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biology cat > ✅16 - Homeostasis > Flashcards

✅16 - Homeostasis Flashcards

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1
Q

What is homeostasis?

A

The maintenance of an internal environment within restricted limits in organisms

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2
Q

What does homeostasis involve?

A

Trying to maintain the chemical make-up, volume and other features of blood and tissue fluid within restricted limits

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3
Q

What does homeostasis ensure?

A

That the cells of the body are in an environment that meets their requirements and allows them to function normally despite external changes

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4
Q

What are some examples of things maintained by homeostasis?

A

pH
Temperature
Water potential

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5
Q

What is the optimum point?

A

The point at which the system operates best

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6
Q

What is the optimum point monitored by?

A

A receptor

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7
Q

What is a coordinator?

A

Coordinates the information from receptors and sends instructions to appropriate effectors

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8
Q

What is a feedback mechanism?

A

The way by which a receptor responds to a stimulus created by the change to the system brought about by the effector

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9
Q

What is negative feedback?

A

When the change produced by the control system leads to a change in the stimulus detected by the receptor and turns the system off.

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10
Q

What is positive feedback?

A

When a deviation from an optimum causes changes that result i an even greater deviation from the normal

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11
Q

What is an example of positive feedback?

A

When a stimulus leads o a small influx of sodium ions in a neurone and the permeability of the neurone to sodium ions is increased.

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12
Q

Control systems normally have many…

A

…receptors and effectors

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13
Q

What are endotherms?

A

Animals which generate heat from inside their bodies

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14
Q

What are exotherms?

A

Animals which obtain a proportion of their body heat from sources outside their bodies

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15
Q

Where are hormones produced?

A

In glands, which secrete the hormone directly into the blood (endocrine glands)

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16
Q

What do hormones act on?

A

Target cells, which have specific receptors on the cell surface membrane that are complementary

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17
Q

What is the secondary messenger model?

A

One mechanism of hormone action, used by the two hormones in blood glucose regulation, adrenaline and glucagon

18
Q

How does the secondary messenger model work for adrenaline and glucagon?

A

Adrenaline binds to a transmembrane protein receptor within the cell surface membrane of a liver cell
The binding causes the protein to change shape on the inside of the membrane
The change in protein shape leads to activation of an enzyme adrenal cyclase which converts ATP to cyclic AMP
The cAMP acts as a second messenger that binds to protein kinase enzyme, changing its shape and activating it.
The active protein kinase enzyme catalysed the conversion of glycogen into glucose which moves out of the liver cell by facilitated diffusion and into the blood, through channel proteins

19
Q

What is the role of the pancreas in regulating blood glucose?

A

It produces enzymes for digestion and hormones insulin and glucagon for regulation of blood glucose

20
Q

Which cells produce the hormones?

A

Islets of Langerhans

21
Q

What do the islets of langerhans include?

A

Alpha cells and Beta cells?

22
Q

What is the function of alpha cells?

A

Larger cells which produce glucagon

23
Q

What is the function of Beta cells?

A

Smaller cells which produce insulin`

24
Q

What is the role of he liver in regulating blood glucose?

A

The hormones produced by the pancreas take effect in the liver

25
Q

What is glycogenesis?

A

Conversion of glucose into glycogen when glucose concentration is higher than normal

26
Q

What is glycogenolysis?

A

The breakdown of glycogen to glucose, when blood glucose concentration is lower than normal

27
Q

What is gluconeogenesis?

A

The production of glucose from sources other than carbohydrate such as glycerol and amino acids

28
Q

What are the consequences if blood sugar falls too low?

A

Cells will be deprived of energy and die, as glucose is a substrate for respiration. Brain cells are especially sensitive

29
Q

What happens if blood glucose concenration is too high?

A

It lowers the water potential of the blood and creates osmotic problems that can cause dehydration

30
Q

What are the three sources of blood glucose?

A

Directly from the diet via hydrolysis of other carbohydrates
From the hydrolysis in the small intestine of glycogen (glycogenolysis)
From glconeogenesis

31
Q

What is insulin?

A

A globular protein made up of 51 amino acids

32
Q

How is insulin detected by cells?

A

Almost all body cells have glycoprotein receptors on their cell surface membrane which bind specifically with insulin

33
Q

What happens when insulin binds with a receptor?

A
  • change in tertiary structure of glucose transport proteins, causing them to change shape and open, allowing more glucose in
  • increase in number of carrier proteins responsible for glucose transport in the cell membrane
  • activation of enzymes that convert glucose into glycogen and fat
34
Q

How are blood glucose concentrations lowered?

A
  • by increasing the rate of absorption of glucose into cells, especially muscle cells
  • by increasing the respiratory rate of cells, which therefore use up more glucose from the blood
  • by increasing the rate of conversion of glucose into glycogen (glycogenesis) in liver and muscle cells
  • by increasing the rate of conversion of glucose to fat
35
Q

What actions does glucagon have?

A
  • attaching to specific protein receptor son the cell membrane of liver cells
  • activating enzymes that convert glycogen to glucose
  • activating enzymes involved in the conversion of amino acids and glycerol to glucose (gluconeogenesis)
36
Q

What is the role of adrenaline in regulating blood glucose levels?

A
  • increase blood glucose concentration
  • attaches to protein receptors on the cell membrane of target cells
  • activating enzymes that causes the breakdown of glycogen to glucose in the liver
37
Q

The hormones insulin and glucagon act in…

A

…opposite directions

38
Q

What are the two types of diabetes?

A

Type 1 (insulin dependent) and Type 2 (insulin independent)

39
Q

What is type 1 diabetes?

A

When the body is unable to produce insulin

40
Q

What is type 2 diabetes?

A

When glycoproteins receptors on body cells are lost or lose their responsiveness to insulin, later onset around 40 years of age

41
Q

What are the controls for type 1 diabetes?

A

Injections of insulin and use of biosensors to monitor blood glucose concentrations

42
Q

What are the controls for type 2 diabetes?

A

Regulating the take of carbohydrate in the diet and matching this to the amount of exercise taken

biology cat (19 decks)

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