Physiology Exam 4 Module 13

hydrogen

Integration of Homeostatic Controls:

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•The ***kidneys and the respiratory system*** work  together to regulate _______ ion concentrations.

ventilation, lowers

Respiratory can respond quickly-within minutes-to changes in H+ (pH) until the renal system can eliminate the imbalance in a period of hours or days



Ex. Increased arterial H+ stimulates _____ (air moves from atmosphere to alveoli),raises/lowers arterial PCO2, which reduces H+

faster

respiratory fixes faster/slower than renal (filter)

co2, hco3, urine

Sources of Hydrogen Ion (GAIN) \n - Finding pH homeostasis

1. generation of H+ from ___ (respiratory)

2. gain of H+ due to loss of ____ in diarrhea or other non gastric GI fluids (digestive)

3. gain of H+ due to loss of HCO3 in the ____ (urinary)

vomit, hyper

Sources of Hydrogen Ion (LOSS) \n - Finding pH homeostasis

loss of H+ in ____ (digestive)

loss of H+ in urine (urinary)

____ventilation (respiratory

acidosis

metabolic _________

due to processes other than respiration, low blood pH

Examples:

•Lactic acid build-up due to severe exercise

•Diarrhea (This gets rid of bicarbonates-creating more acidic environment)

alkalosis

metabolic __________ due to processes other than respiration, rising blood pH

•Examples:

•Excessive vomiting (HCL)

•Intake of excess bases - antacids

7\.4

•***Extracellular fluid*** should be at a pH of ___



•This pH value corresponds to the concentration of H+



•***Buffering*** reversibly binding H+



•The major extracellular buffer is the ***CO2/HCO3- system.***



•The kidneys eliminate or replenish hydrogen ions from the body by altering plasma bicarbonate concentration.



•For example: Reabsorption of bicarbonate leaves little H+ in the tubules, H+ is secreted into the tubule

aciddosis, alkalosis

•Range for pH of blood: 7.35 – 7.45

•PCO2 was 40mmHg, Range: 35-45

Bicarbonate range: 21-26 mEq/

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higher co2 is ___________

higher bicarbonate is _______

full, not, partial

Ph is leaning to one category → co2 is in that category → co2 is respiratory = respiratory alk (b/c leaning to alk)



Though ph is leaning it is still considered normal so full compensation



________ compensation = ph is normal



______ → other variable is normal



________ → acid/alka each hold a variable, ph is not normal

renal

_______ functions: Regulate by increasing or decreasing secretion

nephrons

Each kidney has approx. 1 million _________!

glomerular

renal blood vessels

•Two sets of capillaries

•___________ (ball of capillaries): filtration

peritubular

renal blood vessels

__________ : reabsorption of filtrate to blood supply

afferent , efferent

•Two sets of arterioles



•______ : where blood flows into glomerular capillaries



•__________ : where blood leaves the glomerulus

glomerulus, pct, loh, dct

order 1. 2. 3. 4.

ureters

**__________** transport urine from kidneys to bladder (peristalsis of smooth muscle help move urine)

**Bladder**: store urine until voided from body

**Urethra**: carry urine from bladder to the outside of the body

filtrate: anything that you filter

filtrate (nephron) → urine (ureter)

smooth

•The bladder stores urine until it is excreted from the body by the ***micturition reflex***  



•Micturition is initiated by a nervous reflex which causes the ______ muscle of the bladder walls (***detrusor muscle***) to contract and expel the urine. (innervated by neurons)



•Action potentials can exhibit automaticity in response to stretch but stimulation is required for bladder emptying



renal

shut

micturition:

As bladder fills, pressure increases stimulating receptors for control of muscle & sphincters

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stimulate = contract = _________ (no role)

urinating

during voiding reflex, both sphincters are inhibited so we are doing what?

secretion

•A substance may enter tubules through glomerular filtration or tubular **______** (capillary to lumen).

reabsorption

•A substance may leave the tubule through **__________** (passing of substances from the lumen (tubules) to the capillary) or **excretion** (out of the body)

•Reabsorption and secretion require a substance to move across a layer of epithelial cells

proximal

•Reabsorption occurs constantly in ***__________ and loop of Henle tubules*** and is not subject to hormonal control. Distal and collecting tubules *are* subject to this control.

(more than secretion)

glucose

Products reabsorbed at high rates:



• **______ & most organic nutrients**



•For products like these, the kidneys just help in ***maintaining*** plasma levels of the nutrients



•**Water and many ions**



•Kidneys can aid in ***regulating*** these



•Ex. Water intake decreases, kidneys water reabsorption increases

reabsorption

•Most ___________ occurs in proximal tubule, 65%



tubule/lumen (nephron) → blood

active

•Sodium reabsorption:



•_______ process



•occurs in all tubular segments



**except** the descending limb

osmosis

•Water reabsorption:



•_______



•dependent upon sodium reabsorption

primary

Throughout tubule, Na+ is reabsorbed by ***__________ active transport***

Na+

___ reabsorption drives reabsorption of cotransported substances (such as Cl-) and secretion of H+

water

Na+ and Cl- combine to form NaCl in the interstitial fluid which will drive the reabsorption of ***________***

(then 2ndary at)

passive

Coupling of Water reabsorption to sodium reabsorption

***_______ process-*** water follows ions as they move

rewatch video for this part? slide 25

impermeable

•Na+ & water in proximal tubule is reabsorbed in the same proportions



\
But in the Loop of Henle…



•The descending loop of Henle is relatively ***__________*** to solutes and freely permeable to water.

permeable

•The ascending limb is ***_________*** to solutes, but not water.

hypertonic

Urine Concentration: The Countercurrent Multiplier System

__Descending loop__: Water is drawn out by osmosis



The interstitial fluid is ***_________*** (water will move to the higher concentration of solutes)

osmolality

at the bottom of the loop, __________ is at its max

hypertonic environment keeps returning

cl and k

Urine Concentration: The Countercurrent Multiplier System

__Ascending loop__:



•Na+ moves across the epithelial cells of the thick portion of the tubule via the electrochemical gradient, this drives the secondary active transport of and ___



•K+ diffuses back into filtrate, Na+ is pumped into interstitial fluid, Cl- passively follow

urea = solute

positive

Urine Concentration: The Countercurrent Multiplier System

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•A ***_______ feedback system*** is generated.



The system sets up a concentration favoring water reabsorption ;



Water leaves and immediately goes to bloodstream (doesn’t stay) that’s why hypertonic (increased osmolality)

atp pumps

•Max concentration (the end to the positive feedback) is determined by the **number of** __**_______**__

channels

Regulation of reabsorption and/or secretion of many substances is achieved by regulating the activity or concentrations of the appropriate ***transport proteins or ion ________*** .



if channels aren’t present, nothing moves

vasopressin, ADH

Na + H2O

Must ingest these substances to replace your loss, kidneys will minimize excretion until you do so

•Thirst is triggered by ***increase in plasma osmolality and decrease in ECF*** (extracellular fluid)

•These are the two factors that stimulate ***______ (?)***



•More vasopressin - more aquaporins - more water retained - less water excreted



•Most mammals like Salt-we consume more than we need

hormones

______ in charge of binding and inserting more channels

proximal

•Permeability varies depending on location in tubule and presence of ***aquaporins***

•***______ tubule*** location for highest water permeability (ie highest # of aquaporins)

•Vasopressin stimulates presence of aquaporins in the collecting ducts, without it permeability is low

diuresis

water ____

•large amounts of water in urine due to low vasopressin

ach

vasopressin



•After vasopressin locks in, a secondary messenger activates an enzyme that causes proteins to increase rate of fusion of vesicles to the membrane



if we go L

K+

what is secreted into the renal tubules



•Substances such as hydrogen ion, potassium, and organic anions move from the peritubular capillaries into the tubular lumen.

•Tubular secretion is an important mechanism for:

1\.Excess __

2\. controlling blood ph (H+)

3\.Disposing of drugs and drug metabolites



\*this is why most drug tests are urine tests

okay

How do I know if the cause is metabolic (renal) or respiratory



1\.Look at ph (ph reflects H+ concentrations) both systems influence ph



2\.Look for if the H+ changes (ph) aligns to CO2 or HCO3 changes outside of normal. When ph aligns to one, that variable is causing the changes (both leaning acidic, bicarbonate is responsible for ph changes à metapholic acidosis)



3\.Since both systems influence pH, if one causes a condition then the other should fix (compensate)



Co2 not regulated by renal system (respiratory only) , bicarbonate is not respiratory