homeostasis

• Communication is essential for the survival of organisms as they must detect and respond to changes in their internal and external environments
• In multicellular organisms, changes necessary for survival are triggered by the nervous and endocrine systems
• Cell signalling involves communication between cells through electrical signals carried by neurones or with the help of hormones
• Neuronal cell signalling is faster and short term, while chemical signalling is slower and long term
• Endocrine signalling can be used for long-distance signalling, carried by the circulatory system
• Examples of signalling include paracrine signalling between cells in close proximity and autocrine signalling where a cell stimulates its own receptors
• Homeostasis ensures a constant internal environment is maintained despite changes in the external environment
• Achieved through negative feedback which counteracts changes in internal conditions
• Elements needed for negative feedback pathway: sensory receptors to detect changes, effectors like muscles and glands for response
• Positive feedback increases the original change in conditions, e.g., dilation of the cervix during childbirth
• Ectotherms regulate body temperature with external sources, while endotherms maintain a constant body temperature
• Endotherms use thermoreceptors to monitor core body temperature changes and coordinate responses through the hypothalamus
• Actions taken by endotherms for temperature control include shivering, sweat production, hair position changes, and arteriole dilation/constriction
• Excretion is essential for removing waste products produced during metabolism
• Liver plays a crucial role in excretion by breaking down harmful substances and converting them into less harmful forms
• Liver is involved in detoxification, breakdown of excess amino acids, and conversion of ammonia to urea
• Kidneys excrete waste products like urea in the form of urine
• Ultrafiltration in the kidneys involves the Glomerulus, Bowman’s Capsule, and selective reabsorption in the nephrons
• Control of water potential in the blood involves negative feedback and the role of hormones like antidiuretic hormone (ADH)
• ADH makes walls of DCT and collecting duct more permeable to water, increasing reabsorption to produce concentrated urine
• Kidney failure can be caused by infections, high blood pressure, leading to toxic waste build-up and fluid accumulation
• Treatment for kidney failure includes renal dialysis and kidney transplant
• Dialysis can be haemodialysis or peritoneal dialysis, while kidney transplant is a long-term solution requiring a suitable donor
• Patients may need to wait for a suitable donor with the same blood type and tissue type to minimize the risk of rejection
• Immunosuppressants are still required by the patient to prevent rejection
• In most cases, a family member is the donor due to the degree of similarity
• Only one kidney is required for survival
• Urine samples can be used for diagnostic tests such as pregnancy testing using monoclonal antibodies to detect human chorionic gonadotropin
• Urine samples can also be used to test for the presence of anabolic steroids
• Anabolic steroids are used to build muscle mass and are banned due to their dangerous side effects as well as to ensure fair competition among athletes
• Detection of stimuli involves receptors which are specialized cells that convert one form of energy into another form
• Pacinian corpuscles are pressure receptors found in the skin that convert mechanical energy into electrical energy
• All action potentials have the same magnitude, and the brain interprets the strength of the stimulus based on the frequency of action potentials
• Hormones are signaling molecules secreted by ductless endocrine glands that affect target cells with complementary receptors on their plasma membrane
• Adrenal glands secrete adrenaline in response to danger, stress, or excitement, and the adrenal cortex produces mineralocorticoids and glucocorticoids
• The pancreas functions in both an endocrine and exocrine way, with the Islets of Langerhans secreting insulin and glucagon directly into the blood
• Blood glucose regulation is important to maintain essential processes such as brain cell respiration
• Insulin secretion is controlled by beta cells through a series of actions involving adenyl cyclase and cAMP
• Diabetes mellitus is a disease where the body cannot control blood glucose levels, with Type I being an autoimmune disease and Type II resulting from cells becoming less responsive to insulin
• Genetically engineered bacteria can produce insulin for the treatment of diabetes