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MCD > Tissues 8 and 9 - Signalling between cells > Flashcards

Tissues 8 and 9 - Signalling between cells Flashcards

1
Q

List the 4 reasons cells need to communicate

A
  • Process Information
  • Self preservation
  • Voluntary movement
  • Homeostasis
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2
Q

How does self preservation occur?

A
  • Sensory stimuli are detected

- Spinal reflexes and the sympathetic nervous system allow us to appropriately respond to danger

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3
Q

Describe what happens when someone is hypoglycaemic.

A
  • a cells in the islets of Langerhans secrete glucagon
  • Glucagon travels through the blood vessels to the liver
  • Glucagon causes glycogenolysis and gluconeogenesis
  • Increases blood sugar levels
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4
Q

What type of signalling is occurring when glucagon acts on the liver cells?

A

Endocrine signalling

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5
Q

Define endocrine signalling.

A

Hormone travels within blood vessels to act on a distant target cell

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6
Q

Give some examples, not including glucagon action, of endocrine signalling.

A
  • Insulin produced in the pancreas acts on the liver, muscle cells & adipose tissue
  • Adrenaline produced in the adrenal glands acting on the trachea
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7
Q

Describe what happens in hyperglycaemia within the pancreas.

A
  • B cells in the Islets of Langerhans secrete insulin

- Insulin inhibits glucagon secretion from the a cells

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8
Q

What type of cell signalling is insulin inhibiting glucagon secretion in the pancreas?

A

Paracrine signalling

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9
Q

Define paracrine signalling

A

The hormone acts on an adjacent cell

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10
Q

Give some other examples, not including insulin acting on the pancreas, of paracrine signalling.

A
  • Nitric Oxide produced by endothelial cells in blood vessels
  • Osteoclast activating factors produced by adjacent osteoblasts
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11
Q

Describe the process of TCRs binding to MHCs.

A
  • Blood borne virus detected within blood stream by antigen presenting cell (APC)
  • APC digests pathogen, and expresses major histo-compatibility (MHC) class II molecules on surface
  • Circulating T-lymphocyte engages with MHC molecule through T-cell receptor (TCR) interaction
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12
Q

Define cell communication by membrane-attached proteins

A

Plasma membrane proteins on adjacent cells interacting

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13
Q

Give an example of communication by membrane-attached proteins other than TCRs in immunity.

A
  • Bacterial cell wall components bind to toll-like receptors on haematopoietic cells
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14
Q

Define autocrine signalling

A

The signalling molecule acts on the same cell.

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15
Q

List some examples of autocrine signalling

A
  • Activated T cells express IL2 receptors on the cell surface, as well as secreting IL2 - so some of the IL2 will bind to the receptor
  • Acetyl choline on presynaptic receptors
  • Growth factors from tumour cells (mitogenesis)
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16
Q

List examples of intracellular signalling

A
  • Ionotropic receptor
  • G-protein coupled receptor
  • Enzyme-linked receptor
  • Intracellular receptor
17
Q

Describe the process that occurs when a ligand sinds to an ionotropic receptor.

A
  • Change in conformation of channel protein causing opening of a pore
  • Pore allows ions to move in or out of cell according to their respective concentration gradients
18
Q

List examples of ionotropic receptors.

A
  • Nicotinic acetylcholine receptors in the skeletal muscle, which cause muscle contraction
  • GABAa - uses a GABA ligand which decreases neuronal excitability
19
Q

What do mutations in GABAa result in?

A

Seizures

20
Q

Describe the process that occurs when G protein coupled receptors bind to a ligand.

A
  • The receptor conformation changes
  • The G-protein binds and GDP is replaced with GTP
  • G protein dissociates into its alpha subunit and its beta/gamma subunits (attached)
  • Each component binds to target proteins
  • GTP is converted to GDP on the a-subunit
  • The a-subunit dissociates from the target protein and becomes inactive
21
Q

How long are G protein coupled receptors active?

A

They are active as long as receptors are bound

22
Q

list the different types of Ga subunits.

A

Gs, Gi and Gg

23
Q

Describe the function of Gs protein linked receptors

A
  • They stimulate adenylyl cyclase
  • Convert ATP to cAMP (cyclic adenosine monophosphate)
  • cAMP activates PKA (protein kinase A)
24
Q

Give an example of a Gs protein linked receptor

A

Beta 1-adrenergic receptors increase the heart rate

25
Q

Describe the function of Gi protein linked receptors

A
  • Inhibit adenylyl cyclase

- Reduce PKA levels (protein Kinase A)

26
Q

Give an example of a Gi protein linked receptor

A

M2-muscarinic receptors decrease heart rate

27
Q

Describe the function of Gg protein linked receptors

A
  • Stimulates phospholipase C (PLC) - PIP2 –> IP3 + DAG
  • IP3 stimulates Ca2+ release
  • DAG activates PKC
28
Q

Give an example of a Gg protein linked receptor

A

AT-1 angiotensin receptor causes vasoconstriction

29
Q

Describe the structure of a G-protein linked receptor

A
  • 7-TM proteins (transmembrane)
  • Extracellular ligand-binding N-terminus
  • Intracellular G-protein binding C-terminus
30
Q

Describe the process that happens to enzyme-linked receptors once the ligand has bound

A
  • More than one receptor
  • Receptor clustering activates enzyme activity within cytoplasmic domain - Enzymes phosphorylate receptor
  • Binding of signalling proteins to cytoplasmic domain
  • These signalling proteins recruit other signalling proteins
  • Signal is generated within cell
31
Q

What is another name for enzyme-linked receptors?

A

Tyrosine kinase receptors

32
Q

Give examples of enzyme-linked receptors.

A
  • Insulin receptor causes glucose uptake
  • ErbB receptors (growth and proliferation)
  • Guanylyl-cyclase linked receptors
  • Ser/Thr-kinase linked receptors
33
Q

What are the two types of intracellular receptors?

A

Cytoplasmic and Nuclear

34
Q

How do cytoplasmic intracellular receptors work?

A
  • Located within the cytosolic compartment
  • Associated with chaperone molecules (heat shock proteins, hsp) - Hormone binds to receptor, chaperone dissociates
  • 2 hormone bound receptors form a homodimer.
  • The homodimer translocates to the nucleus and binds to DNA
35
Q

How do nuclear cytoplasmic intracellular receptors work?

A
  • Located within the nucleus
  • Binding of hormone ligand
  • Transcriptional regulation
36
Q

Give an example of a cytoplasmic intracellular receptor.

A
  • Glucocorticoid receptor - uses corticol and corticosterone
  • Reduce the immune response and increase gluconeogenesis
37
Q

Give an example of a nuclear intracellular receptor.

A
  • Thyroid hormone receptor
  • Binds to Thyroxine (T4) and triiodothyronine (T3)
  • Causes growth & development

MCD (56 decks)

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