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10 Life Science > Homeostatic control > Flashcards

Homeostatic control Flashcards

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1
Q

How do we maintain homeostasis?

A

The kidneys continuously regulate the chemical composition of the blood

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2
Q

How do you molecules move passively?

A

Move from where there is high concentration to where they are less of them down a concentration gradient

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3
Q

Define water potential

A

Describe how the movement of water molecules in a solution exert pressure on a membrane

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4
Q

Explain osmosis

A

Water moves from a high water potential to lower water potential through a differentially permeable membrane

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5
Q

When is a hypertonic solution formed?

A

Lowering the water potential

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6
Q

How is the water potential lowered?

A

High concentration of sorts decreases the number of free water molecules

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7
Q

When is a hypotonic solution form?

A

Increasing the water potential of a solution

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8
Q

How is water potential increased?

A

Present of a lower concentration of solute in a solution of water – does not decrease the number free water molecules

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9
Q

Define an isotonic solution

A

Solutions on both sides of a membrane are the same and have the same number free water molecules

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10
Q

What is the water potential of pure water?

A

0

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11
Q

What happens when molecules move actively?

A

They combine with a carrier molecule and may move against the concentration gradient - need energy

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12
Q

Regulation of water content

A
  1. Osmoregulation
  2. Hormone ADH
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13
Q

Define osmoregulation

A

Maintains the correct balance between the water and solid content of the body fluids

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14
Q

What is osmoregulation controlled by?

A

Kidney and skin

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15
Q

How do the cells function properly?

A
  1. Amount of water
  2. Concentration of solutes
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16
Q

What does too little water cause?

A

Dehydration of the cells

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17
Q

What does too much water cause?

A

Cells to burst

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18
Q

What is the concentration of solutes in the sound is determined?

A

The osmolarity (osmotic pressure) of body fluids

19
Q

Define osmolarity

A

The number of solid particles dissolved in 1 L of water

20
Q

What happens when there is a greater concentration of solutes?

A

Greater the osmolarity and greater the tenancy forwarder to move in the strong solution – hypertonic

21
Q

What percentage of the body is water is returned from the kidneys into the bloodstream?

A

99%

22
Q

Where is most of the body is water reabsorbed from?

A

Proximal tubule
Descending limb of loop of Henle

23
Q

What does the kidney do when the fluid intake is low?

A

Conserves water - more concentrated urine

24
Q

ADH

A

Antidiuretic hormone

25
Q

What is ADH secreted by?

A

Hypothalamus - brain

26
Q

Where is ADH stored?

A

Posterior pituitary gland - base brain

27
Q

Define diuretic

A

Causing increased output of urine

28
Q

How is ADH secreted?

A

Osmoreceptors in the hypothalamus monitor the osmolarity of the blood

29
Q

When are the osmoreceptors stimulated?

A

Osmolarity increases because of dehydration

30
Q

What does the stimulation of the osmoreceptors stimulate?

A
  1. Thirst centre - hypothalamus
  2. Pituitary gland - release ADH
31
Q

What happens to ADH when it is released?

A

Dissolves in blood plasma and is carried over the body

32
Q

What happens when the 88 reaches the kidney?

A

Cause his paws of the collecting duct to enlarge – more permeable to water

33
Q

What does the pores of the CD enlarging result in?

A
  1. More water moving (osmosis)
    Filtrate in CD into blood in capillaries
    Blood volume + composition - normal
  2. Less, more concentrated urine release
34
Q

Explain as a negative feedback system

A

Osmolarity of blood and body fluid reduces. Receptors are no longer stimulated and less ADH is secreted. Kidneys excrete more urine

35
Q

What is aldosterone?

A

Steroid hormone produced by adrenal glands - top of kidney

36
Q

What does aldosterone control?

A

Concentration of sodium ions

37
Q

How much sodium and chloride is in the renal filtrate that is reabsorbed?

A

65% of sodium - proximal tubules
25% from loop of Henle
Chloride ions passively follow

38
Q

What ions occur most in the body?

A

Sodium ions

39
Q

What may develop if too many sodium ions are absorbed and retained?

A

High blood pressure may develop

40
Q

What is the concentration of sodium ions linked to?

A

Balance of water and regulation of blood pressure

41
Q

When is the secretion of aldosterone triggered?

A
  1. Blood levels of sodium Arlo – drop in osmolarity
  2. Blood volume is low – low blood pressure
42
Q

How does aldosterone ensure that homeostasis is maintained?

A

Sodium ion balance balance is restored and blood volume is increased

43
Q

What does aldosterone cause?

A
  1. Reabsorption of sodium ions from the filtrate returning into bloodstream
  2. Water to follow sodium ions, increase blood volume + pressure

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