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Biology > 15 - Homeostasis > Flashcards

15 - Homeostasis Flashcards

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1
Q

Endotherms​

A

Control their body temperature within strict limits​

Use a variety of mechanisms to control body temperature independent of external temperature

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2
Q

Ectotherms

A

Are NOT able to control body temperature​

Rely on external sources of heat and Body temperature fluctuates with external temperature​

May use behavioural mechanisms to control body temperature

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3
Q

What animals are ectotherms?

A

animals except mammals and birds are ectotherms.​

​

…reptiles, amphibians and fish, invertebrates etc…​

​

Ectotherms obtain most of their heat from outside their bodies​

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4
Q

A number of processes can cause an organism to cool down / warm up:​

A

Exothermic metabolic reactions e.g. respiration​

Latent heat of evaporation – large amounts of thermal energy are required to convert a liquid into a gas​

Radiation – transmission of electromagnetic waves to and from the air / water / ground​

Convection – currents of fluid moving – warm air or water rises and cooler air / water sinks​

Conduction – heating as a result of the collision of molecules transferring energy

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5
Q

Ectothermic regulation​ - Advantages

A

Use less food in respiration​

Need to find less food​

Can survive longer periods without food​

Greater proportion of energy used for growth

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6
Q

Ectothermic regulation​-Disadvantages​

A

less active in cooler temperatures – more at risk of predation​

May not be capable of activity in winter months​

Metabolic reactions are slower

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7
Q

ectotherms Behavioural responses

A

Expose body to sun… bask​

Hide in shade​

Alter body posture e.g. laying flat​

Alter body position e.g. climb off ground​

Bathe / wallow in water or mud

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8
Q

ectotherms ​Physiological responses:

A

rate of metabolic reactions​

Colouring​

Increase breathing movements

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9
Q

Endotherms temp contro

A

​

Endotherms able to control the heat energy released in exothermic reactions to maintain body temperature. ​

​

Endotherms also show behavioural and physiological adaptations to maintain a constant temperature

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10
Q

Endotherm behaviours…

A

Move into shade e.g. burrow​

Increase exposed surface area​

Remain inactive ​

Wallow in water / mud​

Aestivation​

Move into sunlight (basking)​

Press body onto warm surface​

Move about to generate heat in muscles​

Huddling​

Roll into a ball to decrease surface area​

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11
Q

Endotherms Advantages​

A

Constant body temp. regardless of external​

Activity possible even when cool – less risk of predation​

Can inhabit colder parts of planet

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12
Q

Endotherms Disadvantages

A

Significant amount of energy used up to maintain constant temperature.​

More food required​

Less energy used in growth

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13
Q

What detects changes in body temperature?

A

Thermoregulatory centre is in the hypothalamus (brain)

Also peripheral temperature receptors (‘around the outside’)​

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14
Q

Thermoregulatory centre is in the hypothalamus (brain)​

A

Monitors blood temperature​

Detects changes in core temperature​

Acts as a thermostat

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15
Q

three main metabolic waste products?

A

CO2 -> waste product of cellular resiration
Bile pigments -> formed from breakdown of haemoglobin and are excreted in the liver into the small intestine
-> Urea - nitrogenous waste products formed from the breakdown of amino acids by the liver

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16
Q

facts about the liver

A

The largest organ in the human body (excluding the skin)​

Makes up 5% of body mass​

holds 13% total blood at any one time​

Made of left & right lobes​

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17
Q

what is the liver essential for

A

Essential for detoxification, carbohydrate metabolism & storage, fat metabolism, production of proteins, digestion, deamination, thermoregulation, storage of minerals etc.​

​

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18
Q

explain the structure of the liver

A

Liver cells are called hepatocytes​

Hepatocytes form small structures called lobules​

Lobules combine to make both main lobes of the liver (left & right)​

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19
Q

features of hepatocytes, and why?

A

large nuclei, prominent goolgi apparatus and lots of mitochondria
-> very metabolically active

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20
Q

blood supply of the liver

A

Hepatic artery – from the heart so is oxygenated​

(Hepatic) Portal vein – from the digestive system. Rich in nutrients but may also contain toxins and is deoxygenated​

Hepatic vein - takes blood from the live back to the heart (deoxygenated)

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21
Q

Hepatic vein

A

liver -> HV -> vena cava -> heart
- contains deoxygenated blood with some products of digestion
- varying levels of glucose

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22
Q

hepatic artery

A

supply’s the liver with oxygenated blood

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23
Q

Hepatic portal vein

A

Heart -> intestines -> HPV -> liver
- carries products of digestion (glucose AA lipids) to the liver
- it is deoxygenated as the blood has been supplied to the digestive system
3 times more blood

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24
Q

explain a lobule

A
  • collection of different cells in a hexagonal shape
  • The centre of each has a branch of the hepatic vein (leaving the liver)
  • at the corners lobules are branches of the hepatic artery and the hepatic portal vein​ and bile duct (portal triad)
  • sinusoids is the area where blood from the hepatic artery and portal vein mix (surrounded by hepatocytes)
  • Blood moves along multiple layers through the lobule
  • contains Kupffer cells
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25
Q

Hepatocytes lining the SINUSOIDS absorbs ….

A

products in blood and secrete products into the blood as it flows over them.​

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26
Q

Kupffer cells​

A

Specialised macrophages​

The role of these is to destroy worn out red and white blood cells, bacteria and foreign matter arriving from the digestive tract

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27
Q

where does bile travel through a sinusoids

A

Special cells produce​

bile, which flows through BILE CANALICULI.

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28
Q

three functions of the liver

A

carbohydrate metabolism
deamination of excess amino acids
detoxification

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29
Q

carbohydrate metabolism
where? how?

A

in the liver
-> when BGL too high insulin rises, and the hepatocytes are stimulated to convert glucose into carbohydrate storage. same for the revers

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30
Q

what is deamination of amino acids

A

removal of amino group from amino acids

Amino acids are broken down into ammonia & various molecules such as keto acids.​ =-> Ammonia is highly toxic and very soluble, so as soon as the ammonia is made, it enters the next stage of the process.​

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31
Q

Excretion is​

A

Removal of waste products of metabolism from the body​

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32
Q

Metabolism is​

A

the chemical processes that occur within a living organism in order to maintain life​

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33
Q

Homeostasis is​

A

Maintenance of a constant internal environment

34
Q

Sinusoids are​

A

A type of blood vessel that serves as a location for mixing of the oxygen-rich blood from the hepatic artery and the nutrient-rich blood from the portal vein

35
Q

Hepatic Artery is​

A

blood vessel that supplies oxygenated blood to the liver​

36
Q

Hepatic vein is​

A

blood vessel which transports the liver’s deoxygenated blood and blood which has been filtered by the liver to the inferior vena cava​

37
Q

what is it called when ammonia from deamination is converted to urea, and why

A

Due to the high toxicity and solubility of ammonia (NH3), following its production by deamination, it is immediately converted into a less soluble and less toxic substance called urea. This conversion, which occurs in 3 stages, is called the ornithine or urea cycle​

38
Q

the ornithine cycle?

A

Ornithine is an amino acid, which is used to generate the urea​
Needs energy in the form of ATP​

​

One turn of the cycle: ​

consumes 2 molecules of ammonia ​

consumes 1 molecule of carbon dioxide ​

creates 1 molecule of urea CO(NH2)2​

regenerates a molecule of ornithine for another turn.​

​

39
Q

Glycogen is an important polysaccharide that is found as dense granules in the cytoplasm of the ____________ (liver cells) but can also be found in ________ cells. A highly _________ polysaccharide, glycogen is compact and does not occupy a large amount of ______, therefore making it ideal as a _______ of energy. ______ soluble than monosaccharides like glucose, glycogen is also an important provider of energy. Formed of a long chain of ___-glucose molecules, which are held together by both ____ and _____ glycosidic bonds, these molecules can be easily snipped off from the end of the chain by __________ when required for metabolic reactions like ___________​

​

A

hepatocytes
branched
space
store
Less
α
1, 4 and
1, 6
hydrolysis
respiration​

40
Q

Detoxification​

A

Detoxification is the process of converting toxic substances into harmless ones or removing them from the body. Most of which happens in the liver & kidneys.​

41
Q

give two examples of detoxification

A

-> breadown of hydrogen peroxide. catalase splits hydrogen peroxide into oxygen and water
-> alcohol dehydrogenase breaks down ethanol to ethanal. ethanal is converted to ethanoate (can used fo build up fatty acids or cellular respiration)

42
Q

blood supply of the kidneys

A

The kidneys are supplied with blood from the renal artery branching off the aorta​

Blood is taken away via the renal vein connecting to the inferior vena cava​

43
Q

kidney structure

A

cortex- dark outer layer where he filtering of the blood takes place *(has dense capillary network carrying blood form the renal artery to nephrons)

medulla- lighter in colour and contains the tuble of the nephrons that form the pyramids and collecting ducts

pelvis- where the urine collects

44
Q

Overview of kidney structure​

A

The kidney is made of millions of specialised filtering units called NEPHRONS…​

…which drain into the renal pelvis… ​

…which empties into the ureter…​

…which carries urine to the bladder for storage…​

…before the bladder opens and urine passes out of the body through the urethra

45
Q

each part of the nephron
where are they cortex or medulla

A

Bowman’s capsule - cortex
proximal convoluted tubule - cortex
(descending) Loop of Henle (ascending) - medulla
distal convoluted tubule - cortex
collecting duct - medulla

46
Q

Bowman’s capsule

A

The first part of the nephron is the Bowman’s capsule and a specialised bundle of capillaries called the glomerulus which, together, carry out ULTRAFILTRATION.

47
Q

proximal convoluted tubule

A

The second part is the proximal convoluted tubule and SELECTIVE REABSORPTION occurs here.

48
Q

Loop of Henle

A

​

The third part is a long hairpin called the Loop of Henle that passes from the cortex into the medulla. This region is essential for establishing an ion concentration gradient in the surrounding tissue fluid

49
Q

distal convoluted tubule

A

The fourth part is a second twisted tubule called the distal convoluted tubule and is where further selective reabsorption occurs to fine tune the water balance of the body in response to ADH.

50
Q

collecting duct,

A

The final is called the collecting duct, where water balance of the body continues to be fine-tuned in response to ADH.

51
Q

What gets filtered out of the glomerulus and into the Bowman’s capsule​, how?

A

glucose, water, inorganic mineral ions, urea, amino acids

Whether a substance is filtered out of the glomerulus and into the nephron is dependent upon the size of the molecule (< mr 69 000)​

Small molecules are filtered and become part of the filtrate whereas the large molecules are trapped in the blood​

52
Q

arteriole A is wider than arteriole B supplying the glomerulus
name A and B

what does this mean for the glomerulus

A

A is the afferent arteriole
B is the efferent arteriole

  • glomerulus pressure rises
53
Q

outline the three components of the ultrafiltration system

A

capillary endothelium - provides a barrier to cells but not plasma proteins​
basement membrane - water and small molecules can pass through
Epithelium of renal capsule​ contains podocytes

54
Q

capillary endothelium as a filter in the kidney

A
  • very thin
  • perforated with thousands of pores of about 10 nm diameter
  • provides a barrier to cells but not plasma proteins
55
Q

basement membrane as a filter in the kidney

A
  • mesh of collagen and glycoprotein fibres
    • water and small molecules can pass through
  • proteins are too large and are repelled by negative charges on fibres
56
Q

what should not be in the glomerulus filtrate

A

Cells, platelets and plasma proteins cannot pass through the filter and remain in the capillary​

57
Q

what should be in the glomerulus filtrate

A

Small molecules such as;​​
water​​
glucose ​​
amino acids ​​
ions​​
Urea (waste product of protein metabolism)​

58
Q

In a healthy person there should be ​​what in the glomerulus filtrate

A

NO red blood cells​​

NO platelets ​​

NO large plasma proteins ​

59
Q

Describe and explain the differences and similarities in blood plasma concentrations and glomerular filtrate concentrations of molecules​

A

. Ultrafiltration​

. Proteins have a much lower conc in the glomerular filtrate ​

. Because most are too large to pass through filter​

Or because only some (0.05) small enough to pass through filter​

. At least 3 of: water, inorganic ions, urea, uric acid, glucose, amino acid concentrations the same​

. Because all get filtered out​

. As all are small molecules

60
Q

what does the bowman’s capsule lead into

A

proximal convoluted tubule

61
Q

what happens at PCT​​
why

A

All glucose, amino acids, vitamins and hormones reabsorbed back into blood by active transport.​​

Approx. 85% water and sodium chloride reabsorbed.​​

Na+ moved by active transport​​

Cl- follows by diffusion​​

Water moves out of tubule into blood by osmosis​

62
Q

Adaptations of proximal convoluted tubule​

A

Microvilli give large surface area for exchange of materials​​

Large numbers of mitochondria (ATP from respiration for active transport)​

63
Q

How does the proximal convoluted tubule reabsorb amino acids?​

A
  • Na+ ions are pumped out of the epithelial cells (active transport)​
  • Na+ concentration gradient is created between the PCT and the epithelial cytoplasm​
  • Diffusion of Na+ down its concentration gradient provides the energy to move glucose and amino acids through co-transporters into the epithelial cell (indirect active transport)​
  • Amino acids and glucose move by facilitated diffusion down their concentration into the capillary​
64
Q

1) Descending Limb​

A

As water moves down the descending limb into the medulla the water potential gradient increases because…. ​

There is a high concentration of ions in the surrounding tissue fluid of the medulla (as a result of activity of the ascending limb)​

Descending limb is permeable to water but impermeable to ions, so water moves out by osmosis.​

​
Water in the tissue fluid continues to move into the capillary network surrounding the loop of Henle​

Tubule fluid reaching the bottom of the hairpin is VERY concentrated (and HYPERTONIC) to the blood in the capillaries​

65
Q

2) Ascending Limb​
Lower part of ascending limb​

A

Filtrate is very concentrated because… water has left in the descending limb​

It is permeable to sodium and chloride ions​

This causes… diffusion of ions e.g. salts out of the loop down their concentration gradient

66
Q

2) Ascending Limb​
Upper part of ascending limb​

A

As the water potential of the filtrate becomes close to the water potential in the surrounding tissue fluid…​

Active transport of sodium and chloride ions out of the nephron into surrounding medulla tissue causes :​

Water potential of filtrate… to increase (becomes more dilute)​

Solute concentrations of filtrate…to decrease​

Ultimately, this means… tissue fluid of the medulla develops a very high concentration of ions so that water will move out by osmosis (in the collecting duct) and urine will be more concentrated than blood​

67
Q

3) Distal convoluted tubule

A

Fluid in the tubule entering the DCT is hypotonic to blood again (more dilute)​

If the body lacks salt, sodium ions are actively pumped out of nephron into blood, and chloride ions follow passively down their electrochemical gradient.​

Permeability of the DCT to water changes, depending on requirements of the body. Water can leave the DCT to conserve water and produce a smaller volume of concentrated urine.

68
Q

ADH and the collecting duct ​

A

The walls of the collecting duct can be made more or less permeable to water according to the needs of the body.​

This allows more or less water to be reabsorbed back into the blood.​

Controlled by antidiuretic hormone (ADH) in the blood

69
Q

What if there is less ADH in the blood?

A

Less ADH in the blood means that less water is reabsorbed.​

The cell surface membrane folds inwards to create new vesicles that remove the aquaporins from the membrane.​

The wall is less permeable and more water passes out in urine.

70
Q

Osmoreceptors & neurosecretory cells​

A

Neurosecretory cells in the hypothalamus produce ADH in their cell body, which flows down the axon to the posterior pituitary gland where it is stored until needed. ​

Osmoreceptors in the hypothalamus monitor the blood’s water potential

71
Q

response to low water potential in the blood

A

Dehydration​
Decreased water potential of blood​
Osmoreceptors cells in hypothalamus lose water (so shrink)
Stimulates posterior pituitary gland to release ADH
ADH carried in the blood
ADH arrives at the collecting duct
ADH stimulates cAMP and the insertion of aquaporins into the wall

72
Q

Kidney failure causes

A

Kidney infections- structure of podocytes and tubule may be damaged – blood and /or protein in urine​

Raised blood pressure- can damage epithelial cells and basement membrane of Bowman’s capsule​

  • blood and/or protein in urine​

Genetic conditions e.g. polycystic kidney disease, where kidney tissue is replaced by fluid filled cysts or the cysts damage the kidney tissue​

Diabetes (high blood sugar can damage blood vessels in kidneys)​

Overuse of some drugs e.g. aspirin

73
Q

Consequences of complete kidney failure​

A

The body is no longer able to control the balance or excretion of urea, mineral ions & water. This causes:​

Electrolyte imbalance : excess Na+ , K +and Cl- cannot be excreted creating osmotic imbalance in tissues which can be fatal.​

Urea builds up and poisons cells causing illness & death.​

High blood pressure - water balance is not maintained, so causes rise in blood pressure leading to heart problems and strokes.

Joint Pain – due to build up of certain proteins in the blood.​

Weakened bones – calcium/phosphorus balance cannot be maintained, affecting the mineralisation of bones.​

Anaemia – kidneys produce hormone erythropoietin which stimulates bone marrow to produce erythrocytes. Decreased hormone production leads to decreased number of erythrocytes and tiredness and lethargy as a result.

74
Q

How do we test for kidney failure?​

A

First sign​

blood and /or protein in urine​

Detection of other symptoms associated with kidney failure

How is this tested & quantified?​

Measuring the “glomerular filtration rate”

75
Q

Glomerular filtration rate (GFR)

A

Indication of the rate at which blood is filtered at the Bowman’s capsule into the tubule.​

It is estimated indirectly by measuring creatinine levels in blood
Creatinine not reabsorbed or secreted, exclusively filtered through the kidneys.​

rate of excretion = rate of filtering​

Higer blood creatinine levels = lower GFR

76
Q

Treating kidney failure

A
  1. Kidney dialysis​

​

2 types:​

a) Haemodialysis​

b) Peritoneal dialysis​

​

  1. Kidney transplant
77
Q
  1. Haemodialysis
A

Passive process relies on concentration gradients​

No active processes​

Takes about 8 hours per session​

Must be repeated several times a week​

Must manage diet carefully- low protein and salt diet. Control water intake. Why?​

Can eat and drink what they like at start of dialysis process

78
Q

how does haemodialysis work

A
  1. Blood enters under pressure from radial artery.​
  2. Pump controls pressure /flow​
  3. Blood thinners prevent clotting​
  4. Blood flows between selectively permeable dialysis membranes​
  5. Filtered blood passes through trap for air bubbles before returning to radial vein.

Concurrent flow

79
Q

What is in the dialysis fluid?haemodialysis ​

A

Always contains​

Water​

Glucose​

Mineral ions​

Also may contain (bicarbonate, acetate, amino acids etc.)​

These all must be in appropriate proportions to maintain the delicate balance in the blood.​

​

Never contains​

Urea​

Other waste products (e.g. urobilin)

80
Q

Peritoneal dialysis

A

Dialysis fluid introduced into abdomen.​

Left for several hours​

Diffusion occurs across the membranes (especially peritoneal membrane), moving waste products into the dialysis fluid.​

Dialysis fluid containing waste is drained.

Biology (24 decks)

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