Circulation and infection

Question 1

What is the blood brain barrier

Answer 1

A highly selective semipermeable border formed from capillary endothelial cells that prevents solutes in the circulating blood from non-selectively crossing into the extracellular fluid of the central nervous system where neurons reside

Question 2

What are the 3 main ways in which pathogens can spread to access the CNS

Answer 2

• Neurotropic spread
• Haematogenous spread
• Septic focus (neural abscess)

Question 3

What 2 substances couple brain microvascular endothelia cells

Answer 3

• Adherens

- Tight junction proteins

Question 4

What is the role of P-glycoproteins in the blood brain barrier

Answer 4

Actively eject undesired substances from the CNS extracellular fluid into the blood

Question 5

How are virulence factors important for pathogens in crossing the BBB

Answer 5

• Viruses have host cell binding proteins that bind receptors on the endothelia of the capillaries of the BBB
• Bacteria have adhesions that interact with host cell ligands to increase adhesion of bacteria to cells

Question 6

What are 3 common routes for pathogens to cross the blood brain barrier

Answer 6

• Transcellular
• Paracellular
• Trojan horse

Question 7

What is meant by the transcellular mechanism of BBB passage

Answer 7

Passage of the pathogen through the endothelia cells without detection or disruption

Question 8

What is meant by the paracellular mechanism of BBB passage

Answer 8

Passage of the pathogen between endothelia cells with or without disruption

Question 9

What is meant by trojan horse mechanism of BBB passage

Answer 9

Infected phagocytes carry the pathogen through the BBB

Question 10

What are 5 neurological signs of CNS infection

Answer 10

Throat spasm
Muscle atrophy 
Constipation
Ataxia
Severely altered behaviour

Question 11

What type of cells will be in increased number in the CNS in a viral infection

Answer 11

Mononuclear lymphocytes

Question 12

What type of cells will be in increased number in the CNS in a bacterial infection

Answer 12

Degenerative/ toxic neutrophils

Question 13

What types of cells will be in increased number in the CNS in a parasitic infection

Answer 13

Eosinophils

Question 14

What does pantropic mean when describing a pathogen

Answer 14

Causes infection in more than one bosy system because the receptors for cell infection are found on many cell types