3.6.4 Homeostasis is the maintenance of a stable internal enviroment Flashcards
3.6.4 Homeostasis is the maintenance of a stable internal enviroment
define homeostasis
Homeostasis is the maintenance of a constant internal environment within a living organism despite fluctuations in its external and internal environment
what is it meant by internal enviroment
the internal conditions that are present within a living organism
list seven things that are controlled in the body of a mammal
tempreature
water potential (solute)
waste (like CO2 and urea)
concentration of oxygen
blood pressure
glycose
amino acids
pH
Why is homeostasis important?
Enzymes are sensitive.
Homeostasis will keep the fluctuations of temperature, pH and concentrations minimal so that enzymes can continue to function at their optimum rate.
give three examples of homiostasis
Glucoregulation = keeping blood sugar levels constant
Thermoregulation = keeping body temperature constant at 37 °c
Osmoregulation = keeping water and ion levels constant
how would an animal have a greater chance of surviving if there external enviroment is extream for them
by modifying there internal enviroment
what are the 5 things needed for homiostasis inorder to change its internal enviroment
The optimum point. This is monitored by:
A receptor which detects any deviation from the optimum point and sends a signal to:
A co-ordinator which sends information in the form of chemical hormones or nerve impulses from the receptor to an:
Effector which is either a muscle or gland which causes changes to return the system to the optimum point. This return to normality creates a:
Negative Feedback mechanism
what is a dynamic equilibrium
Dynamic equilibrium refers to a condition in which the parts of a system are in continuous motion, but they move in opposing directions at equal rates so that the system as a whole does not change.
what do Alpha cells secreate
glycogon
they are also larger than beta cells
waht do Beta - cells secreate
insulin
they are also smaller than alpha cells
what are the two system within the pancrease and give a small breife on them
hint : one is for digestion and one is for glycoregulation
exocrine - secreates pancreatic enzymes into the pancreatic duct
endocrine - contains islets of langerhan which contain alpha and beta cells wich secreate insulin and glycogon homones into the blood vessels
give an example of positive feedback
action potential - when the threshold is reached depolarisation with allways reach the action potential
pregnancy - cervix keeps growing bigger the more you push
waht is a feed back loop
when a receptor is informed of the new changes
what could ulter your normal blood glucose level
Hormones:
Insulin
Glucagon
Adrenaline
diet , and storage of glucose from liver and muscles can ulter the level of concentration of blood glucose
also glucose
where are carbohydrates digested into glucose
mouth
duodenum
Ileum
where is glucose absorbed
the the epithelial cells via co-transport into the blood vessels
what is role of the pancreas in regulating blood glucose:
The pancreas detects the concentration of glucose in the blood
The pancreas produces digestive enzymes (protease, amylase and lipase)
The pancreas produces the hormones insulin and glucagon for regulating blood glucose.
waht is islets of langerhan
The islets of langerhan are groups of hormone producing cells within the pancreas
what are the effects of having a high blood glucose level
Lowers water potential in the blood. Water diffuses out of the cells by osmosis into the blood
This leads to thirst and a lot of urine being produced
Very high blood glucose can damage brain cells, causing a coma.
High blood glucose encourages bacterial growth on the skin, leading to infections (e.g. boils, thrush)
Bacterial growth on skin means wounds are slow to heal
High glucose levels in the eye can enter the fluid of the lens and cause cloudiness.
what are the effects of having a low blood glucose level
Low blood glucose causes tiredness/fatigue, trembling, sweating and shakiness
More severe cases can cause confusion, blurred vision, headache and a difficulty concentrating
Extreme low blood sugar can result in a loss of consciousness
what effect does insulin have on uptake of glucose
it opens gated glucose channels
or makes vesicles with glucose gated channels on them which fuse with the membrane making the cell more permiable to glucose.
how does insulin help reduce blood glucose levels down
High blood glucose detected by Beta cells of pancreas
Pancreas releases insulin into the blood. This helps to lower blood glucose in a number of ways:
- Insulin binds with cell surface glycoprotein receptors and causes a change in the tertiary structure of glucose transport protein channels so channels open which increases the rate of absorption of glucose into the cells.
- Insulin activates enzymes in the liver to convert glucose to insoluble glycogen (glycogenesis)
- Insulin converts glucose to fats
- Insulin also increases the respiratory rate of cells which therefore burns glucose in oxidation
Glucose level drops in liver and sets up a concentration gradient so glucose diffuses from the blood into the liver
Blood glucose level drops
coverts glucose to lipds by activating enzymes
how does glycogon increase glucose levels up
Low blood glucose detected by alpha cells in pancreas
Pancreas releases glucagon
Glucagon binds to liver receptor cells
Glucagon activates enzymes to increase breakdown of stored glycogen in liver and muscles to soluble glucose (. Glycogenolysis)
Glucagon also causes amino acids and glycerol to combine in the liver to form glucose (Gluconeogenesis)
Glucose level in liver rises which sets up a concentration gradient between liver and the blood
Glucose diffuses into the blood
Blood glucose concentration increases
what is the facy word for converting glucose to glycogen
glycogenesis
what is the facy word for glycogen to glucose
glycogenolysis
what is the facy word for amino acids / glycerol ( lipids) to glucose
Gluconeogenesis
describe the second messenger midel
1) glycogon / hormones bind to receptor that is spesific to them in the liver or muscle e.g. glycogon reseptor ( these hormones are called the first messenger molecules )
2) this activates the G protien which then activates the adenyl cyclase
3) when adenyl cyclase is activated it causes ATP to form into cyclic ATP (second messenger molcule)
4) cyclic ATP causes inactive protein kinase to activates
5) active protein kinase causes inactive phophorylase to turn into active phosphorylase
6) which then cause glycogen to conver to glucose
what is the advantage of the 2nd messenger model
allows for a range of hormones to controll one action , which may be beneficial to survival
Effects of Adrenaline info card
Adrenaline released on excitement or stress
Adrenaline binds to liver receptors and activates the enzyme causing breakdown of glycogen to glucose and also inactivates the enzyme which synthesizes glycogen from glucose
The combined effect raises blood glucose level by glycogenolysis which allows greater respiration and ATP production
Increases Heart rate to speed up blood flow
Constricts arterioles to digestive system
Dilates arterioles to liver and muscles increasing blood flow and supply of glucose and oxygen
Pupils dilate
what are the symptoms of diabetes
Lack of insulin will cause high blood glucose.
The kidney filtrate will also contain high glucose concentration and glucose is excreted in urine
Due to the high level of glucose in the kidney Filtrate, the water potential of the filtrate will be low so water will diffuse out of the blood and will not enter the blood from the filtrate.
High water content of kidney filtrate will result in more urine.
The blood and body will be dehydrated.
Brain cells will detect lower water content and there will be a sensation of thirst.
Glucose will not be entering cells and weight loss will occur also tiredness & blurred vision due to clouding of the lens.
High blood glucose encourages bacteria and skin infections e.g. boils & thrush.
what is type one diabetes
and how is it managed
Autoimmune disease which destroys Beta insulin producing cells in pancreas
No insulin released so glucose channels remain shut
Managed by :
Diet: mainly starches that are digested slowly so prevents sudden rise in blood glucose levels.
Insulin injection at regular times e.g. after breakfast. (may include genetically engineered insulin). Insulin injections not given orally, since insulin is a protein and it would be digested.
Blood glucose needs to be monitored to calculate insulin dose.
waht is type two diabetes
and how is it managed
Insulin is produced but receptor cells are desensitized to insulin
Receptor cells become furred up by fats so insulin cannot bind
If some insulin does bind the channels will not open properly
Glycoprotein receptors are lost so less insulin binds and less glucose can enter
Managed by:
Control of carbohydrate intake in diet.
Weight loss
Drugs to slow the rate of carbohydrate absorption from intestine.
Add more Insulin
what is osmoregulation
Osmoregulation - The control of the water content and solute composition of body fluids
why are kidneys important
They remove nitrogenous waste material – urea
They are involved in osmoregulation. That is they help to maintain the water potential of the blood within narrow limits.
draw out a kidney structure
https://open.oregonstate.education/aandp/chapter/25-1-internal-and-external-anatomy-of-the-kidney/
should have :
medulla
cortex
renal artiery/vein
ureter
pyrimid
renal pelvis
nephron
draw out the structure of a nephron with an affrant and effrant arteiols
affront goes in , effront goes out
https://www.youtube.com/watch?app=desktop&v=T4y0qpcFH50
how is urea formed not spec
Amino acids are formed by digestion of protein
Excess amino acids cannot be
stored in the body
Excess amino acids are metabolised
by the liver in a process called DEAMINATION
Ammonia is a waste product of this metabolic process.
Ammonia is a strong alkali.
(the rest of the deaminated amino acid becomes an organic acid that can be respired in Krebs cycle and yield ATP)
Ammonia combines with another waste product of metabolism, carbon dioxide and urea is formed.
list four functions of the kidney and the part of the nephron which carries out the functions
ultrafiltration - glomeris and bowmans capsule
selective reabsorbtion - proximal conviluted tubual
secreation of Na+ and Cl- -controll of blood pH distilate conviluted tuble
osmoregulation - acending and decending limb
where does controll of blood pH happen
distle convoluted tuble
what is ultrafiltration and describe how it works
The renal artery (containing urea) divides to form the afferent arterioles to supply the nephrons with blood.
Each arteriole divides many times to form a knot of capillaries called the glomerulus.
The tiny branches of capillaries re-join to form the efferent arteriole to take away blood clean of urea) from the nephron.
Afferent arteriole is wider than the efferent arteriole.
This creates a higher blood pressure than normal in the glomerulus (high hydrostatic pressure). (Like a bottle neck).
ultrafiltrate forms what
glomerular filtrate
comapre the shape of the afferent arteriol and the glomerious
afferent artierol is larger than the glomerious
what is the basement membrane made of
made of collogen and glycoproteins
what are the hole cells called in the bowmans capsule
podocytes
what is diffrent in glomerious cappiliary cells compared to regular capilliary cells
glomerious capilliary cells have holes / lot more than regular ones
how do things move from the capilliarys to become glomerous filtrate
capilary holes in glomerous , then through basement membrane then though the podocytes into the proximal conviluted tuble
what are the chemicals that leave the blood by ultrafiltration
Na + / Cl-
water
glucose
amino acids
urea
vitamins
chemicals and structurs that do not leave the blood by ultrafiltration
proteins / enzymes
red blood cells / cells
what is the definition of ultrafiltration
a High pressure filtration through semipermiable membrane in which large particals are retained while small sized and the solvent are forced to move across the membrane by hydrostatic pressure
name 4 materials that are reabsorbed in the proximal conviluted tubual
water
glucose
amino acids
na + / cl - / Ca 2+
what happens in selective reabsorbtion
The process of control and regulation in the kidney begins with a non discriminating filtration (ultrafiltration) that removes just as many useful substances as harmful ones from the blood to make filtrate.
The kidney then takes back from the filtrate to the blood those substances that it still requires in the blood.(Selective Reabsorption)
The beauty of the way the kidney works is that it is able to control how much of a substance it reabsorbs back into the blood (Regulation)
Reabsorb water by osmosis *N.B. Most water reabsorbed here
Reabsorb all glucose by active transport (co transport)
Reabsorb Na+ and Cl- by active transport
Not to reabsorb urea
i.e. this is the selective nature – urea is not absorbed!
How is water reabsorbed? in selective reabsorbtion
The blood leaving the Glomerulus has a very low water potential because it has retained the large soluble plasma proteins and very little water after ultrafiltration
In the glomerular filtrate there is a high water potential due too much water and fewer solutes compared to the tissue fluid in the kidney and the blood in the efferent arteriole (blood vessels around the pct)
So water moves by osmosis from the filtrate into the blood
how are sodium ions reabsorbed in selective reabsorbstion
Sodium ions are actively transported out of the cells lining the proximal convoluted tubule into blood capillaries which carry them away.
This lowers the sodium concentration of the sodium ions in these cells so that sodium ions will diffuse from the lumen of the proximal convoluted tubule into the epithelial cells through carrier proteins down a concentration gradient by facilitated diffusion.
Reabsorption of glucose and amino acids in selective reabsorbtion
Glucose and amino acids are transported along with sodium ions by specific protein carriers into the epithelial cells (This is co-transport) generating a high concentration within them.
Glucose and amino acids move then by Facilitated
diffusion into the blood as there is a concentration gradient which is maintained by the flow of blood
Reabsorption of chloride ions. in selsctive reabsorbtion
This occurs in a similar way to glucose and amino acids i.e. co- transport with sodium ions using protein carrier molecules
what are the two adaptions of the proximal conviluted tuble
lots of micro villi
lotsof mitochondria
what are two adaptations of cells in the proximal convulited tubels
tightly packed cells also capiliarys are close to the cell
lots of transport proteins
describe the loop of henle
The numerous Loops of Henlé concentrates salt by creating a water potential gradient in the tissue fluid of the medulla of the kidney
This high concentration of salt causes an osmotic flow of water out of the collecting ducts thereby concentrating the urine making it hypertonic to the blood.
This uses a principle called a hair-pin counter current multiplier
Is a hair pin loop runs deep into the medulla (the descending limb) and back to cortex (the ascending limb).
The ascending limb is permeable to salts and impermeable to water.
The descending limb is permeable to water and less permeable to salts.
what is it meant by the counter current flow
when two liquids flow in opposite directions past each other the exchange of substances is greater than if they flowed in the same diraction
describe how the loop of henle performs osmoregulation
1) Na+ and Cl- ions are
actively pumped out of
the ascending limb.
2) This creates a
decreasing y in
interstitial region.
3) Walls of descending
limb are permeable to
water so water leaves
by osmosis into
interstitial space before
entering capillaries
(Vasa Recta).
4)Water is progressively
lost down the descending
limb reaching -1200 Kpa
at the base. (*Longer
loops can reach much
lower water potential).
5) water potential of filtrate rises up the
ascending limb as Na+
and Cl- ions are actively
pumped out.
6) This creates a decreasing
water potential as you descend in the
medulla.
7) Water passes out of
collecting duct by
osmosis into interstitial
region before being
passing into blood
vessels that occupy this
space.
8) As water passes out of
filtrate in collecting duct
water potential is lowered. The y of
the filtrate is always
higher than the interstitial
region so water will
continue to leave by
osmosis. This is referred
to as a counter current
multiplier. i.e. when two
liquids flow in opposite
directions past each other
the exchange of
substances between them
is greater than if they
flowed in the same
direction**.
** remember the gills?
what is the function of the distal convoluted tubule and how can it be affected
Cells are similar to PCT, they possess microvilli, many mitochondria.
They are affected by ADH.
Some water is absorbed here
The main role of the DCT is to make final adjustment to the salts that are reabsorbed and to control blood pH by selecting which ions to absorb.
The permeability of the cells in the walls of the DCT can be altered by various hormones.
what does ADH do
ADH inserts more aqua porins in the membranes of the cells of the DCT and collecting duct.
These means that
more water will be reabsorbed from the filtrate and go back into the blood.
how are ADH (anti diaretic hormones relesed)
Osmoreceptors in brain’s Hypothalamus detect a lower blood water potential , then send impulses to the Posterior Lobe of the Pituitary Gland which secretes Anti Diuretic Hormone (ADH) into blood.
The target cells are the epithelial cells that make up the wall of the DCT and Collecting Duct
ADH molecules bind to protein receptors on the cell-surface membrane of these epithelial cells leading to the activation of an enzyme called phosphorylase within the cell
The activation of phosphorylase causes vesicles within the cell to move to, and fuse with the its cell-surface membrane
These vesicles contain aquaporins (water channel proteins) which when inserted into the cell membrane of the epithelial cells in the wall of the collecting duct making these epithelial cells to water much more permeable to water.
