Homeostasis Flashcards
1
Q
What is homeostasis
A
- same state
- maintaining internal body environment
- stability
2
Q
Importance of homeostasis
A
- enzyme activity
- proteins, receptors opt temp and pH
- water potential of blood and tissue fluid
- blood glucose concentration
- ability to survive in external environments in extremes
3
Q
Importance of maintaining glucose
A
- if too high water pot reduced causing water to diffuse out of cells by osmosis - will shrivel and die
- if too low cells unable to metabolise or respire properly to provide energy
4
Q
Negative feedback
A
- effectors to counteract change if too high or to low
- back to normal
- e.g.body temp kept at 37 degrees C roughly
- if too BIG of a change then can’t reverse
5
Q
Positive feedback mechanisms
A
- amplify change from normal level
- effector increase level away form normal
- e.g. blood clot after injury
- ## hypothermia = low body temp
6
Q
How is blood glucose monitored
A
Cells in pancreas
7
Q
What happens when there is excess glucose
A
- blood plasma and tissue fluid around cells too concentrated
- damages cells e.g. shrinking RBC
8
Q
Low bloos sugar causes …
A
Make cells swell up and burst
LYSIS
9
Q
What is islets of langerhans
A
- structure in pancreas
- contains alpha cells = secrete glucagon
- beta cells = secrete insulin
10
Q
Function of insulin
A
- lowers blood glucose concentration when too high
- binds to receptors on membranes of liver and muscle cells
- increases permeability of muscle cell membranes to glucose so the cell takes up more glucose
- increased number of channel proteins
11
Q
Insulin and enzymes
A
- activated enzymes in liver and muscle cells converting glucose to glycogen
- cells store glycogen on cytoplasm as energy source
- increases rate or respiration
12
Q
Process of forming glycogen from glucose
A
Glycogensis
13
Q
Function of glucagon
A
- raises blood glucose concentration when too low
- binds to specific receptors
- activated enzymes to break down glycogen to glucose
- decreases rate of respiration
14
Q
Glycogen to glucose
A
Glycogenolysis
15
Q
Process of forming glucose from non-carbohydrates
A
Gluconeogenesis
16
Q
Beta cells responce and insulin
A
- Receptors in beta cells detect rise in blood glucose
- Beta cells make insulin which goes to blood
- Insulin combines with receptors on body cells (except rbc)
- Glucose transports carrier proteins tertiary structure alters and they change shape + open (facilitated diffusion)
- Vecicles constraining more glucose transport and fuses with membrane increasing number of carrier proteins
17
Q
Adrenaline function
A
- hormone secreted from adrenal glands
- secreted when low concentration of glucose in blood when stressed or excited
- binds to receptors in cell membranes or liver cells
- activates glycogenolysis
- inhibits glycogenosis
- activates glucagon secretion and inhibits insulin secretion
- flight or fight
18
Q
How do adrenaline and glucagon activate glycogenolysis inside cell even tho they bind to receptors on outside of cell …
A
- specific tertiary structures comp to hormones
- activate enzyme adenylate cyclase
- this converts ATP into chemicals signal called “second messenger”
- called cyclic AMP (cAMP)
- camp activates protein kinase A activating cascade (chan of reactions) that breaks down glycogen to glucose - glycogenolysis
19
Q
Type 1 diabetes
A
- pancreas fails to produce insulin to control blood glucose
- triggered by autoimmune response when T cells attack B cells
- lack of insulin affects glycogen stores
- symptom of fatigue
- insulin net ions + appropriate diet
20
Q
Type 2 diabetes
A
- pancreas still produces insulin but receptors have reduces in number or no longer respond to it
- reduced sensitivity to insulin
- sugar and fat controlled diet + exercise regime
21
Q
Components to the kidney
A
- renal capsules
- renal pelvis
- medulla
- renal artery
- calyces
- renal vein
- ureter
22
Q
Function of kidney
A
- excrete waste products like urea
- regulate water potential
- cortex filters blood
23
Q
Ultrafiltration
A
- blood passes through capillaries in cortex of kidneys
- substances filtered out into long tubules that surround capillaries
24
Q
Cortex
A
Outer layer
25
Unwanted substances go where?
Bladder
26
Proximal convoluted tubule
- na+ actively transported from tubule cell into blood to maintain diffusion gradient in tubule cell
- na+ diffuse from filtrate into tubule fell through co-transporter by facilitated diffusion
27
Nephrons
- long tubules along with bundle of capillaries where blood is filtered
(1 million in each kidney)
28
Where does blood enter
Small arterioles in cortex
29
Glomerulus
- arterioles split into glomeruli which are bundles of capillaries looped in side a hollow ball called the bowman’s capsule
30
Bowman’s capsule
- bundle of capillaries looped inside hollow ball hollow ball
- where ultrafiltration takes place
31
Affferent arteriole
- takes blood into each glomerulus
32
Efferent arteriole
- takes blood away from glomerulus
- smaller diameter to afferent
- so blood in glomerulus is under higher pressure
- forces liquid and molecules in blood OUT of capillary and in to bowman’s capsule
33
Where does liquid and small molecules travel
- though 3 layers to get to bowman’s capsule
- enter nephron tubules - capillary wall, basement membrane and BC epithelium
34
What happens to large molecules in the kidney
- large molecules like proteins and blood cells can’t pass though
- stay in blood
-
35
Substance entering bowman’s capsule
Glomerular filtrate
36
What and where does the glomerular filtrate go and do
- passes along nephron so useful substances are absorbed
- passes through collecting duct
- passes out of kidney along ureter
37
Where are useful substances reabsorbed
Nephron tubules
38
Where does selective rtsbsorption take place
Glomerular filtrate flows along:
- proximal convoluted tubule (PCT)
- loop of Henle
- distal convoluted tubule (DCT)
39
Where doe useful substances go
- leave nephrons and enter capillary network surrounding them
- reabsorbed by epithelium with microvilli (large SA)
- glucose (useful solute) reabsorbed along PCT by active transport and facilitated diffusion
- water enters blood by osmosis due to lower WP in blood than filtrate
- water reabsorbed by PCT, LOH, DCT and collecting duct
- filtrate remains in urine passing along ureter to bladder
40
What’s in urine
Water
Dissolved salts
Urea
Hormones
Excess vitamins
41
What’s not in urine
Proteins
Blood cells
Glucose
42
How is water potential controlled in the blood
Kidneys - osmoregulation
43
How is water lost
Excretion
Urea
Sweat
44
What happens if WP in blood is low (dehydrated)
-more water reabsorbed by osmosis into blood form tubules of nephrons
- concentrates urine so less water lost during excretion
45
What is WP too high - too hydrated
- less water reabsorbed into blood from nephron tubules
- urine diluted so more water lost during excretion
46
Where does water regulation take place
- loop of Henle
- DCT
- collecting duct
- controlled by hormones
47
Where is loop of Henle
Medulla - inner layer of kidneys
48
What is LOH made up of
Ascending limb
Descending limb
- control movement of sodium ions so water can be reabsorbed by blood
49
Where does blood enter kidney
Renal artery
Though small arteriolar in cortex
50
Arterioles
Split into glomerulus - bundle of capillaries looped inside hollow ball called - Bowman’s capsule
51
Bowman’s capsule
- bundle of capillaries inside hollow ball
- where ultrafiltration happens
-
52
Loop of Henle
Maintains sodium gradient
53
Ascending limb
- na+ pumped out into medial by AT
- impermeable to water so water stays inside tubule
- creates low WP in medulla due to high conc of ions
- bottom of AL, na+ diffuse out into medulla lowering WP
- no aquaportins
- nacl diffuses out by AT
54
Pathway of filtrate and water through kidney system
- bowman’s capsule
- PCT
- loop of Henle
- DCT
- collecting duct
55
Descending limb
- water out as lower WP in medulla by osmosis
- permeable to water
- makes filtrate more concentrated as ions CANT diffuse out
- water in medulla reabsorbed into blood through capillary
- aquaporins for water to move out and into interstitial fluid
- continuous increasing solute conc down DL as water diffuses out
56
DCT
Walter moves out distal convoluted tubule by osmosis and reabsorbed into blood
57
What causes water reabsorption after loop of Henle
- increase in ion concentration in medulla lowers WP
- water moves out of collecting duct by osmosis
- water reabsorbed into blood by through capillary network
58
How can volume of water reabsorbed into capillaries be controlled
By changing the permeability of DCT and collecting duct
59
Water reabsorption controlled by…
Hormones
60
Where are osmoreceptors
Part of brain called hypothalamus
61
Decrease in water potential in blood ….
- water moves out of osmoreceptor cells by osmosis
- cell volume decreases
- sends signal to other cells in hypothalamus
- signal to posterior pituitary gland
- release of hormone ADH (antidiuretic hormone) in blood
62
Function of ADH
Makes wall of collecting duct and DCT more permeable to water so more water can be reabsorbed from tubules in medulla by osmosis
- small amounts of concentrated urine produced meaning guess water loss
63
ADH when dehydrated
- ADH level rises If water content/ potential drops
- detected by osmoreceptors
- PPG stimulated to release more ADH
- DCT and collecting ducts more permeable to water
- less water loss due to les more concentrate urine released
64
ADH when hydrated
- ADH levels fall When high WP
- osmoreceptors dented and PPG release less ADH
- DCT and CD less permeable
- less water reabsorption
- more water excreted and more diluted urine
65
Loop of Henle mechanism
- counter current mechanism
-
66
Interstitial fluid
Hypertonic so water diffused in from descending limb
- higher solute conc than filtrate
67
DCT
Ph regulation
