Human Physiological Systems - Essay Example

?HUMAN PHYSIOLOGICAL SYSTEMS Question A The standard procedure of measuring the arterial blood pressure fora human subject is through the use of sphygmomanometer (Plange et al, 2006). This instrument has a blood pressure cuff which is fixed and inflated around the arm with a view of shutting the blood flow along the brachial artery to give the systolic blood pressure. The release of the pressure during the opening of the brachial artery then gives the diastolic blood pressure. The values of the arterial blood pressure are recorded by the sphygmomanometer and reported in terms of millimeters of mercury. Through the arterial blood pressure measurement, the variation between the diastolic and systolic blood pressure during the cardiac cycle is measured. In accordance to Plange et al, (2006), arterial blood pressure can also be measured through the invasive method where the blood pressure is monitored within the arteries or intra-arterial blood pressure measurement and monitoring. Intra-arterial blood pressure measurement is where there is insertion of an arterial line into an artery such as brachial artery and taped to prevent backflow of blood. The cannula needle which is inserted into the artery is then connected into an electronic pressure transducer. Invasive blood pressure has advantages of accuracy and continuous monitoring. Question 1 B In the homeostatic regulation of blood pressure, the baroreceptor reflex through the baroreceptors on the walls of the heart muscle act to sense the changes in blood pressure. When change of arterial blood pressure is detected by the baroreceptors, there is activation of sensory nerves of the heart. The sensory nerves then send information on change of arterial blood pressure to the medulla oblongata of the brain. In the medulla the change in blood pressure is then interpreted. Marieb and Hoehn (2007) point out that depending on the kind of the signals received the medulla oblongata then decides whether the blood pressure is to be increased or reduced. The motor neurons within the parasympathetic and sympathetic divisions of the autonomic nervous system are then activated so that relevant adjustments are made so that the blood pressure is maintained. Gupta and Patidar (2008) demonstrate that a reduced blood pressure leads to the action of the sympathetic nervous system on the heart muscles to increase the heart rate and make the heart to contract more forcefully. On the other hand an increase in blood pressure leads to the action of the parasympathetic nervous system acts to decrease the heart rate and thus decrease the blood pressure. Epinephrine and norepinephrine are secretions of the adrenal gland which also acts in the increase of blood pressure through their constricting action of the blood vessels and increase in the blood amount which is pumped to the heart each minute (Sherwood, 2007). Question 2 The exocrine and endocrine features of the pancreas comprise the mechanism for the production of pancreatic enzymes and fluid for the digestion process. Marieb and Hoehn (2007) reveal that the secretion of pancreatic enzymes and juices is mediated and controlled by secretagogues. It is within the islets of Langerhans, that lays the endocrine function of the pancreas. It is in this group of cells which secrete glucagon and insulin with the control of secretagogues. Glucagon which is secreted by alpha cells of the islets of Langerhans acts to increase the amount of glucose in the blood while insulin, a product of the beta cells decreases the level of blood glucose. Somatostatin acts to control or regulate the functions of alpha and beta cells of the islets of Langerhans. In this regard therefore, somatostatin controls the production of glucagon and insulin and thus the blood sugar level. As an exocrine gland, the pancreas acts to promote the digestion process through the production of pancreatic enzymes such as pancreatic lipase and peptidase. These enzymes are contained in the pancreatic fluid which passes to the ileum or small intestine to facilitate the digestion of proteins, carbohydrates and facts. The secretion of pancreatic fluid and enzymes is controlled by secretagogues with the whole process being regulated through the autonomic nervous system. Question 3 A It is through the sliding filament model that the contraction of the skeletal muscles is achieved. The contraction of skeletal muscles is initiated by the action potentials which emanate from the central nervous system (Marieb and Hoehn (2007)). The propagation of the action potentials along axons is made possible through the activation of sodium channels. This leads to the influx of calcium into the muscle axons. Calcium then acts to cause release of acetylcholine which binds with its receptors and thus the opening of sodium and potassium channels at the neuromuscular junction of skeletal muscle cells. The muscle fibers have a network called T-tubules through which the action potential spreads to cause depolarization of the inner part of the skeletal muscle fiber. The sarcoplasmic reticulum of the skeletal muscle also plays an important in contraction as it mediates the release of calcium ions across the T-tubule membrane (Gupta and Patidar, 2008). Question 3 B Sherwood (2007) points out that unlike skeletal muscle, smooth muscle does not have troponin. Instead, smooth muscle has tropomyosin which is a thin protein filament and other proteins such as calponin and caldesmon which play a role in contraction of the smooth muscle. Calcium activated phosphorylation of myosin initiates contraction in smooth muscle. This is unlike in skeletal muscle where calcium binds to troponin to initiate contraction. It is thus through agents which increase intracellular calcium in smooth muscle cells that contraction of the smooth muscle is achieved. The mechanism of smooth muscle contraction involves the depolarization of the sarcolemma. This is followed by the entry of the extracellular calcium to smooth cells through calcium channels of the L-type. At the same time there is release of calcium from the sarcoplasmic reticulum. The binding of calcium to calmodulin acts to activate myosin light chain kinase enzyme which forms a complex for the initiation of smooth muscle contraction. Question 4 During sexual intercourse, sperms travel through the cervix and uterus so that they could come into contact with a mature female ovum. When the sperm comes into contact with the ovum, enzymes are produced by the sperm to enable it to penetrate the membrane of the ovum. Marieb and Hoehn (2007) says that these enzymes are produced by the acrosome of the sperm cell. The sperm burrows through the coat of the ovum followed by the fusion of the sperm and egg membranes. The flagellum of the sperm them disconnects itself from the head. The process of fertilization involves the release of many sperms by the male but only one is allowed to penetrate the ovum due to regulatory mechanisms of the fertilization process. Gupta and Patidar (2008) explain that after a single sperm has entered the oocyte’s cytoplasm, a process called cortical reaction occurs. This reaction acts to prevent more sperms from the fertilization process of a single egg. After the sperm oocyte fusion, the oocyte goes through the second meiotic division which leads to the production of a haploid ovum and the release of a polar body. At this stage, the sperm nucleus comes into contact with the ovum and thus causing fusion of the sperm and egg genetic materials. The fusion of the sperm and the ovum during the fertilization process leads to the formation of the zygote. The zygote is formed through a contribution of 23 chromosomes by each of the parent cells. After the fertilization process, the zygote then moves to the uterus and undergoes division forming a morula, which is a cluster of cells that appear after three days since fertilization (Marieb and Hoehn, 2007). References Gupta, H, and Patidar, D 2008, Medical Physiology Made Easy, Jaypee Brothers Medical Publishers Marieb, E. N. and Hoehn, K. (2007). Human Anatomy and Physiology (Seventh Ed.). San Francisco, CA: Pearson Benjamin Cummings. Plange, N, Kaup, M, Daneljan, L, Predel, H, Remky, A, and Arend, O 2006, '24-h blood pressure monitoring in normal tension glaucoma: night-time blood pressure variability', Journal Of Human Hypertension, 20, 2, pp. 137-142 Sherwood, L. (2007). Human physiology: from cells to systems. Australia, Thomson/Brooks/Cole. Read More