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Biology > Topic 6 C > Flashcards

Topic 6 C Flashcards

(40 cards)

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1
Q

What is homeostasis?

A

Maintaining a stable internal environment

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2
Q

What is negative feedback?

A

Restoring levels back to normal from too high or too low

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3
Q

What is positive feedback?

A

Amplifying a change Not part of (homeostasis)

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4
Q

What hormones control blood glucose?

A

Insulin and glucagon

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5
Q

Where are the hormones secreted from?

A

Islets of Langerhans in the pancreas

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6
Q

What are the two types of cells in the islets of langerhans?

A

Beta and alpha cells

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7
Q

What do beta cells secrete?

A

Insulin

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8
Q

What do the alpha cells secrete?

A

Glucagon

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9
Q

What happens if there is a fall in blood glucose levels?

A

Detected by alpha cells, glucagon is secreted, binds to receptors on cell membrane of liver cells and activates enzymes that break down glycogen into glucose and formation of glucose from glycerol and amino acids

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10
Q

What happens if there is a rise in blood glucose?

A

Detected by beta cells, insulin is secreted and binds to receptors on cell membranes of muscle and liver cells. Increases the permeability so they take up more glucose (channel proteins in membrane increase), activates enzymes that convert glucose into glycogen to store

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11
Q

What is glycogenesis?

A

Converts glucose to glycogen (activated by insulin)

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12
Q

What is glycogenolysis?

A

Converting glycogen to glucose (activated by glucagon and adrenaline)

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13
Q

What is gluconeogenesis?

A

Converts glycerol and amino acids to glucose (activated by glucagon)

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14
Q

What is GLUT4?

A

Glucose transporter, Low levels stored in vesicles in cytoplasm, when insulin binds to receptors it triggers GLUT4 to move into the membrane so glucose can be transported into the cell

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15
Q

Where is adrenaline secreted from?

A

Adrenal glands

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16
Q

What does adrenaline do?

A

It binds to receptors of membranes of liver cells, activates glycogenolysis and inhibits glycogenesis, activates glucagon secretion and inhibits insulin secretion

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17
Q

What is the second messenger model?

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A

When a hormone binds to receptors and activates an enzyme on the inside of a cell membrane which produces a chemical known as a second messenger

18
Q

How does adrenaline and glucagon use the second messenger model?

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A

Bind to receptors and activate enzyme called adenylate cyclase which converts ATP into cyclic AMP which is the second messenger. cAMP activates protein Kinase A which activates cascade that breaks down glycogen into glucose

19
Q

What is ultrafiltration in the kidneys?

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A

When substances are filtered out of the blood into long tubules that surround capillaries

20
Q

What is selective reabsorption in the kidneys?

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A

When useful substances are reabsorbed back into the blood

21
Q

What are nephrons?

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A

Long tubules with bundles of capillaries where blood is filtered

22
Q

Where does ultrafiltration take place?

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A

In the bowmans capsule

23
Q

What is the arteriole that takes blood into the glomerulus called?

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A

Afferent arteriole

24
Q

What is the arteriole that takes blood away from the glomerulus called?

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A

efferent arteriole

25
How does ultrafiltration occur?
Efferent arteriole has a smaller diameter so blood in glomerulus is under high pressure. This forces liquid and small molecules into the bowmans capsule. Pass through capillary endothelium, basement membrane and epithelium of bowmans capsule Larger molecules stay in the blood
26
What is the substance that enters the bowmans capsule called?
Glomerular filtrate which passes along nephron and useful substances are reabsorbe
27
How does selective reabsorption occur?
Filtrate flows along the proximal convoluted tubule, loop of henle, and along the distal convoluted tubule. Usefule subtances leave tubules and reenter blood
28
Where is water reabsorbed?
PCT, loop of henle, DCT and collecting duct (leftover filtrate is urine which passes along ureter to the bladder
29
What is osmoregulation?
Regulating water potential of the blood
30
What happens when water potential is too low?
More water is reabsorbed into the blood from tubules (urine more concentrated, less water lost through excretion)
31
What happens when water potential is too high?
Less water is reabsorbed into the blood from tubules (urine is more dilute, more water lost through excretion)
32
Where is the loop of henle located?
In the medulla
33
What is the loop of henle made of?
Two limbs, descending and ascending
34
What do the limbs do?
Control movement of sodium ions so water can be reabsorbed
35
How does the loop of henle work?
Na+ ion as are actively pumped into the medulla at the top of the ascending limb, water stays inside tube (low water potential in medulla), water moves out of the descending limb into medulla, glomerular filtrate is more concentrated, water in medulla reabsorbed into blood. near the bottom of ascending limb Na+ ions diffuse out into medulla lowering the water potential further in the medulla, Water moves out of distal convoluted tubule and reabsorbed into the blood, low water potential in medulla causes water to move out of collecting duct and water in medulla is reabsorbed into the blood through the capillary network
36
What is water potential monitored by?
Osmoreceptors in the hypothalamus
37
Why is antidiuretic hormone released and how into the blood?
Water potential decreased, water moves out of osmoreceptor cells causing cell to decrease in volume, signals are sent to other cells in the hypothalamus which send signals to the posterior pituitary gland
38
How does antidiuretic hormone work?
Binds to receptors on plasma membrane of the cells of the collecting duct, aquaporins are inserted into the plasma membrane allowing water to pass through via osmosis. DCT and collecting duct more permeable, more water is reabsorbed into the emdulla and into the blood, causing water to be more concentrated and less is lost from the body
39
Type 1 diabetes
Immune system attacks beta cells so insulin cant be produced so glucose levels rise and stays high (hyperglycaemia), treated using insulin injections, some have a genetic predisposition, may be triggered by viral infection
40
Type 2 diabetes
Developed later on in life, linked with obesity lack of exercise age and poor diet, family history, beta cells dont produce enough insulin so blood glucose conc is higher than normal, treated by eating healthy, weight loss and excercise

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