1
Q
what is the role of the kidneys?
A
make urine by filtering waste products out of the blood and reabsorbing useful molecules, one of the main functions is to excrete waste products such as urea, regulate the water potential of the blood
2
Q
how do the kidneys excrete waste and regulate blood water potential?
A
as the blood passes through capillaries in the cortex, substances are filtered out of the blood and into long tubules that surround the capillaries in ultrafiltration, useful substances such as glucose and water are reabsorbed into the blood in selective reabsorption, the remaining unwanted substances pass through the ureter to the bladder and are excreted as urine
3
Q
what are nephrons?
A
the long tubules along with the bundle of capillaries where the blood is filtered, around one million in each kidney
4
Q
what happens before ultrafiltration?
A
blood from the renal artery enters arterioles in the cortex, each arteriole splits into a glomerulus, where ultrafiltration takes place
5
Q
what is a glomerulus?
A
a bundle of capillaries looped inside a hollow ball called a Bowman’s capsule
6
Q
what is the process of ultrafiltration?
A
the blood enters the glomerulus through the afferent arteriole, and leaves through the efferent arteriole, the efferent is smaller in diameter creating high hydrostatic pressure, forcing liquid and small molecules out of the capillary and into the Bowman’s capsule, passing through three layers to get into the bowman’s capsule and enter the nephron tubule, capillary wall, basement membrane and epithelium of the BC, larger molecules like proteins can’t pas through so stay in the blood. The substances that enter the BC are called the glomerular filtrate, which goes through selective reabsorption before travelling through the collecting duct and out via the ureter
7
Q
what is the afferent arteriole?
A
how blood enters the glomerulus, larger in diameter
8
Q
what is the efferent arteriole?
A
how blood leaves the glomerulus, smaller in diameter
9
Q
what are the structural features of the kidney?
A
renal artery, renal vein, cortex, medulla, ureter (leading to bladder and urethra), nephrons
10
Q
what are the structural features in one nephron?
A
afferent arteriole, bowman’s capsule, glomerulus, efferent arteriole, proximal convoluted tubule (PCT), loop of Henle, distal convoluted tubule (DCT), collecting duct, renal vein, ureter
11
Q
what is meant by water potential?
A
describes the tendency of water to move from one area to another, water will move from an area of higher WP to an area of lower WP - it moves down the water potential gradient
12
Q
what is urine usually made up of?
A
water, dissolved salts, urea, other substances such as hormones and excess vitamins (CHLOE REMEMBER WHEN THE YOU HAD A VITAMIN OVERDOSE AND THE DOCTOR TOLD YOU YOUR WEE WOULD BE YELLOW? THIS IS WHY!!)
13
Q
what does urine usually not contain?
A
proteins and blood cells - they’re too big to be filtered out of the blood, glucose because it is actively reabsorbed back into the blood
14
Q
what is selective reabsorbtion?
A
the process whereby certain molecules (e.g. ions, glucose and amino acids) are reabsorbed from the filtrate as they pass through the nephron
15
Q
which blood vessel supplies the kidney with blood?
A
the renal artery which branches into the afferent arteriole before reaching the glomerulus
16
Q
by which two processes is glucose reabsorbed from the proximal convoluted tubule (PCT)?
A
active transport and facilitated diffusion
17
Q
explain how the glomerular filtrate is formed at the glomerulus/bowman’s capsule (2 marks)
A
The efferent arteriole has a smaller diameter than the afferent arteriole, so the blood in the glomerulus is under high pressure. The high pressure forces liquid and small molecules into the Bowman’s capsule, forming the glomerular filtrate.
18
Q
would you expect the concentration of glucose to be lower at the proximal convoluted tubule or the loop of Henle (1 mark)
A
the loop of Henle, because glucose is reabsorbed in the PCT, so by the time it reaches the loop of Henle there will be less glucose remaining
19
Q
what is the glomerular filtration rate?
A
the rate at which the kidneys filter the blood, GFR usually around 6300cm^3hour^-1
20
Q
what is osmoregulation?
A
the kidneys regulate the water potential of the blood and urine so the body has just the right amount of water
21
Q
how is water lost from the body?
A
mammals excrete urea in solution so water is lost in excretion, also through sweat (involved in thermoregulation)
22
Q
what happens if the water potential of the blood is too low?
A
the body is dehydrated, more water is reabsorbed by osmosis into the blood from the tubules of the nephrons, urine is more concentrated so less water is lost during excretion
23
Q
what happens if the water potential of the blood is too high?
A
the body is too hydrated, less water is reabsorbed by osmosis into the blood from the tubules of the nephrons, urine is more dilute, more water is lost during excretion
24
Q
where does the reabsorption of water take place?
A
water is reabsorbed into the blood along almost all of the nephron, but regulation of water potential mainly takes place in the loop of Henle, distal convoluted tubule and collecting duct, the volume of water reabsorbed by the DCT and collecting duct is controlled by hormones
25
what is the loop of Henle?
the loop of Henle is located in the medulla (inner layer) of the kidneys. It's made from two limbs - the descending limb and the ascending limb. The limbs control the movement of sodium ions so that water can be reabsorbed into the blood
26
why is ADH called antidiuretic hormone?
because diuresis is when lots of dilute urine is produced, so anti means a small amount of concentrated urine is produced
27
what is dehydration?
dehydration is what happens when you lose water, e.g. by sweating during exercise, so the water content of the blood needs to be increased
28
how do blood ADH levels rise when you're dehydrated?
water content of blood drops so its water potential drops, this is detected by osmoreceptors in the hypothalamus, the posterior pituitary gland is stimulated to release more ADH into the blood, more ADH means the DCT and collecting duct become more permeable so more water is reabsorbed by osmosis, a small amount of highly concentrated urine is produced so less water is lost
29
how do blood ADH levels fall when you're hydrated?
water content of blood rises so its water potential rises, detected by osmoreceptors in the hypothalamus, the posterior pituitary gland releases less ADH into the blood, less ADH so DCT and collecting duct become less permeable so less water is reabsorbed, a large amount of dilute urine is produced so more water is lost
30
describe what happens along the descending limb of the loop of Henle
there's a lower WP in the medulla than in the descending limb so water moves out of the descending limb into the medulla by osmosis, this makes the filtrate more concentrated (the ions can't diffuse out as the descending limb isn't permeable to them). The water in the medulla is reabsorbed through the capillary network
31
which cells monitor the water content of the blood?
osmoreceptor cells in the hypothalamus
32
explain the cause of the increase of ADH in the blood during strenuous exercise (4 marks)
strenuous exercise causes more sweating so more water is lost. This decreases the water potential of the blood. This is detected by osmoreceptors in the hypothalamus, which stimulates the posterior pituitary gland to release more ADH
33
explain the effect that increased ADH levels in the blood have on kidney function (2 marks)
the ADH increases the permeability of the walls of the distal convoluted tubule and collecting duct. This means more water is reabsorbed into the medulla and into the blood by osmosis
34
Gerbils have longer loops of Henle than mice, suggest and explain how this helps gerbils to produce less urine than mice (4 marks)
A longer descending limb means that more water can be absorbed into the blood from the nephron in the descending limb. A longer ascending limb means more ions are actively transported into the medulla . This means more water moves out of the collecting duct into the capillaries, giving a low volume of urine.
35
what is meant by homeostasis?
the maintenance of a constant internal environment
36
what is the internal environment?
made up of tissue fluids that bathe each cell, supplying nutrients and removing wastes, maintaining the features of this fluid at the optimum levels protects the cells from changes in the external environment, giving the organism a degree of independence
37
what does homeostasis involve?
trying to maintain the chemical make up, volume, and other features of blood and tissue fluid within restricted limits
38
what does homeostasis ensure?
that the cells are in an environment that meets their requirements and allows them to function normally despite external changes
39
how is homeostasis not no changes?
continuous fluctuations brought about by variations in internal and external conditions such as temperature, pH and water potential, occurring around an optimum point, homeostasis is the ability to return to that optimum point to maintain a balanced equilibrium
40
why is homeostasis important for maintaining a constant pH and temperature?
enzymes that control biochemical reactions and proteins such as channel proteins, are sensitive to changes in pH and temperature, which can reduce the rate of enzyme controlled reactions or denature enzymes/proteins, even small fluctuations can impair the function of proteins
41
why is the control of water potential important?
changes to the WP of the blood and tissue fluid may cause cells to shrink, expand or burst (osmotic lysis) as a result of water entering or leaving by osmosis, so cells cannot operate normally, WP also affects the rate of reactions by changing the concentration of enzymes/substrates
42
why is maintaining a constant blood glucose concentration important?
ensures a constant water potential, and a reliable source of glucose for respiration
43
what is the series of stages in control mechanisms?
the optimum point monitored by a receptor which informs coordinator, sending information to the effector, creating a feedback mechanism
44
what is the optimum point?
the point at which the system operates best, monitored by a receptor
45
what is a receptor?
detects any deviation from the optimum point, i.e. a stimulus and informs the coordinator
46
what is the coordinator?
coordinates information from receptors and sends instructions to the appropriate effector
47
what is an effector?
often a muscle or a gland, which brings about the changes needed to return the system to the optimum point, this return to normality creates a feedback mechanism
48
what is a feedback mechanism?
a receptor responds to the change in the system brought about by the effector
49
what is negative feedback?
when the change produced by the control system leads to a change detected by the receptor and turns the system off e.g. the regulation of blood glucose
50
what is positive feedback?
when a deviation from an optimum causes changes that result in an even greater deviation from the normal e.g. in neurones a stimulus leads to a small influx of sodium ions increasing the permeability to sodium ions, more ions enter causing a further increase in permeability and an even more rapid entry of ions
51
why is there many receptors and effectors?
allows them to have separate mechanisms that each produce a positive movement towards optimum, allowing a greater degree of control for the factor being regulated, important to ensure that the information provided by the receptors is analysed by the coordinator before action is taken e.g. temperature receptors in the skin may signal that the skin is cold so the body temperature should be raised, however information from regions in the hypothalamus may indicate that blood temperature is already above normal, e.g. during strenuous exercise when blood temps rise but sweating cools the skin; by analysing the information from all receptors the brain can decide the best course of action, to not raise body temp
52
how does the action of the effectors work harmoniously?
the control centre must coordinate the action of the effectors so that they operate harmoniously e.g. sweating would be less effective in cooling the body if it were not accompanied by vasodilation
53
what are endotherms?
inside heat, derive most of their heat from the metabolic activities that take place inside their bodies, e.g. birds and mammals
54
what are ectotherms?
outside heat, obtain a proportion of their heat from sources outside their bodies, from the environment, e.g. reptiles such as lizards
55
how do ectotherms regulate their body temperature?
body temperature fluctuates with that of the environment, they adapt their behaviour to changes in the external environment, by: exposing themselves to the sun, taking shelter, gaining warmth from the ground,
56
how do ectotherms regulate body temperature by exposing themselves to the sun?
orientate themselves so that the maximum surface area of their body is exposed to the warming rays
57
how do ectotherms regulate body temperature by taking shelter?
lizards shelter in the shade to prevent overheating when the sun's radiation is at it's peak, retreat into burrows at night to reduce heat loss when external temperature is low
58
how do ectotherms regulate body temperature by gaining warmth from the ground?
press their bodies up against areas of hot ground to warm themselves up, when required temperature is reached, they raise themselves off the ground on their legs
59
how do endotherms regulate body temperature?
gain most of their heat from internal metabolic activities, body temperature remains relatively constant despite fluctuations in the external temperature, like ectotherms they use behaviour to maintain a constant body temperature but also a range of physiological elements
60
how have endotherms adapted to cold climates?
evolved in cold climates to survive in these environments, e.g. small surface area to volume ratio, as heat is produced in volume and lost in surface area, mammals and birds in cold climates are relatively large (polar bears and penguins) and have smaller extremities, such as ears, and thick fur, feathers or fat layers to insulate the body
61
what mechanisms do endotherms have to make rapid body temperature changes in response to cold environments?
vasoconstriction, shivering, raising of hair, increased metabolic rate, decreased sweating, and behavioural mechanisms
62
how do endotherms increase/conserve body temperature through vasoconstriction?
diameter of arterioles near surface of skin made smaller to reduce the volume of blood reaching the skin surface through capillaries, most of the blood entering the skin passes beneath the insulating layer of fat so loses little heat to the environment
63
how do endotherms increase/conserve body temperature through shivering?
the muscles of the body undergo involuntary rhythmic contractions that produce metabolic heat
64
how do endotherms increase/conserve body temperature through raising of hair?
the hair erector muscles in the skin contract, raising the hairs on the body, this enables a thicker layer of still air, which is a good insulator, to be trapped next to the skin
65
how do endotherms increase/conserve body temperature through increased metabolic rate?
more of the hormones that increase metabolic rate are produced, metabolic activity, including respiration is increased so more heat is generated
66
how do endotherms increase/conserve body temperature through decreased sweating?
sweating reduces or ceases in cold conditions
67
how do endotherms increase/conserve body temperature through behavioural mechanisms?
sheltering from wind, basking in the sun and huddling together
68
how have endotherms adapted to a warm environment?
long term adaptations to a warm environment include having a large surface area to volume ratio and lighter coloured fur to reflect heat
69
what rapid responses do endotherms have that enable heat to be lost when the environment temperature is high?
vasodilation, increased sweating, lowering of body hair, behavioural mechanisms
70
how do endotherms decrease body temperature through vasodilation?
the diameter of the arterioles near the surface of the skin become larger allowing warm blood to pass close to the skin surface through the capillaries, the heat from this blood is then radiated away from the body
71
how do endotherms decrease body temperature through increased sweating?
evaporating water from the skin surface requires energy in the form of heat, in relatively hairless mammals (i.e. humans), sweating is an effective way to lose heat. In mammals with fur, cooling is achieved by the evaporation of water from the mouth and tongue during panting. The high latent heat of vaporisation of water makes sweating an effective way to lose heat
72
how do endotherms decrease body temperature through lowering of body hair?
the hair erector muscles in the skin relax and the elasticity of the skin causes them to flatten against the body, reducing the thickness of the insulating layer and allows more heat to be lost to the environment when internal temp is higher than external temp
73
how do endotherms decrease body temperature through behavioural mechanisms?
avoiding the heat of the day by sheltering in burrows and seeking out shade to help to prevent the body temperature from rising
74
How is blood glucose concentration lowered?
By increasing the rate of absorption of glucose into the cells, especially in muscle cells. By increasing the respiratory rate of the cells, which therefore use up more glucose, thus increasing their uptake of glucose from the blood. By increasing the rate of conversion of glucose into glycogen (glycogenolysis) in the cells of the liver and muscles. By increasing the rate of conversion of glucose to fat.
75
How is the role of insulin and B-cells of the Pancreas negative feedback?
The effect of these processes is to remove glucose from the blood and so return its concentration to the optimum, this lowering of blood glucose concentration causes the B cells to reduce their secretion of insulin (=negative feedback)
76
what is homeostasis?
the maintenance of a constant internal environment e.g. osmoregulation, tissue fluid, oxygen levels, thermoregulation, composition of the blood, blood glucose levels
77
explain why the control and maintenance of internal conditions is important for an organism
allows organisms to live in and adapt to changeable environments without affecting internal environments
78
why is the control of temperature important?
effects proteins, enzymes, protein channels, actin/myosin, denaturing
79
why is the control of oxygen levels important?
aerobic respiration, ATP, active transport, sodium potassium pump, muscle contraction, respiratory needs
80
why is the control of water levels important?
cells may shrivel (plasmolysed) or burst (lysed), turgidity in plants
81
why is the control of the composition of the blood important?
CO2 and O2 concentrations, too much CO2 blood acidic can lead to death
82
why is the control of tissue fluid important?
must supply cells with nutrients and remove waste
83
why is the control of blood sugar levels important?
maintains water potentials, glucose for respiration
84
what is a stimuli?
change to the system, internal or external
85
what are receptors?
detect variation
86
what is the control unit?
coordinates the response
87
what is an effector?
bring about the change
88
what is the output?
returns the body to set point
89
what is meant by feedback loop?
output is now stimuli, tells receptor about a change
90
what is thermoregulation?
the control of internal body temperature
91
what is an ectotherm?
maintain a proportion of their heat from sources outside of the body e.g. lizards, snakes (cold blooded)
92
what is an endotherm?
derive heat from sources and metabolic activities inside of their bodies e.g. mammals and birds (warm blooded)
93
what is the hypothalamus?
the control unit for most responses, links the nervous system to the endocrine system via the pituitary gland, responsible for the production of most hormones
94
what is the role of the hypothalamus?
produces hormones for temperature regulation, thirst, hunger, sleep, mood, release of other hormones within the body
95
How do insulin and glucagon act antagonistically?
They act in opposite directions, insulin lowers blood glucose concentration whereas glucose increases it
96
How is the system of blood glucose regulation selfie regulating?
Through negative feedback, it is the concentration of glucose in the blood that determines the quantity of insulin and glucagon produced, in this way the interaction of these two hormones allows highly sensitive control of blood glucose concentration
97
Why does the concentration of glucose fluctuate around an optimum point i.e. not constant?
Because of the way negative feedback mechanisms work - only when the blood glucose concentration falls below the set point is insulin secretion reduced (negative feedback) leading to a rise of blood glucose concentration; in the same way, only when the concentration exceeds the set point is glucagon secretion reduced (negative feedback) causing a fall in the blood glucose concentration.
98
what is the second messenger model of hormone action?
hormones are not lipid soluble so can't pass through the cell surface membrane (phospholipid bilayer) therefore adrenaline binds to a transmembrane protein receptor within the cell-surface membrane of a liver cell, this causes the protein to change shape on the inside of the membrane, leading to the activation of an enzyme called adenylate cyclase which converts ATP to cyclic AMP (cAMP), which acts as a second messenger that binds to protein kinase enzyme changing its shape and activating it, which catalyses the conversion of glycogen to glucose that moves out of the liver cell and into the blood by facilitated diffusion through channel proteins.
99
what is diabetes?
a metabolic disorder caused by an inability to control blood glucose concentration due to lack of or loss of responsiveness to insulin, has two forms type 1 and type 2
100
what is type one diabetes?
insulin dependent, body is unable to produce insulin, normally begins in childhood, may be the result of an autoimmune response where the body's immune system attacks it's own beta cells, develops quickly, usually over a few weeks, symptoms normally more obvious
101
what is type two diabetes?
insulin independent, normally due t o glycoprotein receptors on body cells being lost or losing responsiveness to insulin, or an inadequate supply of insulin from the pancreas, usually develops in people over 40 but increasing number of cases of obesity leading to diabetes in adolescents, develops slowly, symptoms usually less obvious and go unnoticed, people who are overweight are likely to develop it, 90% of diabetics are type 2
102
what are the signs/symptoms of diabetes?
high blood glucose concentration, presence of glucose in urine, need to urinate excessively, genital itching or regular episodes of thrush, weight loss, blurred vision, tiredness, increase thirst and hunger
103
what is a promising treatment/cure for diabetes?
transplanting insulin producing cells
104
how is type one diabetes controlled?
injections of insulin produced by GM bacteria, injected 2-4 times a day, dose must be matched to the glucose intake, if a person takes too much insulin they will experience low blood glucose concentrations that can result in unconsciousness, correct dose ensured by monitoring blood glucose concentration with biosensors
105
how is type 2 diabetes controlled?
regulating carbohydrate intake and matching this to the amount of exercise, can be supplemented by insulin injections or drugs that stimulate insulin production, other drugs can slow the absorbtion of glucose
106
what is the pancreas?
a large, pale-coloured gland that is situated in the upper abdomen, behind the stomach, produces enzymes for digestion and hormones for regulating blood glucose concentration (insulin and glucagon), made up of mostly cells that produce digestive enzymes with groups of hormone producing cells (Islets of Langerhans) scattered throughout
107
what are alpha cells?
smaller, produce glucagon
108
what are beta cells?
larger, produce insulin
109
what is insulin?
a globular protein made up of 51 amino acids
110
what is the role of the beta cells?
beta cells have receptors that detect the stimulus of a rise of blood glucose concentration and respond by secreting insulin into the blood plasma
111
what happens when insulin binds to glycoprotein receptors on body cells?
brings about a change in the tertiary structure of the glucose transport carrier proteins, causing them to change shape and allowing more glucose in via facilitated diffusion, an increase in the number of carrier proteins responsible for glucose transport in the cell surface membrane, at low insulin levels this protein is part of vesicles, a rise in insulin causes vesicles to fuse with the cell surface membrane, activation of enzymes that convert glucose into glycogen and fat
a level biology
flashcards
Decks in class (21)
# Cards
-
3.2.1 cellular biology88
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Stem Cells31
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Nervous Coordination52
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3.8 the control of gene expression0
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3.3.4 Mass Transport162
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3.3 Exchange With The Environment121
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3.4 Genetic Information, Variation And Relationships Between Orgainisms154
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3.2.4 immunology87
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3.1.5 - 3.1.8 DNA (structure and replication), ATP, water, inorganic molecules i’m78
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3.2.2 all cells arise from other cells55
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3.1 biological molecules139
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3.2.3 Transport across cell membranes66
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3.5 energy transfers in and between organisms66
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3.7 genetics populations evolution and ecosystems75
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3.6 organisms respond to changes in their internal and external stimuli97
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photosynthesis63
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muscle structure54
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Respiration65
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homeostasis111
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inheritance60
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paper 14
