Homeostatic control Flashcards
How do we maintain homeostasis?
The kidneys continuously regulate the chemical composition of the blood
How do you molecules move passively?
Move from where there is high concentration to where they are less of them down a concentration gradient
Define water potential
Describe how the movement of water molecules in a solution exert pressure on a membrane
Explain osmosis
Water moves from a high water potential to lower water potential through a differentially permeable membrane
When is a hypertonic solution formed?
Lowering the water potential
How is the water potential lowered?
High concentration of sorts decreases the number of free water molecules
When is a hypotonic solution form?
Increasing the water potential of a solution
How is water potential increased?
Present of a lower concentration of solute in a solution of water – does not decrease the number free water molecules
Define an isotonic solution
Solutions on both sides of a membrane are the same and have the same number free water molecules
What is the water potential of pure water?
0
What happens when molecules move actively?
They combine with a carrier molecule and may move against the concentration gradient - need energy
Regulation of water content
- Osmoregulation
- Hormone ADH
Define osmoregulation
Maintains the correct balance between the water and solid content of the body fluids
What is osmoregulation controlled by?
Kidney and skin
How do the cells function properly?
- Amount of water
- Concentration of solutes
What does too little water cause?
Dehydration of the cells
What does too much water cause?
Cells to burst
What is the concentration of solutes in the sound is determined?
The osmolarity (osmotic pressure) of body fluids
Define osmolarity
The number of solid particles dissolved in 1 L of water
What happens when there is a greater concentration of solutes?
Greater the osmolarity and greater the tenancy forwarder to move in the strong solution – hypertonic
What percentage of the body is water is returned from the kidneys into the bloodstream?
99%
Where is most of the body is water reabsorbed from?
Proximal tubule
Descending limb of loop of Henle
What does the kidney do when the fluid intake is low?
Conserves water - more concentrated urine
ADH
Antidiuretic hormone
What is ADH secreted by?
Hypothalamus - brain
Where is ADH stored?
Posterior pituitary gland - base brain
Define diuretic
Causing increased output of urine
How is ADH secreted?
Osmoreceptors in the hypothalamus monitor the osmolarity of the blood
When are the osmoreceptors stimulated?
Osmolarity increases because of dehydration
What does the stimulation of the osmoreceptors stimulate?
- Thirst centre - hypothalamus
- Pituitary gland - release ADH
What happens to ADH when it is released?
Dissolves in blood plasma and is carried over the body
What happens when the 88 reaches the kidney?
Cause his paws of the collecting duct to enlarge – more permeable to water
What does the pores of the CD enlarging result in?
- More water moving (osmosis)
Filtrate in CD into blood in capillaries
Blood volume + composition - normal - Less, more concentrated urine release
Explain as a negative feedback system
Osmolarity of blood and body fluid reduces. Receptors are no longer stimulated and less ADH is secreted. Kidneys excrete more urine
What is aldosterone?
Steroid hormone produced by adrenal glands - top of kidney
What does aldosterone control?
Concentration of sodium ions
How much sodium and chloride is in the renal filtrate that is reabsorbed?
65% of sodium - proximal tubules
25% from loop of Henle
Chloride ions passively follow
What ions occur most in the body?
Sodium ions
What may develop if too many sodium ions are absorbed and retained?
High blood pressure may develop
What is the concentration of sodium ions linked to?
Balance of water and regulation of blood pressure
When is the secretion of aldosterone triggered?
- Blood levels of sodium Arlo – drop in osmolarity
- Blood volume is low – low blood pressure
How does aldosterone ensure that homeostasis is maintained?
Sodium ion balance balance is restored and blood volume is increased
What does aldosterone cause?
- Reabsorption of sodium ions from the filtrate returning into bloodstream
- Water to follow sodium ions, increase blood volume + pressure
