Homeostatic control

Question 1

How do we maintain homeostasis?

Answer 1

The kidneys continuously regulate the chemical composition of the blood

Question 2

How do you molecules move passively?

Answer 2

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

Question 3

Define water potential

Answer 3

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

Question 4

Explain osmosis

Answer 4

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

Question 5

When is a hypertonic solution formed?

Answer 5

Lowering the water potential

Question 6

How is the water potential lowered?

Answer 6

High concentration of sorts decreases the number of free water molecules

Question 7

When is a hypotonic solution form?

Answer 7

Increasing the water potential of a solution

Question 8

How is water potential increased?

Answer 8

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

Question 9

Define an isotonic solution

Answer 9

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

Question 10

What is the water potential of pure water?

Answer 10

0

Question 11

What happens when molecules move actively?

Answer 11

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

Question 12

Regulation of water content

Answer 12

1. Osmoregulation
2. Hormone ADH

Question 13

Define osmoregulation

Answer 13

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

Question 14

What is osmoregulation controlled by?

Answer 14

Kidney and skin

Question 15

How do the cells function properly?

Answer 15

1. Amount of water
2. Concentration of solutes

Question 16

What does too little water cause?

Answer 16

Dehydration of the cells

Question 17

What does too much water cause?

Answer 17

Cells to burst

Question 18

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

Answer 18

The osmolarity (osmotic pressure) of body fluids

Question 19

Define osmolarity

Answer 19

The number of solid particles dissolved in 1 L of water

Question 20

What happens when there is a greater concentration of solutes?

Answer 20

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

Question 21

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

Answer 21

99%

Question 22

Where is most of the body is water reabsorbed from?

Answer 22

Proximal tubule
Descending limb of loop of Henle

Question 23

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

Answer 23

Conserves water - more concentrated urine

Question 24

ADH

Answer 24

Antidiuretic hormone

Question 25

What is ADH secreted by?

Answer 25

Hypothalamus - brain

Question 26

Where is ADH stored?

Answer 26

Posterior pituitary gland - base brain

Question 27

Define diuretic

Answer 27

Causing increased output of urine

Question 28

How is ADH secreted?

Answer 28

Osmoreceptors in the hypothalamus monitor the osmolarity of the blood

Question 29

When are the osmoreceptors stimulated?

Answer 29

Osmolarity increases because of dehydration

Question 30

What does the stimulation of the osmoreceptors stimulate?

Answer 30

1. Thirst centre - hypothalamus 2. Pituitary gland - release ADH

Question 31

What happens to ADH when it is released?

Answer 31

Dissolves in blood plasma and is carried over the body

Question 32

What happens when the 88 reaches the kidney?

Answer 32

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

Question 33

What does the pores of the CD enlarging result in?

Answer 33

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

Question 34

Explain as a negative feedback system

Answer 34

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

Question 35

What is aldosterone?

Answer 35

Steroid hormone produced by adrenal glands - top of kidney

Question 36

What does aldosterone control?

Answer 36

Concentration of sodium ions

Question 37

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

Answer 37

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

Question 38

What ions occur most in the body?

Answer 38

Sodium ions

Question 39

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

Answer 39

High blood pressure may develop

Question 40

What is the concentration of sodium ions linked to?

Answer 40

Balance of water and regulation of blood pressure

Question 41

When is the secretion of aldosterone triggered?

Answer 41

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

Question 42

How does aldosterone ensure that homeostasis is maintained?

Answer 42

Sodium ion balance balance is restored and blood volume is increased

Question 43

What does aldosterone cause?

Answer 43

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