Describe the circulation of blood through the heart and explain how the cardiac cycle is controlled.
Access Biology Describe the circulation of blood through the heart and explain how the cardiac cycle is controlled. The blood circulatory system is responsible for providing a continuous flow of blood throughout the body to provide oxygen and nutrients to the tissues and remove the waste products and carbon dioxide. The circulatory system also acts as a means of transport for hormones and antibodies, and serves to distribute heat. The heart is the pump which tirelessly carries out the task of moving the blood around the body, beating at about 60 times a minute for an entire lifetime. It takes approximately one minute for blood to circulate from the heart, around the body and back again. The heart consists of four chambers, two atria (labelled auricles on diagram) and two ventricles, and is mainly composed of muscle. It is lined with a thin layer of cells called the Endocardium, and is enclosed within a double layered membrane sac called the Pericardium, which attaches it to the breastbone, diaphragm and thorax membranes. The deoxygenated blood is carried into the heart directly by the Vena Cava vein; the Superior Vena Cava drains blood from the head, neck and arms, and the Inferior Vena Cava drains the blood from the rest of the body, and firstly enters the Right Atrium. The right of the heart deals with blood from the body. Veins carry deoxygenated blood towards the
The Endocrine System.
Endocrine System Is a group of specialized organs and body tissues that produce, store, and secrete chemical substances known as hormones. As the body\'s chemical messengers, hormones transfer information and instructions from one set of cells to another. Because of the hormones they produce, endocrine organs have a great deal of influence over the body. Among their many jobs are regulating the body\'s growth and development, controlling the function of various tissues, supporting pregnancy and other reproductive functions, and regulating metabolism. Endocrine organs are sometimes called ductless glands because they have no ducts connecting them to specific body parts. The hormones they secrete are released directly into the bloodstream. In contrast, the exocrine glands, such as the sweat glands or the salivary glands, release their secretions directly to target areas-for example, the skin or the inside of the mouth. Some of the body\'s glands are described as Endo-exocrine glands because they secrete hormones as well as other types of substances. Even some nonglandular tissues produce hormone-like substances-nerve cells produce chemical messengers called neurotransmitters, for example. The earliest reference to the endocrine system comes from ancient Greece, in about 400 BC. However, it was not until the 16th century that accurate anatomical descriptions of many of the
Nutrition diary. The recommended calorie intake for men is 2500 kcal. My average intake was only 1749 kcal. My average expenditure was far greater than this, at 2972 kcal. This is because I was attempting to get fitter over the Easter holidays and so was
Nutrition Introduction Throughout everyday life energy is intaken and expended. This energy comes from the food that is eaten and drunk and is used in all tasks, from breathing to sleeping to running a marathon. This can be termed more specifically as energy is used to maintain basal metabolism, used in muscular activity and used to digest and metabolise food. When talking about basal metabolism, this is the minimum amount of energy the body needs at rest, and the rate of the calories spent on this maintenance is the Basal Metabolic Rate (BMR). Activities that are included in basal metabolism are things that happen unconsciously in the body such as the heart beating and oxygen being inhaled. BMR varies from person to person. It is at its lowest when a person is lying down at rest, not digesting any food, but in normal everyday circumstances the lowest it will get is during sleep, though this is slightly higher because there is always muscular movement during sleep. BMR is influenced by age and gender. A younger person, who is still growing will have a higher BMR because cells are undergoing division. After growing stops, BMR will continually decrease as age increases. BMR is also influenced by the shape and size of a person's body. Someone with a larger body surface area will have a higher metabolism because they have more skin to lose heat through and so BMR needs to be
Shock Syndromes Shock is defined as an alteration in tissue perfusion that occurs at the cellular level.
Shock Syndromes Shock is defined as an alteration in tissue perfusion that occurs at the cellular level. Shock is a process that causes the eventual shutdown of all body systems in a systematic order. The final common pathway in all types of shock is the switching of cellular metabolism from aerobic to anaerobic. Anaerobic metabolism results in activation of the inflammatory response, decreased circulatory volume and decreasing pH. Three major classifications: . Hypovolemic 2. Cardiogenic 3. Distributive -anaphylactic shock -neurogenic shock -septic shock Hypovolemic Shock * Occurs when there is a significant loss of circulating blood or fluid, either by direct loss, or redistribution (third-spacing) * Most common causes are hemorrhage, burns and dehydration * May be seen when the total circulating blood volume has been decreased by 15-20% (approx. 500-1500 ml) Cardiogenic Shock * Occurs when the pumping action of the heart fails * Most common causes are myocardial infarction, cardiac trauma, cardiomyopathy and congestive heart failure Distributive Shock * Occurs when blood vessels dilate without a subsequent increase in circulating blood volume * Blood volume is normal, but the vascular bed is greater in size Anaphylactic Shock * A profound hypersensitivity reaction with a systemic antigen-antibody
What are the alternatives to animal experiments?
What are the alternatives to animal experiments? Alternative research methods At the start of the 21st Century, non-animal techniques have become the cutting edge of medical research. Animal experiments are being replaced by a range of alternative methods that frequently prove cheaper, quicker and more effective - as well as saving lives. Cell culture It is possible to obtain human cells and tissues from biopsies, post-mortems, placentas, or as waste from surgery, and grow them in the laboratory. Cell cultures are used in many medical fields, and have contributed enormously to our understanding of the underlying mechanisms of cancer, Parkinson's disease, and AIDS. Cell cultures are routinely used in vaccine production, toxicity testing, drug development and to diagnose disease. It is important that human cells, rather than animal cells, are used for medical research, to avoid the problem of relating results from one species to another. To encourage the use of human tissue the Dr Hadwen Trust has helped establish the Human Tissue Bank at Leicester. The Trust has funded research using human cells and tissues to replace animal experiments, into Alzheimer's disease, cancer, rheumatism, cataracts, allergies, meningitis, and more. Molecular methods Technological advances are resulting in new and improved molecular methods for analysing and identifying new compounds and
What causes cystic fibrosis?
What causes cystic fibrosis? Cystic fibrosis (CF) is an autosomal recessive, hereditary disease, affecting 7500 people in the UK (Cystic fibrosis trust UK). The first documented case in 1936 described the condition as fibrocystatic disease of the pancreas. Before the 1960's the average life expectancy was five years; today it stands at around 31 and is expected to grow to around 40 years in the next decade as a result of advances in treatment methods. Every week five babies are born with CF and three people a week die from it usually as a result of lung damage (Cystic fibrosis trust UK). The common feature for affected systems is epithelial layers that secrete a mucus layer; including: the respiratory system, gastro-intestinal tract (including the pancreas) and the genito-urinary tract. Most complications associated with the disease arise from infection of the airways or other organs by a number of pathogenic bacteria, most notably Pseudomonas aeruginosa. Other bacteria and/or viruses may colonise mucosal surfaces and lead to infection or pave the way for more serious infections. CF is caused by a mutation, which occurs in the Cystic Fibrosis Transmembrane conductance Regulator (CFTR) gene. The most common mutation gives rise to a protein missing amino acid 508, termed ?F508 CFTR, and accounts for around 70% of the cases reported in the UK. Patients homozygous for ?F508
Contractions in skeletal muscle are regulated by stimulus strength, stimulus frequency, and sarcomere length.
Contractions in skeletal muscle are regulated by stimulus strength, stimulus frequency, and sarcomere length 425-55-6522 BIOL 4161 November 2, 2004 Abstract The electrical responses and muscle contractions of the skeletal muscle of Rana pippiens in response to various stimulus strengths, stimulus frequencies, and muscle stretch were studied in this experiment. We identified the minimum stimulus voltage required to produce a muscle twitch. Electromyogram (EMG) generally increased in response to increasing stimulus strength. Recordings of contraction force and the duration of the muscle twitch showed no distinct pattern over increasing stimulus strength. The time between the stimulus pulse and the start of the contraction decreased with increasing stimulus strength. The time delay from the start of the muscle contraction until the maximum tension was reached generally decreased with increasing stimulus strength. Baseline tension of the muscle increased with increasing frequency of a stimulus pulse. Change in baseline tension of the muscle showed a general increase with increasing muscle stretch up to a certain point. The muscle contraction force also increased with increasing change in muscle length up to a point. In this experiment we learned about skeletal muscle contraction in response to changes in stimulus strength and frequency and sarcomere length.
The physiology of eating disorders.
The physiology of eating disorders The erratic eating habits of those with eating disorders, including starvation, vomiting and diuretic or laxative abuse, can start a sequence of events leading to the medical consequences of eating disorders. These consequences reach every system of the body and some are serious enough to cause death. They are also not acute conditions and even after refeeding many conditions will remain. Reproduction Part of the diagnosis of anorexia nervosa involves the cessation of menses in women. This could either be primary amenorrhoea if the severe weight loss has occurred before menarche has occurred or secondary amenorrhoea if the patient has previously menstruated. The control of menstruation is very complex involving the hypothalamic-pituatory- gonadal axis. The process is shown on the flow chart below. The hormones of FSH, LH, oestrogen and progesterone then interact to control the menstrual cycle and ovulation as seen below ,119 Puberty and first menarche is controlled by an increase in pulsatile GnRH secretion. It is not known why this occurs but it is likely to be due to maturation of the central hypothalamic mechanisms. The most important factor for the occurrence of puberty seems to be body weight, with a critical weight for puberty beginning at 30kg and menarche occurring at 47kg. This is signalled by leptins, proteins produced by
A 75-year-old man has experienced a cerebral vascular event, which has resulted in motor problems affecting the right side of his body - "Explain the pathophysiological reasons for the problems this man is experiencing."
Contributory Science Year 2 Entry 56 Stroke Essay: Part I A 75-year-old man has experienced a cerebral vascular event, which has resulted in motor problems affecting the right side of his body. "Explain the pathophysiological reasons for the problems this man is experiencing." Cerebrovascular events (CVE) are the third leading cause of death and the single greatest cause of severe disability (Department of Health 2001, Wilkinson 1999). In the UK 110,000 people experience a first CVE, 30,000 go on to have further CVEs (Department of Health 2001). Initially CVE presents as an acute medical emergency, initially requiring complex care, and may result in long-term disability. Part I of this essay will explain the pathophysiology of a left hemisphere CVE resulting in motor dysfunction on the right side of the body. CVE is a descriptive term for the end point of several different pathological processes (Warlow 1987). Symptoms of CVE are a result of the interruption of the blood flow by occlusion of blood vessels causing ischaemia or haemorrhage caused by damage to blood vessels which causes anoxic damage to brain tissue (Gleb 2000). CVE due to cerebral ischaemia accounts for 80% cases (Gleb 2000). The human brain has a high metabolic rate, using 20% of the body's oxygen at rest (Cohen 1999). Ischaemic CVE occurs when cerebral blood supply is interrupted causing
Anatomical Pathology - lecture 2Aetiology: the cause of disease Pathogenesis: the course of disease
Anatomical Pathology - lecture 2 * Aetiology: the cause of disease * Pathogenesis: the course of disease * Aetiological factors: 33% external causes acquired Environment, chemicals (toxins & drugs), micro-organisms. 66% host causes predisposition Age, sex, nutrition, constitution, hormones and genetics * Aetiological factor classification: i. Congenital (born with) ii. Trauma iii. Inflammation iv. Neoplastic (new growth) v. Homeostatic disturbance eg dehydration vi. Nutrients * Injury is caused by forces which can be physical, chemical or organismal * Inflammation: a sequence of changes in living injured tissue: providing the injury is not severe enough to destroy the tissue immediately. (response of living tissue to injury) * Atrophy: wasting or diminution in all sizes of an organ or tissue seen as a decrease in number of cells in that organ or tissue * Hypertrophy: an enlargement of an organ or part of an organ due to an increase in size of the cells. eg muscle build up (irregular nuclei, build up everything but not divide) * Heart hypertrophy is due to high blood pressure which cause less oxygen and less nutrients pass to the body * Hyperplasia: an increase in cell number resulting as a response from either abnormal multiplication or physiological need. * Possible causes of injury i. Ischaemia: loss of blood supply ii. Hypoxia: lack of oxygen or Anoxia: