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Needed Flashcards

1
Q

What makes up the university of Wisconsin solution

A

No sodium or chloride to prevent influx and swelling

extracellular impermeant solutes e.g. raffinose

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2
Q

Define tonicity

A

The strength of a solution that takes into account cell permeability

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3
Q

Define osmolarity

A

Osmolarity is a measure of the concentration of all solute particles in a solution

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4
Q

How much of fluids does interstitial fluid make up

A

36%

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5
Q

Give an example of a fibrotic disorder

A

Liver cirrhosis

Excessive production of fibrous connective tissue

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6
Q

Describe osteoarthritis

A

excessive loss of ECM so cushioning properties are lost

Cleavage of aggrecan by aggrecanase and metalloproteinase - loss to the synovial fluid

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7
Q

What is the function of aggrecan and how is structure related

A

Resistance of compressive forces

-ve charge helps retain water which is lost when compressed but then regained

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8
Q

Describe the structure of aggrecan

A 
GAGs are highly sulphated and present in a no. of carboxyl groups
-ve charge (sodium attracted)
Feather like structure 
Chondroitin sulfate attachment largest
Keratan sulfate attachment
Hyaluronan binding region
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9
Q

Describe hyaline cartilage

A

Abundant type of cartilage found in many places
Cushions ends of long bones
Rich in Aggrecan

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10
Q

Describe decorin

A

Small proteoglycan

Binds to collagen, essential for fibre formation

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11
Q

Describe hyaluronan

A

Long repeated disaccharide with NO core protein
Unsulphated
Synthesised at the cell surface

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12
Q

Describe the structure of a GAG

A

1 of the 2 sugars is always amino sugar

sulphated or carboxylate -> highly -ve

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13
Q

Which property of GAGs contribute to function

A

Large volume to mass ratio and the hydrated gel can be very resistant to compression

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14
Q

What is a proteoglycan

A

GAGs are long, unbranched sugars of repeating disaccharides

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15
Q

What is the function of fibronectin

A

Regulating cell adhesion and migration in embryogenesis and tissue repair
wound healing
continuum with actin

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16
Q

Describe the structure of fibronectin

A 
Multi-adhesive
Large multi domain molecule
open hairpin shape/horeshoe 
Collagen, integrin and heparin binding sites 
50nm
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17
Q

What occurs in congenital muscular dystrophy

A 
Absence of 𝛼2 in laminin 2
Symptoms evident from birth
Hypotonia 
Weakness
Deformities of joints
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18
Q

Give an example of a condition associated with laminins

A

Interacts with receptors such as integrins and dystroglycan

Self-associate with the basement membrane and other components (type IV collagen, proteoglycans)

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19
Q

Describe the structure of laminins

A 
𝛼 chain, β chain, 𝛾 chain
Very large (160-400 AA) and multi-adhesive
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20
Q

Describe the structure of multi-adhesive glycoproteins

A

Large and modular

Multifunctionality due to multiple binding sites for matrix components and receptors

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21
Q

Describe the structure of the basement membrane

A

Describe the structure of the basement membrane

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22
Q

Give an example of a disorder relating to the basement membrane

A

Alport syndrome
Mutations n gene for type IV collagen
Basal membrane is split and laminated - filtration issues and loss of kidney function

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23
Q

Describe elastin

A

Important for elasticity e.g. skin, blood vessels, lungs
Core of elastin and surface microfibrils rich in fibrillin
Interwoven with collagen to limit extent of stretching

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24
Q

Give an example of a disorder relating to elastin

A

Marfan’s

Elastic fibres cannot function due to mutations in fibrillar 1

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25
Q

Describe type IV collagen

A

network-forming collagen
Present in all basement membranes
assembles into a sheet-like network

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26
Q

Describe the biosynthesis of collagen

A
  1. Synthesis on the RER
  2. Ribosomes synthesise collagen polypeptides
  3. Hydroxylation with lysine and proline
  4. Glycosilation
  5. 3 chains form the helix
  6. Release from the cell via a vesicle
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27
Q

Describe the structure of collagen

A

3 𝛼 chains in a triple helix

Every 3rd amino acid is a glycine that occupies the interior as it is the only AA small enough

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28
Q

What is the function of the brainstem

A

Target source of all cranial nerves with numerous functions

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29
Q

Describe astrocytes

A

Most abundant in the CNS
Able to proliferate
Neuroglial

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30
Q

What are the functions of astrocytes

A

Structure
Cell repair
Immune cells
Neurotransmitter release and re-uptake

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31
Q

Describe an oligodendrocyte

A

Variable morphology and function
Numerous projections that form internodes of myelin
Myelinates axons

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32
Q

What is the function of Schwann cells

A

Produces myelin for peripheral nerves

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33
Q

What is the function of Microglial cells

A

Immune functions in the CNS

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34
Q

What is the function of ependymal cells and where is it found

A

Regulates the production and movement of cerebrospinal fluid. Found lining fluid filled ventricles

35
Q

Describe the ultrastructure of skeletal muscle myofibres

A 
Consists of myofibres (bundles)
large and cyclindrical
multinucleated
packed with myofibrils
sarcoplasmic reticulum - calcium stores 
T-tubules
36
Q

Describe the structure of a sarcomere

A

Z-line - Lateral boundaries
Actin - Polymeric thin filament composed of two twisted 𝛼-helices - displays polarity
Myosin - Thick filaments with globular heads that interact with actin
Titin - Very large springy filaments anchoring myosin to the Z-line
Nebulin - Large filaments associated with actin
Tropomyosin - Elongated protein bound to actin
CapZ & Tropomodulin - associated with +ve & –ve ends of actin, respectively

37
Q

Explain sliding filament theory

A
  1. Ca2+ release -> movement of troponin from tropomyosin
  2. Exposure of the myosin binding site on the actin chain
  3. Charged myosin heads bind to the exposed sites
  4. Binding + ADP discharge causes the myosin head to pivot (power stroke), pulling the actin filament towards the centre of the sarcomere
  5. ATP binding releases myosin head from the actin chain
    ATP hydrolysis provides energy to recharge the myosin head
38
Q

Explain the process of excitation in skeletal muscle

A
  1. Action potential propagates along the myofibre membrane (sarcolemma) 7 T-tubules
  2. Depolarisation activates dihydropyridine receptors (DHPR)
  3. Conformational change in DHPR
  4. Transmission to ryanodine receptors (RyR) on sarcoplasmic reticulum
  5. Opening of RyR & release of Ca2+ from intracellular stores
  6. Depolarisation -> increase in intracellular Ca2+
39
Q

Describe excitation contraction coupling in cardiomyocytes

A

Same as skeletal muscle

depolarisation opens voltage-gated calcium channels

40
Q

What effects does calcium have in cardiac muscle

A

Ca2+ induced Ca2+ release by binding to RyR on SR
Initiate contraction binding to troponin
Further depolarisation

41
Q

Describe the structure of smooth muscle

A

in walls of hollow organs e.g. blood vessels and the GI tract
doesn’t have the regular arrangement of actin and myosin

42
Q

Explain the process of excitation contraction coupling in smooth muscle

A
  1. Depolarisation activates voltage gated Ca2+ channels
  2. Ca2+-CaM complex activates myosin light chain kinase
  3. MLCK phosphorylates myosin light chains
  4. Cross -bridges form with actin filaments -> contraction
43
Q

Describe signalling by membrane attached proteins and give an example

A

plasma membrane proteins on adjacent cells interacting
APCs presenting parts of the pathogen through MHC I
circulating T cells engage with MHC molecules through TCR
others: HIV GP120 glycoprotein
bacterial cell wall components

44
Q

Describe ionotropic receptors

A

Ligand binding opens an ion permeable pore leading to a signal transduction event

  1. ligand binds to receptor
  2. change in conformation of channel
  3. pore opens
  4. movement of ions according to gradient
45
Q

Give an example of ionotropic receptor action

A

nicotinic acetylcholine
Acetylcholine causing muscle contraction in skeletal muscle

GABAa (gamma amino butyric acid) causes a decreases in neuronal excitability in neurones

46
Q

Describe G-protein coupled receptors

A

Ligand binds to activate an intracellular G-protein
1. 7-TM receptor + heterotrimeric G-protein are inactive
2. Ligand binds changing conformation of the receptor
3. G-protein binds to the receptor
4. GDP exchanged for GTP
5. G-protein dissociates into 2 active units (alpha & gamma+beta)
6. units bind
7. GTPase dephosphorylates GTP to GDP
8. alpha subunit dissociates and becomes active
Receptor is active as long as the ligand is bound

47
Q

What are the 3 types of G-protein coupled receptors and what are their functions (+examples)

A

Gs - stimulates adenyl cyclase
ATP -> cyclic AMP -> Activated protein kinase A
e.g. beta adrenergic receptor to increase heart rate

Gi - inhibits adenylyl cyclase
reduces PKA levels
e.g. Muscarinic receptor to decrease heart rate

Gq - stimulates phospholipase C
PIP2 -> IP3 + DAG -> calcium release + PKA activation
e.g. angiotensin receptor to vasoconstrict

48
Q

Describe enzyme-linked receptors

A

Ligand binds to cause clustering of receptors

  1. ligand binds
  2. receptors cluster to activate enzymes
  3. enzymes phosphorylate the receptor
  4. signal proteins bind to cytoplasmic domain
  5. recruit other signal proteins to generate the signal
49
Q

Give an example of enzyme-linked receptors

A 
insulin receptor (CD220)
insulin causes glucose uptake

ErbB
Epidermal growth factor causing cell growth and proliferation

Guanylyl-cyclase
Atrial natriuretic peptide causes vasodilation to decrease blood pressure

Ser/Thr-kinase
Transforming growth factor beta causes apoptosis

50
Q

Describe type 1 signal transduction

A

cytoplasmic
association with chaperone molecules (heat shock proteins)
1. hormone binds to receptor
2. HSP dissociates
3. 2 hormone-bound receptors -> homodimer
4. translocates -> nucleus + binds to DNA

51
Q

Describe type 2 signal transduction

A

nuclear

  1. hormone ligand binds
  2. transcriptional regulation
52
Q

Give an example of signal transduction

A

glucocorticoid
cortisol/corticosterone causes a decrease in immune response and an increase in gluconeogenesis

Thyroid hormone
T4 and T3 cause growth and development

53
Q

Describe the Stratum corneum

A

corneocytes (flat with no nuclei)
Protective
Filagrin gene mutation leads to eczema

54
Q

Describe Stratum Spinosum

A

prickle/spinous cells that produce keratin

Desmosomes

55
Q

Describe Stratum Basale

A

Basal cells that connect to eh basement membrane

Keratinocytes found here

56
Q

Give some other components of the epidermis

A 
Melanocytes (production of melanin)
Langerhans cells (antigen presenting)
Merkel cels (sensation)
57
Q

Describe the basement membrane in the skin

A

Highly specialised region where epidermis meets dermis
via hemidesmosomes, anchoring plaques and proteins
Blisters are common e.g. epidermolysis bullosa

58
Q

Describe the structure of the basement membrane in skin

A

hemidesmosomes
tonofilaments
demo-epidermal junctions
anchoring fibrils

59
Q

Describe the dermis

A

supportive connective tissues - collagen, elastin, GAG
Thickness varies between 0.1mm and 3mm
contains fibroblasts that synthesises collagen, elastin and GAG
Dendritic cells found here

60
Q

Describe the subcutaneous layer

A

Connective tissue and fat

61
Q

What are the two types of sweat glands found in skin

A

Apocrine - only located in the axillary and groins that produce discus sweat - subject to bacteria and therefore produce odour
Eccrine

62
Q

What are the components of the dermo-epidermal junction

A 
Lamina lucida
Lamina densa
Anchoring fibrils
Hemidesmosomes 
Anchoring filaments
63
Q

Explain the role of melanocytes and their development

A

Dendritic cells in Stratum Basale
Produces melanin pigment in the melanosome, which is then packed into granules that are transferred to adjacent keratinocytes via phagocytosis
Granules form a protective cap around the nuclei to protect DNA from UV (which stimulates melanin production)
Variation in pigmentation is from no. and size of melanosomes

64
Q

Describe anagen in hair growth

A

growth phase (85% cells)
Energy intensive + highly vascularised
Most metabolically active
Rate depends on body site

65
Q

Describe catagen in hair growth

A

Cell devision slows and stops
End of shaft keratinises to form a club shape
Dermal papillae and club moves to the base of muscle insertion

66
Q

Describe telogen in hair growth

A

Hair is shed actively
Next anagen phase begins
Club hair takes 4-6 weeks

67
Q

Give the actions of antibody-antigen

A 
Neutralisation
Agglutination
Opsonisation
Complement activation
Bound by cells expressing Fc receptors (innate immunity: phagocytes, NK cells)
68
Q

Describe IgG

A 
gamma heavy
Most abundant
Has 4 subclasses
Actively transported across the placenta
Major activator of the classical complement pathway (1&3)
Blood and extracellular fluid
69
Q

Describe IgA

A 
alpha heavy
2nd most abundant
2 subclasses
Occurs as a monomer or dimer
secretory 
Protects mucosal surfaces from pathogens
Across epithelia
70
Q

Describe IgM

A 
Micro heavy
First Ig synthesised after exposure
Multiple low affinity binding sites
Large pentamer
Agglutination and complement activation
Blood
71
Q

Describe IgE

A 
E heavy
Allergic reactions
Parasitic infections
Binds to mast cell receptors and basophils to release histamine
Very low levels
72
Q

Describe IgD

A

Delta heavy
Expressed in B cell development and activation
very low levels

73
Q

Give examples of antibody-cross reactivity

A

Vaccination with cowpox induces antibodies which are able to recognise smallpox
ABO blood group antigens
Antibodies made against Microbial antigens on common intestinal bacteria may cross-react with carbs on RBC

74
Q

What are hyper variable regions

A

there are 3 in antibodies: CDR 1,2,3)

CDS = complement determining regions that acts as binding sites for antigens

75
Q

What are the secondary effector functions of immunoglobulins after binding

A

Complement activation
Opsonisation (promotion of phagocytosis)
Cell activation via antibody-binding receptors (Fc receptors)

76
Q

Describe natural killer cells

A

10% of blood
Infected cell lysis, secretion of interferon gamma, activating and inhibitory receptors (NO antigen receptor), binds to opsonised cells
Large granulated lymphocytes (cytotoxic)
Bind to opsonised cells
Cancer and viral infections

77
Q

Describe dendritic cells

A

APC and cytokine secretion
migration to lymph node
network site of infection
adaptive

78
Q

Describe mast cells

A

Phagocytosis, granule release (pro-inflammation), histamine and leukotrienes
Mucosal in the lung or connective tissue in the skin
Activation by complement products (anaphylatoxins)
vasodilation (red skin) and increased vascular permeability (inflammation)

79
Q

Describe monocytes

A

phagocytosis , killing, cytokine release, APC
less abundant
dispersed in tissue
Signal infection to soluble mediators
Become macrophages when the leave the blood

80
Q

Describe basophils

A

Granule release

Acts as an APC for type 2 immunity

81
Q

Describe eosinophils

A

phagocytosis and granule release
Defence against parasites
Helps B cells in GALT (IgA production)

82
Q

What are NETs

A

neutrophil extracellular traps

Release of granules and chromatin to form extracellular fibres

83
Q

Describe a neutrophil

A 
Phagocytosis
40-75% of leukocytes
short-lived
circulates the blood
First cells recruited
84
Q

Describe the process of extravasion

A
  1. Naive T cells rolls along the endothelium
  2. They bind to proteins and carbs along the epithelium
  3. HEV has chemokine bound to the cell surface
  4. Lymphocytes have receptors for this and binds to the receptor
  5. Lymphocytes deliver a signal to the T cell, changing the structure of integrin
  6. Integrin becomes high affinity binding and binds to the epithelium to stop movement
  7. Transport through epithelium

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