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91

Title the figure

Phospholipase C mechanism (PLC)

92

Give the steps of the phospholipase C (PLC) mechanism

  1. Activation of G-protein
  2. Stimulates Phospholipase C
  3. Converts membrane phospholipids → IP3/DAG

93

IP3

  • Binds to IP3 receptor (on the surface of Ca2+ sequesters)
  • The receptor is an ion channel 
    • IP3 opens the channel
    • Increasing IC Ca2+
    • Cellular effects

94

DAG

  • Similar behaviour to cAMP
    • Activates type-C protein kinases
    • Triggers several phosphorylation pathways
    • Biological effects

95

Give examples of ligands in the PLC mechanism

  • ACh
  • Histamine
  • Purin
  • PGE
  • TXA2
  • ADH
  • Oxytocin

All of which release Ca2+

96

Give the steps of the Phospholipase A2 (PLA2) mechanism

  1. G-protein activation
  2. Converts phospholipids → arachidonic acid (substrate)
  3. Arachidonic acid → Several products

97

Besides active G-proteins, what else can activate the PLA2 mechanism?

Ca2+

98

Arachidonic acid can pass through which further pathways?

  • Lipoxygenase pathway
  • Cyclooxygenase pathway
  • Epoxygenase pathway

99

List the products of the lipoxygenase pathway

  • Leukotrienes (LT)
  • Lipoxins (LX)

100

List the products of the cyclooxygenase pathway

  • Prostacyclins (PGIs)
  • Prostaglandins (PGs)
  • Thromboxanes (TXs)

101

Describe the mechanism when a receptor is also an IC enzyme

  1. Ligand bond formed on the outer surface
  2. IC polypeptide chain phosphorylates
  3. Activation of the receptor
  4. Biological action

102

Give an example of direct enzyme stimulation

Insulin receptor

The receptor is able to phosphorylate itself and other proteins on the IC part of the cell

103

Auto-phosphorylation

  1. Self phosphorylating enzyme phosphorylates tyrosine residues of the IC receptor sequence
  2. Phosphorylated tyrosine residues bind intracellular proteins
  3. Specific IC responses elicited

104

Describe the processes after autophosphorylation

  1. Autophosphorylation
  2. Receptor-enzyme complex is taken up by the cell
  3. Inactivation

105

Describe the figure

  1. Tyrosine residues are present in the enzyme's IC domain
  2. Ligand binding
  3. Phosphorylation of IC regulatory proteins (RP1+RP2)
  4. Biological effects

106

The hypothalamus is divided into which parts?

  • Magnocellular area (with large cells)
  • Parvocellular area (with small cells)

107

Describe the movement of hormones from the hypothalamus

  1. Hormones produced in the parvocellular area → Adenohypophysis
  2. Hormones produced in the magnocellular area → Neurohypophysis

108

Which nuclei are found in the magnocellular area?

  • Supraoptic nucleus (Oxytocin production)
  • Paraventricular nucleus (ADH production)

109

Which nuclei are found in the parvocellular area?

  • Ventromedial nucleus
  • Dorsomedial nucleus
  • Infundibular nucleus

Inhibit/release substances which can reach the adenohypophysis

110

Describe the transport of neurosecretions from the parvocellular area

  1. Parvocellular area
  2. Portal circulation of pituitary stalk via axons
  3. Arrive at the adenohypophysis
  4. Influence production + release of hormones into the blood

111

Describe the transport of neurosecretions from the magnocellular area

  1. Magnocellular area
  2. From the site of production (Neurone)
  3. The site of release (Neurohypophysis)

112

Title the figure

Axonal transport

113

Describe the steps of axonal transport

  1. Peptide travels from hypothalamic cell → axon
  2. First capillarisation (Median eminence)
  3. Portal circulation
  4. Second capilarisation (anterior pituitary)
  5. Cells of anterior pituitary

114

Basal membrane

115

Axonal transport, neurosecretion

116

First capillarisation (Median eminence)

117

Portal circulation

118

Second capillarisation (anterior pituitary)

119

Which portal vessel do peptides travel down in axonal transport?

Pituitary stalk

120

Give the proteins of axonal transport

  • Kinesin (Transport from soma to synapse)
  • Dynein (Returning of residues to the soma)