D 3.3 Homeostasis

Question 1

Define Homeostasis

Answer 1

maintenance of the internal environment of an organism and variables are kept within preset limits, despite fluctuations in external environment.

Question 2

Give 4 examples of homeostasis in the human body

Answer 2

-body temperature
-blood pH
-blood glucose concentration
-blood osmotic concentration

Question 3

What are the consequences of negative feedback compared to positive feedback?

Answer 3

Negative feedback loops counteract changes, promoting stability, while positive feedback loops amplify changes, potentially leading to extremes or instability.

Question 4

How do negative feedback loops maintain homeostasis?

Answer 4

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.

Question 5

How is blood glucose concentration controlled, including the roles of glucagon, insulin, and the endocrine cells in the pancreatic islets?

Answer 5

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).

Question 6

What are the causes of type I and type II diabetes?

Answer 6

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.

Question 7

What are the treatments for type I and type II diabetes?

Answer 7

Type I diabetes is treated with insulin therapy, while type II diabetes is managed through lifestyle changes, oral medications, and sometimes insulin.

Question 8

What are the risk factors associated with type II diabetes?

Answer 8

Risk factors include obesity, sedentary lifestyle, poor diet, age, family history, and certain ethnic backgrounds.

Question 9

What is thermoregulation?

Answer 9

Thermoregulation is the process by which organisms regulate their body temperature within certain limits to maintain optimal functioning.

Question 10

What types of animals are thermoregulators?

Answer 10

Birds and mammals are thermoregulators, maintaining a constant body temperature regardless of external conditions.

Question 11

How does thermoregulation function as a negative feedback loop?

Answer 11

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.

Question 12

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.

Answer 12

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.

Question 13

What are the physiological and behavioral responses to cold temperatures?

Answer 13

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).

Question 14

What are the physiological and behavioral responses to heat?

Answer 14

Responses include vasodilation (widening of blood vessels to release heat) and sweating (evaporation of sweat cools the body).

Question 15

What are the functions of the kidney?

Answer 15

The kidneys regulate water and electrolyte balance, excrete waste products, and help control blood pressure and pH levels.

Question 16

Describe the structure of a kidney nephron.

Answer 16

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).

Question 17

Outline the processes of osmoregulation and excretion in a kidney nephron.

Answer 17

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.

Question 18

Explain the process of ultrafiltration at the glomerulus and Bowman’s capsule.

Answer 18

Ultrafiltration occurs when blood pressure forces water and small solutes from the glomerulus through the filtration barrier into Bowman’s capsule, forming filtrate.

Question 19

What is filtrate?

Answer 19

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.

Question 20

Why are plasma proteins and blood cells not part of glomerular filtrate?

Answer 20

Plasma proteins and blood cells are too large to pass through the filtration barrier of the glomerulus, which selectively filters based on size.

Question 21

Explain the process of selective reabsorption at the proximal convoluted tubule.

Answer 21

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.

Question 22

Outline the mechanism of reabsorption for substances in the glomerular filtrate that are reabsorbed in the proximal convoluted tubule.

Answer 22

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.

Question 23

Compare the location and osmotic concentrations of the kidney cortex and medulla.

Answer 23

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.

Question 24

What is the overall function of the loop of Henle?

Answer 24

The loop of Henle concentrates urine and helps maintain osmotic gradients in the kidney, allowing for efficient water reabsorption.

Question 25

Describe the structure and function of the descending limb of the loop of Henle.

Answer 25

The descending limb is permeable to water but not to salts, allowing water to be reabsorbed into the medulla, concentrating the filtrate.

Question 26

Describe the structure and function of the ascending limb of the loop of Henle.

Answer 26

The ascending limb is impermeable to water and actively transports sodium and chloride ions out into the medulla, diluting the filtrate and contributing to the osmotic gradient.

Question 27

What are the effects of dehydration and hyperhydration on the osmotic concentration of blood?

Answer 27

Dehydration increases blood osmotic concentration due to higher solute levels, while hyperhydration decreases blood osmotic concentration due to diluted solutes.

Question 28

How is blood osmotic concentration regulated, including the roles of chemoreceptors, the hypothalamus, the pituitary gland, and antidiuretic hormone (ADH)?

Answer 28

Chemoreceptors detect changes in osmotic concentration, signaling the hypothalamus to activate the pituitary gland to release ADH, which increases water reabsorption in the collecting ducts, regulating osmotic balance.

Question 29

How do the collecting ducts of the kidney increase blood osmotic concentration?

Answer 29

The collecting ducts increase blood osmotic concentration by reabsorbing more water in response to ADH, leading to concentrated urine.

Question 30

How do the collecting ducts of the kidney decrease blood osmotic concentration?

Answer 30

The collecting ducts decrease blood osmotic concentration by allowing less water to be reabsorbed when ADH levels are low, resulting in dilute urine.

Question 31

What are the consequences of low blood solute concentration on urine production and water reabsorption?

Answer 31

Low blood solute concentration leads to increased urine volume, decreased solute concentration in urine, reduced permeability of the distal convoluted tubule and collecting duct to water, and decreased water reabsorption.

Question 32

What are the consequences of high blood solute concentration on urine production and water reabsorption?

Answer 32

High blood solute concentration results in decreased urine volume, increased solute concentration in urine, increased permeability of the distal convoluted tubule and collecting duct to water, and increased water reabsorption.

Question 33

What are the benefits of regulating blood supply to organs in response to changes in activity?

Answer 33

Regulating blood supply ensures that active tissues receive adequate oxygen and nutrients while diverting blood from less active areas, optimizing overall physiological efficiency.

Question 34

What are the causes and consequences of vasoconstriction and vasodilation?

Answer 34

Vasoconstriction is caused by signals from the sympathetic nervous system, reducing blood flow and conserving heat. Vasodilation, caused by signals from the parasympathetic system or local metabolic factors, increases blood flow, enhancing nutrient delivery and heat dissipation.

Question 35

How does blood flow to skeletal muscle, gut, brain, and kidneys vary during sleep, vigorous physical activity, and wakeful rest?

Answer 35

During vigorous physical activity, blood flow increases to skeletal muscles and decreases to the gut, while flow to the brain remains relatively constant. During sleep, blood flow decreases to skeletal muscles and the gut, with varying levels to the brain depending on sleep stages. During wakeful rest, blood flow is balanced among these organs.