Toic 6 - Homeostasis

Question 1

What is homeostasis?

Answer 1

Insures a constant internal environment for factors such as temperature, water potential, pH and blood glucose levels despite changes in the excel environment. Essential for enzyme function as extreme changes can lead to enzyme denaturation.

Question 2

What is the negative feedback mechanism as a key process of homeostasis?

Answer 2

A process that reverses a change in internal conditions to restore optimum levels. It involves sensory receptors that detect changes in temperature or glucose levels for example. Information is transmitted via the nervous or hormonal system and the effect bring about a response to restore normal conditions.

Question 3

What is the positive feedback mechanism?

Answer 3

A process that enhances the original change rather than reversing it.

Question 4

What is the importance of homeostasis?

Answer 4

• maintains enzyme activity with optimal ranges.
• Ensure cell function and survival by stabilising internal conditions
• Regulates critical processes such as blood pH and temperature temperature control.

Question 5

What is the importance of negative feedback?

Answer 5

Maintains conditions necessary for enzyme activity and prevents extreme deviations that could cause harm to the organism. Insures stable conditions for survival in a constantly changing environment.

Question 6

What is insulin?

Answer 6

A hormone created by the beta cells in the pancreas. Its role is to reduce blood glucose levels when they rise above the normal range.

Question 7

How is high levels of glucose detected?

Answer 7

Arise in blood glucose concentration is detected by beta cells in the pancreas.

Question 8

How is insulin secreted?

Answer 8

Beta cells secrete insulin which inhibits the action of alpha cells that release glucagon.

Question 9

What are some of the target cells insulin binds to?

Answer 9

Adipose
Muscle cells
Hepatocytes

Question 10

What occurs when insulin binds to receptors on target cells?

Answer 10

The binding of insulin to receptors on the plasma membrane activates the enzyme add adenyl cyclase, which converts ATP into cyclic AMP (cAMP). This triggers a cascade of intracellular reactions.

Question 11

What are the effects of insulin?

Answer 11

1. Increase glucose uptake because more glucose transporter proteins are inserted into the cell membrane increasing the uptake of glucose into the cells via facilitated diffusion.
2. Conversion of glucose glucose is converted into glycogen in liver and muscle cells.(glycogenesis).
3. Increased glucose use because glucose is used for cellular respiration in muscles and other tissues.
4. Reduced glucose release because insulin inhibits processes that increase blood glucose such as glycogenolysis and gluconeogenesis.

Question 12

Summarise insulin role in lowering blood glucose levels

Answer 12

• promotes glucose uptake by cells.
• Encourages glycogenesis and fat storage
• Inhibits glycogenolysis and gluconeogenesis.

Question 13

What is glucagon?

Answer 13

A hormone secreted by the alpha cells in the pancreas. Its role is to increase blood glucose levels when they fall below the normal range.

Question 14

How is low levels of glucose detected?

Answer 14

A drop in blood glucose concentration is detected by alpha cells in the pancreas.

Question 15

How is glucagon secreted?

Answer 15

Alpha cells secrete glucagon which inhibits the action of beta cells in releasing insulin.

Question 16

What are the target cells for glucagon?

Answer 16

Glucagon primarily act on hepatocytes.

Question 17

What are the effects of glucagon?

Answer 17

1. Glycogenolysis: glucagon stimulates the breakdown of glycogen into glucose in the liver cells.
2. Glyconeogenesis: glucagon stimulates the conversion of non-carbohydrate molecules into glucose.
3. Glucose release: the newly produced glucose diffuses out of the hepatocytes into the bloodstream increasing blood glucose levels.
4. Switch to fatty acid use: in the absence of sufficient glucose other cells begin using fatty acids or amino acids for respiration instead.

Question 18

Summarise the role of glucagon in increasing blood glucose levels.

Answer 18

Promote glycogenolysis and stimulates gluconeogenesis. Encourages glucose release and reduces glucose use promoting the use of fatty acids and amino acids in respiration.

Question 19

What is adrenaline?

Answer 19

A hormone involved in increasing blood glucose levels by stimulating the breakdown of glycogen into glucose in the liver.

Question 20

How how does adrenaline increase blood glucose?

Answer 20

1. Adrenaline binds to specific receptors on the cell surface membrane of liver cells/hepatocytes. This binding causes the receptor to change shape on the inside of the membrane.
2. The change in receptor shape activates the enzyme. Adenyl cyclase. Which convert ATP into cyclic AMP which acts as a secondary messenger.
3. Cyclic AMP activate protein kinase enzymes by changing their shape these enzymes catalyse the conversion of glycogen into glucose.
4. The glucose produced diffuses out of the liver cells and into the bloodstream increasing blood glucose levels.

Question 22

What are the key points about adrenaline role?

Answer 22

• Works via the secondary messenger system (cAMP).
• increases blood glucose levels by stimulating glycogenolysis.
• Insures that glucose is available for respiration during periods of stress or activity.

Question 23

Why is the control of blood glucose concentration essential?

Answer 23

Makes sure essential processes such as respiration of brain cells can occur. Blood glucose levels fluctuate based on food intake and energy requirements.

Question 24

What is the correct range of glucose concentration in the blood?

Answer 24

70-99 mg/dl

Question 25

What is glycogenesis?

Answer 25

The conversion of glucose of glycogen for storage when blood glucose levels are high.

Question 26

What is glycogenolysis?

Answer 26

The breakdown of glycogen into glucose which is released into the blood when glucose levels are low.

Question 27

What is gluconeogenesis?

Answer 27

The synthesis of glucose from non-carbohydrate sources such as amino acids and glycerol.

Question 28

What is diabetes?

Answer 28

A condition where the body is unable to regulate blood glucose concentration. There are two main types of diabetes each with different causes and treatment.

Question 29

What is type one diabetes?

Answer 29

Usually occurs early in life and is caused by the immune system attacking and destroying beta cells in the pancreas resulting in no insulin production. Symptoms include high blood glucose levels, excessive urination, extreme thirst, and weight loss.

Question 30

What is the type one diabetes treatment?

Answer 30

- self injecting insulin with doses carefully matched to diet and exercise. - Regular monitoring of blood glucose levels.

Question 31

What is type 2 diabetes?

Answer 31

Typically develops later in life often associated with obesity and poor diet. It is caused by reduced insulin production by the pancreas and target cells becoming unresponsive to insulin due to damaged glycoprotein receptors. Symptoms include fatigue increased thirst and frequently urination. Risk factors include poor diet, obesity and lack of exercise or genetic predisposition.

Question 32

What is the treatment for type 2 diabetes?

Answer 32

- controlling blood glucose through a balanced diet and exercise. - In some cases taking medication to improve insulin sensitivity or increase insulin production.

Question 33

How can the concentration of glucose in urine be calculated?

Answer 33

Using a colorimeter or a calibration curve. This method involves comparing the sample to known concentrations of glucose.

Question 34

what is a nephron?

Answer 34

The functional units of the kidney responsible for the filtration of blood and the formation of urine. It consists of several specialised structures each adapted for a specific role in this process.

Question 35

What is the structure of the kidney?

Answer 35

Fibrous capsule Cortex Medulla Renal pelvis

Question 36

What is the fibrous capsule of the kidney?

Answer 36

The outer layer of the kidney that protects it from damage and infection.

Question 37

What is the cortex feature of the kidney?

Answer 37

The outer region of the kidney which contains the Bowman’s capsule which is the site where filtration begins. The convoluted tubules: proximal and distal tubules for re-absorption and secretion. Blood vessels: deliver blood to the nephrons.

Question 38

What is the medulla as part of the kidney?

Answer 38

The inner region of the kidney containing the loop of Henle: creates a concentration gradient for water reabsorption. Collecting ducts: transport urine up towards the renal pelvis. Blood vessels: network of capillaries aiding in exchange processes..

Question 39

What is the renal pelvis part of the kidney?

Answer 39

A funnel shaped cavity that collects urine from the collecting duct and delivers it to the ureter.

Question 40

What is the Bowman’s capsule?

Answer 40

Cup shaped structure surrounding the glomerulus where ultrafiltration occurs.

Question 41

What is the proximal convoluted tubule?

Answer 41

Reabsorbs glucose amino acids, salt and water into the blood.

Question 42

What is the loop of henle?

Answer 42

Descending limb: permeable to water not salts. Ascending limb: permeable to salts not water. Creates a concentration gradient in the medulla.

Question 43

What is the distal convoluted tubule?

Answer 43

Adjusts the concentration of salts and controls pH through selective reabsorption.

Question 44

What is the collecting duct?

Answer 44

Reabsorbs water under the influence of antidiuretic hormone (ADH).

Question 45

Why does the nephron need to carry out a process to filter the blood?

Answer 45

To maintain a constant water balance and remove waste products efficiently.

Question 46

What is ultrafiltration as a stage of the nephron?

Answer 46

- Blood enters the kidney via the renal artery under high-pressure. - the artery branches into the afferent arteriole leading to a capillary network called the glomerulus. - Water and small molecules are forced out into the bowman’s capsule forming the glomerular filtrate. -Large molecules such as proteins and blood cells remain in the blood as they are too large to pass through. - high-pressure in the flomerulus is maintained because the efferent arteriole leaving the glomerulus narrower than the afferent arteriole entering it.

Question 47

What is selective reabsorption as another process of the nephron?

Answer 47

- Occurs mainly in the proximal convoluted tubule. - Glucose amino acids and some salts are reabsorbed into the blood. - Process involves transport: sodium ions are actively transported from the PCT epithelial cells into the blood. This creates a low sodium concentration in the epithelial cells. sodium ions move into the epithelial cells from the tubule lumen via facilitated diffusion glucose or amino acids with them. Glucose then diffuses into blood capillaries. - Waterfalls by us most due to the concentration gradient created by solute reabsorption.

Question 48

What is the loop of henle as a stage in the nephron?

Answer 48

- Act as a countercurrent multiplier to concentrate solute in the medulla aiding water reabsorption. - Ascending limb: actively transport, sodium ions and chloride ions out into the interstitial space using ATP. In permeable water so water remains inside. - descending limb: permeable to water so water moves out into the interstitial space by Moses where the solute concentration is high. At the hairpin bend the field reaches its lowest potential. - Sodium diffuse out of the bottom at the ascending due to the steep concentration gradient.

Question 49

What is the distal convoluted tubule and the collecting ducts as the fourth stage of the nephron?

Answer 49

- DCT fine-tunes the concentration of solute in the filtrate through selective reabsorption. - Water moves out of the collecting duct biosis following the high solute concentration gradient in the medulla. - The duck descends deeper into the ion concentration increases allowing more water to leave.

Question 50

What is the role of ADH antidiuretic hormone?

Answer 50

- Osmo receptors in the hypothalamus detect changes in blood water potential. - if water potential decreases Osmo receptors shrink stimulating the release of ADH from the posterior pituitary gland. ADH bind to receptors in collecting duct cells activating the enzyme phosphorylase. Vesicles containing. Aquaporins fuse with the cell membrane increasing the duct permeability to water. Urea permeability also increases further reducing water potential in the water by osmosis. - This allows more water to be re-absorbed into the blood reducing water loss in urine.

Question 51

Give a summary of the key functions of the nephron

Answer 51

Ultrafiltration: filters blood to remove small molecules into the nephron. Selective rib absorption: recovers glucose, salts, and water back into the blood. Loop of Henle: concentrates solutes in the medulla to aid water reabsorption. ADH regulation: controls water absorption in collecting duct to maintain hydration.