them to less toxic forms
• In the INTESTINES:
• Levels of nutrients from digestion increase.
• Glucose, amino acids, ions, lipids and other substances from food enter the blood. The increase is through the small intestines reabsorption of food
• In the KIDNEYS:
• Salt and water levels are regulated
• All urea is removed, toxins are excreted into the urine
• The changed blood, again highly deoxygenated, then flows back to the pulmonary circuit.
Oxygen in cells
Describe current theories about processes responsible for the movement of materials through plants in xylem and phloem tissues-
Transport in Plants
o Xylem of flowering plants consists of xylem vessels, tracheids, fibres and parenchyma
o Water and minerals rise through the xylem through pressure from the roots and vacuums from the leaves.
o Phloem consists of fibres, parenchyma, sieve cells and companion cells.
Processes involved in the transpiration stream
- The nephron is a regulatory unit; it absorbs or secretes substances in order to maintain homeostasis.
- This regulation maintains the constant composition of body fluids.
- Salts and water are adjusted to maintain fluid concentration
- Different ions also adjusted to maintain pH.
- These different processes happen in the different sections of the nephron.
- Proximal Tubule:
• Bicarbonate ions are reabsorbed into the capillaries into the blood from the nephron, hydrogen ions are secreted out. This maintains the pH of the blood.
• Drugs, such as aspirin, penicillin and poisons are secreted out of the blood
• Regulation of salts also occurs here. Sodium ions are actively reabsorbed and chlorine ions follow passively. Potassium ions are also reabsorbed
- The Loop of Henle: It has a descending limb and an ascending limb
• In the descending limb, it is permeable to water, not salt.
• Water passes out of the nephron and into the capillaries by osmosis
• In the ascending limb, the walls are permeable to salt, but not water
➢ Ascending limb is thin-walled at the bottom, and thick-walled at the top.
• Salt passively passes out into the capillaries at the bottom, thin-walled section, but is actively passed out in the top, thick-walled section.
- The Distal Tubule:
• Selective reabsorption of sodium ions and potassium ions occurs here again, to regulate the pH of the blood, and the concentration of salts.
- The Collecting Duct:
• This is the end of the nephron, and connects to the ureters.
• The walls are permeable to water only, and water is transported out accordingly to the needs of the body
• The final filtrate is called urine.
- Active transport uses energy to transport substances across a membrane it would normally not be able to cross due to a diffusion gradient or its own properties
- Passive transport is the movement of substances across a membrane without energy expenditure (this is diffusion and osmosis) - completely random.
- A kidney is made up of around a million nephrons. It is within the nephrons that the processes of filtration, reabsorption and secretion occur.
- The STRUCTURE of a nephron:
• It is a long twisted tubule made up of sections: a Bowman's capsule, connected to (1) a proximal tubule, leading to the (2) loop of Henle, which connects to (3) the distal tubule. This all joins to the collecting duct which leads to the bladder.
- The nephrons are densely surrounded by capillaries (this is to provide a large surface area for excretion).
- Three processes occur in the nephrons (kidneys):
• Filtration: Within the Bowman's capsule is the glomerulus, a dense clump of capillaries. The blood pressure here is so high that fluid and substance from the blood are forced into the Bowman's capsule, and form a fluid called the glomerular filtrate. It flows into the nephron and contains:
➢ Substances the body can reuse: Glucose, water, amino acids, etc.
➢ Wastes: Urea and poisons.
• Reabsorption: The substances the body can reuse are reabsorbed into the capillaries surrounding the nephron. E.g. Vitamins and hormones. This is active transport and requires energy. Some other substances passively re-enter the blood. E.g. water by osmosis and salts by diffusion. This occurs in the proximal and distal tubules and in the loop of Henle (discussed in detail later).
• Secretion: This is the process where the body actively transports substances from the blood into the nephron. Some toxins, such as urea, tend to diffuse back into the blood, so it must be secreted back into the nephron. It is also done to regulate salt and water levels again, or to remove additional toxins. This is active transport.
• Halophytes are plants adapted to living in salty environments. They have:
- Salt excluders on their roots
- Salt filtration system
- Excrete salt from the leaves
• Xerophytes are plants adapted to arid and dry conditions. These include:
- Thick leaves or a waxy cuticle
- Small leaves, hairy leaves
- Reflective leaf surfaces
- Vertically hanging leaves
- Thick bark to prevent wilting
2nd EditionAlan S. Willsky, Alan V. Oppenheim, S. Hamid 6th EditionCharles Alexander, Matthew Sadiku 10th EditionR.C. Hibbeler 13th EditionKai Beng Yap, R.C. Hibbeler