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Biology Year 2 > Chapter 16 - Homeostasis > Flashcards

Chapter 16 - Homeostasis Flashcards

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1
Q

What is meant by homeostasis

A

Physiological control systems that maintain a constant internal environment

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2
Q

What are the 3 main parts to homeostasis

A

Thermoregulation
Blood pH
Blood glucose

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3
Q

Why does temperature have to be controlled

A
  • Metabolism is controlled by enzymes
  • Enzymes have optimum
  • Too got will denature
  • Too cold rate of respiration will slow
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4
Q

Why does pH have to be controlled

A
  • Metabolism controlled by enzymes
  • Have optimum
  • Too acidic or too alkaline will cause rate of reaction to fall and maybe enzymes denature
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5
Q

Why does glucose have to be controlled

A
  • Minimum amount is needed as a respiratory substrate
  • Too much glucose decrease the water potential of blood, causing water to move out of cells by osmosis and then cells will shrivel
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6
Q

Explain negative feedback

A

Receptors detect a change away from the normal/optimum, so effectors activate mechanisms to return the body to optimum

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7
Q

Explain positive feedback

A

A response that results in the effectors further amplifying the change away from the normal eg sodium channels threshold and depolarisation
Or
Blood clotting

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8
Q

Explain control of blood glucose when it is too high

A
  • Receptors in pancreas detect an increase eg after eating carbs
  • Beta cells in the islets of langerhans (pancreas) secrete insulin
  • Insulin binds to receptors in liver and muscle cells
  • Increasing their permeability to glucose
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9
Q

What are the 3 responses to reduce glucose levels

A
  • Increase absorption of glucose (as explained before)
  • Perform glycogenesis (concerting glucose into glycogen)
  • Increase rate of respiration to burn off glucose
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10
Q

Explain control of glucose when it is too low

A
  • Receptors in pancreas detect low levels
  • Alpha cells only the islets of langerhans (pancreas) secrete glucagon
  • Glucagon binds to receptors on liver cells
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11
Q

What are the 3 responses to increase glucose levels

A
  • Decrease rate of respiration
  • Glycogenolysis (converting glycogen into glucose)
  • Gluconeogenisis (turning non-carbs into glucose)
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12
Q

What is glycogenesis

A
  • Making glucose into glycogen
  • Insulin is the hormone that does this
  • Occurs when blood glucose is too high
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13
Q

What is glycogenolysis

A
  • Splitting glycogen to make glucose
  • Promoted by glucagon and adrenaline
  • Occurs when blood glucose is too low
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14
Q

What is gluconeogenesis

A
  • Making new glucose from non-carbs
  • Promoted by glucagon
  • Occur when blood glucose is too low
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15
Q

Glucagon
Where is it secrets from, when is it secreted, what receptors does it attach to, what is its effect on blood glucose and what mechanisms is it used for

A 
Alpha cells in islets on langerhans
Low blood glucose
Liver
Increase
- Decrease R.O.R
- Glycogenolysis
- Gluconeogenesis
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16
Q

Adrenaline
Where is it secrets from, when is it secreted, what receptors does it attach to, what is its effect on blood glucose and what mechanisms is it used for

A 
Adrenal glands
Low blood glucose
Liver
Increase
Activates Glycogenolysis and secretion of glucagon 
Inhibits glycogenesis and insulin
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17
Q

Insulin
Where is it secreted from, when is it secreted, what receptors does it attach to, what is its effect on blood glucose and what mechanisms is it used for

A 
Beta cells in islets of langerhans
High blood glucose
Liver and muscles
Decrease
- Increase R.O.R
- Glycogenesis
- Increase muscle and liver cells permeability to glucose
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18
Q

Explain how muscle and liver cells permeability is increased by insulin

A
  • Glucose Cartier proteins are stored in vesicles inside liver and muscle cells
  • Insulin binds with cell surface receptors on membranes causing vesicles to fuse with cell membrane
  • Carrier proteins join the membrane and glucose is absorbed by facilitated diffusion
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19
Q

What is diabetes

A

An illness where blood glucose levels are not controlled

20
Q

What is meant by hyperglycaemia

A

Dangerously high blood glucose concentration

21
Q

What is meant by hypoglycaemia

A

Dangerously low blood glucose concentration

22
Q

What is type I diabetes and how is it caused

A

Body doesn’t produce insulin

Immune system kills Beta cells in the islets of langerhans so can’t produce insulin

23
Q

What is the effect of Type I on blood glucose

A

Hyperglycaemia after eating carbs

This stays high as kidneys can’t remove all glucose from urine

24
Q

What treatments are there for type I

A
  • Insulin injections or pump (too much insulin can cause hypoglycaemia)
  • Avoid simple carbs and sugars
  • Eat at regular intervals
  • Regular exercise to use glucose and reduce need for insulin
25
Q

What is Type II diabetes and how is it caused

A

Beta cells don’t produce enough insulin so
Or
Liver and muscle cells stop responding to it
Can be due to obesity, lack of exercise, poor diet and in elderly

26
Q

What is the effect of type II on blood glucose

A

HyperGlycocaemia after eating carbs

27
Q

Treatments for type II

A 
Improved diet
Regular exercise
Insulin injections
Can use drugs to:
- Reduce amount of glucose released
- Increase body’s sensitivity to insulin
- Make the body produce more insulin
28
Q

Explain the concept of second messengers

A
  • Hormone acts as first messenger eg adrenaline or glucagon are complementary to the receptor protein in cell membrane of target cell
  • Enzyme inside cell is activated
  • This is adenyl cyclate
  • This converts ATP into cAMP
  • cAMP is the second messenger
  • cAMP activates an enzyme called protein kinase A by changing its tertiary structure
29
Q

What is the main purpose of kidneys

A

Filtration of blood

30
Q

What is the renal vein and renal artery

A

To a from the kidney

31
Q

Draw and label a nephron

A

In folder

32
Q

Explain the process of ultrafiltration

A
  • First stage of kidneys processing waste products from blood
  • High hydrostatic pressure as afferent arteriolar is wider than the efferent
  • Small molecules forced out into Bowman’s capsule to form the filtrate
  • Filtrate consists of glucose H2O amino acids ions urea
  • Larger molecules such as proteins and red blood cells don’t fit through caps
  • Gaps in capillary walls, basement membrane and podocytes
33
Q

What is the function of the gaps in capillary walls, the basement membrane and podocytes

A

Prevent large molecules coming through eg proteins

34
Q

What is selective reabsorption

A

When useful products from filtrate are re-absorbed by the nephron
Mostly by the PCT but also by DCT and collecting duct and loop of henle

35
Q

Explain the process of selective reabsoprtion

A
  • Ultrafiltration forms filtrate
  • Capillaries wrap around whole of nephron
  • Useful substances tea sorbet into blood
  • Mostly by PCT, has an adaptation of microvilli to increase
  • Urine is filtrate with useful molecules removed so water, urea and excess ions and vitamins
36
Q

How is each molecule transported from lumen and nephron to PCT

A

Glucose and amino acids (facilitated diffusion)
Urea (simple diffusion)
Water (osmosis)
Glucose and amino acids against concentration gradient and ions (active transport)

37
Q

How are molecules transported into capillaries

A

Diffusion and osmosis

38
Q

Explain the process at the loop of henle

A
  • At ascending limb, sodium and calcium ions are pumped out by active transport (ATP)
  • Decreasing water potential of medulla
  • Ascending limb is impermeable to water, so water can’t leave by osmosis
  • At descending limb it is permeable to water, so water moves out by osmosis
  • Water absorbed into capillaries
  • by removing water from filtrate, urine is more concentrated
39
Q

Explain the process of osmoregulation

A
  • If dehydrated blood has low water potential so is more concentrated
  • This is detected by osmoreceptors in the hypothalamus
  • Causes the posterior pituitary to secrete ADH (antidiuretic hormone)
  • ADH is carried in bloodstream
  • ADH binds to specific receptor proteins on the collecting ducts (and a bit on DCT)
  • This increases their permeability to water
  • Water moves out of collecting duct and DCT by osmosis
  • Because medulla has a very low water potential
40
Q

Explain osmoregulation in very basic terms

A

More ADH
collecting duct wall more permeable
Water moves out of collecting duct
Less puss

41
Q

What is thermoregulation and what are the 2 things it allows for

A

Process whereby animals regulate their body temperature

  • Optimal activity of enzymes and metabolic processes
  • Independence from fluctuating external conditions
42
Q

Describe characteristics of endotherms

A
  • Maintain relatively constant temperature that is mainly independent of the environment
  • Rely on physiological mechanism for temp control
  • Can therefore exploit a wide range of environments and require an abundant food supply
43
Q

How do endotherms gain heat

A
  • Radiation and conduction from environment
  • Muscle contraction
  • General metabolism
44
Q

How do endotherms lose heat

A
  • Radiation, conduction and convection to environment
  • Evaporation of sweat
  • Expiration and excretion
45
Q

Describe the characteristics of ectotherms

A
  • Body temperature tends to fluctuate as environment temperature changes
  • again heat from environment and rely on structural and behavioural mechanisms for control of body temperature
  • Exploit few environments
46
Q

How and where is urea produced

A

Deamination of amino acids in liver

Biology Year 2 (10 decks)

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