paper 2: Homeostasis Flashcards
1
Q
define the term homeostasis
A
maintaining a constant internal environment within restricted limits
2
Q
why does homeostasis take place
A
to prevent damage to cells
3
Q
explain what happens to enxymes when core body temperature is too high
A
- hydrogen bonds break within enzymes
- changing thier tertiary structure and the shape of the active site
- less enzyme-substrate complexes form
4
Q
explain what happens to enzymes when core body temperature is too low
A
- eznymes have too low kinetic energy
- less enzyme-substrate complexes form
- metabolic rate is reduced
5
Q
explain what happens to enzymes when blood pH is too high
A
- hydrogen bonds break within proteins
- chaning the tertiary structure
6
Q
explain what happens to enzymes when blood pH is too low
A
- hydrogen bonds break within enzymes
- changeing their tertiary structure
7
Q
what happens to water potential when blood glucose concentration is too high
A
- blood has lower water potential than cells
- water leaves cells into blood by osmosis
- cells lack water for metabolic reactions such as hydrolysis and as a solvent
8
Q
what happens when blood glucose concentration is too low
A
- glucose is not provided to cells fast enouugh for anhigh enough rate of respiration
9
Q
what happens when blood water potential is too high
A
- water enters cells by osmosis
- too much can cause cell lysis
- lots of water in blood causes high blood pressure
10
Q
what happens when blood water potential is too low
A
- water leaves cells by osmosis
- cells lack ater for metabolic recations such as hydrolysis and as a solvent
11
Q
define negative feedback
A
reverses the direction of change back to its original level
12
Q
how is regulation of the body temperature an example of negative feedback
A
- when body is too high, the body responds to decrease it back to original
- when body temperature is too low, the body responds to increase it back to its original
13
Q
what is the advantage of having separate mechanisms to increase or decrease the factor
A
- separate mechanisms are used to increase or decrease the factor, as this gives a greater degree of control
14
Q
define positive feedback
A
where a change in one direction is amplified
(an increase leads to a further increase)
15
Q
give an example of positive feedback
A
sigmoid curve for oxygen dissociation
16
Q
what type of messenger is a hormone
A
chemical messenger
17
Q
where are hormones secreted from
A
glands
18
Q
how are hormones transported around the body
A
in the blood stream
19
Q
where do specific hormones act and why
A
target cells as they have complimentary hormone receptors
20
Q
describe the effect of hormones. how is this different to the nervours sytem
A
- effect of hormones is widespread and longlasting
WHEREAS - effect of nervous system is local and short term
21
Q
what will make blood glucose rise
A
- eating foods high in glucose and starch as g;uvose is absorbed into the bloodstream
22
Q
what will cause blood glucose to fall
A
- increase in cell respiration
23
Q
when is insulin released
A
when blood glucose is high
24
Q
when is glucagon released
A
when blood glucose is too low
25
which cells produce insulin
beta cells in islets of Langerhans in the pancreas
26
which cells produce glucagon
alpha cells in islets of Langerhans in the pancreas
27
what effect does insulin have on blood glucose
decrease blood glucose levels
28
what effect does glucagon have on blood glucose
increase blood glucose levels
29
what are the target cells for insulin
liver and muscle cells
30
what are the target cells for glucagon
liver cells
31
how does insulin decrease blood glucose levels
- inserting more glucose **channel proteins** into the cell membrane, glucose enters the cell by facilitated diffusion
- activating enzymes to convert glucose into glycogen for storage (**glycogenesis**)
32
how does glucagon increase blood glucose levels
- activates enzymes to hydrolyse glycogen into glucose (**glycogenolysis**)
- activates enzymes to convert glycerol/ amino acds into glucose (**gluconeogenesis**)
33
what is the role of adrenalin in the body
increase blood glucose
34
how does adrenaline increase blood glucose
- adrenalin release from **adrenal glands**
- binds **receptors** on **liver cells**
- enzymes are activated which hydrolyse **glycogen to glucose** (**glycogenolysis**)
35
dra wand label a diagram showing the secondary messenger pathway of glucagon and adrenaline
36
describe type 1 diabetes
- **cant produce insulin** due to the death of beta cells in the islets of Lagerhans
37
describe type 2 diabetes
**insulin is produced** by the beta cells but the **insulin receptors do not respond** to the insulin
- blood glucose decreases more slowly
- can be causes by obesity
38
what 2 ways can a type 1 diabetic control their blood glucose levels
1. inject insulin
2. eat complex carbs over sugars
39
how does injecting insulin help control the blood glucose of a type 1 diabetic
- as insulin cannot be produced due to beta cells being destoryed
- insulin (protein) cannot be taken orally as it will be digested or denatured by stomach acid
40
how does eating complex carbs instead of sugars help control blood glucose of a type 1 diabetic
- prevents a rapid spike in blood glucose
- absorbed more slowly than monosaccharides because gycosidic bonds need to be hydrolysed first before absorption
41
what are the 3 ways of controlling blood glucose of a type 2 diabetic
1. regular exercise
2. loss of weight
3. glucose lowering medication
42
why can a type 2 diabetic not inject insulin to control blood glucose
they already produce insulin as beta cells are present but the receptors do not respond
43
how does regular exercise help control the blood glucose of a type 2 diabetic
more respration so more glucose used so decreases concentration of glucose in cells so more glucose enters by faciliatated diffusion
44
how does a loss of weight help control blood glucose of a type 2 diabetic
due to obesity being a cause of type 2 diabetes
45
what is the function of the kidney
- substances are **filtered** out of the **blood,** including water
- useful substances are **reabsorbed** back into the **blood**
- unwanted substances travel to the bladder where they **excreted** within urine
46
if water potential is too high what happens at the kidney
- less water reabsorbed
- greater urine volume
- lower urine concentation
47
if blood water potential is too low what happens at the kidney
- more water reabsorbed
- lower urine volume
- greater urine concentration
48
label a diagram of a nephron
49
decsribe how ultrafiltration occurs
- there is a **high blood pressure** in the glomerulus
- **water** and **small molecules** *e.g. glucose and amino acids* are forced out
- this forms the **glomerular filtrate** in the tubule
- **proteins** and **cells** are too large to pass through so they **stay in the blood**
50
what are the 3 layers molecules pass through during ultrafiltration
- **pores** in the **capillary endothelium**
- **basement membrane**
- the **Bowman's capsule epithelium** (made of **podocytes**)
51
why does proteinurea occur
- damage made to the basement membrane
52
describe selective reabsoption
most of the useful molecules and water are **reabsorbed** at the **proximal convuluted tubule** into the blood
53
how are the epithelial cell lining the proximal convuluted tubul adapted for absorption
- many mitochondria to provide lots of ATP to be hydrolysed and release energy for active transport
- microvilli - to provide a large surface area for more diffusion of small molecules
- microvilli increases number of channel protiens/ carrier proteins for facilitated diffusion
54
what causes water potential of the blood to be lower after ultrafiltration
- the proteins in the blood that were not filtered
55
describe how glucose is reabsorbed in the proximal convuluted tubule
- Na+ ions are actively transported out of the epithelial cell of the convuluted tubule into the blood to maintain the Na+ concentration gradient
- Na+ ions and glucose are co-transported from the filtrate into the epithelial cell of the proximal convuluted tubule through carrier proteins by facilitated diffusion
- glucose is then transported from the epithelium into the blood by facilitated diffusion
56
describe the steps of how the loop of Henle reabsorbs water in the ascending limb
- Na+ ions are actively transported out of the ascending limb
- this creates a lower water potential in the medulla
- the walls of the ascending limb are impermeable to water so water remains in the tubule
- filtrate becomes less concentrated
57
describe the steps of how the loop of Henle reabsorbs water in the descending limb
- the walls of te descending limb are permeable to water
- water moves out by osmosis into the lower water potential of the medulla
- Na+ actively transported into the descending limb
- due to the loss of water and Na+ moving in, the filtrate becomes more concentrated down the descending limb
- this creates an increasing Na+ concentration deeper into the medulla
58
describe the steps of how the loop of Henle reabsorbs water in the collecting duct
- a water potential gradient is maintained along the whole length of the collecting duct
- water will leave along the whole length of the collecting duct into the medulla
- water is then reabsorbed into the surrounding capillaries
59
how does the length of the loop of Henle effect the concentration of Na+ ions in the medulla
- the longer the loop of Henle, the greater the Na+ concentration, deeper into the medulla.
- the water potential gradient is maitained for longer
- more water is reabsorbed from the collecting duct by osmosis
60
describe osmoregulation by ADH when you are dehydrated
- decrease in blood water potential
- water moves out of osmoreceptors in the hypothalamus in the brain into blood by osmosis
- imoulses are sent to the posterior pituitary gland and it releases more ADH into blood
- more ADH causes collecting duct membrane to become more permeable to water as there are more aquaporins
- more water is reabsorbed into the blood
- urine volume becomesless and is more concentrated
61
describe osmoregulation by ADH when you drink too much water
- increase in blood water potential
- water moves into osmoreceptors in the hypothalamus in the brain out of the blood by osmosis
- sends impulses to the posterior pituitary gland and releases less ADH into the blood
- less ADH causes collecting duct membrane to become less permeable to water as there are less aquaporins
- less water is reabsorbed into the blood
- urine volume becomes more and is less concentrated
