Homeostasis

Question 1

What is homeostasis?

Answer 1

The maintenance of a constant internal environment

Question 2

What is the optimum point?

Answer 2

The level at which the system works best.

Question 3

What is a receptor?

Answer 3

Detects deviations from the optimum point and informs the coordinator.

Question 4

What is the coordinator?

Answer 4

Co-ordinates information from receptors and sends instructions to the effector.

Question 5

What is the effector?

Answer 5

Brings about changes needed to return to the optimum point.

Question 6

What is a feedback mechanism?

Answer 6

Informs the receptor of changes brought about by the effectors.

Question 7

What is negative feedback?

Answer 7

The corrective measures are turned off as the body has reached the optimum point again.

Question 8

What is positive feedback?

Answer 8

Thee feedback causes the corrective measures to remain turned on, causing the system to deviate further from the optimum.

Question 9

How does the second messenger model work?

Answer 9

• Adrenaline binds to a receptor in the membrane of a liver cell.
• Activates the enzyme adenyl cyclase by changing the shape of the receptor inside the cell.
• Adenyl cyclase converts ATP to cyclic AMP (cAMP)
• Binds to protein kinase and activates it.
• Protein kinase converts glycogen into glucose which leaves the liver cell by facilitated diffusion.

Question 10

What does the pancreas produce?

Answer 10

Digestive enzymes and the hormones involved in glucose regulation insulin and glucagon.

Question 11

What are the islets of Langerhans?

Answer 11

Groups of cells in the pancreas which produce hormones, surrounded by cells which produce digestive enzymes.

Question 12

What are the cells which make up the liver called?

Answer 12

Hepatocytes

Question 13

What is glycogenolysis?

Answer 13

The conversion of glycogen to gucose

Question 14

What is the name for the conversion of glycogen to glucose?

Answer 14

Glycogenolysis

Question 15

What is gluconeagenesis?

Answer 15

The production of glucose.

Question 16

What is the name for the process for the production of glucose?

Answer 16

Gluconeagenesis

Question 17

What is glycogenesis?

Answer 17

Conversion of glucose to glycogen.

Question 18

What is the name for the conversion of glucose to glycogen?

Answer 18

Glycogenesis

Question 19

What 4 things affect the level of glucose in the blood?

Answer 19

• Diet,
• Glycogenolysis,
• Gluconeogenesis,
• Level of physical or mental demand.

Question 20

What cells detect a rise in blood sugar using receptors and how do they respond?

Answer 20

B cells, respond by secreting insulin.

Question 21

What happens when body cells bind with insulin?

Answer 21

• Change in the tertiary structure of glucose transport channels, allowing more glucose in,
• Increases the number of carrier proteins,
• activation of enzymes that convert glucose into glycogen and fat.

Question 22

How is does insulin binding to a receptor on a membrane increase the number of glucose carrier proteins?

Answer 22

Vesicles (made up of the protein in the glucose channels) fuse to the membrane.

Question 23

What do a-cells do?

Answer 23

Secrete glucagon into the blood.

Question 24

What causes type one diabetes?

Answer 24

The immune system attacks the Bcells in the islets of Langerhans so they cannot produce insulin. Causing hyperglycemia.

Question 25

What causes type two diabetes?

Answer 25

Often linked with obesity. B cells don't produce enough insulin to body cells don't respond to the insulin properly.

Question 26

Describe ultafiltration in the kidneys.

Answer 26

Blood from renal artery enters arteries which go into the Bowman's capsule. The efferent arteriole carries blood our of the bowman's capsule and is smaller i diameter than the afferent arteriole. So blood in glomerulus in under high pressure. Liquid is forced through capillary wall, basement membrane and epithelium of Bowman's capsule. Proteins stay in blood.

Question 27

Which three places does selective re-absorption occur?

Answer 27

Proximal convoluted tubule, loop of henle, distal convoluted tubule.

Question 28

Where is the loop of henle located in the kidneys?

Answer 28

In the medulla.

Question 29

How does the loop of Henle maintain a sodium ion gradient?

Answer 29

Na+ is pumped out of the top of the ascending limp by active transport. Creating a low WP in medulla. As this is lower than the WP in the descending limb water moves out by osmosis. Making the filtrate more concentrated. More Na+ diffuses out due to low WP in bottom of ascending limb

Question 30

How and where is water potential in the blood monitored?

Answer 30

By osmoreceptors in the hypothalamus. If the WP in the blood is ow then water moves out the osmoreceptors

Question 31

What detects the signal from the osmoreceptors and how does it respond?

Answer 31

The posterior pituitary, secretes ADH (antidiuretic hormone)

Question 32

What does ADH do to the walls of the distal convoluted tubule and colecting duct?

Answer 32

Makes the walls more permeable to water by triggering phosphorylase which makes vesicles containing aquaporins to fuse to the cell surface membranes.