100% satisfaction guarantee Immediately available after payment Both online and in PDF No strings attached
logo-home
Previously searched by you
Previously searched by you
logo
Summary WJEC (England) Eduqas A-Level Biology 3. Requirements for life - 4. Homeostasis & Kidney CA$5.54   Add to cart
Quickly navigate to
Preview
  2.  
  3. WJEC
  4.  
  5. Biology
  6.  
  7. 3. Requirements for life

Summary

Summary WJEC (England) Eduqas A-Level Biology 3. Requirements for life - 4. Homeostasis & Kidney

1 review
 11 views  0 purchase
  • Course
  • 3. Requirements for life
  • Institution
  • WJEC

I achieved a high A* Grade in my final A-Level exams using these notes!!! I believe you can achieve an A* if you can memorise these notes! Simply use blurting, a method of active recall, to write everything you remember from the notes, then identify the parts you couldn’t remember, then repeat ...

[Show more]

Preview 2 out of 5  pages

Document information

  • May 2, 2023
  • 5
  • 2021/2022
  • Summary

Subjects

  • homeostasis
  • kidney
  • negative feedback
  • ultrafiltration
  • selective reabsorption
  • osmoregulation
  • adh
  • kidney failure

Written for

  • A/AS Level
  • WJEC
  • Biology
  • 3. Requirements for life
All documents for this subject (7)

1  review

review-writer-avatar

By: rashmeensheikh2317 • 7 months ago

Seller

avatar-seller
tnotes

Reviews received

Content preview

a. Homeostasis: process of maintaining constant internal environment = dynamic equilibrium
- Temperature
- Glucose levels
- Solute potential


importance of dynamic equilibrium – around set point
- body cells function efficiently – constant & appropriate rate
- conditions of body cell don’t fluctuate with external environment
- biochemical reactions require specific conditions = constant – even during activity
- enzyme optimum
- water potential – don’t plasmolyse




b. negative feedback: restore conditions to set point
receptor – detects change + signal to coordinator (temperature receptor)
control centre – detect signal from receptor + coordinates response via effector (hypothalamus)
effector – bring about response to restore to set point (muscle/gland)

positive feedback: increases change




c. kidney structure – contains million nephrons
blood: renal artery → nephron → renal vein
urine: collecting duct → renal pelvis → ureter → bladder → urethra

Cortex
- Afferent arteriole
- Glomerulus (capillary bundle)
- Bowman’s capsule
- Efferent arteriole
- Proximal convoluted tubule
- Distal convoluted tubule
Medulla
- Loop of Henlé
- Vasa recta: capillaries surrounding LoH
- Collecting duct




Ultrafiltration of blood to remove urea – glomerulus & Bowman’s capsule
 afferent arteriole to narrower efferent arteriole & heart contraction = hydrostatic pressure in glomerulus
 forces out small molecules: glucose / amino acids / salts / water / urea
 Capillary fenestrations/pores
 Bowman’s basement membrane – sieve (cells/proteins too big)
 Podocyte’s (Bowman’s epithelium) pedicels – wrap around capillaries = filtration slits
 Glomerulus hydrostatic pressure > high capsule fluid pressure + high plasma osmotic pressure
= glomerular filtrate in Bowman’s capsule

, d. kidney functions
Osmoregulation: control of water & solutes in bodily fluids (tissue fluid / blood / lymph)
Excretion: removal of metabolic waste products
- excess amino acids deaminated in liver (can’t be stored)
- amino group → ammonia → urea (less toxic) (transported to blood plasma to kidney)



e. Selective reabsorption – proximal convoluted tubule → peritubular capillaries
of filtrate’s required molecules into blood = filtrate isotonic with blood plasma
 all glucose & amino acids = Na+ co-transport (facilitated diffusion) – secondary active transport
up to glucose threshold: max pct can reabsorb (limited by carrier proteins) – rest remains in filtrate → urine
 most water = osmosis – Na+ (co transport) lower blood’s water potential
 most mineral ions = active transport
 some filtered proteins + some urea = diffusion

Proximal convoluted tubule adaptations
- large SA – for reabsorption
o Nephrons: long & millions per kidney
o Cuboidal epithelium: microvilli + basal channels (folds facing capillary)
- Many mitochondria – ATP for active transport
- Tight junctions – prevent reabsorbed materials seeping back to filtrate
- Close to capillaries – short diffusion pathway & increase concentration gradient




Osmoregulation: prevent cells bursting & maintain solute concentrations (enzymes/metabolites)
- ascending limb – impermeable: actively transport Na +/Cl- out filtrate → medulla tissue fluid = salty
- descending limb – permeable: water osmoses out filtrate → medulla tissue fluid
= filtrate most concentrated at loop apex
hair-pin: counter-current multiplier – max concentration at loop apex (& higher in medulla)

- collecting duct: water osmoses out (to concentrated medulla tissue fluid – always higher so osmosis continues)
o filtrate hypertonic to blood = urine
- water reabsorbed → vasa recta blood



f. endocrine glands: secrete hormones for negative feedback
ADH produced by hypothalamus & secreted by posterior pituitary gland


g. ADH antidiuretic hormone: negative feedback – restore blood’s normal osmotic conc = less & more conc urine
 Detector: hypothalamus osmoreceptors – monitor blood solute potential + secrete ADH
o Dehydration: less water intake / sweating / high salt intake – more ADH
o Overhydration: excess water intake / low salt intake – less ADH

 Coordinator: posterior pituitary gland – release ADH

 Effector: permeability of distal convoluted tubule & collecting duct cell membranes to water – increases
o ADH binds to dct & cd membrane receptors
o triggers vesicles with aquaporins to fuse with membrane = inserted
o Aquaporins (intrinsic protein): contain pore allowing water to move out by osmosis
o Aquaporins removed when ADH concentration falls
- water reabsorbed → medulla tissue fluid → vasa recta (blood)
= blood water potential restored

The benefits of buying summaries with Stuvia:

Guaranteed quality through customer reviews

Guaranteed quality through customer reviews

Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.

Quick and easy check-out

Quick and easy check-out

You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.

Focus on what matters

Focus on what matters

Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!

Frequently asked questions

What do I get when I buy this document?

You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.

Satisfaction guarantee: how does it work?

Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.

Who am I buying these notes from?

Stuvia is a marketplace, so you are not buying this document from us, but from seller tnotes. Stuvia facilitates payment to the seller.

Will I be stuck with a subscription?

No, you only buy these notes for CA$5.54. You're not tied to anything after your purchase.

Can Stuvia be trusted?

4.6 stars on Google & Trustpilot (+1000 reviews)

78998 documents were sold in the last 30 days

Founded in 2010, the go-to place to buy study notes for 14 years now

Start selling
CA$5.54
  • (1)
  Add to cart