Refresher of M1 Physiology Flashcards
What are the 7 functions of the kidney?
- excretion of metabolic waste products and foreign chemicals
- regulation of water and elctrolyte balances
- regulation of body fluid osmolarity and electrolyte concentrations
- regulation of arterial pressure
- regulation of acid-base balance
- secretion, metabolism, and excretion of hormones
- gluconeogenesis
What is the central physiologic role of the kidneys?
the central physiologic role of the kidneys is to control the volume
How are fluids distributed in the body? What is the barrier? WHat is the governing force? Use the example of a 70kg man with 42 L TBW
- Intracellular fluid (ICF)= 2/3 total body water (40% or weight)
- Extracellular fluid (ECF)= 1/3 total body water (20% of body weight)
- example:
- ICF= (42L * 2/3)= 28L
- ECF= (42L * 1/3)= 14L
- barrier between ICF and ECF is cell membrane
- distribution is goverened by osmotic forces
WHat is the major cation and anion fo the ICF and ECF?
Extracellular: Na and Cl
Intracellular: K and PO4 and organic anions
A normal individual received a bolus injection of 500ml of 500nM mannitol solution. WHat would happen to their ECF and ICF
the volume fo the ECF would increase
the osmolarity of the ECF would increase
the volume of the ICF would decrease
the osmolarity of the ICF would increase
SO no matter what happens osmolarity in the ICF and ECF must be the same. So you you add hypertonic solution, then the osmolarity of the ECF is higher. therefore the osmolarity of the ICF must increase in order to be the same. this happens by water from the ICF going into the ECF so that the ICF has a higher osmolarity. (note body osmolarity is typically 280-300mOsm)
What is osmolarity?
What is Osmolality?
Osmolarity: the concentration of osmotically active particle in total solution and is expressed in terms of mOsm/L of water
In the body, the osmolarity of the ECF and ICF averages 280-300 mOsm/L. It is nearly identical in all major compartments of the body
Osmolality: is expressed in terms of mOsm/kg of solvent (water). Inrelatively diulte solutions, such as those found in the body osmolarity is about equal to osmolality
What happens to ICF and ECF if you add an:
- isotonic solution:
- add hypotonic NaCl
- Hypertonic NaCl
isotonic: ECF volume increases, no change to ICF no change to osmolarity
hypotonic: ICF and ECF osmolarity decreases. ICF and ECF volume increases
hypertonic: osmolarity of both increases,ECF volume increases, ICF volume decreases
A patient has type II diabetes for 20 yrs. His GFR is 30 ml/min. 5 years ago it was 60ml/min. What happened?
total area of glomerular capillary membranes has decreased
pts with diabetes get sclerotic/firbotic glomeruli. More ECM in glomerulus, loses availability to regulate ECM. therefore you lose glomerular capillaries. this means you lose surface area available for glomerular filtration.
what are the 4 processes of the kidney that determines the composition of th urine?
filtration
reabsoprtion
secretion
excretion
What is the glomerular filtrate?
the glomerular filtrate is an ultafiltrate formed by the net effect of starling forces to move (filter) fluid out of the glomerular capillaries and into Bowman’s space
the filtered fluid contains the same concentration of most salts and organic substances found in the plasma
most large proteins, subtances bound to protein, and cellular elements are exlcuded from the glomerular filtrate
the glomerular filtration rate is a bulk filtration process. the kidneys of a 70kg man will filter the equivalent of his entire plasma volume (3L) every half hour
What is the driving pressure of filtration? what forces oppose filtration? what is the eqution for net filtration pressure?
Driving pressure of filtration is Glomeular hydrostatic pressure (60mg that is higher than most capillary hydrostatic pressures)
opposing: Bowmans capsule pressure and glomerular oncotic pressure
netfiltration pressure (10mgHg)= Glomerular hydrstatic pressure (60) - Bowmans capsule pressure (18)-Glomerular oncotic pressure
WHat is RPF? GFR? EffPF?
RPF= 700ml/min (renal plasma flow)
GFR=125ml/min
EffPF= 575 ml/min (efferent plasma flow)
What is Jv?
What is the thematic equation for GFR?
What is Kf?
Jv=GFR=(ultrafiltration coefficient) (sum of all forces opposing and favoring filtration)
Kf=ultrafiltrationcoefficient which is the product of the hydraulic permeability (aka permeability)
increasing renal perfusion pressure form 100 to 130 will most likely
increase urine flow rate- this is called pressure diuresis. When blood pressure increases the urine flow and Na excretion increases. But GFR will stay the same
what happens for autoregulation of renal blood flow and glomerular filtration rate?
around pressure of 100mHg the GFR will not change as arterial pressure increases.
WHat are the 2 proposed mechanisms of GFR and RBF autoregulation?
Myogenic Mechanism: intrinsic property of blood vessels. stretch of vascular smooth muscle, as experinced during an increase in arterial pressure, elicitis contraction which elevates vascular resistance and maintain blood flow (and GFR) constant (Q=P/R. as pressure increases contraction causes resistance to decresase, therefore the flow stays the same)
Tubuloglomerular feedback: autoregulatory mechanism unique to kidney. In response to an elevation of perfusion pressure, increased fluid is filtered leading to increased delivery of NaCl to the Macula Densa. This increased delivery elicits an increase in vascula rresitance
What is the macula densa feedback in response to decreased arteriole pressure?
decreased glomerular hydrostatic pressure
decreased GFR
decreased Macula Densa NaCl
which leads to decreased afferent arteriolar resistance and increased RAS (which increases efferent arteriolar resitance). both of these things will raise the glomerular hydrostatic pressure
ow do the followng hormnes impact GFR?
Norepiephrine
Epinephrine
Endothelin
Angiotensin II
Endothelial derived nitric oxide
prostaglandins
Norepiephrine- decrease GFR
Epinephrine- decrease GFR
Endothelin-decrease GFR
Angiotensin II-no change or decrease
Endothelial derived nitric oxide-increase GFR
prostaglandins-increase GFR
a patient had uncontrolled hypertension for 20 years. his urinary albumin excretion is 100mg/day. His urinary albumin was 30mg/day 5 years ago. What likely happened?
GLomerular permeability to albumin has increased
What are the 3 layers fo the filtration barrier?
- capillary wall (700 A fenestrations)
- fenestrated, freely permeable to mslal molecules
- negatively charged glycoproteins in surface
- basment membrane
- porous matrix of extracellular proteins including type IV
- collagen, laminin, fibronectin and other neg charged proteins
- podocytes (with processes and slit pores 40x140 A)
- long finger-like processes with negatively charged proteins (small fenestrations)
describe the selectivity of the filtration barrier
size selective: more permeable to small molecules
charge-selective: more permeable to positively charged molecules (proteins generally are negatively charged)
how filterable are the following substances?
water
sodium
glucose
inulin
myoglobin
albumin
- freely
- water-1
- sodium-1
- glucose- 1
- inulin- 1
- medium
- myoglobin-0.75
- not
- albumin- 0.05
WHat is reabsorbed in the proximal tubule? what is secreted? What duretic works here and how?
- reabsorb about 65% of the filtered sodium, chloride, bicarbonate, and potassium and essentially all the filtered glucose and essential amino acids
- secrete organic acids, bases, and hydorgen ions
- diuretic: carbonic anhydrase inhibitors (acetazolamide)
- inhibit H secretion and HCO3 reabsorption
*
- inhibit H secretion and HCO3 reabsorption
how does the osmolarity change across the proxima tubule
intotal it is isoosmotic meanign the sum osmolarity doesnt change. however, the osmolarity of indidivual ions changes. For example creatine and urea increase, and HCO3 and glucose adn amino acids decrease
WHat happens at the thin descending loop of henle?
reabsorption of water secondary to cortical medually osmotic gradint
what happens at the thin ascending loop of henle?
- impermeable to water-dilates tubular fluid
- passive reabsorption of soidum, dilution of tubular fluid
- pereable to urea, urea is secreted
*
Thick ascending loop of henle
reabsorbs 25% of filtered Na/K/2Cl transport
lumen positive potential drives paracelllular reabsorption of soidum, potassium, magnesium and calcium
what happens at the early distal tubule?
reabsorbs Na, Clm Ca2+ and Mg2+
not permeable to water
thiazide sensitive segment
what happens at the principal cells of the late distal tubule and crtical colleting duct?
reabsorbs Na, secretes K
regulated by aldosterone
water permeability regulated by ADH
reabsorption of sodium and secretion of potassium blocked by K-saring diuretic
what channel exists on the principal cells of the late distal tubule and cortical colelcting duct?
the sodium channel on apical membrane of the principal cells is called the ENaC (epithelial sodium channel)
what happens at th medullary collecting duct?
reabsorbs Na (similar to principal cells)
ADH-stimulated water reabsorption
urea reabsorption in medullary CD
where does aldosterone work what does it cause?
acts in the principal cells of late distal tubule and collecting duct
increases Na reabsorption, increases K secretion
where does angiotensin II work and what does it cause?
acts primarily in the proximal tubule
increases Na and water reabsorption, increases H secretion
Where does Antidiuretic hormone (vasopressin, ADH) and what does it cause?
acts in principal cells of late distal tubule and collecting duct, inner medullary collecting duct
increases water reabsorption
where does atrial natriuretic peptide (ANP, ANF) what does it cause?
acts in distal tubule and colelcting decreases Na reabsorption
where does Parathyroid hormone work and what does it cause?
in proximal tubule decreases PO4 reabsorption
in thick ascending loop of Henle and distal tubule increases Ca reabsorption
