Session 1 ILOs - Homeostasis & Examining tissues

Question 1

Define homeostasis with respect to water, temperature and pH balance

Answer 1

Homeostatis is ‘homeo’ meaning sameness and ‘stasis’ meaning standing still - this applies to water, temperature and pH balance

Question 2

Explain concepts behind positive and negative feedback loops

Answer 2

Positive and negative feedback loops act to maintain homeostasis
A negative feedback loop consists of a stimulus, a sensor, a control point (set point) and an effector - which then feeds back to try to remove the stimulus EXAMPLE: Blood glucose levels
A positive feedback loop amplify their initiating stimuli and they move the system away from its starting state EXAMPLE: Blood clotting

Question 3

Explain the importance of acid-base balance for normal human physiology

Answer 3

If acid-base balance is not maintained i.e. too acidic (7-7.35) can because acidosis and too alkaline (7.45-7.8) can because alkalosis

Question 4

State the ‘normal range’ for pH in tissues including blood

Answer 4

pH range: 7.35 - 7.45

Question 5

State the ‘normal range’ for core body temperature

Answer 5

Core body temp: 36.5 - 37.5 degrees

Question 6

Recall the mechanisms (in broad terms) that regulate pH and core body temperature

Answer 6

pH:
Phosphate buffer system
Carbonic acid-bicarbonate buffer system
Protein buffer system (incl. amino acid buffers, haemoglobin buffer system and plasma protein buffers)

Core body temp:

1. Shivering/sweating
2. Vasconstriction/vasodilation
3. Piloerection/pilorelaxation
4. Curling up/stretching flat

Question 7

State the body compartments where fluids accumulate

Answer 7

Of the 42 L of fluid in a standard 70kg male:
2/3 = intracellular fluid (inside the cell)
1/3 = extracellular fluid
(of that 1/3 ECF)
3/4 = interstitial fluid
1/4 = plasma

Question 8

Compare and contrast water balance in males and females (and in very young and very old)

Answer 8

% water = greater in males compared to females (females have a higher proportion of body fat which displaces water)

AGE:
Infants/very young = around 70% of body mass is water
Elderly = around 40-50% of body mass is water

WEIGHT:
Underweight = 10% higher, around 70% for 70kg male
Overweight = 10% Lower, around 50% for 70kg male

Question 9

Outline the difference between dehydration and water toxicity

Answer 9

Dehydration occurs where water loss increases osmolarity (more negative) outside the cell, so water leaves the cell down the osmotic gradient = cell shrinkage
Water toxicity occurs when the increase in water volume dilutes the fluid surrounding the cell, leading to a decreased osmolarity (less negative) and water moves into cell by osmosis = cell bursts

Question 10

Describe the process of oedema

Answer 10

Oedema (fluid retention) occurs when hydrostatic pressure is greater than oncotic pressure which leads to water being forced out of the capillary and into the interstitial space

Question 11

State the percentage of water in a standard 70kg male

Answer 11

60%

Question 12

State the meaning of the term ‘tissue’ and provide an example of each of the 4 types

Answer 12

Defined as cell woven together

1. Epithelial tissue
2. Connective tissue
3. Muscle tissue
4. Nerve tissue

Question 13

State the relationship between milli-, micro- and nano-metres

Answer 13

Each value has a difference of 1,000 or 10^3
Milli = 10^3
Micro = 10^6
Nano = 10^9

Question 14

Define the term, “limit of resolution”

Answer 14

Minimum distance that 2 objects can be apart that you are able to distinguish between the two

Question 15

Explain why electron microscopes are capable of finer resolution than light microscopes

Answer 15

Wavelength of an electron can is much shorter than that of visible light photons, so electron microscopes have a higher resolving power (much greater magnification) than light microscopes

Question 16

Describe common biopsy techniques (e.g. Curettage, needle, transvascular, etc.) giving examples of tissues which can be sampled by each method

Answer 16

1. Endometrial biopsy/cutterage - effectively scratching off cells using a small scoop EXAMPLE endometrial tissue
2. Pipelle - removes a small section of tissue EXAMPLE endometrial tissue
3. Hysterectomy - removal of most or all of the organ EXAMPLE entire uterus
4. Venepuncture - process of obtaining intravenous access for the purpose of venous blood sampling
5. Aspiration (mainly bone marrow) - Jamshidi needle is inserted into the bone marrow to obtain a biopsy

Question 17

Explain why tissue needs to be fixed and state which fixatives are commonly used

Answer 17

Tissues need to be fixed to prevent purification & preserve material as close to their natural state = preserve tissue
Formalin solution (10% buffered) most commonly used

Question 18

Describe how tissue processing can lead to the formation of shrinkage and other artefacts

Answer 18

After fixation, tissues need to be dehydrated by alcohol and this can cause shrinkage. Artefacts can form at any point in tissue processing

Question 19

Discuss the value of histological staining and state the components of tissue stained by routine stains, such as Haematoxylin and Eosin (H&E) and specialist methods, such as immunohistochemistry and immunofluorescence

Answer 19

Staining is used to highlight important features of the tissue as well as to enhance the tissue contrast
Haemotoxylin = stains/binds to acidic structures e.g. nucelus
Eosin = stains/binds to basic structures e.g. cytoplasm or extracellular matrix

Question 20

Outline the advantages conferred by phase contrast, dark field, fluorescence, and confocal light microscopy

Answer 20

Advantages of the below:
Phase contrast - allows manipulation of the cells e.g. work out function of some drugs
Dark field - allows you to view objects that are unstained, transparent and absorb little or no light
Fluoresence - high sensitivity and specifity i.e. only binds to specific target protein
Confocal light microscopy - ability to control depth of field, elimination or reduction of background information away from the focal plane

Question 21

State how a cell functions by describing the structure and function of the major cell components and organelles

Answer 21

Nucleus - contains genetic information/material
Mitochondria - generates most of the chemical energy (ATP)
Plasma membrane - selective membrane that separates the interior of the cell from the outside environment
Ribosomes - site of protein synthesis
Lysosomes - contains digestive enzymes which break down excess or worn-out cell parts and may be used to destroy invading viruses and bacteria
Golgi apparatus - responsible for packaging proteins into vesicles prior to secretion
Rough ER - takes polypeptides and amino acids from the cytosol and continues protein assembly
Smooth ER -

Question 22

State how a cell functions by describing the structure and function of the major cell components and organelles

Answer 22

Nucleus - contains genetic information/material
Mitochondria - generates most of the chemical energy (ATP)
Plasma membrane - selective membrane that separates the interior of the cell from the outside environment
Ribosomes - site of protein synthesis
Lysosomes - contains digestive enzymes which break down excess or worn-out cell parts and may be used to destroy invading viruses and bacteria
Golgi apparatus - responsible for packaging proteins into vesicles prior to secretion
Rough ER - takes polypeptides and amino acids from the cytosol and continues protein assembly
Smooth ER - role in detoxifying some organic chemicals converting them to safer water-soluble products