D 3.3 Homeostasis Flashcards
(35 cards)
Define Homeostasis
maintenance of the internal environment of an organism and variables are kept within preset limits, despite fluctuations in external environment.
Give 4 examples of homeostasis in the human body
-body temperature
-blood pH
-blood glucose concentration
-blood osmotic concentration
What are the consequences of negative feedback compared to positive feedback?
Negative feedback loops counteract changes, promoting stability, while positive feedback loops amplify changes, potentially leading to extremes or instability.
How do negative feedback loops maintain homeostasis?
Negative feedback loops detect deviations from a set point (e.g., body temperature) and trigger responses that counteract these changes, restoring the internal environment to its optimal state.
How is blood glucose concentration controlled, including the roles of glucagon, insulin, and the endocrine cells in the pancreatic islets?
Blood glucose levels are regulated by insulin, which lowers blood glucose by facilitating cellular uptake, and glucagon, which raises blood glucose by promoting glycogen breakdown in the liver. The pancreatic islets contain beta cells (secreting insulin) and alpha cells (secreting glucagon).
What are the causes of type I and type II diabetes?
Type I diabetes is caused by the autoimmune destruction of insulin-producing beta cells in the pancreas, while type II diabetes is primarily due to insulin resistance and insufficient insulin production, often linked to lifestyle factors.
What are the treatments for type I and type II diabetes?
Type I diabetes is treated with insulin therapy, while type II diabetes is managed through lifestyle changes, oral medications, and sometimes insulin.
What are the risk factors associated with type II diabetes?
Risk factors include obesity, sedentary lifestyle, poor diet, age, family history, and certain ethnic backgrounds.
What is thermoregulation?
Thermoregulation is the process by which organisms regulate their body temperature within certain limits to maintain optimal functioning.
What types of animals are thermoregulators?
Birds and mammals are thermoregulators, maintaining a constant body temperature regardless of external conditions.
How does thermoregulation function as a negative feedback loop?
Thermoregulation operates as a negative feedback loop by detecting temperature changes and triggering physiological responses (like sweating or shivering) that counteract deviations from the set temperature.
Explain the process of thermoregulation in humans, including the roles of peripheral and central thermoreceptors, the hypothalamus and pituitary gland, thyroxin, and muscle and adipose tissue as effectors of temperature change.
Peripheral thermoreceptors detect temperature changes in the skin, while central thermoreceptors in the hypothalamus monitor core body temperature. The hypothalamus coordinates responses such as vasodilation, sweating, shivering, and adjusting metabolic rates through thyroxin release from the thyroid gland, involving muscles and adipose tissue in generating or conserving heat.
What are the physiological and behavioral responses to cold temperatures?
Responses include vasoconstriction (narrowing of blood vessels to conserve heat), shivering (muscle contractions generating warmth), uncoupled respiration (increased metabolic rate), and hair erection (to trap air for insulation).
What are the physiological and behavioral responses to heat?
Responses include vasodilation (widening of blood vessels to release heat) and sweating (evaporation of sweat cools the body).
What are the functions of the kidney?
The kidneys regulate water and electrolyte balance, excrete waste products, and help control blood pressure and pH levels.
Describe the structure of a kidney nephron.
A nephron consists of a renal corpuscle (glomerulus and Bowman’s capsule) and a renal tubule (proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting duct).
Outline the processes of osmoregulation and excretion in a kidney nephron.
Osmoregulation involves filtration of blood to form filtrate, reabsorption of water and solutes back into the bloodstream, and secretion of excess substances into the filtrate, leading to urine formation.
Explain the process of ultrafiltration at the glomerulus and Bowman’s capsule.
Ultrafiltration occurs when blood pressure forces water and small solutes from the glomerulus through the filtration barrier into Bowman’s capsule, forming filtrate.
What is filtrate?
Filtrate is the liquid that collects in Bowman’s capsule, containing water, ions, glucose, amino acids, and waste products, but lacking larger molecules like proteins and blood cells.
Why are plasma proteins and blood cells not part of glomerular filtrate?
Plasma proteins and blood cells are too large to pass through the filtration barrier of the glomerulus, which selectively filters based on size.
Explain the process of selective reabsorption at the proximal convoluted tubule.
Selective reabsorption occurs in the proximal convoluted tubule, where essential substances like glucose, amino acids, and ions are reabsorbed back into the bloodstream via active and passive transport mechanisms.
Outline the mechanism of reabsorption for substances in the glomerular filtrate that are reabsorbed in the proximal convoluted tubule.
Reabsorption involves active transport for glucose and amino acids, which are then co-transported with sodium ions, while water follows osmotically. Ions like sodium, potassium, and bicarbonate are also actively reabsorbed.
Compare the location and osmotic concentrations of the kidney cortex and medulla.
The kidney cortex has a lower osmotic concentration, while the medulla has a higher osmotic concentration due to the presence of solutes that promote water reabsorption.
What is the overall function of the loop of Henle?
The loop of Henle concentrates urine and helps maintain osmotic gradients in the kidney, allowing for efficient water reabsorption.
