Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biology A Level > Homeostasis > Flashcards

Homeostasis Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

Excretion is

A

The removal of metabolic waste from the body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Main functions of th kidney include

A

Filtering waste products out of the blood

Reabsorbing useful solutes

Carrying out osmoregulation to control the water potential of the blood by maintaining water and salt , also helps to control PH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Each kidney is supplied with

A

Blood from a renal artery and is drained by blood from the renal vein.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

The kidney removes waste products during variable amounts of salt ad water from

A

The blood and produces urine

It then passes through the ureters to the bladder and released out of the body through the urethra

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

The outer region of the kidney s called
Inner region i called
Centre

A

The cortex
Medulla
Forms the pelvis which drains urine into the ureters

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Each kidney contains thousands of tiny tubules called

A

Nephrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Nephron structure

A

Begins with a cup shaped structure called a renal (bowman s) capsule followed by the proximal convoluted tubule then loop of henle which leads into the distal convoluted tubule and finally joins a collecting duct.
Blood flowing through an afferent arteriole which has branched from the renal. Artery forms a capillary network called the glomerulus within the renal capsule.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

4 stages of formation of urine

A

Ultrafiltration
Selective reabsorption
Water reabsorption
Osmoregulation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Ultrafiltration process

A

Blood flows into the glomerulus from the afferent arteriole which is wider than the efferent arteriole which carries blood away
This increases the pressure in the glomerulus compared to the pressure in the bowmans capsule which forces blood plasma through the pores in the blood capillary, though the basement membrane and epithelial cells of the renal capsule forming glomerular filtrate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Ultra filtration adaptations

A

Endothelial cells; narrow gaps allowing blood plasma through

Basement membrane; mesh of collagen and glycoprotein fibres which act as the filter only allowing molecules through with a relative molecular mass less than 69000, which means large proteins and cells are filtered out, the presence of proteins in the remaining blood lowers the water potential and ensures some water is retained.

Epithelial cells of the renal capsule called podocytes; have finger like projections, fluid passes between these processes into the lumen of the bowmans capsule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Substances that would form the glomerular filtrate

A 
Ions 
Glucose 
Amino acids 
Urea
Water
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Selective reabsorption

2

A

The glomerular filtrate contains many substances that the body still needs .
All the glucose, all the amino acids and some salts are reabsorbed as a result of active transport and facilitated diffusion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Selective reabsorption process

3

A
  1. The sodium-potassium pump actively moves Na+ from the cells lining the proximal convoluted tubule into the tissue fluid by active transport using ATP. This lowers the concentration of Na+ in the cell cytoplasm
  2. Na+ are transported into the cell of the PCT along with glucose and amino acids by a co transporter protein by facilitated diffusion
  3. Glucose and amino acids then diffuse along a concentration gradient out of the epithelial cells into the tissue fluid and then into the blood capillary (some water will also pass in this direction due to the water potential gradient)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Adaptations of the epithelial cells of the proximal convoluted tubule for absorption
4

A
  1. Folding of membrane on capillary side to increase surface area and presence of sodium pottasium pump for active transport
  2. Membrane on lumen side contains co transporter proteins for facilitated diffusion
  3. microvilli of the epithelial cells of the PCT provide a large surface area for absorption
  4. Large numbers of mitochondria to produce ATP for active transport.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Water reabsorption
Loop of henle
5

A

The loop of henle consists of the descending limb and ascending limb
The ascending limb is impermeable to water
The descending limb is permeable to water

The ascending limb can actively transport Na+ and Cl- out which lowers the water potential in the tissue fluid of the medulla ( Na+ and Cl- diffuse out near the bottom of the ascending limb)
Na+ and Cl- ions diffuse into the descending limb

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How water is reabsorbed

A
  1. Na+ and Cl- are actively transported out of the ascending limb into the tissue fluid in the medulla. The ascending limb is impermeable to water, so the water stays inside the tubule.
  2. Because there is a lower water potential in the medulla than in the descending limb, water moves out of the descending limb into the medulla by osmosis. The water in the medulla is then reabsorbed back into the blood through the capillary network.
  3. Some Na+ and Cl- diffuse back into the descending limb
  4. Near the bottom of the ascending limb, Na+ and Cl- diffuse out into the medulla, further lowering the water potential in the medulla.
  5. The water potential gradient in the medulla also causes water to move by osmosis from the DCT and collecting duct into the medulla and then enter the blood capillaries
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Hairpin counter current

A

Describes the arrangement of the tubule in a sharp hairpin, so that one part of the tubule passes close to the other part with fluid flowing on the opposite direction. This allows exchange of material and allows the increase in concentration of ions in the medulla.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

ADH

A

Anti diuretic hormone

Controls water levels in the body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Osmoregulation

In the DCT and collecting duct

A

Water potential of the blood is monitored by osmoreceptors in the hypothalamus of the brain.
Osmoreceptors are cells in the hypothalamus which are sensitive to changes in blood water potential.
When water potential of the blood decreases, osmosreptors cells lose water by osmosis.
They lose volume and sends signals to the posterior pituitary gland causing to to release ADH hormone.
When ADH is released and enters the bloodstream, it is transported to the distal convoluted tubule and collecting duct, where it binds to membrane bound receptors and causes protein channels called aqua porins to move into the membranes.
This makes the walls of the DCT and collecting duct more permeable to water, as this allows more water to move out of the DCT and collecting duct by osmosis back into the blood causing the urine to be more concentrated,

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Dehydration

5

A

The water content of the 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 that the DCT and collecting duct are more permeable, so more water is reabsorbed into the blood by osmosis.
A small amount of highly concentrated urine is produced and less water is lost.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Hydration

5

A

The water content of the blood rises, so its water potential rises
This is detected by the osmoreceptors in the hypothalamus
The posterior pituitary gland releases less ADH into the blood
Less ADH means that the DCT and collecting are less permeable, so less water is reabsorbed into the blood by osmosis
A large amount of dilute urine is produced and more water is lost.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Desert animals loop of henle

A

Very long to conserve water
Longer loop means more Na+ and Cl- are actively transported out of the ascending limb
Therefore the water potential in the medulla. Is even lower, so the more water moves by osmosis from the descending limb, DCT and collecting duct into the medulla and then is reabsorbed back into the blood.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is homeostasis

A

The maintenance of the internal environment in a constant state within an organism despite external changes.
Organisms can only function if internal conditions such as temperature , PH, water potential and blood glucose concentration are kept within a narrow range.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Importance of homeostasis

A

It is particularly important to maintain the right core body temperature and blood PH because temperature and PH affect enzyme activity and enzymes control the rate of metabolic reaction.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Important to maintain the right blood glucose concentration because

A

Cells need glucose for respiration to produce ATP, and blood glucose concentration also affects water potential of the blood.

26
Q

How temperature affects rate of an enzyme controlled reaction
GRAPH 3

A

1- rate of reaction increases when the temperature increases because molecules have more kinetic energy so are more likely to collide and more ESC form
2- optimum temperature, rate of reaction at maximum
3- increase in temperature above optimum causes molecules to vibrate more, breaks some of the hydrogen and ionic bonds bonds that hold the enzyme in its 3D shape. Active site changes shape and substrate no longer fits , enzymedenatures , no ESC

27
Q

PH

4

A

Calculated based on the concentration of hydrogen ions in the environment
Grater the conc of H+, lower PH
Expressed on a logarithmic scale
Each value on scale is ten times larger than one before using log10

28
Q

Why do enzymes become denatured if blood PH is too acidic r alkaline

A

Ionic bonds and hydrogen bonds that hold the enzymes 3D shape are broken so the shape of the enzymes active site changes
Substrate no longer fits , no ESCs

29
Q

Blood glucose conc if too high

A

Water potential of blood is reduced to where water molecules move out of the cells into blood by osmosis down gradient
Can cause the cells to crenate. 9shrivel)

30
Q

Blood glucose conc too low

A

Cells are unable to carry out normal activities because there isn’t enough glucose for respiration to provide ATP

31
Q

Negative feedback

A

Process that brings about reversal of any change in conditions
Ensures that an optimum steady state can be maintained, as the internal environment is returned to its original set of conditions after any change
Any deviation from the norm or set point results in a response being taken which retores the norm
Once the norm is restored, response is inhibited

32
Q

Homeostasis involves multiple negative feedback mechanisms for each thing being controlled because
2

A

Having more than one mechanism gives more control over changes in your internal environment
If there was only one NF mechanism,resp9nse would be slower and would have less control.

33
Q

Positive feed back

A

Increases any change detected by the receptors
Does not lead to homeostasis because it doesn’t keep your internal environment stable
Used to rapidly activate processes in your body
Can also occur when there has been breakdown of homeostatic mechanism

34
Q

Positive feedback example

A

Formation of blood clot after injury

Platelets release chemical which activates more platelets

35
Q

Negative feedback mechanism and glucose concentration

A

BGC regulated by NF

36
Q

Blood glucose concentration vary depending on

A

Food intake and energy requirements
Homeostatic ally controlled
Fluctuates within normal range of 90mg in every 100cm^3 of blood

37
Q

Two hormones in homeostatic regulation of plasma glucose levels

A

Insulin and glucagon

38
Q

Where are insulin and glucagon produced

A

In and alpha and beta islet cells

39
Q

If blood glucose concentration rises too high
HYPERGLYCAEMIA
4+4

A

Detected by alpha and beta cells in pancreas
Causes beta cells to release insulin
Alpha cells stop producing glucagon
Insulin lowers blood glucose concentration by binding to receptor proteins found on the plasma membrane of liver,fat and muscle cells
This leads to;
1. More glucose transport proteins are placed on the cell surface membrane
2, more glucose can therefore enter the cell
3. Enzymes are activated that convert glucose in the cell to glycogen(glycogenesis)
4. More glucose used in respiration

40
Q

Glycogen =

A

Storage carbohydrate

Insoluble so doesn’t affect cells water potential

41
Q

If blood glucose concentration fallls too low
HYPOGLYCAEMIA
7

A

Alpha cells within the islets of langerhan in the pancreas detect this and release hormone glucagon
Beta islet cells of the pancreas stop real easing insulin
Glucagon raises blood glucose concentration by binding to receptors on the plasma membrane of the target cells, liver cells
This causes stored glycogen to be hydrolysed into glucose( glycogenolysis)
The glucose diffuses out of the target cells into the blood
Target cells also take up less glucose and the rate of respiration of glucose decrease. Lipids or amino acids used in respiration instead
Glucagon also activates enzymes that are involved in the formation of glucose from non carbohydrates ( gluconeogenesis)

42
Q

Glucose transporters

2

A

Channel proteins which allow glucose to be transported across a plasma membrane
Skeletal and cardiac muscles cells contain a glucose transporter called GLUT4

43
Q

GLUT4

A

When insulin levels are low GLUT4 is stored in vesicles in the cell cytoplasm
When insulin binds to receptors on the plasma membrane , it causes the movement of GLUT4 to the membrane
Glucose can then be transported into the cell through the GLUT4 protein by facilitated diffusion

44
Q

Glucose

A

Monosaccharide

Respiratory substrate

45
Q

Glycogen

A

Polysaccharide made up of lots of alpha glucose molecules bonded together by glycosidic bonds
Energy storage molecule

46
Q

Glucagon

A

Protein hormone

Binds to complimentary receptors on plasma membrane of target cells

47
Q

Glycogenesis

A

Conversion of glucose into glycogen by condensation reaction s

48
Q

Glycogenolysis

A

Conversion of glycogen into glucose by hydrolysis reaction

49
Q

Gluconeogenesis

A

Conversion of non carbohydrates into glucose

50
Q

Adrenaline secreted from adrenal gland is secreted when

3

A

Low glucose concentration
Stressed
Exercising

51
Q

Adrenaline binds to

Increases blood glucose concentration by (2)

A

Receptors in the plasma membrane of liver cells

Activates glycogenolysis
Inhibits glycogenesis

52
Q

Adrenaline also

2+1

A

Activates Glucagon secretion
Inhibits insulin secretion

Gets the body ready for action y making more glucose available for muscles to respire

53
Q

Diabetes mellitus

A

Disease in which the body is no longer able to control its blood glucose concentration properly.
The disease leads to fluctuations in blood glucose concentrations,

54
Q

Very highglucose concentrations after a meal

A

Hyperglycaemia

55
Q

Vey low blood glucose concentration after exercising or fasting

A

Hypoglycaemia

56
Q

Type 1 diabetes

A

Beta cells of the pancreas are attacked by the immune system therefore they can’t produce insulin
After eating the blood glucose concentration rises and remains high
The kidney can’t reabsorb all the glucose, some of its excreted in the urine
Regular injections of insulin a meal times

57
Q

Type 2 diabetes

A

Usually required later in life
When beta cells don’t produce enough insulin or the target cells become less responsive to insulin due to insulin receptors on plasma membranes not working properly
Risk factors include lack of exercise, obesity, poor diet, family history an ethnic origin
can be controlled initially by diet, losing weight and regular exercise
Glucose lowering medication can be taken if diet and exercise can’t control it
Eventually insulin injections may be needed
Type II is becoming increasingly common n the UK, it is linked with additional health problems including visual impairment and kidney failure

58
Q

Both adrenaline and glucagon activate

A

Glycogenolysis inside a cell even though they bind to receptors on the outside

59
Q

First messengers
2
+2

A

Adrenaline and glucose

When they bind to hormone receptors, this activates an enzyme on the inside of the plasma membrane, which then causes a chemical to be produced.
This is known as a secondary messenger

60
Q

Second messenger activated by adrenaline and glucagon

A

Cyclic AMP

61
Q

Mode of action of adrenaline and glucagon

6

A

Adrenaline or glucagon is the first messsnger
They are unable to enter the target cell
Adrenaline or glucagon binds to their complimentary shaped receptor proteins in their plasma membrane of target cells
Binding activates the enzyme adenylate Cyclase which converts ATP to cyclic AMP- the second messenger inside he cell
CAMP activates a protein called protein kinase A
This starts a cascade of enzyme actions within the cell that causes glycogen to be broken down into glucose

Biology A Level (18 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions