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Bio A2 Level > 14 Homeostasis > Flashcards

14 Homeostasis Flashcards

1
Q

Happens in tubule

Describe and explain how all of the glucose in the glomerular filtrate is reabsorbed back into the blood

A

-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

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2
Q

explain what is meant by homeostasis and the importance of homeostasis in mammals

A
  • 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
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3
Q

define negative feedback

A
  • 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
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4
Q

positive feedback

A

enhances or accelerates the output created by an activated stimulus

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5
Q

Internal vs external stimuli

A

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

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6
Q

state urea is produced in the liver from the deamination of excess AA

Deamination

A
  • 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

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7
Q

look at quizlet for ss of kidney now please

A
  • glomerulus
  • Bowman’s capsule
  • proximal convoluted tubule
  • loop of Henle
  • distal convoluted tubule
  • collecting duct
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8
Q

ss of kidney

A
  • 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
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9
Q

formation of glomerular filtrate by ultrafiltration in the Bowman’s caps

Ultrafiltration

A

-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

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10
Q

selective reabsorption in the proximal convoluted tubule

Process of selective reabsorption

A
  • 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
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11
Q

Adaptations of PCT for selective reabsorption

A
  • 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
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12
Q

excretion

A

removal of unwanted products of metabolism

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13
Q

substances that have to be re-absorbed

A

1) all glucose
2) vitamins
3) much of water
4) some inorganic ions e.g. Na and Cl ions
5) amino acids

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14
Q

⍺-cells of islets of Langerhans

A

secrete glucagon when blood glucose concentration is low

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15
Q

β-cells of islets of Langerhans

A

secrete insulin when blood glucose concentration is high

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16
Q

GLUT 1,2,4

A

G1= brain cells CSM
G2=liver cells CSM
G4=muscle and adipose

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17
Q

where is ADH produced + released into blood from?

A
  • produced in hypothalamus
  • stored + released from the posterior pituitary gland by neuroscretory cells
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18
Q

Explain how dip sticks function to test for glucose in a sample of urine. [8]

A

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

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19
Q

Outline how a glucose biosensor works. [3]

A

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

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20
Q

presence of glucose and ketones in urine

A
  • 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
21
Q

monitoring water potential of blood

A

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

22
Q

ADH affect on kindeys

A
  • 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
23
Q

Loop of henle

A
  • 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
24
Q

whats the Counter current multiplier

A
  • when fluid flows in opp directions in limbs e.g ascending limb goes up + descending down
25
Q

Insulin role

A
  • rise in bgc
  • detected by B cells in islets of langerhans release insulin secreted and transported in blood
  • Insulin binds to receptor in CSM of muscle/liver cells
  • glucokinase phosphorylates glucose in liver cells/ increased absorption of glucose in liver
  • Vesicles w/ glucose cotransporter proteins/GLUT4 fuse w CSM of muscle/adipose cells
  • increases permebaility of glucose in muscle/adipose cells
  • Glucose diffuses into muscle cells down conc gradient
  • increasec cellular uptake of glucose in liver
  • convert glucose to glycogen for storage -activates glycogenesis
  • Increased protein/fat synthesis
  • decreases glycogenolysis
  • Increased rate of resp using glucose
  • Bgc falls, restores norm value via neg feedback
26
Q

factors affecting GFR

A
  1. High BP/Hydro pressure= WP between glomerlus + BC affects GFR
  2. Dehydration= low WP of blood, decreases GFR
  3. ……..
27
Q

Glucagon/adrenaline mode of action

A
  • bgc too low
  • detected by B cells
  • Stops srection of insulin
  • A cells in islets of langerhans in panrease release glucagon in blood
  • adrenaline released from adrenal glands
  • Glucagon + (adrenaline) cause liver cells to break down glycogen to glucose
  • Via glycogenolysis
  • Glucagon/ (adrenaline) bind to receptor in CSM on liver cells
  • Receptor undergoes conformational change + activates a G protein
  • activates adenylyl cyclas
  • catalyses conversion of ATP –>cAMP/second messenger
  • enzyme cascade in liver cells + amplifies signal
  • cAMP binds to inactive protein kinase enzyme + activated
  • phosphorylase kinase enzyme –> active phosphorylase kinase enzyme
  • inactive glycogen phsophorylase enzyme –> active glycogen phsophorylase enzyme
  • breaks 1-6 glycosidic bond
  • increases conc of glucose inside cell
  • glucose diffues through GLUT2 -> blood
  • Liver releaaes glucose into blood
  • Liver cells produce glucose from AA/lipids via gluconeogenesis
  • Fatty acids used in resp (0.7)
  • blood glucose conc rise
  • back to norm value/set point
  • glucagon secretion switched off
  • negative feedback
28
Q

DISPTICK VS BIOSENSOR

A
  • test glucose in urine vs test glucose in blood
  • immbobilized enzymes in both
  • glucose oxidase + peroxidase vs glucose oxidase
  • Comapre to color chart vs e- flow forms curreny detected by electrode
  • qualative vs quantative
  • K+ iodide chromagen indicator vs platinium electrode
29
Q

Factors stomata open due to

A

1) increasing light intensity
2) low carbon dioxide concentrations in the air spaces within the leaf/gain CO2 for photosynth
3) allows O2 out
4) allows transpiration stream to occur which brings water/mineral ion in for photosynth

30
Q

stomata close due to

A

1) darkness
2) high carbon dioxide concentrations in the air spaces in the leaf/Co2 not needed as no photosyn
3) low humidity
4) high temperature
5) to maintain turgidity, when the supply of water from the roots is limited and/or there are high rates of transpiration = prevent water loss

31
Q

explain how stomata have daily rhythms of opening and closing

A
  • Opening during the day maintains the inward diffusion of CO2 + outward diffusion of O2.
  • closure of stomata at night when photosynthesis cannot occur reduces rates of transpiration and conserves water.
32
Q

Guard cell ss

A
  • hoops of cellulose microfibrils = increase in length
    • curve apart/bend to open stomata = thin outer wall bends more easily than thick inner wall so GC curved and opens pore between w cells
  • each stomata has 2 guard cells
  • when GC turgid= change shape/curve apart + open and stomatal pore open
  • when GC flaccid = less bent + pore between in closed
33
Q

GC OPEN

A
  • ABA not present
  • Proton pump activated
  • Protons/H+ pumped out of GC by AT using ATP
  • lower conc of H+ inside cell + more neg than outside
  • K+ ions channel open + enter by FD
  • Cl- ions enter
  • to maintain charge of GC
  • lowers WP + water enters by osmosis
  • GC increases vol of water = GC turgid
  • inner wall thicker than outer wall so GC bends = stomata opens
34
Q

GC SHUT/CLOSED

A
  • ABA binds to receptors on CSM of GC + blocks/inhibits proton pump
  • prevents protons/H+ leaving GC
  • Ca2+ channels open + move in/influx by FD
  • Ca2+ acts a a second messenger
  • K+ diffuses out of the (guard) cell/efflux ;
  • WP (guard) cell increases ;
    -water leaves (guard) cell, by osmosis down WPG
  • (guard) cell becomes flaccid / cell volume decreases (so stoma closes) ;
35
Q

tumor formation

A
  • uncontrolled mitosis/continous cell cycle
  • no programmed cell death/apoptosis
  • mutation of tumor supressor gene (off)
36
Q

semi quantative dipstick why?

A
  • only 3 colors for + test/ small range
  • no numerical value measured
37
Q

describe role of glucagon

A
  • affects liver cells
  • promotoes glycogenolysis
  • promotes use of fatty aciids/AA in resp
  • promotes gluconeogenesis
  • results in rise in bgc back to norm/set point
38
Q

describe role of insulin

A
  • increases cellular uptake of glucose by liver/muscle cells
  • increased resp of glucose/increased glycolysis
  • inhibits glycogenolysis, causes conversion of glucose to glycogen
  • bgc between 80-120mg per 100cm3
39
Q

define endocrine gland

A
  • ductless gland
  • secretes hormone into blood
40
Q

describe parts of pancreas involved in endocrine function

A
  • islets of langerhans
  • a + b cells
  • scattered throighout pancreas
  • blood supply carry hormones away
41
Q

2 adv of treating diabetes w insulin produced by gene tech

A
  • identical to human insulin
  • fewer rejection issues/side effects/allergic reactions
  • ethical/moral/religious reasons
  • cheap to produce in large vol
  • less risk of transmitting disease/infection
42
Q

outline impt of homeostasis in a mammalw several examples

A
  1. Maintence of constant internal enviornment
  2. blood or TF as internal E
  3. back to norm/set point within narrow limits
  4. low temp= slow metabolism/enzymes less active
  5. high temp= enzymes denatured
  6. low WP= water leaves cells/cells shrink/crenation
  7. high WP= water enter cells/cells burst
  8. low bgc= less respiration
  9. high bgc= water leaves cells/cells shrink/crenated
43
Q

describe ss of kidney

A
  1. Cortex
  2. medulla
  3. pelvis
  4. renal artery
  5. renal vein
  6. nephron
  7. PCT + DCT = renal capsule
  8. loop of henle/Collecting duct IN medulla
  9. glomerelus
  10. afferent + efferent arterioles
  11. capillary network in medulla surrounding tubule
44
Q

ENDOCRINE VS NERVOUS SS

A

Endorcrine:
- hormones
- chemical messangers
- ductless glands released into blood
- target organs/cells
- receptors on CSM
- e.g insulin to reduced bgc by convertingglucose to glycogen
- slow effect
- longer lasting
- widespread effect

Nervous:
- action poetntials/impulses
- along neurones/axon
- synapse w/ target/NMJ
- effector/motor neurones
- receptor/sensory neuorone
- faster effect
- shorter lasting
- targeted effect

45
Q

If the water potential of the blood is too high/increase in vol , the exact opposite happens:

A
  • Osmoreceptors in the hypothalamus are not stimulated
  • No nerve impulses are sent to the posterior pituitary gland
  • No ADH released
  • Aquaporins are moved out of the luminal membranes of the collecting duct cells
  • Collecting duct cells are no longer permeable to water
  • The filtrate flows along collecting duct but loses no water and is very dilute
    A large volume of dilute urine is produced
  • This flows from the kidneys, through the ureters and into the bladder
46
Q

explain how if only 80% of Na+ ions in GF absorbed and 20% excreted this would affect normal water absoprtion

A
  • fewer sodium (ions) reabsorbed / more sodium (ions) in filtrate ;
    -decreases WP of filtrate
  • increases WP of the medulla
  • less water reabsorbed, by osmosis down WPG
    -increases volume of urine so blood volume reduced
47
Q

role of aquaporin

A
  • aquaporins are) water channel (proteins) ;
  • (more) aquaporins increase (cell surface) membrane permeability (to water) ; ora
  • of collecting duct (cells)
    -allow water to, be reabsorbed / move into tissue fluid or blood
48
Q

BM and podocytes role in forming GF

A

A basement membrane
1 acts as a, filter / filtration barrier ;
2 only, named molecules / ions / molecules less than 68 000–70 000 (R)MM,
can pass through
or
red blood cells / large proteins, cannot pass through ;

B podocyte
3 has, gaps / slits / projections / pores ;
4 allows, fluid / water / filtrate, to pass into the / Bowman’s capsule ;

Bio A2 Level (8 decks)

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