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Homeostasis Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Define homeostasis

A

Homeostasis involves physiological control systems that maintain the internal environment within restricted limits

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2
Q

Name 2 things homeostasis is important in maintaining

A

A stable core temp
Stable blood pH in relation to enzyme activity

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3
Q

What type of feedback is involved in homeostasis?

A

Negative

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4
Q

How is negative feedback involved in homeostasis?

A

Neg feedback is involved and this is when any deviation from the normal values are restored to their original level
This involved the nervous system often hormones too

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5
Q

When will blood glucose concentrations increase?

A

Ingestion of food or drink containing carbs

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6
Q

When will blood glucose concentration decrease?

A

Following exercise or if you have not eaten

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7
Q

What does the pancreas do in terms of blood glucose concentration?

A

Detects changes in the blood glucose level, islets of Langerhans cells release insulin and glucagon to bring glucose levels to normal

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8
Q

What does insulin do in terms of blood glucose concentration?

A

Released when blood glucose levels are too high it causes a decrease in blood glucose levels

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9
Q

What does glucagon do in terms of blood glucose concentration?

A

Released when blood glucose levels are too low, causing an increase in blood glucose levels

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10
Q

What does adrenaline do in terms of blood glucose concentration?

A

Released by adrenal glands when your body anticipates danger and this results in more glucose being released from hydrolysis of glycogen in the liver

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11
Q

Explain the process of blood glucose levels increasing- what happens after?

A

1) Detected by beta cells in the islets of Langethans (pancreas)
2) Beta cells release insulin
3) Liver cells become more permeable to glucose and enzymes are activated to convert glucose to glycogen
4) Glucose is removed from the blood and stores as glycogen in the cells
5)Levels return to normal

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12
Q

Explain the process of blood glucose levels decreasing- what happens after?

A

1) Detected by the alpha cells in the islets of Langerhans (pancreas)
2)Alpha cells release glucagon, adrenal gland release adrenaline
3) Second messenger model occurs to activate enzymes to hydrolyse glycogen
4) Glycogen is hydrolysed to glucose and more glucose is released back into blood
5) Levels return to normal

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13
Q

What are the 3 actions of insulin?

A

Attaching to receptors on the surfaces of target cells, changing the tertiary structure of the channel proteins resulting in ,for glucose being absorbed by facilitated diffusion

More protein carriers are incorporated into cell membranes so that more glucose is absorbed from the blood into cells

Activating enzymes involved in conversation of glucose to glycogen this results in glycogenesis in the liver

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14
Q

How does having more protein carriers happen and increase glucose absorbed?

A

Insulin binds to insulin receptors
Intracellular chemicals released
Vesicles containing glucose change, proteins fuse with cell membrane
So more protein channels embedded in membrane so more glucose can be absorbed

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15
Q

What are the 3 actions of glucagon?

A

Attaching to receptors on the surface of target cells (liver cells)

When glucagon binds it causes a protein to be activated into adenylate Cyclades and to convert ATP in a molecule called cyclic AMP (cAMP) high activates an enzyme protein kinase that can hydrolyse glycogen into glucose

Activating enzymes involved in the conversion of glycerol and AA into glucose

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16
Q

Explain the second messenger model?

A

Glucagon binding to glucagon receptors on the target cells

Once bound it causes a change in shape to the enzyme adenyl cyclase which activates it

Activates adenyl cyclase enzyme converts ATP into cyclic AMP (cAMP)
cAMP is the second messenger

cAMP coverts inactive protein kinase into active kinase which an hydrolyse glycogen to glucose

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17
Q

What is the role of adrenaline in terms of controlling blood glucose concentration?

A

If the blood glucose is too low the adrenal glands will secrete adrenaline and will increase the blood glucose conc

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18
Q

In what 3 ways does adrenaline increase blood glucose concentration?

A

Adrenaline attaches to receptors on the surfaces of target cells, this causes a protein (G protein) to be activated and to convert ATP into cAMP

cAMP activates an enzyme that can hydrolyse glycogen into glucose

This is known as the second messenger model of adrenaline and glucagon action, because the process results in the formation of cAMP, which acts as a 2nd messenger

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19
Q

What is meant by glucogenesis?

A

Converting glucose into glycogen, this occurs in the liver and is catalysed by enzymes there

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20
Q

What is meant by glucogenolysis?

A

Hydrolysis of glycogen to glucose, this occurs in the liver due to second messenger model

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21
Q

What is meant by gluconeogenesis?

A

Creating of glucose from other molecules, such as amino acids and glycerol in the liver

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22
Q

What is type one diabetes?

A

When people are unable to produce insulin

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23
Q

What’s the treatment for type one diabetes?

A

Insulin injections

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24
Q

What is type two diabetes?

A

Receptors on the tater cells lose their responsiveness to insulin

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25
Q

When and how do people get type one diabetes?

A

Usually starts in childhood and could be results of an autoimmune disease where beta cells are attacked

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26
Q

When and how do people hey type two diabetes?

A

Usually develops in adults due to obesity and poor diet

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27
Q

How do we help to treat type 2 diabetes?

A

Controlled by regulating intake of carbs, increasing expressed
Also insulin injections

28
Q

What is osmoregulaction?

A

Controlling water potential of the blood

29
Q

What is it called when blood has too low of a water potential?

A

Hypertonic

30
Q

What is it called when blood has a too high of of water potential?

A

Hypotonic

31
Q

What’s the problem with hypertonic blood?

A

When too much water will leave the cells and move into the blood by osmosis, cells will shrivel (crenation)

32
Q

What is the problem with hypotonic blood?

A

Too much water will move from the blood into the cells by osmosis
Cells will burst (lysis)

33
Q

What can cause hypertonic blood?

A

Excess sweating
Not drinking enough water
A diet with too many Ions (salty diet)

34
Q

What causes blood to be hypotonic?

A

Drinking too much water
Not enough salt in their diet

35
Q

What’s the correcting mechanism for hypertonic blood?

A

More water is reabsorbed by osmosis into the blood from the tubules of the nephrons
This means that urine is more concentrated as less water is last in the urine

36
Q

What’s the correcting mechanism for hypotonic blood?

A

Less water is re absorbed by osmosis into the blood from the tubules of the nephrons.
This means that urine is more dilute and more water is lost ion the urine

37
Q

Where does osomoregulation occur?

A

Within the nephrons in the kidneys

38
Q

What are nephrons?

A

Long tubules surrounded by capillaries and there are around 1million per kidney

39
Q

What happens at the nephron?

A

The blood is filtered here to remove waste and selectively reabsorb useful substances back into the blood

40
Q

How do the nephrons selectively reabsorb useful substances back into the blood

A

Ultrafiltration occurs due to high hydrostatic pressure, water and small molecules are forced out

41
Q

Explain process of ultrafiltration?

A

1) blood from the renal artery enters smaller arterioles in the cortex of the kidney
2) The arteriole that takes blood into each glomerulus is called the afferent arteiole, and the arteiole that takes the filtered blood away from the glomerulus is called efferent arteriole
3) Efferent arteriole is smaller in diameter than afferent so the blood in glomerulus is under high pressure
4) The high pressure forces liquid and small molecules in the blood out of the cap and into the Bowman’s capsule
5) Large molecules like proteins and blood cells can’t pass through so stay in the blood
6) Glomerular filtrate passes along the rest of the nephron and useful substances are reabsorbed along the way
7) Filtrate flows through the collecting duct and passes out of the kidney along ureter

42
Q

What does each arteriole split into?

A

Glomerulus

43
Q

What is the Glomerulus?

A

A bundle of capillaries lopped inside a hollow ball called Bowman’s capsule

44
Q

Where does ultrafiltration occur?

A

Bowman’s capsule

45
Q

What is the substance that moves into the Bowman’s capsule called?

A

Glomerular filtrate

46
Q

What are the 3 layers tat liquid and small molecules move through to get to the Bowman’s capsule?

A

Capillary endothelium
Membrane
Epithelium of bowman’s capsule

47
Q

Where does selective reabsorption occur?

A

Reabsorption of useful substances takes place as the glomerular filtrate flows along the PCT through the loop of hence and along the DCT, useful substances leave the tubules of nephrons and enter the capillary network that’s wrapped around them

48
Q

What is the PCT?

A

Proximal convoluted tubule

49
Q

What is the DCT?

A

Distal convoluted tubule

50
Q

What happens at selective reabsorption?

A

1) Epithelium of the wall of PCT microvilli provide a large surface area for the reabsorption of useful materials from the glomerular filtrate into the blood
2) Useful solutes like glucose, are reabsorbed along PCT by active transport and facilitated diffusion
3) Water enters the blood by osmosis as the water potential of the blood is lower than that of the filtrate
4) Water is reabsorbed from PCT, loop of henle, DCT and collecting duct
5) Filtrate that remains is urine which passes along the uteter to the bladder

51
Q

What is Urine made up of?

A

Water, dissolved salts p, urea and other substances such as hormones and excess vitamins

52
Q

What isn’t found in urine?

A

Contain proteins or blood cells as they are too big to be filtered out of the blood, glucose is actively reabsorbed back into the blood so isn’t in the urine either

53
Q

Name 2 ways water is lost from the body?

A

Urea and sweat

54
Q

What regulates water potential of the blood?

A

Kidney, by osmoregulation

55
Q

What happens if the water potential is too low?

A

More water is reabsorbed by osmosis into the blood from tubules of the nephrons, meaning the urine is more concentrated so less water is lost during excretion

56
Q

What happens when the water potential of the blood is too high?

A

Less water is reabsorbed by osmosis into the blood from the tubules of the nephrons meaning urine is more dilute so ware is lost during excretion

57
Q

Where is the loop of henle found?

A

Medulla of the kidneys

58
Q

What is the loop of henle made up of?

A

Ascending and descending limb

59
Q

On the loop of henle what do the limbs control?

A

movement of sodium ions so water can be reabsorbed into the blood

60
Q

How does the loop of henle system work?

A

1) Near top the AL, Na+ are actively pumped out into the medulla. AL is impermeable to water so water stays into the tubule, this creates a low water potential in the medulla as there’s a high concentration of ions
2) Lower WP in medulla than DL so water moves out of the descending limb into medulla by osmosis making glomerular filtrate more conc and water reabsorbed through cap network
3) Near bottom of AL Na+ ions diffuse out into medulla, lowering WP in medulla
4) Water moves out DCT by osmosis and reabsorbed into the blood
5) stages 1-3 massive,g increase ion conc in medulla, lowering WP cashing water to move out of collecting duct by osmosis and water from medulla reabsorbed into blood by cap network

61
Q

What controls the volume of water reabsorbed into the capillaries?

A

DCT and collecting duct

62
Q

What is the WP of the blood monitored by and where are they?

A

Osmoreceptors, in the hypothalamus

63
Q

When WP of the blood decreases how do the osmoreceptors act?

A

Water moves out of the osmoreceptors cells by osmosis causing a decrease in volume sending signals to other cells in the hypothalamus sending a signal to posterior pituitary gland which release ADH

64
Q

What does ADH stand for?

A

Antidiuretic hormone

65
Q

How does ADH work when we are dehydrated?

A

Water content of the blood drops, so WP drops
Detected by osmoreceptors in the hypothalamus
The posterior pituitary grand is stimulated to release more ADH into the blood
More ADH means DCT and CD are more permeable so more water is reabsorbed into the blood by osmosis
Small amount of high conc urine is produced so less water lost

66
Q

How does ADH work when we are hydrated?

A

Biology (13 decks)

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