control of fluid volume Flashcards
what are the 3 main compartments of water distribution?
- intracellular space
- interstitium
- vascular space
how are the 3 comparments of water distribution achieved?
- intracellular volume - plasma osmolarity through changes in water balance
- intersitial volume - osmotic pressure generated by proteins
- blood plasma volume - closely related to regulation of Na+
how are the 3 major compartments of body water distribution necessary?
- intracellular volume - necessary for optimal cell function
- interstitial space - necessary for nutrient supply/ waste removal
- blood plasma volume - necessary for optimal tissue perfusion
what are the two essential components of the extracellular fluid?
water and osmolytes
what is the dominant ECf osmolyte?
- Na+
what type of tissues are osmolytes particularly important in?
- cells and tissues that are exposed to fluctuating osmotic environment (kidney and brain)
how do we control the ECF volume?
- modulation of the amount of Na+ in the ECF
what is wrong with having too much and too little ECF?
- too much - increase in BP
- too little - decrease in BP
what does increased cardiac output caused by an increase in ECF volume cause in vessels? (2)
- generalised constriction of arterioles
- increase in peripheral vascular resistance (and BP)
the 3 ways kidneys deal with substances:
- filtration
- absorption
- secretion
what is RAAS? (2)
- renin-angiotensin-aldosterone system
- a complex hormonal system playing a crucial role in regulating blood pressure
what is the renal corpuscle? (3)
- a component of the kidneys nephron
- plays a role in initial filtration of blood to form filtrate in the kidneys
- vital for regulation of electrolytes, fluid balance and waste elimination
what is renin released by?
- the kidneys
what is renin released in response to? (4)
- increased in SNS actvity
- decrease in blood pressure
- decrease in ECF
- decrease in extracellular Na+
what does Renin doo?
- catalyses the conversion of angiotensinogen to angiotensin 1 in the blood
what type of cells is renin synthesised in?
- juxtaglomerular cells
how can the macula densa indirectly effect the release of renin?
reduction in NaCl delivery to the macula densa stimulates renin production
what is ADH released in response to?
- decrease in blood volume and pressure
- increase in osmolarity of body fluids
where is ADH released from?
- pituitary gland
what are the main hormonal controls of blood volume?
- RAAS
- vasopressin (ADH)
- atrial natriuretic peptide
what specific cells stimulate renin production and how?
- macula densa cells
- they contain renal baroreceptors
what is the rate-limiting step in angiotensin 2 formation?
renin
renal baroreceptor sensitivity: (2) & location (1)
- secretion is pressure dependent
- very sensitive to minute changes
- located in afferent arterioles
macula densa chloride sensitivity:
- responds to low Cl-
- not as sensitive as renal baroreceptors
