Renal correction of acidosis and alkalosis, micturition and nitrogenous waste excretion

Question 1

Acidosis types

Answer 1

-decreased HCO3- : metabolic acidosis
-increased CO2: respiratory acidosis

Question 2

Alkalosis types

Answer 2

-increased HCO3-:metabolic alkalosis
-decreased CO2: respiratory alkalosis

Question 3

Kidney compensation for metabolic acidosis

Answer 3

-HCO3- in the extracellular fluid is reduced therefore less HCO3- is filtered and less H+ is used for reabsorption of HCO3- in renal tubule
-since less HCO3- is reabsorbed, more H+ remains in the tubule and excreted

Question 4

Kidney compensation for metabolic alkalosis

Answer 4

-HCO3- in extracellular fluid is increased therefore more HCO3- is filtered and there in no additional H+ for reabsorption of HCO3-
-Since more HCO3- is filtered and reabsorption is not increased, more HCO3- is excreted

Question 5

Kidney compensation for respiratory alkalosis

Answer 5

-PCO2 is the extracellular fluid is reduced and this reduces H+ secretion
-with reduced H+ in the tubule, more HCO3- is excreted

Question 6

Factors affecting renal H+ secretion

Answer 6

1.PCO2 in ECF
2.H+ concentration in ECF
3.Aldosterone
4.Reduced extracellular volume

Question 7

PCO2 in extracellular fluid affect on renal H+ secretion

Answer 7

-increased PCO2 stimulates more reanl H+ secretion
-decreased PCO2 reduces renal H+ secretion

Question 8

H+ concentration in ECF effect on renal H+ secretion

Answer 8

-increased H+ concentration leads to more renal H+ secretion
-decreased H+ leads to reduced renal H+ secretion

Question 9

Aldosterone effect on renal H+ secretion

Answer 9

-increased H+ secretion by intercalated cells in collecting ducts

Question 10

Reduced extracellular volume effect on renal H+ secretion

Answer 10

1.reduced volume increases angiotensin II for more Na reabsorption via increased activity of Na-H counter transports at luminal membrane of tubular epithelial cells
>leads to more H+ secretion
2. Reduced volume also increases aldosterone and this hormone increases H+ secretion

Question 11

Type B intercalated cells in distal and collecting tubules

Answer 11

-can secrete HCO3- which increases with alkalosis
>H+ ions (from formation of HCO3-) are pumped into peritubular capillary at basolateral membrane
>Cl-HCO3- counter transporters at luminal membrane. Pump HCO3- into tubular lumen to be excreted in urine

Question 12

Acid base disorders

Answer 12

-respiratory acidosis
-respiratory alkalosis
-metabolic acidosis
-metabolic alkalosis

Question 13

Respiratory acidosis

Answer 13

-caused by reduced pulmonary ventilation (obstruction, pneumonia, emphysema)
-damage to respiratory centers (eg.medulla)

Question 14

Respiratory alkalosis

Answer 14

-caused by increased ventilation
-not very common. Can occur at high altitude (low oxygen leads to increased respiration and loss of CO2)

Question 15

Metabolic acidosis

Answer 15

-caused by failure of the kidneys to excrete metabolic acids, production of excess metabolic acids, injection or infusion of acids and or loss of base
>chronic renal failure (anions of weak acid not excreted), severe diarrhea and losing bicarbonate in feces, vomiting (from deep GI tract because losing HCO3-) and losing bicarbonate, diabetes mellitus (fat metabolism and formation of acetoacetic acid)

Question 16

Metabolic alkalosis

Answer 16

-caused by excess retention of HCO3- or excretion of H+
-not as common as metabolic acidosis
-from diuretics (because losing water, more Na is reabsorbed by Na-H cotransporters, so more H+ excretion), excess aldosterone (more Na reabsorption and H secretion) , and vomiting from stomach

Question 17

Micturition

Answer 17

-emptying of urinary bladder
-autonomic spinal reflex, but centers in cerebral cortex or brainstem can inhibit or facilitate micturition

Question 18

Steps of micturition

Answer 18

1.Accumulation of urine in urinary bladder and increased tension of the bladder wall
2. Initiation of the micturition reflex for emptying the bladder

Question 19

Muscles of the bladder

Answer 19

-Bladder composed of body and neck
>Smooth muscle: detrusor muscle (has fused fibers to spread action potential) and extends to internal sphincter
>Skeletal muscle: external sphincter muscle

Question 20

Nerve supply of bladder

Answer 20

-pelvic nerves via the S2 and S3 segments
-both sensory and motor nerve fibers
>motor are parasympathetic to body and neck AND the pudendal nerve controls the external sphincter
>sympathetic innervation through hypogastric nerves controlling the blood vessels

Question 21

Micturition reflex

Answer 21

-Sensory stretch receptors initiate a reflex
>sensory signals travel to the sacral segment of cord via the pelvic nerves
>reflex comes back to the bladder through the parasympathetic nerve fibers

Question 22

Partially filled bladder

Answer 22

-shorter and milder contractions

Question 23

Filled bladder

Answer 23

more frequent and stronger contractions

Question 24

Self-regenerative micturition reflex

Answer 24

-contractions stimulate more sensory signals and more sensory signals stimulate more contractions
-if bladder is not emptied the detrusor muscles are fatigued and then bladder is relaxed for up to 1 hour and the cycle starts again but with stronger contractions
>eventually the reflex will send signal through the pudendal nerve to inhibit the external sphincter

Question 25

Brain regulation of micturition reflex

Answer 25

-brain can facilitate or inhibit the autonomic spinal micturition reflex (cerebral cortex and brainstem)
-these centers can partially inhibit the micturition reflex

Question 26

What are amino acids used for?

Answer 26

1.maintenance and growth
2.As osmolytes for protection and regulation of cell volume in marine animals
3.energy product BUT waste is toxic to neurons and needs to be diluted and removed

Question 27

Ammonia or ammonium ion

Answer 27

-waste in most aquatic animals
-excreted in water mostly from gills
-toxic
-highly soluble
-with each molecule only one nitrogen is excreted, so excretion of more nitrogen requires a lot of water (osmolarity)

Question 28

Urea

Answer 28

-waste product for most terrestrial animals
-excreted in urine
-less toxic
-soluble
-2 nitrogen in each molecule so less water is required for the excretion of same amount of nitrogen compared to NH3

Question 29

Uric acid

Answer 29

-waste product used in most reptiles, birds and insects
-excreted in urine
-least toxic
-insoluble
-4 nitrogen in each molecule so less water is required for the excretion of the same amount of nitrogen compared to urea (important to preserve water as they don’t have water access)
-antioxidant; advantage to when egg laying

Question 30

Renal system in birds

Answer 30

-kidneys have mostly reptilian type nephrons with some mammalian type nephrons
>mammalian nephrons have loop of henle and can concentrate urine, whereas reptilian nephrons do not (they are straight)

Question 31

Uric acid in birds

Answer 31

-uric acid is insoluble and precipitates, so crystals are covered with albumin and form urate balls. The urate balls are filtered in the kidney so we have some protein excretion in birds unlike mammals
-urine enters the cloaca and lower intestines. Some water removed from it

Question 32

Bird hyperosmotic urine production?

Answer 32

-most birds do not produce hyperosmotic urine but some birds do not have salt gland can produce hyperosmotic urine
*most marine birds will have nasal salt gland. This allows for salt excretion without excreting water

Question 33

What species excretes protein in urine?

Answer 33

-birds under normal physiological conditions

Question 34

Kidney compensation for respiratory acidosis

Answer 34

-PCO2 in the extracellular fluid is increased and this stimulates more H+ secretion
-with more H+ in the tubule, more excess H+ is excreted