Acids, bases and urinary tract

Question 1

pH is equal to what? What is base excess? What is standard base excess? Acidemia? Alkalemia?

Answer 1

-log10{H+]
Quantity of acid required to return plasma pH to normal
Quantity of acid required to return ECF back to normal.
Low blood pH
High blood pH

Question 2

What is the anion gap? Calculation?

Answer 2

Difference between measured anions (negative) and cations (positive)
[Na+]+ [K+]-[Cl-]-[HCO3-]

Question 3

What does a wide anion gap indicate? Narrow anion gap? Normal value?

Answer 3

Lactic acidosis, ketoacidosis, ingest of acid, renal failure
GI HCO3- loss, renal tubular acidosis
10-16

Question 4

Most common urinary buffer in proximal tubule? When all filtered HCO3- has been combined with secreted H=, what does additional H+ combine with? Increase in HCO3- plasma conc does what?

Answer 4

Alkaline phosphate
Non bicarbonate buffers- namely HPO4 2- to form H2PO4- which is excreted in urine
Alkalinises it

Question 5

Tubular cells, mainly of proximal tubule, take up glutamine from what? Metabolise it to form what? Forms NH4+ using what? Secreted where?

Answer 5

Glomerular filtrate and peritubular plasma
NH3 and HCO3-
H+ from dissociation of H2CO3 or due to Na+ reabsorption
Via Na+/ NH4+ counter transport into lumen and excreted

Question 6

What is respiratory acidosis? Causes? Renal compensation for this? How long does this take?

Answer 6

Failure to get rid of CO2 resulting in decrease in pH as CO2 builds up
Hyperventilation, COPD, any cause of respiratory failure
Increases H+ and more HCO3- into plasma–> increase in pH using ammonium buffer
Days

Question 7

What is respiratory alkalosis? Causes? Renal compensation?

Answer 7

Too much CO2 lost resulting in increased pH
CO2 depletion due to hyperventilation, hypoxia, Type 1 resp failure
Kidneys decrease H+ secretion and decrease in HCO3- reabsorption–> increase in pH

Question 8

What is metabolic acidosis? Causes? Resp compensation?

Answer 8

Excess acid production (by intercalated cells) resulting in pH decrease
Renal failure, GI HCO3- loss, dilution of blood, failure of H+ excretion, ketoacidosis
Enhanced respiration stimulated by lung chemoreceptors–> fall in CO2

Question 9

Causes of metabolic alkalosis? Resp compensation?

Answer 9

Vomiting, volume depletion, alkali ingestion, hyperaldosteronism, hyperkalaemia–> increase aldosterone secretion
Inhibits lungs chemoreceptors–> reduced resp and increasing CO2

Question 10

Where is erythropoietin (EPO) produced? What does it do? Increased in response to what? Decreased when?

Answer 10

In peritubular cells in interstitial space of renal cortex
Stimulates bone marrow- maturation of RBCs
Anaemia, altitude and cardiopulmonary disorders
Polcythaemia, renal failure

Question 11

Why does urine flow through ureters to the bladder? Walls of smooth muscle in bladder known as what? Part of this at bladder neck where urethra begins functions where?

Answer 11

Due to contractions of ureter wall smooth muscle
Detrusor muscles
Internal urethral sphincter

Question 12

Just below internal urethral sphincter ring of skeletal muscle called what? Consists of what?

Answer 12

External striated urethral sphincter

Slow-twitch skeletal muscle- voluntary

Question 13

When the bladder is filling, what input is minimal? At same time strong sympathetic input to where? Strong input by somatic motor neurones to where?

Answer 13

Parasympathetic input- muscle is relaxed, internal sphincter= passively closed.
Internal sphincter
External sphincter- detrusor muscles relaxed and sphincter closed

Question 14

What is the bladder stretch reflex? When is this the spinal reflex overridden?

Answer 14

A primitive spinal reflex- micturition is stimulated in response to stretch
During toilet training by higher brain centres

Question 15

4 steps in bladder stretch reflex?

Answer 15

1) Bladder fills with urine and bladder walls stretch 2) Afferent sensory neurones detect stretch and transmit to the spinal cord 3) Interneurones relay the signal to parasympathetic efferents (pelvic nerve) 4) Pelvic nerve acts to contract the detrusor muscle and stimulate micturition

Question 16

When is the bladder stretch reflex not functional? When can it regain function?

Answer 16

Past childhood

In spinal injuries or ND disease where descending somatic pathway can be damaged–> voluntary micturition- incontinence

Question 17

When bladder fills with urine and pressure increases, stimulates what? Afferent neurones stimulate what to cause what? What happens when detrusor muscle contracts?

Answer 17

Stretch receptors in bladder wall 
Parasymp neurones (S2-S4) to cause detrusor muscles to contract 
Change in shape open internal sphincter

Question 18

Afferent input from bladder stretch receptors also inhibits what?

Answer 18

Symptoms neurones to internal sphincter–> opens, somatic neurones to external sphincter–> also relaxes

Question 19

Parasymp pelvic splanchnic nerve what level? Symp hypogastric nerve what level? Somatic motor pudendal nerve what level?

Answer 19

S2- S4
T1- L2
S2- S4