Homeostatis

• What is homeostasis?

  Mechanisms to maintain relatively constant internal environments by balances changes to internal and external environment.
• What factors fall under homeostasis?

  blood pH, blood glucose, osmotic concentration, body temperature, etc.
• When is homeostasis trigger?

  When there are changes outside the preset range, mechanisms work against the change the variable brings
• What is a positive feedback loop of homeostasis?

  When system enhances/favors the change the variable brings, changing the system even more
• What is a negative feedback loop of homeostasis?

  When system reverses/stops the change the variable brings so that less change is brought on
• Example of positive feedback homeostasis?

  During childbirth, the head of the baby pushing on the cervix creates pressure that simulates the nerves there and cause the pituitary glands to produce and secrete oxytocin that stimulate uterine contractions that causes further pressure on cervix
• Example of negative feedback homeostasis?

  Metabolic activity in the muscles cause body temperatures to increase which activates cooling mechanisms which decrease body temperatures
• Example of negative feedback homeostasis?

  When a meal high in carbohydrates is eaten and blood glucose levels spike, mechanism are enacted to reduce blood glucose levels
• A normal blood glucose level within

  70-100 mg/dL, though this increases during exercise
• What is hypoglycemia?

  low blood glucose
• What is hyperglycemia?

  high blood glucose
• What does the pancrease's endocrine tissues produce

  The islets of Langerhans secrete insulin and glucagon
• Which pancreatic islets produce insulin and why?


  Beta cells produce insulin to lower blood glucose levels by encouraging cell uptake of glucose as glycogen
• Which pancreatic islets produce glucagon and why?


  Alpha cells produce glucagon to simulate the liver and cells to break down and release the glycogen they have stored
• What feedback type is blood glucose control?

  Negative, as glucagon and insulin have opposing effects
• Why aren't skeletal muscles simulated to release glucose?

  They have no known glucose receptors
• What is the hormonal disorder that causes hyperglycaemia?

  Diabetes
• Why is sugary urine produced by patients with diabetes?

  The proximal convoluted tubule can't reabsorb all the glucose in the body
• What happens in a person with diabetes?

  There is an excess build-up of glucose in blood as cells cannot take it all up and burn through their fat and proteins supplies. Much of the glucose is "wasted" and sent to the kidneys to be filtered. As the kidney dilutes the sugars to urine, the body is dehydrated
• What causes type 1 diabetes?

  When the immune system mistakenly destroying beta cells in the pancreas due to autoimmune condition
• Diagnosis and treatment of type 1 diabetes?

  Early childhood diagnosis (usually) though it can occur at any time. No true cure so it needs insulin therapy, dietary modifications, and regular exercise
• What cause type 2 diabetes?

  Cells are insensitive/resistance to insulin causing beta cells to produce more insulin and become exhausted
• Type 2 diabetes diagnosis + treatment?

  Late diagnosis/late onset with clear treatment with weight loss, regular physical exercise and healthy diets
• How does body weight increase risk of Type 2 diabetes?

  Excess body weight increases insulin resistance and decrease glucose metabolism. Even a 5-7% decrease in body weight can significantly decrease risk
• How does age increase risk of Type 2 diabetes?

  Type 2 diabetes is most common in adults over 45 years old but increasingly seen in adolescents
• What controls thermoregulation?

  The nervous system with the hypothalamus acting as the control center from the hormones the pituitary gland releases in response to changes in internal temperature changes detected by the central thermoreceptors or external temperature changes detected by the peripheral thermoreceptors
• What mechanism occurs when body loses heat?

  Thyroid stimulates pituitary gland which simulates the thyroid gland to produce thyroxin using the Thyroid Stimulating Hormone (TSH) to increase metabolic rate and increase heat, decreasing production of thyroxin
• What is shivering and its purpose?

  When in cold environments, skeletal muscles undergo repeated involuntary contractions to generate heat and increase body temperature by simulating metabolic activity. Hair raised during this process traps heat in a layer of air between the skin and hair, improving body's insulation
• What is evaporative cooling?

  It's a response to heat in the body caused by sweat secreted by the skin that evaporates and cools the area
• What does vasodilation do?

  It widens the blood vessels so that more blood flows to the surface and heat conduction of the body increases
• What does vasoconstriction do?

  It narrows the blood vessels so there is a decrease of blood in peripheral blood vessels so that heat is conserved near vital organs
• What is uncoupled respiration?

  When the mitochondria in brown adipose tissue releases energy without producing ATP to increase the body's temperature in response to a cold environment
• The symptoms of type 1 diabetes usually occur very quickly whilst the symptoms of type 2 diabetes tend to occur more slowly. Because the symptoms of type 2 diabetes occur gradually over time, it is easier to miss them and it often takes a long time for patients to seek medical help.
• During the menstrual cycle, follicle stimulating hormones stimulates follicle growth which stimulates FSH release again
• Homeostasis is controlled by negative feedback loops that brings back environments back to set values as soon as deviations has been detected.
• Why do small mammals and babies have more brown adipose tissue than adults or larger animals?

  Due to their high surface area to volume ratio, they are quick to diffuse heat to their surroundings which is bad for retaining a consistent internal temperature as brown adipose tissue acts as an insulator and can generate heat at a rapid rate
• Thyroxine increases metabolic rate in muscles causing them to contract rapidly and shiver which generates heat and increase body temperatures
• The most metabolically active organs (generating over 70% of the body's heat) are the the heart, kidney, lungs and brain
• What increases body temperature?

  The hypothalamus releases thyrotropin releasing hormones (TRH) which stimulates the pituitary gland to produce thyroid stimulating hormones (TSH) and promotes thyroxin (T4) production by the thyroid
• Thyroxin stimulates oxygen consumption, cardiac output, ventilation rate, brain development, and increases the metabolism of basals, carbohydrates, and proteins, creating heat as a waste product