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IMMS > Homeostasis > Flashcards

Homeostasis Flashcards

1
Q

Define homeostasis

A

Maintenance of a constant internal environment

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2
Q

Describe a simple feedback loop

A

Set point

Control centre

Effector

Regulated variable

Sensor

Back to the control centre

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3
Q

What are the two communication types in homeostasis

A

Endocrine - hormones

Nervous - electrical

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4
Q

Define autocrine signalling

A

Cells talking to themselves

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5
Q

Define paracrine signalling

A

Cells talking to neighbouring cells a short distance away

  • signal diffuses across gaps between cells
  • inactivated locally, so does not enter the blood stream
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6
Q

Does paracrine signalling enter the blood stream

A

No

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7
Q

Give two examples of paracrine signalling

A

Interleukins

Platelet derived growth factor

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8
Q

Describe interleukins

A

Signalling in the immune system

Mainly between white blood cells

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9
Q

Describe platelet derived growth factor

A

Released from platelets

Regulates cell growth

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10
Q

Describe endocrine signalling

A

Cells talking to other cells elsewhere in the body

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11
Q

Name the endocrine organs

A

Hypothalamus
Pituitary
Thyroid
Adrenals
Pancreas
Ovaries
Testes

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12
Q

Define a hormone

A

Molecule that acts as a chemical messenger

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13
Q

What are the classifications of hormones

A

By structure

  • amino-acid derivatives
  • peptide
  • steroid
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14
Q

Describe peptide hormones

A

Made of amino acids

Vary in size from few amino acids to small proteins

Some have carbohydrate side chains (glycoproteins)

Hydrophilic (like water)

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15
Q

Do peptide and amino acid hormones produce a quick or slow response in the body

A

Quick

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16
Q

Describe the route of a peptide hormone

A

Hormone pre-made and stored in a cell ready to be released when needed

Hormone dissolved in blood

Receptor on cell membrane

Chemical reactions produces quick response from cell - signal transduction cascade

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17
Q

Describe steroid hormones

A

All made from cholesterol

Different enzymes modify molecule to produce a variety of hormones

Cannot dissolve in water

Can dissolve in lipids

18
Q

Do steroid hormones produce a quick or slow response

A

Slow

19
Q

Describe the route of a steroid hormone e.g. testosterone

A

Testosterone made by cell and diffuses out once made

Transported in blood bound to transport protein as cannot dissolve in water

Receptor is in target cell

Slow response as directly affects DNA

20
Q

Of a 70kg male what is the total body water % and L

A

60%

42L

21
Q

Of a 70kg male what is the intracellular fluid % and L

A

40%

28L

22
Q

Of a 70kg male what is the extracellular fluid % and L

A

20%

14L

23
Q

Of 14L of extracellular fluid what is intravascular

A

3L

24
Q

Of 14L of intracellular fluid what is interstitial

A

11L

25
Q

Describe ECF

A

Na main

Anions Chloride and bicarbonate
Glucose and urea
Protein

26
Q

Describe ICF

A

Main K

27
Q

Describe interstitial fluid

A

Surrounds the cells but does not circulate

28
Q

What is the calculation for estimated plasma osmolality

A

2Na + 2K + urea + glucose mmol/L

29
Q

What osmolality are equal

A

Intra and extracellular

30
Q

What is normal plasma osmolality

A

275-295 mmol/Kg

31
Q

What are the consequences of dehydration

A

Thirst

Dry mouth

Inelastic skin

Sunken eyes

Raised haematocrit

Weight loss

Confusion - brain cells

Hypotension

32
Q

What are the consequences of water excess

A

Hyponatraemia

Cerebral overhydration
- headache
- confusion
- convulsions

33
Q

Define hydrostatic pressure

A

Pressure difference between plasma and interstitial fluid

Water moves from plasma into interstitial fluid

34
Q

Define oncotic pressure

A

Pressure caused by the difference in protein concentration between the plasma and interstitial fluid

Water moves from interstitial fluid into plasma

35
Q

Describe oedema

A

Excess accumulation of fluid in interstitial space

Disruption of the filtration and osmotic forces in circulating fluids
- obstruction of venous blood or lymphatic return
- inflammation = increased capillary permeability
- loss of plasma protein

36
Q

Define serous effusion

A

Excess water in body cavity

37
Q

What are the reasons for oedema and serous effusion

A

Increased fluid leakage into interstitial spaces OR impaired reabsorption of fluids

38
Q

Describe transudate serous effusion

A

Fluid is pushed through the capillary due to high pressure within the capillary

Low protein content

39
Q

Describe exudate serous effusion

A

Fluid leaks around the cells of the capillaries caused by inflammation and increased permeability of pleural capillaries to protein

High protein content

40
Q

Normal reference range for sodium

A

135-145 mmol/L

41
Q

What is the range for serum calcium

A

2.1-2.6 mM

50% serum calcium ionised (free)
50% bound to albumin (so cannot diffuse into cells)

42
Q

What are the three routes to get to serum calcium

A

GI - Vit.D

Kidney - PTH/Vit.D/FGF23

Bone - PTH/Vit.D

IMMS (16 decks)

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