Physiology Flashcards
1
Q
- Define osmolarity
- What is it measured in?
- How is it calculated?
- What is the difference between osmolality and osmolarity?
A
- Concentration of osmotically active particles present in a solution
- mosmol/L (milliosmoles per litre)
- Number of osmotically active particles multiplied by the molar concentration
- Osmolarity= osmol/L Osmolality= osmol/kg
2
Q
- Define tonicity
2. What is the difference between a Hypertonic/isotonic/hypotonic
A
- The effect that a solution has on cell volume
2. Hypertonic- volume decreases, isotonic stays the same, hypotonic- volume increases
3
Q
- How does Total Body Water percentages differ between males and females?
- What is the ratio between ICF and ECF in humans?
- What does the ECF consist of?
- The concentration of Na+ and _____ is highest in the _______ whereas the concentration of K+ is highest in the _______.
A
- 60% mass males, 50% mass females
- 67% intracellular fluid 33% extracellular fluid
- 20% plasma, 80% interstitial fluid
- Cl-, ECF, ICF
4
Q
- What are the three main determinants of plasma osmolarity?
- How might the plasma osmolarity be estimated?
A
- Na+, Cl-, HCO3-
2. By doubling the plasma sodium ion concentration
5
Q
- Define fluid shift
- If NaCl concentration increases osmolarity Increases in the _______ and decreases in the _____ because Na+ is excluded from the _____.
A
- Movement of water between the ICF and ECF in response to an osmotic gradient
- ECF, ICF, ICF
6
Q
- What is the primary function of the kidneys?
- What is the point where the afferent and efferent arterioles cross over the distal convoluted tubule called?
- Name the two types of nephrons
- How do they differ?
- Name the cells that produce and secrete renin
A
- Regulation of the volume, composition and osmolarity of body fluids
- Juxtaglomerular apparatus
- Juxtamedullary (20%) and Cortical (80%)
- Juxtamedullary much longer loop of Henle
- Granular cells
7
Q
- What is the equation for the rate of filtration of a substance?
- What is the equation for rate of excretion?
- What is the equation for the rate of reabsorption?
- What about rate of secretion?
A
- Rate of filtration of X= [x]plasma x GFR
- Rate of excretion of X= [x]urine x Vu (urine flow rate)
- Rate of reabsorption= rate of filtration - rate of excretion
- Rate of secretion= rate of excretion - rate of reabsorption
8
Q
- How much of the plasma that enters the glomerulus is filtered?
- What property of the basal lamina makes it an effective barrier to plasma proteins?
- Name the two pressure forces that oppose Glomerular Capillary Blood Pressure
A
- 20%
- Negatively charged
- Bowmans capsule hydrostatic blood pressure, Capillary oncotic pressure (due to plasma proteins)
9
Q
- How is GFR calculated?
- On average how many times is our blood plasma filtered every day?
- What is the main variable that effects the GFR?
- What effect does vasoconstriction/vasodilatation of the afferent arteriole have on GFR?
A
- GFR= Net filtration rate x Filtration Coefficient (how permeable the membrane is)
- 65 times
- Glomerular capillary blood pressure
- Vasoconstriction- decreased GFR, Vasodilatation- increased GFR
10
Q
- Name the two forms of autoregulation in the kidneys that result in the constriction of the afferent arterioles
- Explain each of these
- Name the tubular cells that detect NaCl levels in the tubular fluid
- Which starling forces increase due to a) Kidney stones and b) diarrhoea?
A
- Myogenic, Tubuloglomerular feedback
- Myogenic- when the afferent arteriole stretches the smooth muscle constricts to narrow the lumen.
Tubuloglomerular feedback- when GFR becomes to high more NaCl flows through the tubule leading to afferent arteriole constriction - Macula densa
- a) Bowmans capsule hydrostatic pressure
b) Glomerular capillary oncotic pressure BOTH CAUSE DECREASE IN GFR
11
Q
- Define plasma clearance
- How is clearance calculated?
- What is the unit for this?
- Name an exogenous substance which can be used to measure GFR that is not used clinically
- What substance is usually used clinically?
- What is the average GFR in a healthy individual?
A
- Volume of the plasma completely cleared of a substance per minute
- Clearance of substance x = Rate of excretion of X divided by plasma concentration of x
- ml/min
- Inulin with which GFR is equal to Rate of inulin excretion
- Creatinine
- 125ml/min
12
Q
- What is PAH used to measure?
- What is the average renal plasma flow in a healthy individual?
- What is the filtration fraction?
- How is it calculated?
- How much of the cardiac output do the kidneys receive at rest?
A
- Renal Plasma Flow (RPF)
- 650ml/min
- The fraction of glomerular plasma that is filtered into the tubules
- Filtration fraction = GFR divided by Renal Plasma Flow
- 25%
13
Q
- Which components of the glomerular filtrate are 100%, 99%, 50%, 0% reabsorbed?
- Approximately what volume of the glomerular filtrate is reabsorbed per minute in the proximal tubule?
- Identify some substances that are secreted by cells into the proximal tubule
- Name the capillaries into which the proximal tubule drains
- What is the difference between primary and secondary active transport?
A
- 100- Glucose and amino acids, 99- salt and fluid, 50- urea, 0- creatinine
- 80ml/min reabsorbed
- H+, toxins, drugs, Hippurates, neurotransmitters, Bile pigments, uric acid
- Peritubular capillaries
- Primary- uses energy from ATP
secondary- molecule is transported coupled to the concentration gradient of an ion e.g. Na+
14
Q
- In the proximal tubule Na+ ions are reabsorbed _______ which drives the __________ reabsorption of _____ ions. The net reabsorption of _____ leads to the passive paracellular reabsorption of _______
- How does glucose reach the capillary?
- What does Tm stand for?
- What is the renal threshold for plasma glucose levels above which glucose is excreted? Why is this clinically significant?
A
- Transcellularly, paracellular, Cl- ions, NaCl, water
- Secondary active transport into the tubule cells then facilitated diffusion into the basolateral interstitial fluid
- Transport maximum
- 12mmol/L explains glycosuria in diabetes
15
Q
- What is the function of the loop of Henle?
- The descending limb reabsorbs ________ not ______. The ascending limb reabsorbs ________ not ________.
- How does NaCl gain entry to the cells of the ascending limb? How does Na+ enter the interstitial fluid?
- What drugs block the Triple co-transporters?
A
- Generates a cortico-medullary solute concentration gradient allowing the creation of hypertonic (concentrated) urine
- water, NaCl, NaCl, water
- Triple co-transporter, Na+/K+ ATPase
- Loop Diuretics
16
Q
- What is the name of the mechanism of the loop of Henle?
- Name the two solutes that create the cortico-medullary concentration gradient.
- Where is urea reabsorbed?
- What happens to filtrate osmolality as it moves down the descending limb and up the ascending limb? 5. In what other vessel is this replicated in juxtamedullary nephrons?
A
- Countercurrent multiplier
- NaCl and urea
- Collecting duct
- down- osmolality increases because water lost and solute retained, up- osmolality decreases because solute lost and water retained
- Vasa recta
17
Q
- Name the hormone which acts to increase water reabsorption
- What is the effect of aldosterone
- What about Atrial Natriuretic hormone?
- Which part of the kidney is affected by these?
A
- ADH
- Na+ reabsorption and H+/K+ secretion
- Decreased Na+ reabsorption
- Collecting ducts
18
Q
- How does the early collecting duct differ from the late?
- Where is ADH created and stored?
- When is ADH released?
- The binding of ADH to the basolateral membrane leads to an increase in ____________ resulting in the opening of __________. High ADH causes the production of a _______ urine because there is increased water __________.
A
- Early- similar to distal tubule, Late- low ion permeability and ADH controlled permeability to Water and urea
- Created- hypothalamus, Stored- posterior pituitary
- In response to high plasma osmolality (dehydrated)
- Cyclic AMP, Aquaporins, hypertonic, permeability
19
Q
- Name the two types of diabetes insipidus
- What are the two main symptoms
- What is the main treatment for central diabetes insipidus?
A
- Central- problem in hypothalamus and nephrogenic- problem with responding to circulating ADH
- Constant thirst, Large volumes of dilute urine
- ADH replacement
20
Q
- When is aldosterone secreted?
- Where is it secreted from?
- What does it do?
- An increase in plasma _______ directly stimulates the adrenal cortex to secrete ________ thus stimulating the secretion of ________ in the kidneys. A decrease in plasma _________ causes an indirect secretion of ________ by means of the ______ _______ of the juxtaglomerular apparatus.
A
- In response to rising K+ and falling Na+ or following activation of the renin-angiotensin system.
- Adrenal cortex
- Na+ reabsorption and K+ secretion
- K+, aldosterone, K+, Na+, macula densa
21
Q
- Identify the four effects of Angiotensin II.
2. Which two sites on the cells of the distal tubule and collecting duct are effected by aldosterone?
A
- Increased Vasopressin, Increased Thirst, Increased arteriolar vasoconstriction, Aldosterone secretion from adrenal glands
- Apical Na+ pump and basolateral Na+/K+ ATPase
22
Q
- Where does ANP originate?
2. What effect does ANP have?
A
- Atrial muscle cells- secreted when they are stretched
2. Promotes excretion of Na+ ions and diuresis thus decreasing plasma volume
23
Q
- Name three effects of acidosis
- What is the equation for pH and pK
- Henderson-Hasselbalch equation?
- What is the most important buffer system in the body?
- How does the kidney contribute to this system? What is this driven by?
- Name the enzyme that is essential in this process
- When HCO3- levels are low what buffers are used?
- For every hydrogen ion secreted ______ HCO3- is reabsorbed. For every H2PO3- ion/NH4+ lost in the urine one _____ ____________ ion is transfered to the blood.
A
- Depression of the immune system, Influence K+ levels, Influence enzyme activity
- pH= -log[H+] pK= -log[K]
- pH = pK+ log [A-]/[HA]
- HCO3- PCO2 system
- Reabsorption of HCO3-, driven by H+ reabsorption
- Carbonic anhydrase
- Phosphate ions, ammonia- said to be ‘new’ HCO3- made
- one, new bicarbonate
24
Q
- What is the difference between compensation and correction?
- Define respiratory acidosis
- How does the kidney compensate for respiratory acidosis?
- Define respiratory alkalosis
- How do the kidneys compensate for respiratory alkalosis?
A
- Compensation is restoration of plasma pH to normal whereas correction is restoration of pH AND HCO3 and PCO2 back to normal
- Retention of CO2 in the body thereby increasing H+ and HCO3- (pH below 7.35 and pCO2 below 45mmHg
- The rise in pCO2 stimulates H+ ion secretion into the filtrate
- Excessive removal of CO2 from the body causing H= and HCO3- to fall
- The kidneys further decrease HCO3- to swing the concentration gradient around
25
Q
- What causes metabolic acidosis?
- How do the lungs and kidneys respond?
- Define metabolic alkalosis
- How do the lungs and kidneys compensate?
A
- Excess H+ from any source other than CO2 levels (low pH and low bicarbonate)
- Hyperventilation to decrease CO2 and generation of ‘new’ HCO3-
- Excessive loss of H+ from the body (High pH and High bicarbonate)
- Reduced breathing rate and increased HCO3- secretion