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Biology - BY4 > 4.6: Control Systems > Flashcards

4.6: Control Systems Flashcards

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0
Q

Why does your body require a certain constant environment?

A

Mostly because of your enzymes which are sensitive to temprature and pH

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1
Q

Define homeostasis.

A

The mechanisms by which a constant environment is maintained within a living organism.

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2
Q

Give three examples of homeostatic control systems.

A

Maintaining constant blood glucose levels. Thermoregulation (maintenance of a constant temprature) osmoregulation (maintenance of constant water/solute levels in body fluids)

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3
Q

Why is homeostasis important?

A

It allows conditions inside the cell to remain at their optimum. This desired optimum level at which the system operates is known as the Norm or set point. Homeostasis allows cells to function normally regardless of the outside environmental conditions.

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4
Q

What are the two ways through which your body can react to changes in the environment?

A

Nerve signals (electrical signals) Hormones (endocrine chemical systems.)

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5
Q

Outline the properties of nerve signals.

A

These are fast and useful for immediate response.

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6
Q

Outline the properties of hormones.

A

These have a slower response than nerve signals - minutes, hours, days, weeks They consist of proteins secreted by glands They are carried by the blood to their target organ.

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7
Q

Outline a nervous response.

A

Sense organs detect a stimulus and send a signal to the brain via nerves which then sends a signal back to the muscles and nerves.

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8
Q

What is an endocrine gland?

A

These secrete hormones directly into the bloodstream. e.g thyroid gland, pituitary gland, adrenal gland.

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9
Q

What is an exocrine gland?

A

Exocrine glands secrete proteins like enzymes through ducts. E.g salivary glands, gastric glands.

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10
Q

What is the aim of a homeostatic process?

A

To maintain the NORM.

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11
Q

Outline a negative feedback loop.

A

1.) a receptor detects a stimulus (a change from the norm) 2.) a coordinator receives information from the receptor and initiates the required corrective mechanism - it may communicate with one or several effectors. 3.) an effector carries out the corrective mechanism to restore the NORM 4.) information is sent back to the receptor to switch off the loop once the correction has been made.

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12
Q

Give some examples of stimuli and their receptors.

A

Blood sugar is monitored by detectors in the pancreas. Blood water levels are monitored by osmo receptors in the brain Body temperature is monitored by the hypothalamus. Blood pressure is monitored by stretch receptors in blood vessels.

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13
Q

What can a negative feedback system only respond to?

A

Problems. I.e blood sugar being too high or too low.

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14
Q

Define negative feedback

A

A series of changes that result in the substance/condition being returned to its normal level.

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15
Q

What makes a homeostatic mechanism efficient?

A

When there is minimal fluctuation around the NORM/set point.

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16
Q

Give an example of a positive feedback loop.

A

The prolactin loop.

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17
Q

What does your body need to balance in order to maintain the water potential of the blood in a roughly steady state?

A

Water uptake from diet Water loss from sweating Water loss by evaporation from the lungs Water loss from faeces Water loss from urine.

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18
Q

What organ is responsible for osmoregulation?

A

The kidneys.

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19
Q

What is another function of the kidneys?

A

Removal of nitrogenous waste from the blood.

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20
Q

What are the three main connections to the kidney?

A

The renal artery - provides oxygenated blood The renal vein - removes deoxygenated blood Ureter - removes urine produced in the kidneys and transports it to the bladder.

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21
Q

What is the nitrogenous waste product in mammals?

A

Urea.

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22
Q

How is urea produced?

A

Unwanted amino acids are deaminated in the liver producing ammonia which is then converted urea which diffuses into the bloodstream.

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23
Q

What is the detector/receptor, coordinator and effector n the insulin loop?

A

Detector/receptor: pancreas Coordinator: insulin Effector: liver

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24
Q

label this diagram of kidney system structure.

A
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25
Q

Label this diagram of the kidney/

A
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26
Q

label the parts of this nephron.

A
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27
Q

What is the name of the vessel that takes blood to the glomerulus?

A

The afferent arteriole.

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28
Q

What is the name of the vessel that takes blood away from the glomerulus?

A

The Efferent arteriole

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29
Q

What is the function of the Cortex?

A

Mostly filtering waste products and readsorbing nutrients.

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30
Q

What is the function of the Medulla?

A

Mostly involved in concentrating urine.

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31
Q

What is the function of the Pelvis?

A

Collection of urine for excretion

32
Q

What is the function of the Glomerulus and bowman’s capsule?

A

Ultrafiltration.

33
Q

What is ultrafiltration?

A

This is filtration under pressure through a basement membrane.

34
Q

What is contained in the blood passing through the afferent arteriole?

A

Blood cells, plasma, protiens,

35
Q

What are fenestrated capillaries?

A

These are capillaries with large numbers of fenestrations (“windows”) which are spaces in the capillary epithelium covered by a basement membrane.

36
Q

What is filtered out by the blood capillary fenestrations, basement membrane and Bowman’s capsule podocytes?

A

Blood cells and plasma protiens.

37
Q

Label this diagram of a nephron and surrounding capillaries.

A
38
Q

label this diagram of a nephron.

A
39
Q

What are podocytes?

A

These are the “foot like” cells that wrap themselves around the fenestrated capillaries of the glomerulus - making up part of the bowman’s capsule - and providing slits through which blood can be filtered.

40
Q

What does the filtrate in the bowman’s capsule contain?

A

Glucose, salts, water and urea.

41
Q

Why does they hydrostatic pressure in the glomerulus have to be high?

A

To overcome the back pressure in the bowman’s capsule due to the presence of colloidal plasma protiens in the blood.

42
Q

Define hydrostatic pressure.

A

The pressure exerted or transmitted by the fluid (e.g. water) at rest

43
Q

Why is hydrostatic pressure high in the glomerulus?

A

The renal artery is close to the aorta and so blood is pumped through at high pressure

this pressure is further increased because the lumen of the capillaries are much smaller so more resistance.

The efferent arteriole is smaller than the afferent arteriole, further increasing risistance to the passage of blood and increasing pressure.

44
Q

What is the function of the proximal convoluted tubule?

A

Selective reabsorbtion

45
Q

What is selective reabsorbtion?

A

this is the reabsorbtion of all the small molecules that need to go back into the blood, not to be excreted in urine. (e.g all the glucose and most of the salts) by active transport and some of the water by osmosis.

46
Q

How is the proximal convoluted tubule adapted for its function?

A

It is the longest region of the nephron (14mm) and widest part (60um) part of the nephron in order to increase the surface area for reabsorbtion.

The wall is made out of a single layer of cells in order to keep the diffusion distance short.

The renal capillaries are close to the tubule, providing a short diffusion pathway for reabsorbtion.

47
Q

How are the cells of the proximal convoluted tubule adapted for its function?

A

The cells in the tubule walls (filtrate side) have lots of microvilli to increase the surface area for reabsorbtion (to fit in lots of carrier protiens). They also have lots of mitochondria to produce ATP by aerobic respiration to provide energy for active treansport. On the other side of the cells next to the capillaries (basolateral membrane) the membrane is also highly folded - giving rise to inercellular spaces.

48
Q

Why is the proximal convoluted tubule able to reabsorb water passively by osmosis?

A

Because it just passed all the solutes (glucose, salts, amino acids) back to the blood capillaries which still have their colloidal plasma protiens. These factors results in a lower water potential in the blood than in the tubules so 85% of the water moves back into the blood by osmosis.

49
Q

Outline selective reabsorbtion in the Proximal convoluted tubule.

A
  1. ) solutes are actively transported into the epithelial cells from the filtrate by carrier protiens.
  2. ) Solutes are then actively transported out of the epithelial cells and into the intercellular spaces by carrier protiens.
  3. ) Solutes are now in the intercellular space between the epithelial cells and capillaries, reducing the water potential of the intracellular spaces and causing the solutes to move into the capillaries by diffusion where they are then removed by the bloodstream to the renal vein and away.
  4. ) This sets up a concentration gradient between the filtrate and epithelial cells so solutes can also move from the filtrate into the epithelial cells by facillitated diffusion.
50
Q

What is in the medulla?

A

The collecting duct and loop of henle

51
Q

What is in the cortex?

A

Glomerulus and bowman’s capsule

proximal and distal convoluted tubules.

52
Q

What is the function of the loop of henle?

A

Reabsorbtion of water and Na⁺ and Cl⁻ ions.

53
Q

How does the loop of henle create a water potential gradient?

A

By actively pumping out Na⁺ and Cl⁻ ions out f the ascending limb into the surrounding medulla tissue fluid.

54
Q

How does the loop of henle facilitate water reabsorbtion by osmosis?

A
  1. ) A ψ gradient is established by pumping out ions in the ascending limb which is impermeable to water.
  2. ) as water cannot leave the ascending limb it moves out of the descending limb which is water permeable and is taken away in the bloodstream making the filtrate more concentrated in the descending limb. The descending limb is impermeable to ions.

The higher osmolarity filtrate in the descending limb then moves into the ascending limb and Is made hypotonic by the actions of the Na⁺ and Cl⁻ pumps. This is a hairpin loop counter-current multiplier system resulting in increasing concentration gradient differences between the limbs as you go down the loop.

55
Q

What is the function of the distal convoluted tubule?

A

Acidifying urine, osmoregulation (the cell walls become permeable to water by the action of ADH in the same way as in the collecting tubules) and sodium reabsorbtion.

56
Q

What is the structure of the distal convoluted tubule

A

Does not have microvilli, large numbers of mitochondria to provide energy in the form of ATP to power active transport of salt. ADH receptors in the basolateral membrane.

57
Q

What are the three main processes involved in the functioning of the nephron?

A

Ultrafiltration, selective reabsorbtion, secretion and osmosis.

58
Q

What are the main functions of the nephron/kidney?

A

Osmoregulation and excretion.

59
Q

What is excretion and why is it important?

A

Excretion is the removal of waste products of metabolism from the body. If these waste products are allowed to build up inside tissues and cells these waste products can be toxic.

60
Q

What are the main waste products of animal metabolism?

A

Carbon dioxide from respiration

nitrogenous waste from the breakdown of excess amino acids and nucleic acids.

bile from the breakdown or erythrocytes.

61
Q

What is deamination?

A

The process by which excess amino acids which are not assimilated are broken down into harmless products through the removal of the amino group. The rest of the amino acid (keto acids) is either used in respiration or converted to carbohydrate/lipid to be stored.

62
Q

In what form do fish excrete nitrogenous waste?

A

In fish (and other aquatic organisms) the amino group is converted to ammonia which is a highly toxic waste product, so cannot be allowed to build up in cells. It cannot be stored and needs to be removed from the body immediately. Ammonia is small and soluble so fish can overcome these problems by using allot of water to dilute it to non toxic levels and excrete it safely.

63
Q

In mammals the ammonia produced through deamination is converted to urea

A
64
Q

Why do fish have a problem with water balance?

A

Because their cells have a lower ψ than their surroundings because their

65
Q

Why do mammals excrete urea?

A

mammals don’t have large amounts of water available to dilute ammonia because of issues with dehydration. Urea is much less toxic than ammonia so it can be stored for a little while in the tissues and requires less water to dilute it to safe levels.

66
Q

How do bacteria convert between ammonia and urea?

A

By using an enzyme called urease to convert urea to ammonia.

67
Q

How do eukaryotes convert between ammonia and urea?

A

Via a process called urea biosynthesis (ornithine cycle) which requires three A.T.P.

68
Q

Where does deamination occur in mammals?

A

Mainly in the liver.

69
Q

In what form do reptiles, birds and insects excrete nitrogenous waste and why?

A

As uric acid. Uric acid has a low toxicity and can be stored for long periods of time and can be excreted safely with very little water. This makes it very handy if an organism lives somewhere arid (e.g desert lizards) or if you can’t carry lots of water around (e.g birds). It’s also safe enough to let it accumulate inside the egg without causing damage. It is excreted as a semi-solid white paste. Making uric acid is energetically expensive.

70
Q

What are the factors that affect what form of nitrogenous waste an organism excretes?

A

The availability of fresh water within an organisms habitiat

how much control is needed over water loss

Whether waste needs to be stored

weather an organism develops in an amniote egg as an embryo

71
Q

What is another means of controlling water balance?

A

Organisms have evolved different length loops of henle in response to the water conditions of their habitat. Due to the hairpin loop counter-current multiplication effect the solute concentration is greater at the bottom of the loop than at the top. So if you want to lose less water you have a longer loop of henle as the longer the loop the higher the alt concentration at the bottom. This allows you to reabsorb more water in the loop of henle and collecting ducts by osmosis.

72
Q

What is metabolic water?

A

Metabolic water is water produced from the oxidation of food reserves. E.g camels release water from stored fat in their humps through respiration.

73
Q

On what kind of system does osmoregulation work on?

A

Negative feedback.

74
Q

What are the receptors involved in osmoregulation?

A

Osmoreceptors in the hypothalamus. Osmoreceptors work by looking at the concentration of Na⁺ ions in the blood.

75
Q

What happens when osmoreceptors in the hypothalamus detect a deviation from the norm?

A

They send a neuronal signal to another part of the brain - the posterior lobe of the pituitary gland. The prosterior pituitary gland acts as the coordinator.

76
Q

What happens when the pituitary gland receives an neuronal response from the hypothalamus? (ADH negative feedback loop)

A

The pituitary gland secretes a hormonal messenger - Anti diuretic hormone (A.D.H). This binds to receptors on the basolateral(capillary side) membrane of the cells that make up the collecting duct (and distal convoluted tubule) which causes vesicles with water channels (aquaporin 2) in their membranes within the cells to merge with the apical (lumen side) membrane making the cell permeable to water encouraging further water reabsorbtion.

77
Q

What happens once the norm water potential is restored in the ADH negative feedback loop?

A

The osmoreceptors in the hypothalmus detect that the norm has been restored and this causes the rate of neruronal impulses to the prosterior pituitary gland to fall and this in turn causes less ADH to be secreted. This finally results in the permeability of the distal convoluted tubule and collecting ducts to water to drop and a higher volume of hypotonic urine is produced.

Biology - BY4 (6 decks)

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