How the Arterial Blood Pressure of an Individual Can Be Measured - Assignment Example

Running header: Biology Student’s name: Instructor’s name: Subject code: Date of submission: 1 Briefly describe how the arterial blood pressure (ABP) of an individual can be measured and list two factors that can influence the ABP. There are various methods adopted in measuring arterial blood pressure. The methods include the standard method as well as the invasive, intra arterial pressure monitoring. The standard method makes use of a blood pressure cuff or sphygmomanometer. The cuff is inflated around the arm so as to shut off the brachial artery blood flow hence giving the systolic pressure then releasing the pressure so as to determine when the artery reopens i.e. the diastolic blood pressure. On the other hand, invasive intra arterial pressure monitoring is where an arterial line is inserted into an artery and taped in place with a bag of pressurised fluid which prevents the backflow of blood from the artery owing to the intense pressure in the artery (Eldra, 2009). The line is used in sampling arterial blood flow to measure dissolved gases in it as well as measuring blood pressure continuously. Factors that affect arterial blood pressure include; a) Stress the effects of stress on blood pressure vary although long-term, chronic stress has the effect of raising blood pressure (Eldra, 2009). Various relaxation techniques which include deep breathing, progressive relaxation, massage as well as psychotherapy help in stress management hence helping in lowering stress induced blood pressure elevations. b) Smoking – this causes peripheral vascular disease or narrowing of the arteries carrying blood to the legs and the arms as well as hardening of arteries. This can cause heart disease and stroke and is a major contributing factor to high blood pressure. 2. Briefly describe the major risk factors shown below thought to play a role in development of coronary heart disease. (5 marks) Hereditary – children born of parents with coronary heart disease are more likely to develop the condition themselves. In other words, there is a high risk of a person getting the coronary heart disease for a person born in a family with a history of the disease all other factors held constant. This implies that there is need for such a person to avoid exposing him/herself to the causative agents to reduce the risk of getting the disease. Diabetes Diabetes is a major factor in causing and acceleration of the hardening and narrowing of arteries. This can lead to strokes, coronary heart disease and other blood vessel diseases.evn with blood sugar level under control, diabetes increases the risk of coronary heart disease although the risk is greater when the sugar level is out of control (Eldra, 2009). It is estimated that three quarters of people with diabetes die out of coronary heart disease. Lack of exercise Lack of exercise or physical inactivity is a risk factor for coronary heart disease. Regular moderate to vigorous exercise helps in preventing the disease. This is because physical activity helps in controlling blood cholesterol and reduces the risk of coronary heart disease as well as blood pressures Smoking The probability of having the disease is 2-4 times higher in smokers compared to non smokers. Smoking is a powerful factor for unexpected cardiac demise in people with the disease. This also heightens the danger of having coronary heart disease. Chemicals in cigarettes smoke damage the lining of the coronary arteries leading to fuming of the arteries and hence coronary heart disease. Hypertension Hypertension is a chief cause of coronary heart disease. It increases the heart’s workload causing it to thicken and become stiffer. This increases the risk of coronary heart disease. When high blood pressure combines with smoking, diabetes or even physical inactivity, the risk of getting coronary heart disease increases several times. 3. With the aid of a diagram give a brief description of the ion-channel mediated events that underlie the generation of an action potential. In generating an action potential, ligand gated ion channels open and Na+ begin entering the cell making the inner surface of the membrane less negatively charged in comparison to the outside. The inward flow of Na+ rapidly depolarises the membrane and initiates an action potential that propagates itself along the membrane sequentially triggering adjacent voltage sodium channels (Eldra, 2009). The initial ion channel involved in action potential is the Na+ channel that when opened allows positively charged sodium ions to enter the neuron and further contribute to the spike of the action potential. The Ca2+ channels open next and positively charged calcium ions enter the neuron further contributing to the spike of the action potential. The entry of the calcium ions is also important for the release of transmitter molecules and calcium ion entry activates ion channels that carry an outflow of potassium ions involved in arresting the action potential. Activation of the K+ channels result in afterhyperpolarisation of the membrane after the action potential. The ion-channel mediated events that underlie the generation of an action potential can be summarized as follows; 1) the sodium channels open and sodium ions begin to enter the cell 2) This triggers the potassium channels to open and potassium ions begin to leave the cell. 3) Na+ become intractable and no more Na+ enter the cell 4) Potassium ions continue leaving the cell causing the membrane potential to return to resting level. 5) Potassium channels close while sodium channels reset 6) Extra potassium ions on the outside diffuse away. 7) The process to action potential repeats itself if triggered. 4. The cell types present within the alveoli and the role(s) that each of the cell types fulfils. These are small balloon like structures attached to the branches of the bronchial passages where gaseous exchange takes place in the lungs. The alveoli have various cells that assist in gaseous exchange. These cells include; -type I alveolar cells (simple squamous epithelial cells) which cover almost 95% of the alveolar service (Eldra, 2009). The cells are interconnected by tight junctions to reduce leakage of tissue fluid into the airs spaces. They contain many pinocytotic vesicles and they permit gaseous exchange. -type II alveolar cells which are characterised by lamellar bodies that contain pulmonary surfactant which is composed of a variety of lipids and proteins. The cells control alveolar fluid levels by water recapture using active sodium transport to return excessive alveolar surface water to the interstitial fluid. The cells also proliferate to replace both type I and type II cells after injury. Alveolar macrophage (dust cell) - the cells phagocytosize any foreign particles and infectious microorganisms that reach the alveoli. They also transport indigestible materials such as soot and silica dust to the lymph nodes of the lungs for storage. Capillary endothelial cells – they form the capillary wall and permit gas exchange. Erythrocytes (RBC) - essential for oxygen transport and to a lesser degree, carbon dioxide transport within the blood. 5. This is the pathway that a sperm cell would follow from the point of production to the point of ejaculation. The sperms are produced in the somniferous tubules they then migrate from the seminiferous tubules to the epididymis where they mature while they are stored in the structures. From here the ejaculation process begins when the penis is stimulated. Mature sperms travel from the epididymis through the vas deferens which is a muscular tube that propels sperms forward through smooth muscle contractions (Eldra, 2009). At first, the sperms arrive at the ampulla where secretions from the seminal vesicles are added. From here, the sperm is propelled forward along the ejaculatory duct towards the urethra, first by the prostate gland where a milky substance is added forming semen. Lastly, the sperm/semen is ejaculated through the far end of the urethra. (5 marks) 6. Briefly describe how the structure of the liver contributes to its ability to carry out its many physiological roles. The liver is unique in many ways including its lobed structure, its extensive circulatory system, its ability to regenerate as well as its role in a large number of essential processes in the human body. The liver is composed of two lobes which are covered in a network of connective tissue which divide into segments called lobules. It has an extensive vascular (circulatory) system through which the blood flows and is filtered. It also has a series of ducts and channels known as the billiary system which carry bile which helps in carrying waste away from the liver (Eldra, 2009). The liver cells known as hepatocytes metabolise carbohydrates fats and proteins thus helping in maintaining blood glucose levels, store and produce energy and also cleanse the blood. In addition, the terminal branches of the hepatic portal vein and hepatic artery empty together and mix as they enter sinusoids (which are distensible vascular channels lined with highly fenestrated endothelial cells and bounded circumferentially by hepatocytes) in the liver. As the blood passes through the sinusoids, a big amount of plasma is filtered. 7. With the aid of a labelled diagram, briefly describe the important structural features found in the mammalian Bowman’s capsule. The Bowman’s capsule is a saclike structure that surrounds the glomerulus.. The various structures of the Bowman’s capsule include; a) the vascular pole which is the side with the afferent and efferent arteriole. b) The urinary pole which is the side with proximal convoluted tubule. Inside the Bowman’s capsule, the following structures are found; a) The parietal layer which is a single layer of simple squamous epithelium and does not function in infiltration. b) Bowman’s space (capsular space) which is found between the visceral and parietal layers. This is where the filtrate enters after passing through podocyte’s filtration. c) Visceral layer which lies above glomerulus basement membrane and is composed of podocyte’s. Beneath the layer are found the glomelular capillaries. d) Filtration barrier which is made of fenestrated endothelium of the glomelular capillaries, fuse basal lamina of the endothelial cells, the podocyte’s and their filtration slits (Eldra, 2009). It permeates the passage of water, ions as well as small molecules from the blood stream to the bowman’s space. it prevents the passage of large and negatively charged proteins (5 marks) 8. Briefly describe the processes involved in the digestion and absorption of protein after consuming a meal. (5 marks) The initial physical breakdown of proteins takes place in the mouth. The stomach then continues the physical breakdown through the action of the enzyme pepsin in the presence of hydrochloric acid produced in the stomach. Here, pepsin breaks apart the protein into amino acid. Muscles in the stomach wall eventually move the food into the duodenum- the first part of the small intestine (Eldra, 2009).protein digestion continues in the small intestine where pancreatic enzymes which include trypsin and chymotrypsin act on it to complete the chemical breakdown of protein into single amino acid molecules. The small intestines through its numerous blood capillaries then absorb the amino acid molecules into the blood stream. The amino acids are then carried to the rest of the body. 3. Cellular processes that take place during sperm-egg interaction during fertilisation. During ejaculation, millions of sperms are released into the vagina to fertilise the single matured egg. However, of the million sperms released, millions of them die or leave the female system due to gravity and only few sperms succeed in the journey to the vagina (Eldra, 2009). The sperms quickly swim from the vagina to the cervix after ejaculation towards a waiting egg at the fallopian tube. The egg emits special chemicals that attract the sperm towards it. Of the many sperms released, only one succeeds in penetrating the egg. New chemicals are then released by the egg to seal it hence preventing other sperm from breaking through. Fertilisation then involves fusing of chromosomes from the egg with those from the sperm. Fertilisation proceeds through a number of processes. Initially, the sperm finds the egg through the process of sperm motility and chemotaxis. On making contact with the outer coat of the oocyte (zona pellucida), the sperm undergoes an acrosome reaction which facilitates its movement through the zona pellucida so that the sperm can gain entry to the oocyte plasma membrane so that sperm induced oocyte activation can occur. Sperm deposited in the vagina migrate to the uterus by actively swimming and by being propelled by muscular contractions of the genital tract. Once in the storage site, the sperms undergo the process of capacitation to enable them continue with their journey towards the egg. Capacitation process makes the sperms competent to follow the thermal and chemical gradients which guide them up the oviduct. Role of calcium ions Ca2+ plays an important role in the sperm motility. The beat frequency is regulated by the ions acting on an axonemal site at the base of the flagellum. Hyperactivity of the sperm is induced by an increase in ca2+ which can be derived from both the internal and external sources. During the acrosome reaction, the acrosome found in the head of the sperm releases its hydrolytic enzymes through the process of exocytosis (Eldra, 2009). The acrosome reaction is similarly induced by increase in ca2+ which is induced by a combination of stimuli that act on the sperm as it approaches the oocyte. Such stimuli include the action of progesterone that sensitizes the sperm to the components of the zona pellucida which trigger acrosome reaction. Zona pellucida is a thick extracellular coat surrounding the oocyte that has to be broken by the sperm to gain access to the oocyte plasma membrane. Sperm induced oocyte activation This process starts when the sperm plasma membrane comes into contact with the oocyte plasma membrane. The close contact between the egg and sperm membranes is closely followed by sperm egg fusion. When the sperm fuses with the oocyte, it introduces the sperm specific phospholipase which induces actions responsible for Ca2+ oscillations which persists for hours before ceasing when pronuclei forms.. The oscillations trigger the release of cortical granules, they provide a block to polyspermy, and they complete meiosis and also initiate the cell cycle programme leading to embryo development. The slow block to polyspermy is necessary so as to prevent multiple fertilisations on one egg. This starts after fertilisation has occurred elsewhere on the egg. It depicts sperm approaching the plasma membrane of the egg while cortical granules containing hyaline and enzymes are releasing their contents into what was membrane of the cell. This creates a thick barrier between the cytoplasmic contents of the egg and the approaching sperm. The sperm is then released from the newly formed fertilisation envelop thus preventing polyspermy. The pulses of Ca2+ act through Ca2+ dependent protein kinase II and initiate the sequence of events which lead to chromosome separation. The pulses also activate the oocyte to begin multiple rounds of cell proliferation which occur at the beginning of development. 4a. Explain how the secretion of saliva is controlled by the autonomic nervous system. (6 marks) Saliva is secreted from salivary glands with the basic units of the salivary glands being clusters of cells called acini. The cells secrets fluid containing water, mucus, electrolytes and enzymes which flow from the acinus into the collecting ducts. The composition of the secretion is altered where much of the sodium is reabsorbed; potassium and large quantities of bicarbonates are secreted within the ducts. Small collecting ducts within the salivary glands lead into large ducts which eventually give rise to one large duct which empties into the oral cavity. Saliva secretion is controlled by the autonomic nervous system that controls both the volume and type of saliva secreted. For example, a dog fed by dry dog food produces saliva which is predominantly serous while dogs on meat diet secrete saliva with much more mucus (Eldra, 2009). Possible stimuli for increased salivation include the presence of food or irritating substances in the mouth, thought of food or even the smell of food. The parasympathetic impulses travel from the salivatory nuclei in the brain stem (salivation centres) reach the salivary glands through the facial and glossopharyngeal nerves which stimulates saliva production and salivary flow. The possible stimulants of the salivatory centres are grouped into three groups namely; Impulses from the higher brain which include thoughts about food which one finds delectable. Impulses from the mouth and throat which include taste sensations –sour and urnami as well as tactile sensations (smooth objects in the mouth stimulate salivary flow while rough objects inhibit salivation). Impulses from the stomach and proximal part of the small intestine which include irritation of the lining of these part of the alimentary tract. Parasympathetic stimulation from the brain as demonstrated by Ivan Pavlov gives rise to greatly enhanced secretion as well as increased blood flow to the salivary glands. Conversely, enhanced blood flow to the salivary glands for reasons other than parasympathetic stimulation also enhances salivation. 4b. Discuss the cellular mechanisms by which the autonomic neurotransmitters can elicit salivary enzyme and fluid secretion from the salivary glands. Saliva production is stimulated by both the sympathetic and parasympathetic nervous system. Saliva stimulated through sympathetic innervation is thicker while saliva stimulated parasympatheically is more watery. Sympathetic stimulation facilitates respiration while parasympathetic stimulation facilitates digestion. Parasympathetic stimulation leads to acetylcholine (Ach) being released into the salivary acinar cells. The Ach binds to muscarinic receptors and cause an increased intracellular calcium ion concentration. This causes vesicles within the cells to fuse with apical cell membrane which leads to secretion formation. Ach also induces the salivary gland to secret kalikrein –an enzyme which converts kininogen to lysyl-bradykinin which acts upon blood vessels and capillaries of the salivary gland to generate vasodilatation as well as increased permeability. This results in increased blood flow to the acinar allowing production of more saliva. Both sympathetic and parasympathetic nervous stimulation can also lead to myoepithelium contraction that causes expulsion of secretions from the secretory acinus into the ducts and eventually to the oral cavity. References: Eldra, P2009, Biology, Routledge, London. Read More