Physiology Final Exam - non cumulative portion

Urinary system 3 main functions

filter blood (waste removal)

maintain fluid/electrolyte balance

regulate blood pressure

Anatomy of urinary system

nephron (functional unit)

filtration barrier (3 layers)

Nephrons per kidney

approximately 1 million per kidney

Filtration barrier (3 layers)

fenestrations (capillary endothelium)

basement membrane

podocyte foot processes (filtration slits)

What do fenestrations block

blood cells & large particles

What do fenestrations allow through

water, ions, and small molecules

What does the basement membrane block

most plasma proteins

basement membrane has what barrier

a physical and charge

What do podocyte foot processes (filtration slits) block

medium-sized proteins

what do podocytes foot processes (filtration slits) allow through

water, ions, and small solutes

Nephrons 3 main functions

Filtration, Reabsorption, and Secretion

Filtration in the nephron is located at

the glomerulus

Filtration at the nephron occurs through what process

blood plasma is filtered into Bowman’s capsule

Filtration at the nephron - what is filtered into bowman’s capsule?

water, electrolytes (Na+, K+, Cl-), glucose, Amino acids, nitrogenous wastes (urea, creatinine)

Filtration at the nephron - what is NOT filtered (kept out)?

blood cells (RBC, WBC), platelets, large proteins (albumin)

Reabsorption at the nephron - location

mostly the proximal convoluted tubule

Reabsorption process at the nephron

useful substances are reclaimed from the filtrate into the blood

Reabsorption at the nephron transport pathways

Transcellular & paracellular

What is transcellular pathway

through cells

What is paracellular pathways

between cells

How is Na+ reabsorbed in the nephron

Active transport basolaterally

cotransported apically

and is most transcellular

how is water reabsorbed in the nephron

by osmosis (follows Na+)

through aquaporins

both transcellular and paracellular

how is glucose reabsorbed in the nephron

secondary active transport with Na+ (apically)

by facilitated diffusion basolaterally

transcellular

has a transport maximum

how are amino acids reabsorbed in the nephron

cotransported with Na+

transcellularly

How is urea reabsorbed in the nephron

passive diffusion

mostly paracellular and some transcellular

How is K+ reabsorbed in the nephron

passive diffusion (paracellular early on)

active reabsorption later on

how is Cl- reabsorbed in the nephron

follows Na+ passively

both paracellular and transcellular

how is Ca2+ reabsorbed in the nephron

passive via PCT

Active via DCT & regulated by PTH

Paracellular & transcellular

Na+ gradient in reabsorbtion

high to low from the lumen to the cytosol

Na+ gradient in reabsorption

low to high - active

from cytosol to basolateral

how is glucose & amino acids reabsorbed

against the gradient with Na+

from the lumen to the cytosol

how is glucose and amino acids reabsorbed down their gradient

from the cytosol to basolateral

how is water reabsorbed

follows solute osmotic gradient

What is transport maximum

maximum rate of reabsorption

limited by carrier-mediated transport

Example of transport maximum

glucose in diabetes (glycosuria)

mechanisms reaching transport maximum

saturation of transport proteins

limited speed of carrier proteins

finite number of transporters

Reabsorption and filter efficiency

180 L filtered/day: 178.5 L reabsorbed per day

third function of a nephron

secretion

Where secretion from a nephron is located

distal tubule & collecting duct

Process of secretion in a nephron

waste/excess actively transported from blood into filtrate

What gest secreted in the nephron

potassium (K+)

hydrogen ions (h+)

waste products (creatinine, drugs, toxins)

Importance of secretion

fine-tuning chemical balance (pH & K+)

detoxifying blood

bowman’s capsule tonicity of nephron

it is isotonic at 300mOsm/L

Proximal Tubule tonicity in nephron

isotonic

solutes & water reabsorbed proportionally

Descending loop of Henle tonicity in nephron

hypertonic

water leaves & solutes stay

ascending loop of Henle tonicity

hypotonic

solutes leave & water stays

Distal tubule tonicity in nephron

hypotonic

unless ADH present

Collecting duct tonicity in nephron

variable

hypotonic without ADH

hypertonic with ADH

Proximal tubule epithelial

simple cuboidal, with brush border (microvilli)

for reabsorption

Descending loop epithelium

simple squamous, thin & water permeable

Ascending loop epithelium

thicker, impermeable to water

active solute transport

Distal tubule/collecting duct epithelial

cuboidal, few microvilli

hormone-regulated transport

For concentrating urine in juxtamedullary nephrons

there are long loops of henle in the medulla

Descending limb in juxtamedullary nephron

water reabsorption occurs here — osmosis

Ascending limb juxtamedullary nephron

solute reabsorption - active

urea secretion (impermeable to water)

Vasa recta in juxtamedullary nephron

maintain medullary osmotic gradient

collecting ducts in juxtamedullary nephron

final water/urea reabsorption (ADH regulated)

Regulation of blood pressure in urinary system

intrinsic - autoregulation of glomerular filtration rate

Regulation of blood pressure in urinary system

extrinsic - systemic regulation

Intrinsic controls of blood pressure

myogenic mechanism - afferent arteriole stretching

Intrinsic controls of blood pressure

tubuloglomerular feedback

macula dense senses NaCl

Extrinsic control of blood pressure

neural control - sympathetic NS - constricts afferent

extrinsic control of blood pressuer

hormonal controls such as RAAS, ADH, and ANP

RAAS is

Renin-Angiotensin-Aldosterone system

Where does renin come from in RAAS

granular cells - kidneys

How is renin released from granular cells

stimulated by low blood pressure, low NaCl, and sympathetic activation

What does renin do

converts angiotensinogen to angiotensin 1

Where does angiotensin from RAAS come from

the liver

Where does aldosterone come from in RAAS

the adrenal cortex

What does RAAS do

helps regulate blood pressure, BV, and Na+/K+ balance in body

Raises blood pressure and conserves Na+ and H2O to restore BP & BV

ACE does what in RAAS

converts angiotensin 1 (from renin) → angiotensin II

Where is ACE from

mostly found in the lungs

Angiotensin II - the active form does what

vasoconstriction = raises BP

Stimulates Aldosterone

Stimulates ADH

Increases thirst

What does aldosterone do

targets the distal convoluted tubule

Allows reabsorption of Na+ and secretion of K+

What is ADH

vasopressin and from the posterior pituitary

Target of ADH

collecting ducts

Action of ADH

increases water reabsorption (aquaporins)

Atrial Natiuretic peptide comes from

the heart atria

ANP is stimulated by

High blood pressure

Action of ANP is

to promote Na+ & H2O excretion which inhibits renin/aldosterone

Regulation of GFR & Blood flow from

kidney arterioles

Intrinsic controls of GFR and Blood flow

myogenic & tubuloglomerular

Extrinsic controls of GFR & Blood flow

sympathetic NS & RAAS

Afferent arterioles

into the glomerulus

Afferent arterioles are

wider than efferent arterioles

dilation increases GFR

constriction decreases GFR

Efferent arterioles are

out of the glomerulus

Efferent arterioles

constriction increases GFR

dilation decreases GFR

GI tract - alimentary canal

Mouth, pharynx, esophagus, stomach, small intestine, large intestine

Mouth digestion

mechanical - chewing

chemical - salivary amylase & lingual lipase

Mouth secretions

saliva: amylase, lipase, mucus, lysozyme, IgA

Mouth motility

chewing & swallowing

Mouth regulation

parasympathetic NS

Pharynx

is a common pathway - food & air

Pharynx motility

swallowing reflex

Pharynx secretions

mucus

Esophagus motility

peristalsis

Esophagus secretions

mucus

Esophagus sphincter

lower esophageal sphincter - LES

Stomach functions

as storage and mixing

Stomach digestion

mechanical - churning

chemical - pepsin, gastric lipase