14 Homeostasis Flashcards
(48 cards)
Happens in tubule
Describe and explain how all of the glucose in the glomerular filtrate is reabsorbed back into the blood
-sodium enters cells from filtrate/lumen by FD
- sodium co transports glucose into cell = Secondary AT
- AT pumping sodium out of PCT epithelial cells into blood
- Sodium-potassium pumps in basal membrane
- sodium conc decreases inside cells
- FD of glucose/AA out of cells into blood
explain what is meant by homeostasis and the importance of homeostasis in mammals
- maintenece of constant internal enviornment despite changes in external enviornment
- changes in stimuli detected by receptor e.g blood glucose conc increases+ deteccted by pancreatic receptors b cells in islet of langerhans
- Impulse from receptor to SN transmitted to CNS/brain
- impulse to motor neurone to effector
- transmitted to target cells e.g make insulin for increased glycogenesis
- corrective action by effector/response so return to set point after deviations away from the norm value
- negative feedback
define negative feedback
- change in parameter/fluctuation away from norm value
- detected by receptor
- hormone released or nerve impulse sent
- hormone / impulse reaches effector
- corrective action by effector
- return to set point
positive feedback
enhances or accelerates the output created by an activated stimulus
Internal vs external stimuli
INTERNAL EXAMPLE:
- glucose conc, if too little resp slows/stops depriving cells of energy
- if too much, water leaves cell by osmosis (h to l wp down wp gradient), sells shrink/crenation
EXTERNAL EXAMPLE:
- touch, pain, smell, taste , vision, sound
state urea is produced in the liver from the deamination of excess AA
Deamination
- Excess protein
- Amine group removed from AA
- NH2 (amine group) reacts w H+ = NH3 (ammonia)
- Accumulates in tissues beacuse not soluable/toxic= damages tissue
- ammonia reacts w CO2= urea in ornithine cycle
- Creatinine and uric acid formed
- Urea water sol + less tox so dissolves in water and excreted as urine
- Ketoacid formed + used in aerobic resp as resp subst (0.9) = make ATP
- Fed into krebs as acetate + entrs OP and Chemiosmosis
amino acid → keto acid + ammonia
ammonia + CO₂ → urea
*keto acids (enter Krebs Cycle) are respired, or converted to glucose, glycogen or fat
look at quizlet for ss of kidney now please
- glomerulus
- Bowman’s capsule
- proximal convoluted tubule
- loop of Henle
- distal convoluted tubule
- collecting duct
ss of kidney
- Renal artery carries oxyeganted blood to kidneys
- RA turns into afferent arterioles + blood transported to glomerelus (network of capillaries) which is in cup of renal capusule
- blood removed from glomerlus by effernt arteriole –> capillary network —> blood to renal vein
- EFFERENT IS NARROWER THAN AFFERENT = maintain high bp
- ureter takes urine from kidney to bladder
- begining of nephreon is renal capsule in the coretex
- tube from renal capsule to PCT –> medulla = loop of henle –> coretx —> DCT —> medulla = collecting duct = pelvis of kidney
formation of glomerular filtrate by ultrafiltration in the Bowman’s caps
Ultrafiltration
-ultrafiltration in glomerulas and BC
- higher pressure as Afferent arteriole wider than effernt arteriole
- to generate HIGH BP/ hydrostatic pressure ;
to force, plasma / fluid INTO BC
- Increased resist to blood flow
- capillary endothelium has / gaps / holes / pores ;
- so small mols/ glucose / AA water, can leave, blood/ capillary / glomerulus + ENTER , capsule / filtrate / tubule ;
- basement membrane forms filtration / selective, barrier ;
- Smaller than 68000mm can pass through
- RBC and large proteins cannot pass through
- podocytes increase SA for increased glomerular filtration rate
selective reabsorption in the proximal convoluted tubule
Process of selective reabsorption
- 100% of glucose reabosrbed
- Na2+ ions move out of cells into TF from PCT by AT using ATP/pump
- creates low conc of sodium ion inside PCT E cell
- Na2+ ions enter PCT E cell from lumen via FD
- w glucose by cotransport through COTRANSPORTER
- WP of cells decrease
- Na2+ ions enter down conc gradient
- Glucose enters against conc gradient
- Sodium ions and glucose create low WP
- Water enters PCT E cell by osmosis
- Glucose leaves PCT E cells –> blood via FD
- Blood low WP
- sodim/potassium pump in BM
- Water leaves PCT E cells into blood via osmosis
Adaptations of PCT for selective reabsorption
- many mitochondria to provide ATP for AT of Na2+ out of cells
- microvilli to increase SA= more protein channels, + co transporters can fit
- Cotransporters of glucose/AA into intraceullar fluid
- tight junctions to hold cells together to prevent leakage of fluid
excretion
removal of unwanted products of metabolism
substances that have to be re-absorbed
1) all glucose
2) vitamins
3) much of water
4) some inorganic ions e.g. Na and Cl ions
5) amino acids
⍺-cells of islets of Langerhans
secrete glucagon when blood glucose concentration is low
β-cells of islets of Langerhans
secrete insulin when blood glucose concentration is high
GLUT 1,2,4
G1= brain cells CSM
G2=liver cells CSM
G4=muscle and adipose
where is ADH produced + released into blood from?
- produced in hypothalamus
- stored + released from the posterior pituitary gland by neuroscretory cells
Explain how dip sticks function to test for glucose in a sample of urine. [8]
1) stick has a pad containing the immobilised enzymes
2) glucose oxidase + peroxidase
4) stick dipped in urine
5) glucose + O2 reacts w/ glucose oxidase = hydrogen peroxide
6) hydrogen peroxide reacts with a colourless substance (chromogen)/ peroxidase
7) chromoagen oxidised
7) to give a coloured substance aft color change
8) compare with colour chart
9) more glucose gives darker colour
Outline how a glucose biosensor works. [3]
1) pad contains glucose oxidase
2) put blood on strip of biosensor
2) glucose oxidase reacts with glucose in the blood = gluconic acid + hydrogen peroxide
3) oxygen detected
4) electric current generated/flow of e-
5) detected by platnium electrode
6) gives numerical value of bgc
presence of glucose and ketones in urine
- person may have diabetes.
- If the conc rises above the renal threshold, then not all glucose has been absorbed from the filtrate in PCT–> so will be present in the urine
monitoring water potential of blood
1) WP of blood is monitored by osmoreceptors in hypothalamus
2) when decrease is detected,osmoreceptors shrink + nerve impulses from neuroscrentory cells are sent along neurones to the posterior pituitary gland
3) stimulate the release of ADH
4) ADH reduces water loss in urine by making kidneys absorb as much as possible
ADH affect on kindeys
- ADH is signalling mol
- low WP detected by osmoreceptors in hypothalamus
- neurosecretory cells in the hypothalamus produce ADH.
- ADH is transported down specialised axons (of Neurosecratory cells which are specialized nerve cells) to the posterior pituitary gland
- When the ADH reaches the posterior pituitary, it is stored/immediately released into the blood
- ADH binds to receptors on CSM of collecting D
- Activates G protein + adenyl cyclase activated
- cAMP/second messanger produced + actiavets protein kinase/binds to kinase enzyme
- enzyme cascade +cAMP made from ATP
- activates active phosphorylase enzyme
- causes vesicles containing Aquaporin to move and fuse with CSM
- aquaporins added to collecting duct/increase CSM permeability to water
- water leaves CD + enters Medulla by FD through Aquaphor, and osmosis through PPM
- small vol of conc urine excreted
- increases WP to set point
Loop of henle
- Ascending limb imperable to water
- Na2+ and Cl- ions move out by AT into medulla = lowers WP in medulla
- Water enters medulla by osmosis
- at bottom of loop of henle, diffusion of Na2+ and Cl- ions by FD in osmoreg
- Longer loop of henle = more water reabsorbed into blood
- Counter current multiplier
- creates max conc of Na2+ ion inside and outside loop of henle
whats the Counter current multiplier
- when fluid flows in opp directions in limbs e.g ascending limb goes up + descending down
