D3.3 Homeostasis Flashcards
What is homeostasis?
Homeostasis = ability to maintain a constant internal environment at preset values despite fluctuations from external environment.
How does homeostasis work?
It works by monitoring levels of variables & making corrections by negative feedback mechanisms.
What does internal environment consists of?
Internal environment consists of blood circulating in body & fluid that circulates among cells (tissue fluid that forms from blood plasma), delivering nutrients & removing waste products while bathing cells. Mammals are excellent examples of animals that maintain remarkably constant internal conditions.
Which factors must stay “the same” inside body to maintain a steady stage?
- glucose level of blood = blood glucose conc
- water content of blood = blood osmotic conc
- Conc of essential ions
- pH of blood
- heart rate
- pressure of blood in arteries
- conc of respiratory gases in blood (pCO2, pO2)
What are all homeostatic functions controlled by?
All homeostatic functions of an organism are under control of a feedback loop, which uses info about outcome of a process to make adjustments.
What a cell’s environment? And examples in plants & animal cells?
Immediate surroundings outside plasma membrane. E.g. plant cell, this is cell wall, & fluid held in it
E.g. animal cell, there may be an extracellular matrix of collagen, elastin & other materials, & there is always tissue fluid filling other gaps between cells. Blood is unusual in that volume of tissue fluid, in this case plasma, is very large & separates cells completely; blood is a liquid tissue.
What is a positive feedback?
Positive feedback amplifies their initiating stimuli - they move systemawayfrom its starting state. It increases gap between original & new level.
Only few examples exist in human body (e.g. During menstrual cycle release of FSH stimulates follicle growth which in turn stimulates FSH release)
What is a negative feedback?
Negative feedback counteracts changes of various properties from their target value (set points) – decreases gap – so original level is restored. They form basis of homeostatic control systems used to keep internal conditions within narrow limits. They require energy but keep body at stable conditions which allows extreme environments to be inhabited.
What is homeostasis controlled by?
Homeostasis is controlled by negative feedback. This is type of control in which conditions are brought back to a set value as soon as it is detected that they have deviated from it.
What is an examples of role of hormones in homeostasis?
Regulation of blood glucose as an example of role of hormones in homeostasis.
What is role of glucose and what is its level in the blood?
Transport of glucose to all cells is a key function of the blood circulation. In human blood a set value of around 90mg/100ml (5 mmol L-1) blood is normal.
What situations cause the blood sugar level to drop above or below that value?
For example, during an extended period without food, or after prolonged & heavy physical activity, blood glucose may fall to as low as 70 mg. After a meal rich in carbohydrate has been digested, blood glucose may rise to 150 mg.
What are the two reasons for maintenance of a constant level of this monosaccharide in the blood plasma?
- Respiration is a continuous process in all living cells. To maintain their metabolism, cells need a regular supply of glucose, which can be quickly absorbed across cell membrane. Glucose is main respiratory substrate for many tissues. Most cells (including muscle cells) hold reserves in form of glycogen which is quickly converted to glucose during prolonged physical activity. However, glycogen reserves may be used up quickly. In brain, glucose is only substrate cells can use &, here, there is no glycogen store held in reserve. If our blood glucose falls below 60 mg per 100 cm3, we have a condition called hypoglycaemia. If this is not quickly reversed, we may faint. If body & brain continue to be deprived of adequate glucose levels, convulsions & coma follow.
- An abnormally high conc of blood glucose, known as hyperglycaemia, is also a problem. Since high conc of any soluble metabolite lowers water potential of the blood plasma, water is drawn from cells & tissue fluid by osmosis, back into blood. As volume of blood increases, water is excreted by kidney to maintain correct conc of blood. As a result, body tends to become dehydrated & circulatory system is deprived of fluid. Ultimately, blood pressure cannot be maintained. For these reasons, it is critically important blood glucose is held within set limits.
why does hyperglycaemia increases the blood pressure?
Water moves in by osmosis bc of high con of glucose. Thus increasing volume, leading to an increased blood pressure.
What two hormones adjust blood sugar levels?
Blood sugar levels are adjusted by two hormones: Insulin & Glucagon, which are produced in pancreatic cells (Langerhans islets), which are hormone-secreting glands (endocrine glands). Hormones are transported in body by blood to reach their target cells. Langerhans islets contain two types of cell, α cells (releases glucagon) & β cells (releases insulin).
Which two hormones are responsible for the homeostatic control of blood sugar levels?
Insulin & Glucagon
Where is insulin produced?
Islets of Langerhans, β cells
Where is glucagon produced?
Islets of Langerhans, α cells
What is an exocrine gland?
An exocrine gland is a gland which releases its products into a duct (e.g. digestive enzymes)
What is an endocrine gland?
An endocrine gland is a gland which secretes products (e.g. hormones) into bloodstream.
What happens when blood glucose levels are high?
- Stimulation of β cells , which secrete hormone insulin into blood stream ( capillary network).
- Insulin causes skeletal muscle fibre & liver cells to absorb insulin.
- Insulin causes conversion of glucose to glycogen in cells (glycogenesis), & to fatty acids & fats (adipose tissue). Excess insulin is removed via kidneys from blood.
What happens when blood glucose levels are low?
- Stimulation of α cells of pancreas to secrete hormone glucagon.
- Glucagon activates enzymes to convert glycogen & amino acids to glucose (gluconeogenesis).
- It also reduces rate of respiration. Excess glucagon is removed from blood via kidneys.
What are the consequences of the interactions between insulin and cell membrane receptor?
Insulin causes migration of membrane proteins & absorption into the cell
What are the consequences of the interactions between glucagon and cell membrane receptor?
Glucagon causes breakdown of polymer storage products in liver.
What does hypoglycaemia cause? And what are the symptoms?
Can lead to seizures, coma, or death if severe. Symptoms include:
- Sweating
- Shakiness
- Extreme hunger
- Nausea
- Dizziness
- Confusion
- Fast heart rate
- Behaviour changes
What does hyperglycaemia cause? And what are the symptoms?
Can lead to heart disease, stroke, kidney damage and eye damage.
Symptoms include:
- Increased thirst
- Increased urination
- Fatigue
- Light-headedness
- Dry mouth
- Headache
- Blurry vision
- Shortness of breath
Why is it important to control blood glucose?
Blood glucose homeostasis is maintained by balancing amount of glucose removed from blood with the amount that is added.
What are the receptors involved in maintenance of blood glucose levels?
RECEPTOR: Chemoreceptor proteins in carotid artery in neck sense changes in blood glucose conc.
What are the control centre involved in maintenance of blood glucose levels?
CONTROL CENTER: hypothalamus in brain senses & responds to changes in blood glucose levels by triggering release of hormones from pancreas
What are the effectors involved in maintenance of blood glucose levels?
- Pancreas: endocrine cells in the pancreas secrete the hormones insulin and glucagon
- Liver: responds to hormones by storing or releasing glucose
What is the negative feedback for insulin? ( Receptor, control centre, stimulus, effector, response)
What is the negative feedback for glucagon? ( Receptor, control centre, stimulus, effector, response)
What happens once insulin is released?
What is diabetes?
Diabetes is condition in which a person has consistently elevated blood glucose levels even during prolonged fasting. It is a chronic disease. This leads to presence of glucose in urine. Continuously elevated glucose causes damage to tissues, particularly their proteins. It also impairs water reabsorption during urine production in kidney, resulting in greater loss of water in urine & therefore dehydration.
What are the two types of diabetes?
- Type I diabetes (early onset)
- Type II diabetes (late onset)
What is the cause of type I diabetes?
Type I diabetes is a disease resulting from insufficient or no insulin production usually due to autoimmune destruction of beta cells of pancreatic islets (when body’s immune system mistakenly attacks healthy tissue).
Onset of Type I diabetes is sudden, often in childhood.
What happens during high blood glucose if they have type I diabetes?
What are the symptoms of Type I diabetes?
- Excessive thirst: Body tries to compensate for fluid loss due to frequent urination, leading to increased thirst.
- Blurred vision: High blood glucose can affect lens of eye, causing it to swell & change shape. This can lead to temporary blurred vision.
- Vaginal yeast infections: Yeast thrives on glucose, & excess sugar in bloodstream provides a plentiful food source
- Excessive hunger
- Unexplained weight loss: Even though food is consumed, body cannot effectively use glucose for energy. This can lead to weight loss, despite increased appetite.
- Slow healing of cuts & sores: Poor blood circulation & impaired immune function due to high blood sugar can hinder wound healing
- Fatigue: Cells are deprived of glucose, their primary energy source. This can lead to weakness & fatigue.
- Frequent urination: Kidneys attempt to filter out excess glucose from blood, leading to increased urine production.
What is the treatment of Type I diabetes?
- Type I diabetics must monitor blood glucose levels regularly to guard against sudden falls in blood glucose.
- Primary treatment for Type I diabetes is insulin therapy, which involves taking insulin injections or wearing an insulin pump to manage blood sugar levels.
- Scientists are working to differentiate stem cells into insulin-producing beta cells, which could then be transplanted into patients with Type I diabetes. This would potentially restore body’s ability to produce insulin on its own.
What is the cause of type II diabetes?
Type II diabetes is a disease resulting from a deficiency of insulin receptors on target cells.
Onset of Type II diabetes is gradual, often in overweight adults
What happens during high blood glucose if they have type II diabetes?
What are the symptoms of Type II diabetes?
- Increased thirst: Body tries to compensate for fluid loss due to frequent urination, leading to increased thirst.
- Unexplained weight loss
- Increased hunger: Even though food is consumed, body cannot effectively use glucose for energy. This can lead to weight loss, despite increased appetite.
- Fatigue: Cells are deprived of glucose, their primary energy source. This can lead to weakness & fatigue.
- Blurred vision: High blood glucose can affect lens of eye, causing it to swell and change shape. This can lead to temporary blurred vision.
- Frequent urination: Kidneys attempt to filter out excess glucose from blood, leading to increased urine production.
- Slow heading: Poor blood circulation & impaired immune function due to high blood sugar can hinder wound healing
- Numbness in hands or feet: High blood sugar levels can damage nerves & impair their ability to send signals. High blood sugar can also damage small blood vessels that supply nerves with oxygen & nutrients.
What is the treatment type II diabetes?
Type II diabetes is treated by:
- Reduction in weight & modification of dietary habits.
- Sometimes antidiabetic drugs are also used to stimulate pancreas to produce more insulin.
What are risk factors that contribute to development of diabetes?
- Family history:Having a family history of diabetes increases risk of developing condition. If a close family member, such as a parent or sibling, has diabetes, risk is higher.
- Body weight:Being overweight or obese is a significant risk factor for developing type 2 diabetes. Excess body weight increases insulin resistance & impairs glucose metabolism. Adopting and maintaining a healthy weight through a balanced diet & regular physical activity is one of the most effective ways to prevent type 2 diabetes. Losing even a small amount of weight (around 5–7% of body weight) can significantly reduce risk.
- Lifestyle:Lack of physical activity or a sedentary lifestyle is linked to an increased risk of type 2 diabetes. Regular exercise helps maintain a healthy weight, improves insulin sensitivity & reduces risk of developing diabetes.
- Diet:Consuming a diet high in processed foods, sugary beverages & unhealthy fats increases risk of developing type 2 diabetes. A diet low in fruits, vegetables & whole grains contributes to weight gain & insulin resistance.
- Age:Risk of developing diabetes increases with age. Type 2 diabetes is more common in adults over age of 45, although it is increasingly being diagnosed in younger individuals as well.
What food should a type II diabetes eat?
- Foods need to have a low glycaemic index – which is percentage of area under blood glucose response curve as a percentage of area produced by ingesting same quantity of glucose.
- Glycaemic index therefore ranges from 0 to 100.
Distinguish between type I and type II diabetes with respect to their cause, effects and treatment.
Explain what happens in a person when they develop type I diabetes.
- insulin is necessary to control/regulate blood glucose conc OR insulin is necessary for cells to take up glucose (for energy);
- insufficient insulin is made by pancreas OR autoimmune response/antibodiesdestroy (β) cells of pancreas that make insulin;
- reduced uptake of glucose from blood / glucose accumulates in blood / elevated blood glucose levels;
“sugar” is NOT accepted in place of glucose. However, this should only be penalized once; i.e., utiltize ECF.
State how type I diabetes should be treated to avoid harmful health consequences of the condition.
- inject insulin / monitoring blood glucose / devices that release insulin;
- decrease consumption of sugars/CHO / diet modification;
- increase exercise;
- keep weight in healthy range;
What is an endotherms?
Endotherms generate heat internally to maintain a steady body temp. Endotherms can increase their internal heat production when they are cold, & decrease it when they are hot. They can also shiver to warm up, & sweat or pant to cool down. Examples of endotherms include birds & mammals.
What is an ectotherms?
Ectotherms rely on external heat sources to regulate their body temperature. Their body temperature changes with the temperature of their environment. Examples of ectotherms include lizards and most fish.
What is thermoregulation?
Thermoregulation is maintenance of a core body temp despite fluctuations in external temperatures by balancing heat generation with heat loss.
