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Biology > Excretion and Homeostasis > Flashcards

Excretion and Homeostasis Flashcards

1
Q

Excretion

A

The removal of waste substances of metabolic reactions and respiration.

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2
Q

Egestion

A

The removal of undigested food from the body as faeces

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3
Q

Metabolic wastes produced by the body include:

A
  • Carbon dioxide and water from aerobic respiration

- Urea produced by the breakdown of excess proteins in the liver

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4
Q

Forms of excretory wastes:

A
  • Urine: produced by the kidney and stored in the bladder
  • Sweat: excreted from the body through the skin
  • Carbon dioxide: exhaled from the lungs
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5
Q

Toxicity

A

Waste products can have toxic effects if they are allowed to reach high concentrations.
Carbon dioxide dissolves in water easily to form an acidic solution which can lower the pH of cells. This can reduce the activity of enzymes in the body which are essential for controlling the rate of metabolic reactions

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6
Q

Osmotic effect

A

Body fluids can become more concentrated due to higher amounts of waste products, this can cause water to move out of cells, changing their water potential and preventing them from carrying out essential reactions.

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7
Q

Using up necessary storage

A

Space within an organism is limited and is required for the storage of more useful molecules

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8
Q

The waste products

A

urea, excess salts and water which come together to form urine.

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9
Q

Excretory organs

A
  • Kidney: urine
  • Lungs: CO2 and H2O
  • Skin: excess mineral ions and water (sweat)
  • Liver: breakdown proteins into urea
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10
Q

Two key functions of the urinary system are:

A
  • > To filter waste products from the blood and expel it from the body as urine
  • > To control the water levels of the body (osmoregulation)
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11
Q

Urinary System

A

Consists of two Kidneys -> joined to the Bladder by two tubes called the Ureter -> another tube called the Urethra (which is where the urine passes through to excreted).

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12
Q

What is the kidney also connected to?

A

Renal artery and Renal vein

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13
Q

Renal artery

A

Comes from the aorta and delivers oxygenated blood to the kidney

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14
Q

Renal vein

A

Delivers the deoxygenated blood from the kidney to the vena cava

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15
Q

Inner part of the kidney

A

Medulla

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16
Q

Outer part of the kidney

A

Cortex

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17
Q

Nephrons

A

The individual structures which filter the blood

18
Q

The functions of the kidney:

A
  • They regulate the water content of the blood

- They excrete the toxic waste products of metabolism and substances in excess of requirements.

19
Q

The section of the Nephron

A 
Bowman’s capsule
Proximal convoluted tubule
Loop of Henlé
Distal convoluted tubule
Collecting duct
20
Q

What is Homeostasis?

A

Keeping the conditions in the internal environment of the body constant

21
Q

What is Osmoregulation?

A

The maintenance of the water and salt content of the internal environment.

22
Q

What is Ultrafiltration?

A

In which water, ions ,glucose and other small molecules pass into the tubule (but not proteins or cells)

23
Q

What is Selective Reabsorption?

A

The process where certain molecules (e.g. ions, glucose and amino acids), being filtered out of the capillaries along with nitrogenous waste products (i.e. urea) and water in the glomerulus, are reabsorbed from the filtrate as they pass through the nephron.

24
Q

The process of Ultrafiltration

A

Arterioles branch off the renal artery and lead to each nephron, where they form a knot of capillaries (the glomerulus) sitting inside the cup-shaped Bowman’s capsule
The capillaries get narrower as they get further into the glomerulus which increases the pressure on the blood moving through them (which is at high pressure because it is coming from the renal artery which is connected to the aorta)
This eventually causes the smaller molecules being carried in the blood to be forced out of the capillaries and into the Bowman’s capsule, where they form what is known as the filtrate

25
Q

The process of Selective Reabsorption

A

In the proximal convoluted tubule, glucose is reabsorbed into the bloodstream by active transport. It is important that the blood can claim back all of the glucose to be used for respiration.
Further along the nephron, in the collecting duct, as much water as needed is reabsorbed back into the bloodstream. If we happen to be dehydrated, more water will move from the nephron into the bloodstream. This leaves the waste products in the nephron tubule which travel as urine through the ureter to be stored in the bladder.

26
Q

Reabsorption of glucose and Diabetes

A

People with diabetes cannot control their blood glucose levels and they are often very high, meaning that not all of the glucose filtered out can be reabsorbed into the blood in the proximal convoluted tubule.
As there is nowhere else for the glucose to be reabsorbed, it continues in the filtrate and ends up in the urine
This is why one of the first tests a doctor may do to check if someone is diabetic is to test their urine for the presence of glucose

27
Q

The importance of Osmoregulation?

A
  • > Too much water in the blood results in cells swelling as water moves into them, this has a diluting effect and can lead to cell lysis (bursting)
  • > Too little water in the blood (or too high an ion concentration) and the cells lose water by osmosis, this has a dehydrating effect and can lead to cell death
28
Q

Loop of henle

A

It is involved with concentrating the fluid in the tubule by causing more water to be reabsorbed in the blood.

29
Q

What is ADH?

A

ADH is a hormone that helps regulate the amount of water in your body. It works to control the amount of water your kidneys reabsorb as they filter out waste from your blood.

30
Q

What does ADH control?

A

If the water content of the blood is too high then less water is reabsorbed, if it is too low then more water is reabsorbed.

31
Q

What releases ADH?

A

The pituitary gland in the brain constantly releases ADH.

How much ADH is released depends on how much water the kidneys need to reabsorb from the filtrate

32
Q

What if the water content of the blood is too high?

A

The pituitary gland releases less ADH which leads to less water being reabsorbed in the tubules of the kidney (the tubules become less permeable to water)
As a result, the kidneys produce a large volume of dilute urine.

33
Q

What if the water content of the blood is too low?

A

The pituitary gland releases less ADH which leads to less water being reabsorbed in the tubules of the kidney (the tubules become less permeable to water)
As a result, the kidneys produce a large volume of dilute urine.

34
Q

What is negative feedback?

A

When the feedback causes the corrective measures to be turned ‘off’, so it returns the system to its original or normal level.

35
Q

Meaning of Diuresis

A

The flow of urine from the body

36
Q

Meaning of anti-diuresis

A

producing less urine. ADH starts to work when your body loses too much water.

37
Q

Hypothalamus

A

They are receptor cells in a region of the brain. It has a vital role in controlling many bodily functions including the release of hormones from the pituitary gland.

38
Q

Role of ADH

A

The ADH travels in the bloodstream to the kidney. At the kidney tubules, it causes the collecting ducts to become more permeable to water, so that more water is reabsorbed back into the blood. This makes urine more concentrated, so that the body losses less water and the blood becomes more dilute.

39
Q

Large quantities of urine?

A

Pale yellow in colour because it is less concentrated.

40
Q

Small quantities of urine?

A

Darker yellow / orange in colour because it is more concentrated.

41
Q

Process of ultrafiltration

A

Renal Artery transports Oxygenated blood to the Glomerulus within the Bowman’s Capsule under high pressure
The hydrostatic pressure forces the small molecules to leave the glomerulus and enter in the Bowman’s capsule.
Blood is therefore filtered at high pressure to produce Glomerular Filtrate composed of Water, Glucose, Salts and Urea
However, as Proteins and Red blood cells are too large to be filtered through base membrane - material between Glomerulus and Bowman’s Capsule, they will remain in blood

Biology (5 decks)

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