Homeostasis 6.4

Question 1

What is homeostasis?

Answer 1

Maintaining a constant internal environment within retracted limits

Question 2

What happens if core body temperature gets too high?

Answer 2

-Hydrogen bonds in enzymes break
-Changes the tertiary structure
-Active site changes shape
-Less enzymes substrate complexes

Question 3

What happens if core body temperature gets too low?

Answer 3

-Enzymes kinetic energy too low
-Less enzyme substrate complexes form
-Metablolic rate is reduced

Question 4

What happens if Blood PH gets too high or low?

Answer 4

Hydrogen bonds break within proteins changing their tertiary structure

Question 5

What happens if Blood glucose concentration gets too high?

Answer 5

Blood has lower water potential than cells
Water leaves cells into blood by osmosis
Cells lack water for metabolic reactions eg hydrolysis

Question 6

What happens if Blood glucose concentration gets too low?

Answer 6

Glucose is not provided to cells fast enough for a high rate of respiration

Question 7

What happens if Blood water potential gets too high?

Answer 7

Water enters cells by osmosis
Too much water causes cell lysis
Lots of water in the blood causes high blood pressure

Question 8

What happens if Blood water potential gets too low?

Answer 8

Water leaves cells into blood by osmosis
Lack of water for metabollic reactions and to act as a solvent

Question 9

What is the definition of a negative feedback mechanism? Give an example

Answer 9

Reverses the direction of change back to its original level
eg. Regulation of body temp

Question 10

What is the definition of a positivie feedback mechanism? Give an example

Answer 10

A change in one direction is amplified leading to a further increase
eg. haemoglobin binds to oxygen increasing affinity so oxygen can bind more easily

Question 11

What is a hormone? Where are they secreted from? How are hormones transported around the body? Where do specific hormones act?

Answer 11

A chemical messenger
Secreted from Glands
Transported in Blood
Target cells

Question 12

How is the effect of hormones different to the nervous system?

Answer 12

Wide spread vs localised
Long lasting vs short lasting

Question 13

What cells produce insulin and glucagon?

Answer 13

Insulin- Beta cells in Islets of Langerhans in pancreas
Glucagon- Alpha cells of Islets of Langerhans in pancreas

Question 14

How does insulin decrease blood glucose concentration?

Answer 14

-(Blood glucose concentration too high)
-(Insulin secreted from beta cells in pancreas)
-Binds to receptors on liver cells
-Causes more channel proteins to be inserted into the cell membane
-Glucose enters by facilitated diffusion (down a conc grad)
-Activates enzymes to convert glucose to glycogen for storage (glycogenesis)

Question 15

How does Glucagon increase blood glucose concentration?

Answer 15

-(Blood glucose concentration too low)
-(Glucagon secreted from alpha cells in pancreas)
-Binds to receptors on liver cells
-Activates enzymes which hydrolyse glyogen into glucose
-Glucose moves into blood by facilitated diffusion
-(Glycogenolysis)
OR
-activates enzymes which convert Glycerol/Amino acids into glucose
(Glucaneogenesis)

Question 16

How does Adrenaline increase blood glucose concentration?

Answer 16

-Adrenaline released from adrenal glands
-Binds to receptors on liver cells
-Activates enzymes which hydrolyse glycogen into glucose
-(Glycogenolysis)

Question 17

What is the second messenger model of adrenaline and glucagon?

Answer 17

-binds to receptors on liver cells
-Activates Adenylate cyclase which produces cyclic AMP
-This activates protein Kinase
-This activates enzymes for Glycogenolysis/Gluconeogenesis

Question 18

Describe these three processes that occur in the liver:
-Glycogeneis
-Glycogenolysis
-Glucaneogenesis

Answer 18

Glycogenesis- Converting glucose into glycogen for storage
Gylcogenolysis- Hydrolysing glycogen into glucose for storage
Gluconeogenesis- Converting amino acids/glycerol into glucose

Question 19

What is the difference between type I diabeties and type II diabetes

Answer 19

Type I - Insulin cannot be produced due to Beta cells being destroyed (autoimmune)
Type II - Receptors dont respond to insuling (can produce insulin)

Question 20

What is the treatment for type I diabeties? Why can’t insulin be taken orally? Why should complex carbohydrates be eaten instead of sugar?

Answer 20

-Insulin injections
-Insulin would be digested or denatured
-Complex carbs hydrolysed and absorbed more slowly than sugar, preventing rapid increase in blood glucose

Question 21

What is a cause of type II diabeties? What is a treatment of type II diabeties? Why won’t insulin injections treat type II?

Answer 21

-Obesity
-Regular exercise to decrease blood glucose concentration (respiration, glucose enters cells by facilated diffusion)
-Loss of weight
-Glucose lowering medication
-Insulin injections do not help as the body can produce insulin but receptors do not respond to it

Question 22

What is osmoregulation?

Answer 22

The control of the blood water potential

Question 23

Name each part of the nephron and their function?

Answer 23

1.Glomerulus -Ultrafiltration
2. Basement membrane -Ultrafiltration
3. Bowmans capsule
4. Proximal convoluted tubule - Selective reabsorption
5. Loop of Henle - reabsorbing more water from glomerular filtrate by producing Na+ concentration gradient in the medulla
6. distal convoluted tubule
7. collecting duct - reabsorbing water into blood (osmoregulation)

Question 24

What are the 3 layers the substances pass through in Ultrafiltration?

Answer 24

-pores in the capillary endothelium
-Basement membrane
-Bowmans capsule epithelium (made of podocytes)

Question 25

What is the process of ultrafiltration?

Answer 25

-High blood pressure in glomerulus
-small molecules eg water glucose and amino acids forced out (of blood into Bowmans capsule)
-Forms glomerular filtrate in the Bowmans capsule
- Proteins and cells are too large to pass through so stay in the blood

Question 26

What is proteinurea?What is it caused by?

Answer 26

High quantity of protein in the urine, caused by damage to the basement membrane

Question 27

What is selective reabsorption where does it take place?

Answer 27

85% of useful molecules and water reabsorbed at the proximal convoluted tubule into the blood
-Water reabsorbed by osmosis (lower water potential in blood due to higher concentration of proteins)
-Glucose reabsorped by active transport

Question 28

How are the epithelial cells lining the proximal convoluted tubule adapted for absorption?

Answer 28

Microvilli which increase surface area to maximise rate of diffusion.
Many mitochondria for active transport of glucose into capillary
Epithelium cells are 1 cell thick so short diffusion pathway

Question 29

What does the Loop of Henle do and how does it do this (generally)

Answer 29

Involved in reabsorbing more water from the glomerular filtrate
By producing a Na+ concentration gradient in the medulla

Question 30

How does the descending limb cause water to move out by osmosis?

Answer 30

-Descending limb is permeable to water
-Water moves out by osmosis into the lower water potential of the medulla
-Na+ is actively transported into the descending limbb
-Due to the loss of water and Na+ moving in the filtrate becomes more concentrated down the descending limb
-Creates an increasing Na+ concentration deeper into the medulla

Question 31

How does the ascending limb of the Loop of Henle lower water potential in the medulla and lower the concentration of the filtrate?

Answer 31

-Na+ are actively transported out of the ascending limb
-This creates a lower water potential in the medulla
-The ascending limb is impermeable so water stays in the tubule
-Filtrate becomes less concentrated (higher water potential)

Question 32

How is water reabsorbed along the collecting duct?

Answer 32

-A water potential gradient is maintained along the whole length of the collecting duct (lower water potential in the medulla
-Water will leave along the whole length of the collecting duct into the medulla
-Water is then reabsorbed into the surrounding capillaries

Question 33

What are the steps that occur when Dehydrated to increase blood water potential?

Answer 33

-Decrease in blood water potential
-Water moves out of osmoreceptors into blood by osmosis (inhypothalamus in brain)
-This sends an impulse to the posterioir pituitary gland which releases more ADH into the blood
-ADH causes collecting duct membrane to become more permeable to water
-More aquaporins are inserted into membrane of distal convoluted tubule
-More water reabsorbed into the blood
-Urine volume less and more concentrated

Question 34

What are the steps that occur when blood water potential too high? (in terms of ADH)

Answer 34

-Water moves into osmosreceptors from blood by osmosis (in the hypothalamus in the brain)
-This sends an impulse to the posterior pituitary gland which releases less ADH into the blood
-ADH causes collecting duct membrane to become less permeable less aquaporins are inserted
-less water reabsorbed into the blood
-Urine volume more and is less concentrated

Question 35

explain why glucose is found in the urine of someone with untreated diabetes

Answer 35

-High concentration of glucose in the blood filtrate
-All carrier proteins are in use maximum rate
-Not all glucose reabsorbed at the proximal convoluted tubule