1. What is homeostasis?
2. How is body temperature maintained including why this is necessary for the organism?
• Water is important for homeostasis how are water levels maintained within the body and why it is important to do so?
• Insulin and Glucagon are homeostatic hormones how is this case and why are they necessary?
3. For each of the subdivision you have labelled above explain their functions within the nervous system and in the case of certain answers their relationships to each other
• Nervous system, central nervous system, peripheral nervous system.
4. Explain the relationship between structure and functions of the excretory system and what organs are involved in the excretory system and what structures do they carry out this role use annotated diagrams as part of your answer?
1. Homeostasis is a process of maintaining optimum conditions of all the biochemical and metabolic interactions in the body of any organism to sustain their lives in constantly changing environment. The body temperature and balance of acidity and alkalinity that is pH is also maintained by the process of homeostasis (He et al. 2012). When body encounters an imbalance in the normal range of any one of the important metabolites; it immediately activates its endocrine, nervous, renal and other associated systems to restore the normal body conditions. Homeostasis is a characteristic feature of all organisms from unicellular to multicellular organisms. The process enables different organs and systems of our body to work cooperatively in order to achieve the desired result (Hooper & Macpherson, 2015).
2. Temperature regulation in the body is done by homeostasis. There are two different kinds of animal endotherms- those who generally maintain a constant body temperature and ectotherms- those whose body temperatures changes with eternal factors. In case of humans the body temperature is regulated by the hypothalamus. Hypothalamus is the thermoregulatory center of the human body which acts as a sensor and detects small variations in the body temperature (Forster, Hirst & Atkinson, 2012). There are two different lines of thermo receptors beneath the skin which senses the change in the temperature and tranduces the signal to the hypothalamus. If it is too hot then the heat loss centre of the hypothalamus is activated but when it is too old then heat generating centre gets activated. The hypothalamus then sends response to the effectors of the autonomic nervous system.
Temperature homeostasis is very important for animals to live in this constantly changing environment. Human body comprises of so many organ systems for performing specific works. The biochemical pathways performed by these systems involve active participation of a wide array of enzymes. Enzymes need an optimum temperature for their activity. The ambient temperature or the normal body temperature of humans generally serves as the optimum temperature for the enzymes to carry their normal funtion. So if temperature of the body changes then these enzymes will not function properly thereby hindering the cascade of the biochemical pathway. In addition to that enzymes are denatured at high temperature that is their native structure gets destroyed and the enzyme no longer remains functional. The biochemical pathways are catalyzed by enzymes but if their native structure is lost then the metabolic pathways will be blocked (Culling, 2013). The ultimate result of this will be dysfunctioning of the organs and the systems. So temperature homeostasis is necessary to keep all the physiological and metabolic pathways of our body in their normal condition.
Water is the important component of all cells because 55% of the cell comprises of water. Water activity is an essential feature of every cell. This term determines the percentage of water content in a cell. Water is the main component of blood too as it maintains blood volume. Water potential of blood needs to be regulated in order to prevent water loss from the cells. This regulation is also done by the hypothalamus which contains osmoreceptors. The osmoreceptors detect small change in water potential. A drop in the blood volume causes a sudden fall of blood pressure. The hypothalamus signals the brain to impart a feeling of thirst indicating requirement of water in the body. Hypothalamus also releases Antidiuretic hormone which opens the water channels of the endothelial cells of the collecting tubule of the nephrons (Ainsworth et al 2014). A hormone called rennin, released by the kidney activates another hormone Angiotensin II which constricts the blood vessels and in turn increases blood pressure. Water also receives the toxins from the cells and excretes them out of the body. Gaseous substances like oxygen and carbon-di-oxide are also carried by water. These two gases are carried by the blood and blood is mostly composed of water. Oxygen get dissolved in the watery portion that is the plasma of the blood and carried to the cells to meet the requirement of oxygen. On the other hand carbon-di-oxide, released due to excretion of the cells, get dissolved in the plasma of blood and forms carboic acid, a mild acid, and finally comes to the lungs (Hannon et al. 2012). There in the lungs the CO2 diffuses out of the blood and finally from the lungs. Body temperature is also regulated to some extent by water. Water provides an efficient mean of regulating the body temperature. During sweating, water is released from the sweat glands and evaporates from the skin; this in turn decreases the body temperature because when water evaporates it takes the heat from the body so the temperature lowers.
Glucose is the principal carbohydrate which is transported in the cells. Glucose level needs to be controlled in all the cells. Generally glucose concentration should remain within 0.8 to 1 g/dm3 of blood. When glucose level in the blood rises up then the situation is called hyperglycaemia and when it falls then it is known as hypoglycaemia. Both the cases are fatal and even can lead to death. Glucose homeostasis is done by two hormones called insulin and glucagon. Both the hormones are released from the endocrine glands pancreas. Pancreas contains a region of hormone secreting cells called Islets of Langerhans. The hormones insulin and glucagon are secreted by the ? and ? cells of the Islets of Langerhans. Pancreas has receptors which sense the concentration of glucose in the blood. Insulin and glucagon have antagonistc effect on the blood glucose level (Trung et al. 2012). Insulin stimulates cells to uptake glucose for using in the cellular respiration process. Insulin turns on a signal transduction pathway that converts glucose into glycogen by the process called glycogenesis. This process causes polymerization of glucose into glycogen and thus concentration of free glucose in the blood decreases. On the other hand, glucagon cleaves glycogen polymer and produces glucose monomer by a process called glycogenolysis. After taking a full meal free glucose level in the blood increases. This high blood glucose stimulates the pancreas to release insulin from the ? cells. The insulin triggers the glycogenesis process to switch on and polymerize free glucose into glycogen. But when blood glucose level is very low then the endocrine system triggers the glycogenolysis process to turn on and break down glycogen into glucose rendering an increase in the free glucose level in blood.
Both insulin and glucagon are essential for the cells otherwise blood glucose level will be disturbed. If insulin is not released during rise in blood glucose then free glucose will not be utilized by the cells. As a result hyperglycaemia will be caused. This situation is commomnly known as diabetes mellitus. High concentration of glucose often spills out in the urine causing a serious health problem. So diabetic patients commonly need insulin therapy in which insulin is given to the patient intravenously from outside. If glucagon is not secreted properly then a condition called hypoglycaemia occurs in which the blood glucose level suddenly falls. Hypoglycaemia can lead to coma and even death. So these two hormones need to be secreted properly otherwise diabetes or hypoglycaemia may lead to serious health concern (Cantley & Ashcroft, 2015).
3. Nervous system, central nervous system, peripheral nervous system
Nervous system is the signaling centre of the body. It controls and coordinates different physiological, morphological and metabolic functions in the body. The main function of the nervous system is to respond to any internal or external stimulus of the constantly changing environment. Nervous system coordinates muscular activity as well as the internal relationship of the internal organs (Mathias & Bannister, 2013).
Function of the central nervous system:
The three parts of the central nervous system performs three different functions. The forebrain helps in thinking, analyzing, learning, coordinating the activities of the motor nerves. The mid brain controls motor function, helps in visual and auditory functions. The hind brain transmits sensory information. It also helps to maintain body balance, movement, digestion, respiration and maintain heart rate. The spinal cord delivers information to and from the brain. The spinal cord is the main component of the reflex arc so it controls and coordinates reflex actions (Cantley & Ashcroft, 2015).
Function of the peripheral nervous system:
Peripheral nervous system is involved in the voluntary actions by the skeletal musles. It contains three types of nerves-spinal, cranial and association nerves. Spinal nerves transmit signals to the spinal cord. Cranial nerves helps in smell, vision, taste etc.
Association nerves help in coordinating motor and sensory functions.
4. The system which helps to remove waste products from the body is called the excretory system. The principal organs of the excretory system are two kidneys. Kidneys are bean shaped and composed of its structural and functional units the nephrons. The kidneys are located on the either side of the backbone. There are two regions in the kidneys- the outer cortex and inner medulla (Ransohoff & Brown, 2012). Waste products from the cells enter into the kidneys through blood. Renal artery carries blood to the kidneys and renal vein carries blood from the kidneys. The blood containing waste products get purified in two kidneys.
Figure: Excretory System
(Source: My organ donation project, 2015)
The waste formed in the kidneys then pass through ureters and stores in the form of urine in the urinary bladder. Urine is formed in the nephrons by reabsorption of water which is aided by a hormone called Anti-di-uretic hormone or ADH. Urine contains salts, organic compounds and most importantly uric acid and urea. Uric acid is formed due to nucleic acid decomposition and urea is the product of amino acid metabolism (Tortora & Grabowski, 2003).
Nephron is the structural and functional unit of kidney. It contains a capsule like structure called Bowman’s capsule below which there is a tubular part called the proximal convoluted tubules. The proximal convoluted tubule is followed by a U shaped tube known as Henle’s loop and then another tubule called the distal convoluted tubule. The distant convoluted tubule ultimately opens in a wide tube known as collecting tubule. The collecting tubule receives the urine. Bowman’s capsule contains a complex network of blood capillaries called the glomerulus. Blood enters the glomerulus by renal artery and gets purified over there. Due to the high pressure the plasma is separated from the blood producing glomerulus filtrate.
Carbohydrate, protein and fat metabolism produces different toxic waste products in the body which should be washed off from the body. Excretory system of our body performs this task. Metabolism releases nitrogenous and non-nitrogenous wastes in the cells. These wastes are highly toxic for the cells and if not removed they will exert cytotoxic effects. Proper functioning of the excretory system eliminates nitrogenous wastes, toxins and all other metabolic wastes from the cells (Tindale, 2014).
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