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MCD Medicine > Tissues > Flashcards

Tissues Flashcards

1
Q

What is the difference between mircopinocytosis and endocytosis?

A

Micropinocytosis, also known as cell drinking, brings small particles into the cell. Endocytosis uses energy to transport larger molecules into the cell

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2
Q

What is a peroxisome?

A

A peroxisome is a membrane bound vesicles which carries out lipid and oxygen metabolism. It contains enzymes such as peroxidase and catalase

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3
Q

What are the 3 main filaments that make up the cytoskeleton?

A
  1. Intermediate filaments e.g cytokeratins and vimentin
  2. Microtubules e.g. tubulin
  3. Microfilaments e.g. actin
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4
Q

What monomers made up the microtubules and what is their function?

A

Polymers of alpha and beta tubulin, about 20nm in diameter.

Function: cell shape and tracks for movement e.g spindle formation and cilia/flagella

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5
Q

What are intermediate filaments and what is their function?

A

Polymers of filamentous proteins which form a rope like structure, 10-15 nm diameter

Epithelia = cytokeratins 
Mesenchymal = vimentin
Neurons = neurofilament
Desmosomes = connected by cytokeratins 
Nuclear laminins = on nuclear envelope to stabilise envelope

Function = giving mechanical strength to cells

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6
Q

What are microfilaments and what is their function?

A

Polymers of globular actin.

Function: cell shape and movement
Example: associate with adhesion belts

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7
Q

List 4 different types of cell-cell junction and their functions

A
  1. Gap junctions: passage of ions and small molecules between cells
  2. Desmosomes: Provides mechanical continuity between cells
  3. Adhesion belts: Controls stability of other junctions
  4. Tight junction: Seals paracellular pathways. Segregates apical and basolateral polarity
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8
Q

List the different types of classification for epithelia and give an example for each

A
  1. Simple squamous: lung alveolar, mesothelium
  2. Simple columnar: enterocytes
  3. Simple cuboidal: kidney collecting ducts
  4. Psuedostratified: upper (bronchi) respiratory tract
  5. Stratified squamous:
    - Keratinizing (cannot see nuclei) e.g. epithelium
    - Non-keratinizing (can see nuclei) -e.g. vagina, oesophagus, lining of mouth - kept moist by bodily secretions
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9
Q

Which parts of the kidney are associated with absorptive epithelium and which with transporting epithelium?

A

The distal tubule - transporting

The proximal tubule - absorbing

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10
Q

The pancreas has:

a) Endocrine function
b) Exocrine function
c) Both

A

c) Both
Exocrine = secretes into the lumen/gut e.g. acinar cells
Endocrine = secretes into the blood e.g. islets of langerhans

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11
Q

In tissues whose main purpose is secretory, the epithelium is arranged into ducts/tubules. List the different types

A

Simple: Tubular, branched tubular, coiled tubular, branched alveolar
Compound: Tubular, alveolar

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12
Q

What is the extracellular matrix and what are its functions?

A

The ECM is a complex network of proteins and carbohydrates filling spaces between cells (both fibrillar and non fibrillar proteins).
Function: physical support; determine physiochemical and mechanical properties of the tissue; influences growth, adhesion and differentiation of cells in the tissue; essential for development, embryogenesis and function

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13
Q

What are the main components of the extracellular matrix and give examples of each

A
  1. Collagens e.g. type 1-3 collegen are fibrillar, type 4 is basement membrane
  2. Multi adhesive glycoproteins e.g. fibronectin, laminin, fibrinogen
  3. Proteoglycans e.g. decorin, aggrecan
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14
Q

Give 3 human disorders that are caused by gene mutations in matrix proteins

A
  1. Epidermylosis bullosa = laminin 5
  2. Alports syndrome = collagen IV
  3. Marfan’s syndrome = fibrillin 1
  4. Congenital muscular dystrophy = fibrillin 2
  5. Osteogenesis imperfecta = collagen I
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15
Q

What is the most abundant protein in mammals?

A

Collagen

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16
Q

Describe the structure of collagen

A

Three alpha helices from a triple helix
Gly-x-y repeat (x is often proline and y is often hydroxyproline)
Left handed helix. Every third amino acid is a glycine

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17
Q

Which vitamin deficiency results in unhydroxylated collagens?

A

Vitamin C deficiency

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18
Q

Which amino acids in collegen are hydroxylated to contribute to the hydrogen bonding?

A

Lysine and proline

Note: lysine and hydroxylysine are also involved in covalent cross linking in collegen

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19
Q

Name two non fibrillar collagens

A
  1. Type IX
  2. Type XII
    =They regulate the organisation of fibrillar collagens
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20
Q

Describe the structure of an elastic fibre

A

Elastin core and microfibrils which are rich in the protein fibrillar.
Elastin has hydrophobic regions and alpha helical regions (rich in alanine and lysine– many lysine are covalantly linked) which alternate along the polypeptide chain

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21
Q

What is a basement membrane and give an example

A

A basement membrane is a thick mat of extracellular matrix underlying epithelial sheets and tubes. They separate the cells from underlying tissue and also act as a filter.
Example: Kidney glomerulus- the basement membrane separates the blood and the urine

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22
Q

Describe the structure of a laminin

A
  • Laminins are glycoproteins which which consist of an alpha, beta and gamma chain which forms a cross shaped structure.
  • Each chain is between 160-400kDa (very large)
  • Interact with cell surface receptors e.g. integrin
23
Q

Describe the structure and function of fibronectin

A

Insoluble fibrillar matrix or soluble plasma protein.
500kDa dimer
Forms many interactions with cell surface receptors and other matrix proteins.
Function: cell migration and adhesion in embryogenesis and tissue repair and also needed for wound healing.
Integrin binds to RGF motif and forms link between ECM and cytoskeleton

24
Q

List 4 different proteoglycan families

A
  1. Basement membrane e.g. perlecan
  2. Aggregating e.g. aggrecan
  3. Small leucine rich e.g. decorin
  4. Cell surface e.g. syndecans 1-4
25
Q

List the 4 main glycosaminoglycan groups

A
  1. Chrondroitin sulphate (glucoronic acid and N acetylgalactosamine 4 sulphate) and dermatan sulphate (iduronic acid and N acetylgalactosamine 4 sulphate)
  2. Heperan sulphate
  3. Keratan sulphate
  4. Hyaloronan (glucoronic acid and N acetyll glucosamine)
26
Q

Discuss the distinct features of hyaloronin

A

No core protein, made at cell surface, unsulfated, up to 25,000 repeating disaccharides: glucuronic acid and N acetylglucosamine

27
Q

Decorin binds to…..?

A

Collagen fibres

28
Q

Define cartilage matrix and give an example

A

Cartilage matrix is the filamentous network of proteoglycans with embedded collagen fibrils
Example: Hyaline cartilage = the most abundant, found in nose, larynx, trachea, bronchi, end of ribs and long bones. Cushions ends of long bones. Rich in aggrecan

29
Q

Describe the structure of aggrecan

A

Core protein + linker proteins + hyaloronan + chrondroitin sulfate and keratan sulfate (very negative so attract water)

30
Q

What is osmolarity?

A

The concentration of solute particles in a solution

31
Q

What is tonicity?

A

The strength of a solution as its affects final cell volume - takes into account membrane permeability and solute concentration

32
Q

What are the four functional regions of the cerebral hemisphere?

A

Parietal, occipital, frontal, temporal

33
Q

List the regions of the brainstem in descending order

A

Midbrain, pons, medulla

34
Q

What is the function of the cerebellum?

A

Motor coordination, balance and posture

35
Q

What are the 4 neurone morphologies?

A

Unipolar, bipolar, psuedo-unipolar, multipolar

36
Q

What common features do all neurones share?

A
  • Excitable cells
  • Non dividing
  • Soma, axon and dendrites
37
Q

What is the most abundant cell type in the CNS?

A

Astrocytes = structural cells, cell repair, immune cells, neurotransmitter uptake and release

38
Q

What is the function of oligodendrocytes and Schwann cells and how do they differ?

A

They both produce myeline.
Oligodendrocytes produce myelin for the central nervous system and one oligodendrocyte can myelinate many axons.
Schwann cells produce myelin for the peripheral nervous system and one Schwann cell myelinates one axon segment

39
Q

What is the function of ependymal cells in the CNS?

A

Epithelial cells to line fluid filled ventricles. They regulate production and movement of CSF

40
Q

What is the resting membrane potential of neuronal cells?

A

-40 to -90 mV (the inside of the cell is always more negative compared to the outside)

41
Q

Myeline has:

a) high resistance and low capacitance
b) low resistance and low capacitance
c) low resistance and high capacitance
d) high resistance and high capacitance

A

a) high resistance and low capacitance (this prevents the AP from spreading)

42
Q

Antagonist pairs of muscles consist of….?

A

Flexor and extensor

43
Q

Describe the structure of the myofibrils

A

They are made up of lighter and darker bands which gives them a striated appearance.
A band = darker band with dark H zone
I band = lighter region with dark line, Z line
Sarcomere = functional unit of muscle and lies between two Z lines
The Z line is made up of alpha actinin and CapZ

44
Q

Describe the excitation of a myofibre?

A
  1. The action potential moves along the T tubule membrane and the sarcolemma (myofibre membrane).
  2. It causes the dihydropyridine receptors on the sarcolemma to activate and change conformation to contact ryanodine receptors.
  3. This activates the ryanodine receptors on the T tubules causing intracellular calcium stores to be released
45
Q

Describe the steps involved in the sliding filament theory

A
  1. Calcium ions bind to troponin causing movement of tropomyosin
  2. This exposes myosin binding site on actin
  3. ADP phosphorylation causes the myosin head to pivot, the power stroke.
  4. ATP hydrolysis recharges myosin head
46
Q

Describe the excitation process in cardiac muscles

A
  1. Action potential moves along T tubules and sarcolemma
  2. VGCCs open releasing calcium:
    - Calcium induced calcium release via ryanidine receptors
    - Initiates contraction
    - Further depolarisation
47
Q

Describe excitation process in smooth muscles

A
  1. Depolarisation activates VGCCs
  2. Calcium calmodulin complex — activates myosin light chain kinase — phosphorylates myosin light chains —- cross bridges with actin filaments = contraction!
48
Q

List 4 reasons why cells need to communicate

A
  1. Homeostasis
  2. Process information
  3. Voluntary movement
  4. Self preservation
49
Q

What is endocrine signalling? Give two examples

A

Hormones travel within blood vessels to act on distant targets

  1. Insulin released by beta cells acts on adipose tissue, muscles and the liver
  2. Adrenaline released from adrenal glands acts on the trachea
50
Q

What is paracrine signalling? Give two examples

A

Hormone released acts on the adjacent cell

  1. Nitric oxide produced by endothelial cells in vessels
  2. Osteoclast activating factors produced by osteoblasts
51
Q

Give two examples of cellular communication via membrane bound proteins

A
  1. HIV GP120 glycoprotein —- CD4 receptors on T lymphocyte
  2. Bacterial cell wall —- toll like receptors
52
Q

What is autocrine signalling? Give three examples

A

Cell secretes autocrine agents which then acts back on itself

  1. T cell released IL-2
  2. Acetylcholine on presynaptic M2 muscarinic receptors
  3. Growth factors from tumour cells
53
Q

List the four different types of receptors

A
  1. GPCR
  2. Intracellular
  3. Ionotropic
  4. Enzyme linked

MCD Medicine (4 decks)

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