3.6.4 Homeostasis is the maintenance of a stable internal enviroment

Question 1

define homeostasis

Answer 1

Homeostasis is the maintenance of a constant internal environment within a living organism despite fluctuations in its external and internal environment

Question 2

what is it meant by internal enviroment

Answer 2

the internal conditions that are present within a living organism

Question 3

list seven things that are controlled in the body of a mammal

Answer 3

tempreature
water potential (solute)
waste (like CO2 and urea)
concentration of oxygen
blood pressure
glycose
amino acids
pH

Question 4

Why is homeostasis important?

Answer 4

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.

Question 5

give three examples of homiostasis

Answer 5

Glucoregulation = keeping blood sugar levels constant

Thermoregulation = keeping body temperature constant at 37 °c

Osmoregulation = keeping water and ion levels constant

Question 6

how would an animal have a greater chance of surviving if there external enviroment is extream for them

Answer 6

by modifying there internal enviroment

Question 7

what are the 5 things needed for homiostasis inorder to change its internal enviroment

Answer 7

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

Question 8

what is a dynamic equilibrium

Answer 8

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.

Question 9

what do Alpha cells secreate

Answer 9

glycogon

they are also larger than beta cells

Question 10

waht do Beta - cells secreate

Answer 10

insulin

they are also smaller than alpha cells

Question 11

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

Answer 11

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

Question 12

give an example of positive feedback

Answer 12

action potential - when the threshold is reached depolarisation with allways reach the action potential

pregnancy - cervix keeps growing bigger the more you push

Question 13

waht is a feed back loop

Answer 13

when a receptor is informed of the new changes

Question 14

what could ulter your normal blood glucose level

Answer 14

Hormones:
Insulin
Glucagon
Adrenaline

diet , and storage of glucose from liver and muscles can ulter the level of concentration of blood glucose

also glucose

Question 15

where are carbohydrates digested into glucose

Answer 15

mouth
duodenum
Ileum

Question 16

where is glucose absorbed

Answer 16

the the epithelial cells via co-transport into the blood vessels

Question 17

what is role of the pancreas in regulating blood glucose:

Answer 17

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.

Question 18

waht is islets of langerhan

Answer 18

The islets of langerhan are groups of hormone producing cells within the pancreas

Question 19

what are the effects of having a high blood glucose level

Answer 19

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.

Question 20

what are the effects of having a low blood glucose level

Answer 20

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

Question 21

what effect does insulin have on uptake of glucose

Answer 21

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.

Question 22

how does insulin help reduce blood glucose levels down

Answer 22

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:

1. 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.
2. Insulin activates enzymes in the liver to convert glucose to insoluble glycogen (glycogenesis)
3. Insulin converts glucose to fats
4. 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

Question 23

how does glycogon increase glucose levels up

Answer 23

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

Question 24

what is the facy word for converting glucose to glycogen

Answer 24

glycogenesis

Question 25

what is the facy word for glycogen to glucose

Answer 25

glycogenolysis

Question 26

what is the facy word for amino acids / glycerol ( lipids) to glucose

Answer 26

Gluconeogenesis

Question 27

describe the second messenger midel

Answer 27

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

Question 28

what is the advantage of the 2nd messenger model

Answer 28

allows for a range of hormones to controll one action , which may be beneficial to survival

Question 29

Effects of Adrenaline info card

Answer 29

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

Question 30

what are the symptoms of diabetes

Answer 30

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.

Question 31

what is type one diabetes

and how is it managed

Answer 31

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.

Question 32

waht is type two diabetes

and how is it managed

Answer 32

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

Question 33

what is osmoregulation

Answer 33

Osmoregulation - The control of the water content and solute composition of body fluids

Question 34

why are kidneys important

Answer 34

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.

Question 35

draw out a kidney structure

Answer 35

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

Question 36

draw out the structure of a nephron with an affrant and effrant arteiols

Answer 36

affront goes in , effront goes out

https://www.youtube.com/watch?app=desktop&v=T4y0qpcFH50

Question 37

how is urea formed not spec

Answer 37

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.

Question 38

list four functions of the kidney and the part of the nephron which carries out the functions

Answer 38

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

Question 39

where does controll of blood pH happen

Answer 39

distle convoluted tuble

Question 40

what is ultrafiltration and describe how it works

Answer 40

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).

Question 41

ultrafiltrate forms what

Answer 41

glomerular filtrate

Question 42

comapre the shape of the afferent arteriol and the glomerious

Answer 42

afferent artierol is larger than the glomerious

Question 43

what is the basement membrane made of

Answer 43

made of collogen and glycoproteins

Question 44

what are the hole cells called in the bowmans capsule

Answer 44

podocytes

Question 45

what is diffrent in glomerious cappiliary cells compared to regular capilliary cells

Answer 45

glomerious capilliary cells have holes / lot more than regular ones

Question 46

how do things move from the capilliarys to become glomerous filtrate

Answer 46

capilary holes in glomerous , then through basement membrane then though the podocytes into the proximal conviluted tuble

Question 47

what are the chemicals that leave the blood by ultrafiltration

Answer 47

Na + / Cl-
water
glucose
amino acids
urea
vitamins

Question 48

chemicals and structurs that do not leave the blood by ultrafiltration

Answer 48

proteins / enzymes
red blood cells / cells

Question 49

what is the definition of ultrafiltration

Answer 49

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

Question 50

name 4 materials that are reabsorbed in the proximal conviluted tubual

Answer 50

water
glucose
amino acids
na + / cl - / Ca 2+

Question 51

what happens in selective reabsorbtion

Answer 51

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!

Question 52

How is water reabsorbed? in selective reabsorbtion

Answer 52

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

Question 53

how are sodium ions reabsorbed in selective reabsorbstion

Answer 53

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.

Question 54

Reabsorption of glucose and amino acids in selective reabsorbtion

Answer 54

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

Question 55

Reabsorption of chloride ions. in selsctive reabsorbtion

Answer 55

This occurs in a similar way to glucose and amino acids i.e. co- transport with sodium ions using protein carrier molecules

Question 56

what are the two adaptions of the proximal conviluted tuble

Answer 56

lots of micro villi

lotsof mitochondria

Question 57

what are two adaptations of cells in the proximal convulited tubels

Answer 57

tightly packed cells also capiliarys are close to the cell

lots of transport proteins

Question 58

describe the loop of henle

Answer 58

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.

Question 59

what is it meant by the counter current flow

Answer 59

when two liquids flow in opposite directions past each other the exchange of substances is greater than if they flowed in the same diraction

Question 60

describe how the loop of henle performs osmoregulation

Answer 60

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?

Question 61

what is the function of the distal convoluted tubule and how can it be affected

Answer 61

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.

Question 62

what does ADH do

Answer 62

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.

Question 63

how are ADH (anti diaretic hormones relesed)

Answer 63

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.