study guide

10 Pages
Unlock Document

Biological Sciences
Stephen Reid

Lecture 19 Study Notes Slide 1 • Osmolarity in descending limb is always equal to peritubular fluid osmorality o Both are higher by 200 mOsm to the ascending limb of the Loop of Henle • Tubular fluid in the loop of Henle leaves with lower mOsm it had when it came in o 100 mOsm as opposed to 300 mOsm • The medullary osmotic gradient helps us to produce concentrated urine (1200 mOsm) o As opposed to producing dilute urine of 300 mOsm • Remember also that the descending limb is only permeable to water, not ions o While the ascending limb is permeable to ions not water • Water diffusing out of the descending loop of henle follows ions diffusing out of the ascending limb osmotically Slide 2 • The Loop of Henle ESTABLISHES a countercurrent-multiplier: because the fluid is flowing in opposite directions in two compartments in close proximity o The vasa recta (capillaries around the loop of Henle) maintain the osmolarity gradient Prevent pooling of solutes and disruption of medullary osmotic gradient Slide 3 • Blood (not tubular fluid as in Loop of Henle) enters vasa recta with 300 mOsm (leaves with 325 mOsm) o Descending and ascending portions of vasa recta are both permeable to water and ions Descending portion: Loses water; Gains solutes Ascending portion: Gains water; Loses solutes Slide 4 • Blood leaving the vasa recta has a higher mOsm than blood that enters vasa recta o Entering: 300 mOsm o Leaving: 325 mOsm o Caused by: 1. Solute (ion) reabsorption 2. Urea reabsorption 3. Colloid osmotic pressure of plasma (protein caused) Slide 5 • Watch this section in lecture Slide 6, 7, and 8 • Fluid leaving ascending loop of Henle enters distal tubule of juxtaglomerular nephron at mOSm of 100 • Some water can be reabsorbed by collecting duct or distal tubule IF permeable to water o Permeability is regulated by hormones Antidiurectic Hormone (ADH)/ Vasopressin (Reduces urination, but concentrates it as it causes reabsorption of water into blood [vasa recta]) • Synthesized by Paraventricular Nucleus of Hypothalamus • Stored in posterior pituitary • ADH/Vasopressin stimulates water reabsorption from collecting duct/distal tubule (where urine is concentrating) into vasa recta o Released in response to osmolarity o Stimulates insertion of Aquaporin 2 on apical membrane facing tubular lumen o Aquaporin 3 is always on the basolateral membrane and not under hormonal control o If distal tubule and collecting duct are permeable to water (i.e. water going out) urine has Low volume High concentration (max of 1400 mOsm) o If distal tubule and collecting duct are not permeable to water (i.e. water going out) urine has High volume Low osmolarity Slide
More Less

Related notes for BIOC34H3

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.