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Biology IGCSE > Chapter #13 - Homeostasis > Flashcards

Chapter #13 - Homeostasis Flashcards

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1
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A
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2
Q

Homeostasis

A

Maintaining a constant internal enviornment.

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3
Q

What internal enviornments are kept constant in our bodies?

A
  • Temperature
  • Amount of water
  • Blood glucose concentration.
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4
Q

Why is temp. kept constant in the body?

A

Around 37 degrees celcius because it is the optimum for enzymes.

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5
Q

Why is water kept constant in the body?

A

So that cells are not damaged by losing/gaining water through osmosis.

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6
Q

Why is blood glucose concentration kept constant in the body?

A
  • Cells need a steady amount of glucose to respire, or they will not be able to release the energy needed.
  • Too much glucose in the blood can cause water to leave the cells via osmosis. Then they cannot carryout metabolic reactions.
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7
Q

What is blood glucose conc. controlled by?

A

Controlled by hromones secreted by the pancreas.

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8
Q

Set point

A

The normal value or range of values for a particular parameter - for example, the normal range of blood glucose conc. or the normal body tmp.

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9
Q

What is the normal blood glucose concentration?

A

Normal blood glucose conc. is 0.8 - 1.1 mg/cm^3 of blood (this is a range and is not constant).

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10
Q

Negative feedback

A

A mechanism that detects a move away from away from the set point and bring about the actions that take the values back towards the set point.

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11
Q

How does the pancreas contribute to homeostatis.

A

It has islets which produce two hormones which hlep control glucose concentration in blood. These islets are scattered around the pancres.

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12
Q

How does the body respond to an increase in blood glucose conc?

A
  1. Pancreas secretes insulin into blood, which reaches the liver.
  2. Causes liver to abdsorb glucose from blood and store it as glycogen. (an insoluble polysaccharide.)
    => Small amount oif glucose is used for resoeration (not stored).
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13
Q

Polysaccharide

A

Something with more than molecules (e.g. proteins).

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14
Q

How does the body respond to insulin?

A

Causes liver to absorb glucose from th blood and store it as the blood and store it as glycogen.

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15
Q

How does the body respond to an decrease in blood glucose conc?

A
  1. If blood glucose conc. falls too low, the pancreas secreted glucagon.
  2. This cause liver cells to break down glyccogen to glucose an release it into the blood.
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16
Q

What is type one diabetes?

A

A condition in which insuffivient insulin is secreted by the pancreas, so that blood glucose conc. is nor controlled.

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17
Q

Is negative feedback instantaneous?

A

No, it takes a short time for the body to detect change in internal enviornment, and then more time to implament corrective measure and for the corrctive measure to start working. Only then will the internal enviornment return to the set point.

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18
Q

Is the internal enviornmet always constant?

A

No, because negative feedback is not instantaneous so the lag, causes the internal enviornment to vary around the set point.

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19
Q

What is type 1 diabetes throught to be a result of?

A

The body’s imune system attcaking itself.

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20
Q

When does type 1 diabetes usually develop?

A

In childhood

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21
Q

When does type 1 diabetes affect people (what time of the day)?

A
  • After eating meal (carb) blood glucose increases.
  • Between meals.
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22
Q

What happens when people with type one diabetes have a meal (especially a high carb one)?

A
  • Blood glucose increases
  • But there is no sighn of secretion of insulin.
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23
Q

Effects of high blood glucose concentration with type 1 diabetes?

A
  • Blurred vision
  • Thirsty
  • High heart rate
24
Q

What happens when people with type one diabetes are between meals (especially a high carb one)?

A
  • Since no insulin is secreted, there is no glycogen to be released/make into glucose.
  • This means no glucose can be released from stores.
25
Q

Effects of low blood glucose concentration with type 1 diabetes?

A
  • confused
  • becomes unconcious + die
26
Q

How do you measure blood glucose levels for type 1 diabetes?

A
  • A sensor with blood
  • Dipstick for urine
27
Q

How do you measure blood glucose conc. using a dipstic?

A

Urine, should not contain any glucose, but if blood sugar is high, kidneys cannot reabsorb it all from the filtrate in the nephron, and some is excretd.

28
Q

How can you treat type 1 diabetes?

A
  • Inject insulin (two types)
    => Rapid acting insulin (around melas and you adjust the dose depending on the amount of carbs they will eat).
    => Long-acting (once a day to maintain insulin levels).
  • Eat little and often
  • Eat more when excersising
29
Q

What are the two types of insulin?

A
  • Rapid acting insulin (around melas and you adjust the dose depending on the amount of carbs they will eat).
  • Long-acting (once a day to maintain insulin levels).
30
Q

What is the difference between animals that can keep there body temp. alemost constant and animals that change body temp. with enviornment?

A
  • Animals that mantaine temp. can continue metablosinging despite wither or time of day (day/night).
  • Animals that mantaine temp. can remain active.
  • Animals that don’t mantaine temp. may be too cold to move.
31
Q

What are the features of human skin?

A
  • Covered with layer of dead cells
  • Sweat glands
  • Small blood vesseld
  • Hair erector muscles
  • Diffenrets reseptors
  • Layer of fat under skin
32
Q

What is the function of the layer of dead cells over skin?

A
  • Prevents water evaportating out of living cells.
  • Keeps pathogens out
33
Q

How do sweat glands work?

(on human skin)

A

Extract water and ions from the blood and produce sweat. It travels up the sweat duct and is released through a pore.

34
Q

How do small blood vessels in human skin work?

A

Arteriols, capillaries and venules (small blood vessels) carry blood to cells.

35
Q

How do hair erector muscles on human skin?

A

They pull the hair upright

36
Q
A
37
Q

Hypothalamus

A

Part of the brain involved in controlling body temperature.

38
Q

What are the 2 types of temperature receptors in the body?

A
  1. Hypothalamus
  2. Near surface of skin
39
Q

How does hypothalamus work?

A

It contains temperature receptors to sense the temperature of blood running through it.

40
Q

What occures if body temp is +/- 37 degrees celcius?

A

The brain sends electrical impulses to parts of the body to help keep temperature and blood at its set point.

41
Q

What exactly does hypothalamus measure?

A

The temperature of blood

42
Q

What exactly do the receptord near the surface of the skin measure?

A

They measure the temp. of air/water around us and gives an indication of possible body body temperature change. So… the body can react in advance.

43
Q

What occurs when body temperature falls

(in humans)

A
  • Hair stands up
  • Metabolism increases
  • Shiver
  • Vascoconstriction
  • Sweat glands reduce secretion
44
Q

How does hair stand up when body temp. decreases?

A
  • Hair erector muscles in skin contract
  • This pulls hairs straight
    In humans this does not do anything important
45
Q

What is the function fo heair standing up to control body temp?

A
  • When body temp. falls, hair erector muscles in skin contract, pulling hairs straight.
  • In humans this does not do anything important.
  • But in hairy mammals it traps a thick layer of warm air near the skin (acts as an insulator)
46
Q

Why does metabolism increase when controlling body temp?

A
  • The speed of chemical reactions in tissue increase when body temp. decreases.
  • This is because for example, liver cells respire and release more heat.
47
Q

Why do your muscles contract when body temp. decreases?

A
  • They get energy for this from respiration and some of it is released as heat.
  • Heat generated in muscles warms the blood as it flows through them.
  • Blood flows through rest of the body and warms it.
  • This process is called shivering
48
Q

What happens when you shiver?

A
  • Muscles contract and relax quickly.
  • Called shivering
  • Get energy for this from respiration (some is released as heatt)
49
Q

Vasoconstriction

A

Narrowing of arteriols, caused by contractions of muscles in their walls.

50
Q

Why does vasoconstriction occure to contol body temp?

A
  • Vasoconstriction occurs when body temp. decreases
  • Arteriols near durface of skin become narrower.
  • This causes blood to mainly flow through larger vessels beneathe insulating tissue.
  • Stops blood from losing heat through air.
51
Q

What occurs when body temp. increases?

A
  • Hairs lie flat
  • Vasodilation
  • Sweat production increases
52
Q

Vasodilation

A

Widening of arteriols, caused by reaxation of the muscles in their walls

53
Q

What happesn when hairs lie flat when body temp. increases?

A
  • Erector muscles relax
  • This allows heat to leave skin into air.
54
Q

What happesn when sweat production increases?

(To control body temp. increase)

A
  • Sweat glands secrete more.
  • Sweat evaporates form surafece, taking heat with it.
55
Q

Why does vasodilation occure to conrol body temp.

A
  • Happens when nody temp. rises
  • Arteriols near surface of skin widen.
  • Blood flows near surface, so more heat is lost.

Biology IGCSE (15 decks)

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