6.4 Homeostasis Flashcards
1
Q
Define homeostasis in mammals
A
Involves physiological control systems that maintain the internal environment within restricted limits.
2
Q
What does negative feedback do
A
Restores systems back to their original levels
3
Q
What does negative feedback use to return levels to optimum point
A
Corrective mechanisms
4
Q
What is positive feedback
A
Enhancing an effect further which results in even greater deviation from the normal
5
Q
With negative feedback, what provides a greater degree of control
A
The possession of separate mechanisms which controls the departure in different directions from the optimum point
6
Q
What are the 2 control systems
A
- Nervous system
- Endocrine system
7
Q
How are responses communicated in the endocrine system
A
By chemicals in the blood steam
8
Q
How are response communicated in the nervous system
A
By electrical impulses through neurones and synapsesf
9
Q
Is hormonal or nervous coordination, more wide spread
A
Hormonal
10
Q
Is hormonal or nervous coordination more localised
A
Nervous coordination
11
Q
What is the name of the group of cells in the pancreas that contain alpha and beta cells
A
Islet of Langerhans
12
Q
What secrete insulin
A
Beta cells
13
Q
In response to what do Beta cells secrete insulin
A
In response to increased glucose concentrations
14
Q
What secretes glucagon
A
Alpha cells
15
Q
In response to what, do alpha cells secrete glucagon
A
In response to lowered glucose concentration
16
Q
What is meant by the term glycogenesis
A
Forming glycogen from glucose
17
Q
What is meant by glycogenolysis
A
The hydrolysis of glycogen into glucose
18
Q
What is meant by gluconeogenesis
A
Synthesis of glucose from molecules that are not carbohydrates such as amino acids and fatty acids
19
Q
What detects the increase in glucose levels
A
Beta cells
20
Q
What are the 4 things that homeostasis controls
A
- Core body temperature
- Blood glucose concentration
- Blood pH
- Blood water potential
21
Q
After what activity will your blood glucose concentrations increase
A
After ingestion of food or drink containing carbohydrates
22
Q
After what activity will your blood glucose concentrations decrease
A
Following exercise or if you have not eaten food or drink containing carbohydrates
23
Q
What is the organ that detects the change in blood glucose levels
A
The pancreas
24
Q
What affect does insulin have on blood glucose levels
A
Decreases
25
What affect does glucagon have on the blood glucose levels
Increases
26
Where is adrenaline released from
The adrenal glands
27
What affect does adrenaline have on the blood glucose concentration
Increases
28
Why does adrenaline increase blood glucose concentration
As more glucose is being released from the hydrolysis of glycogen in the liver
29
What 3 effects arise as a result of insulin binding to glycoprotein receptors
- Increase in the number of glucose carrier proteins in the cell's membrane
- Changes in the tertiary structure of glucose carriers so they open and allow uptake of glucose by faciliatated diffusion
- Activation of enzymes that convert glucose to glycogen and fats (Glycogenesis)
30
List the steps that happen when the blood glucose levels increase
- Detected by beta cells in the Islets of Langerhans
- Beta cells release insulin
- Liver cells become more permeable to glucose and enzymes are activated to convert glucose to glycogen
- Glucose is removed from the blood and stored as insoluble glycogen in cells
- So the normal blood glucose levels have been restored
31
List the steps that happen when the blood glucose levels decrease
- Detected by alpha cells in Islets of Langerhans
- Alpha cells release glucagon and adrenal glands release adrenaline
- Second messenger model occurs to activate enzymes to hydrolyse glycogen into glucose
- More glucose is released back into the blood
- Normal blood glucose levels are restored
32
What are the 3 actions of glycagon
- Attaches to receptors on the surfaces of liver cells
- Once bound to receptors a protein is activated enzymes involved in glycogenolysis
- Activates enzymes involved in gluconeogenesis
33
What are 3 main sources when glucose enters the blood
- Absorption from the gut after digestion
- Hydrolysis of stored glucose
- Conversion of non carbohydrates into glucose
34
What happens after glucagon has bound to the receptors on target cells
The protein changes shape
35
After the glucagon-receptor complex has formed, what is activated
Adenyl cyclase
36
What reaction does Adenyl cyclase catalyse
Converts ATP to cyclic AMP
37
What is the name of the enzyme that cAMP activates
Protein kinase
38
What reaction does protein kinase catalyse
Conversion of glycogen to glucose, glycogenolysis
39
Glucagon also causes the production of glucose from other sources, name 2 examples
Glycerol and amino acids
40
Does adrenaline and glucagon effect the cells directly
No
41
What effect do adrenaline and glucagon have on the cell they bind to
The binding causes a cascade of reactions
42
What is the enzyme that acts as the secondary receptor
cAMP
43
What are the causes of type 1 diabetes
Body being unable to produce insulin
44
What causes type 2 diabetes
Due to glycoprotein receptors on body cells being lost or becoming less sensitive to the presence of insulin
45
How is type 1 diabetes controlled
Injections of insulin to match the glucose intake
46
How is type 2 diabetes controlled
Regulating intake of carbohydrates and improving exercise levels
47
What is diabetes
Inability to control blood glucose concentrations
48
What process takes place in the kidneys
Osmosregulation
49
What is osmoregulation
The control of water potential in the blood
50
What is the name of the functional unit of the kidney
Nephron
51
What is the name of the beginning of the tubule that makes up the nephron
Bowman's capsule
52
What is the name of the network of capillaries that surrounds the Bowman's capsule
Glomerulus
53
What is produced in the first step of filtration of the blood in the nephron that takes place in the Bowman's Capsule
Glomerular filtrate
54
What is the name of the artierole that flows into the Glomerulus
Afferent arteriole
55
What is the name of the arteriole that flows/ out of the Glomerulus
Efferent artierole
56
Does the afferent arteriole or the efferent arteriole have a wider lumen
Afferent arteriole
57
In the nephron, what does PCT stand for
Proximal Convoluted Tubule
58
What happens at the proximal convoluted tubule
Site of selective reabsorption
59
What 2 things are reabsorbed from the Glomerular filtrate through the PCT
- Glucose
- Water
60
The Loop of Henle produces a low water potential where in the kidney
In the medulla
61
What are the names of the 2 limbs that the Loop of Henle consist of
- Ascending limb
- Descending limb
62
The ascending limb is ____________ to water
Impermeable
63
The descending limb is _________ to water
Permeable
64
What is reabsorbed at the collecting duct
Water
65
If water potential of blood is low, is more or less water reabsorbed at the collecting duct
More water is absorbed
66
If water potential of blood is high, is more or less water reabsorbed at the collecting duct
Less water is absorbed
67
What creates the high hydrostatic pressure in the Glomerulus
The lumen width of the afferent arteriole being wider than the lumen width of the efferent arteriole
68
What does the high hydrostatic pressure in the Glomerulus result in
The blood plasma leaving the capillaries and entering the Bowman's capsule
69
What is the name of the membrane in the capillary that stops larger molecules from leaving the capillary
Basement membrane
70
Due to the basement membrane, what remains in the capillary
- Large plasma proteins
- Blood cells
71
What is the name of the cells in the inner Bowman's capsule membrane
Podocytes
72
What 5 things are inside the Glomerular Filtrate
- Water
- Amino acids
- Urea
- Glucose
- Inorganic ions
73
What does the renal artery supply blood to
The Glomerulus
74
What is the role of the ureter
Carries urine from kidney to bladder
75
What does the renal cortex contain
- Bowman's capsule
- Convoluted tubules
76
What does the medulla of the kidney contain
- Loop of Henle
- Collecting duct
77
What is the role of the fibrous capsule
Protects kidney
78
At this card label a diagram of a nephron
79
Podocyte cells have long _________ extensions that _______ around the __________
1. Cytoplasmic
2. Wrap
3. Capillary
80
What is the name of the gap between podocytes
Filtration slits
81
Where does selective reabsorption occur
In the proximal convoluted tubule
82
What is the first step in the selective reasborption process
The sodium ions are actively transported out of the epithelial cells lining the proximal convoluted tubule and into the surrounding blood capillaries
83
What is the effect of actively pumping sodium ions out of the cells lining the proximal convoluted tubule
The sodium ion concentration in the cells lining the PCT so a sodium ion concentration gradient is established
84
What happens once the sodium ion concentration gradient has been established in the PCT
Sodium ions diffuse down concentration gradient via facilitated diffusion through a carrier protein from lumen of PCT and into the epithelial cells
85
What is also transported into the epithelial cells with sodium ions in the PCT
- Glucose
- Amino acids
86
What happens to the glucose/ amino acids once they're inside the cells lining the PCT
Move by facilitated diffusion into the blood stream
87
What decreases the water potential of the cells lining the PCT
Moving sodium ions from lumen
88
What does water do the counteract the decrease in water potential gradient in the cells lining the PCT
Move from the lumen of the PCT, into the cells lining the PCT via osmosis
89
What are 4 adaptations of the cells of the PCT
- Microvilli provide a large surface area
- Many carrier proteins for facilitated diffusion
- Many carrier proteins/ sodium ions-potassium ion pump for active transport
- Many mitochondria produce ATP for active transport
90
Where does the Loop of Henle dips down into in the nephron
Into the medulla
91
What is the Loop of Henle responsible for
Setting up a salt (NaCl) gradient
92
What are the names of the 2 limbs in the loop of Henle
- Descending Limb
- Ascending Limb
93
Which limb of the Loop of Henle is permeable to water
The descending limb
94
Which limb in the Loop of Henle is relatively permeable to salt (NaCl)
The ascending limb
95
In which limb of the Loop of Henle does water leave as the water potential of the tissue fluid decreases
Descending limb
96
What is the bottom of the Loop of Henle called
Hairpin
97
Where in the Loop of Henle, is the concentration of salt (NaCl) the highest
In the hairpin
98
By what process, does water leave the descending limb of the Loop of Henle
Osmosis
99
Where is water that is lost from the Loop of Henle taken
Reabsorbed into the blood in the surrounding capillaries via osmosis
100
What diffuses out of the ascending limb of the Loop of Henle
Sodium ions and chloride ions
101
By what process do sodium ions and chloride ions leave the ascending limb at the top of the limb
Active transport
102
Why at the top of the ascending limb, are sodium and chloride ions transported by active transport
Since the concentration of these ions in the filtrate has decreased and the concentration in the medullar tissue fluid has increases, so a concentration gradient isn't there
103
Further down into the medulla, does the water potential increase or decrease and why
Decrease as there is a higher concentration of salt in the medulla tissue fluid
104
What does the filtrate pass through to reach the collecting duct from the ascending limb
Distal convulated tubule
105
What is the collecting duct permeable to
Water
106
What process occurs in the collecting duct, when water leaves
Osmosis
107
How does osmosis occur down the entire collecting duct
As the salt concentration increases deeper into the medulla, so the water potential is lower in the medullar tissue fluid compared to the collecting duct, so water potential gradient is maintained, so osmosis occurs
108
Is the urine that leaves the kidney hypotonic or hypertonic
Hypertonic
109
Does the urine that leaves the kidney have a higher or lower water potential than the blood
Lower water potential than the blood
110
Why is water reabsorbed in the collecting duct
To conserve water to prevent dehydration
111
What type of system operates in the Loop of Henle
Countercurrent multiplier system
112
What 3 steps are involved in the countercurrent multiplier system
- As filtrate moves down the collecting duct, it loses water, which lowers the water potential
- However, due to the pumping of ions out of the ascending limb, the water potential of surrounding tissues in the medulla is even lower than in the collecting duct
- Allowing water to continue to move out of the filtrate down the whole length of the collecting duct
113
Why does water not move from the tissue fluid into the ascending limb down a very large water potential gradient
The cells lining the ascending limb of the Loop of Henle are impermeable to water
114
Why do cells in the ascending limb of the Loop of Henle have a large number of mitochondria
- NaCl needs to be actively transported out of the ascending limb by active transport which requires energy in the form of ATP which is provided by mitochondria
115
Explain the term counter current multiplier
Counter-current = Filtrate flowing down the descending limb of the Loop of Henle in the opposite direction to filtrate in ascending limb
Multiplier= NaCl leaves ascending limb which lowers the water potential of the MTF so water moves out of the descending limb which in turns results in more NaCl leaving- and so on, positive feedback
116
Why is it necessary for the Loop of Henle to set up a water potential gradient through the medullary tissue fluid
So water potential gradient between collecting duct and tissue fluid is maintained along the entire length of collecting duct so the maximum water reabsorbance is reached so water is conserved
117
Why would a mammal living in a dry environment have an extended loop of Henle
- Greater maximum concentration of NaCl at the hairpin
- More concentrated medullary tissue fluid
- Lower water potential gradient of the medullary tissue fluid
- More water drawn from collecting duct into the medullary tissue fluid and into the blood
- So more water is conserved
118
What does ADH stand for
Anti-diuretic hormone
119
What are the target cells for ADH
The epithelial cells of the collecting duct and the distal convoluated tubule
120
What effect does ADH have on the target cells
Increases the cells permeability to water
121
What system(s) are involved in osmoregulation
- Endocrine
- Nervous
122
What may cause a decrease in blood water potential
- Sweating
- Not drinking enough water
- Too much salt in the diet
123
What detects a change in the blood water potential
Osmoreceptors
124
Where are osmoreceptors found
In the hypothalamus
125
Where is ADH produced
In the hypothalamus
126
Where is ADH released from
The posterior pituitary gland
127
If there's a low blood water potential, does the posterior pituitary gland receive a higher or lower frequency of impulses from the osmoreceptors
Higher frequency
128
What does a higher frequency of impusles from the osmoreceptors cause the posterior pituitary gland do
Release more ADH into blood plasma
129
When there's a high concentration of ADH, what is the urine concentration and volume like
- Small volume
- Concentrated
130
What detects a change in blood water potential
Osmoreceptors
131
When there's an increase in blood water potential, what is the frequency of impulses from osmoreceptors like to the posterier pituitary gland
Lower frequency of impulses
132
What is the effect of a lower frequency of impulses from osmoreceptors to the posterior pituitary gland
Less ADH is released into blood plasma
133
What effect does less ADH in blood plasma have on the epithelial cells of the collecting duct
Less permeable to water
134
What is the volume and concentration of urine like when there's an increase in blood water potential
- Large volume
- Dilute urine
135
Once ADH has reached the capillary by the epithelial cells of the collecting duct, what happens to ADH
ADH diffuses through tissue fluid between capillary and the epithelial cell and binds to an ADH protein receptor on the basal membrane
136
What is the effect of ADH binding to ADH protein receptor
The binding triggers vesicles to move towards the apical membrane
137
What is the name of the proteins in the apical membrane and the basal membrane where water flows through
Aquaporins
138
What do the vesicles in the epithelial cell of the collecting duct contain
Contain aquaporins
139
How does ADH increase the permeability of the epithelial cells of the collecting duct
By increasing the number of aquaporins in the epithlial membrane
140
What are primary messengers
Messengers that don't enter cells
141
What are examples of primary messengers
Hormones
142
What do primary messengers bind to
Receptors on the cell surface membrane
143
What is the name of the enzyme that converts ATP to cyclic AMP
Adenylate cyclase
144
Explain why a change in the amino acid sequence of insulin prevents insulin binding to its receptors (2 marks)
1. Changes tertiary structure;
2. No longer complementary (to receptor);
145
Explain why glucose is found in the urine of a person with untreated diabetes (3 marks)
1. High concentration of glucose in blood/filtrate;
Accept tubule for filtrate.
2. Not all the glucose is (re)absorbed at the proximal convoluted tubule;
3. Carrier/co-transport proteins are working at maximum rate
OR
Carrier/co-transport proteins/ are saturated;
146
Describe the role of glucagon in gluconeogenesis (2 marks)
1. (Attaches to receptors on target cells and) activates/stimulates
enzymes;
2. Glycerol/amino acids/fatty acids into glucose;
147
Explain how increasing a cell's sensitivity to insulin will lower the blood glucose concentration (2 marks)
1. (More) insulin binds to receptors;
2. (Stimulates) uptake of glucose by channel/transport proteins
OR
Activates enzymes which convert glucose to glycogen;
148
Explain how inhibiting adenylate cyclase may help to lower the blood glucose concentration (3 marks)
1. Less/no ATP is converted to cyclic AMP/cAMP;
2. Less/no kinase is activated;
3. Less/no glycogen is converted to glucose
OR
Less/no glycogenolysis;
149
Give 2 reasons why pancreas transplants are not used for treatment of type 2 diabetes
1. (Usually)Type II produce insulin;
2. Cells / receptors less sensitive / responsive (to insulin)
OR
Faulty (insulin) receptors;
3. (Treated / controlled by) diet / exercise;
150
Give 2 ways in which people with type 1 diabetes control their blood glucose concentration
1. Treat with insulin (injection/infusion);
2. (Control) diet/control sugar intake;
151
Describe how ultrafiltration occurs in a glomerulus (3 marks)
1. High blood/hydrostatic pressure;
2. Two named small substances pass out eg water, glucose,
ions, urea;
3. (Through small) gaps/pores/fenestrations in (capillary)
endothelium;
4. (And) through (capillary) basement membrane;
152
Explain why the concentration of fluid in the tubule remains constant in the PCT (1 mark)
Water is also reabsorbed
153
Give the location of the osmoreceptors in the body of a mammal
Hypothalamus
154
Explain why, when a person is dehydrated the cell volume of an osmorecptor decreases (2 marks)
1. Water potential of blood will decrease;
2. Water moves from osmoreceptor into blood by osmosis
155
Describe and explain how the secretion of ADH affects urine produced by the kidneys (4 marks)
1. Permeability of membrane / cells (to water) is increased;
2. More water absorbed from / leaves distal tubule / collecting duct;
3. Smaller volume of urine;
4. Urine becomes more concentrated.
156
Apart from age and gender, give 2 factors that could affect the concentration of creatinine in the blood
Muscle / body mass
Ethnicity
Exercise
Kidney disease
157
Explain how the binding of insulin leads to an increase in the rate of respiration in cells (2 marks)
1. (Insulin) leads to more transport proteins / channel (proteins) / carrier (proteins) for glucose;
2. More glucose (for respiration / glycolysis) enters cell;
158
Give the location of the receptors that detect a decrease in blood pressure
1. Aorta
OR
Carotid artery/sinus;
159
Explain how the release of ADH will affect blood pressure
1. (ADH) increases (re)absorption of water;
2. Increases volume of (blood) and pressure
increases
OR
Increases volume of (blood) and pressure
returns to normal;
160
Describe the role of epithelial cell membranes in the PCT in the reabsorption of glucose
- Sodium ions are actively transported out of the PCT epithelial cells into the blood via the sodium/potassium pump, lowering the sodium ions concentration inside the cell
- Sodium ions diffuse back into the PCT epithelial cells from the filtrate via co-transport proteins, bringing glucose with them
- Glucose moves from the epithelial cells into the blood via facilitated diffusion through a specific carrier protein
- The epithelial cell membranes have microvilli, which increase the surface area for absorption, ensuring maximum reabsorption of glucose
161
Describe the role of epithelial cell membranes in the collecting duct in the reabsorption of water
- ADH binds to specific receptors on the epithelial cell membranes of the collecting duct
- This stimulates the insertion of aquaporins into the membrane, increasing its permeability to water
- Water moves out of the collecting duct epithelial cells into the surrounding MTF by osmosis, down a water potential gradient
- The surrounding MTF has a very low water potential due to ion concentration, maintaining the gradient. Reabsorbed water then enters blood capillaries, preventing dehydration and maintaining blood volume
162
Describe the role of liver cell membranes in the regulation of blood glucose
Glucagon binds to specific receptors on the liver cell membranes, initiating the activation of an enzyme pathway
- This stimulates the activation of enzymes like adenyl cyclase, leading to an increase in cAMP levels within the liver cell
- The elavated cAMP activates protein kinases, which promote the breakdown of glycogen into glucose through glycogenolysis
- The glucose produced is then released from the liver cells into the bloodstream, raising blood glucose levels
163
Explain the importance of regulating blood glucose concentration
- Maintaining a stable blood glucose concentration ensures a constant supply of the primary respiratory substrate, especially in the brain and muscles
- If blood glucose levels are too high, it can cause damage to tissues and organs as cells lose water and dehydrate, while too low can lead to insufficient energy for celluar activities
- The regulation of blood glucose concentration is essential for homeostatsis
164
Explain the importance of regulating blood water potential
- Regulating blood water potential ensures that cells maintain their shape and function by preventing excessive water loss or intake
- Maintaining blood water potential helps control the osmotic balance, which is essential
- Proper regulation of water potential also contributes to maintaining blood volume and pressure, supporting overall circulatory function
165
The scientists repeated the investigation using much higher doses of STZ. This led to destruction of pancreatic cells. The scientists concluded that these rats would not be
suitable for studying type II diabetes.
Give two reasons why the scientists made this conclusion (2 marks)
1. (Type II) still produce/release insulin;
2. (Type II) cells/receptors less/not
responsive/sensitive to insulin;
3. Pancreatic cells not destroyed (in type II
diabetes);
4. Damage to pancreatic cells may affect
processes/reactions (in the body);
166
Name the part of the body which releases antidiuretic hormone (ADH) into the blood
Posterior pituitary;
167
Alcohol decreases the release of ADH into the blood.
Suggest two signs or symptoms which may result from a decrease in ADH. (2 marks)
1. Dehydration/thirst;
2. Frequent urination
OR
Increase in volume of urine;
3.Less concentrated urine
OR
Dilute urine
OR
Urine paler/lighter in colour;
168
Describe the effect of ADH on the collecting ducts in kidneys (3 marks)
1. (Stimulates) addition of channel proteins into
membrane;
2. Increases permeability to water
OR
(More) water (re)absorbed;
3. By osmosis;
169
Give 2 reasons why a weight-loss programme could be used to treat type II diabetes but not type I diabetes (2 marks)
- Type I do not produce insulin
- Type II receptors less sensitive to insulin
- Weight not linked to type I diabetes
