Glial cells - Cells and Tissues of the nervous system Part 3 Flashcards
What are glial cells?
non-excitable supporting cells
What is more abundant: neurones or glial cells?
glial cells
smaller but more abundant
What is the most populous glial cells?
astrocytes
What do astrocytes do?
maintain the blood-brain barrier
What are the 4 types of glial cells in the CNS?
Astrocytes
microglia
ependymal cells
oligodendrocytes
What do the end feet of astrocytes surround?
capillaries and synapses
What is the main role of microglia?
phagocytosis and scar tissue formation
Why does the brain need microglia to carry out phagocytosis?
because of the blood-brain barrier
prevents WBC moving out and needs to be a function of a resident cell of the brain
Where do you find the ependymal cells?
line cavities of the brain called ventricles
and central anal of the spinal cord
What is the role of oligodendrocytes?
secrete myelin for myelination
What are the 2 glial cells of the PNS?
Schwann cells
satellite cell
What is the role of Schwann cells?
myelination
Where do you find satellite cells?
surround neuronal cell bodies
Why are the glial cells important clinically?
tumours of the brain called glioma
common
What is the blood brain barrier?
barrier created between blood flowing in the capillaries and brain tissue surrounding the capillaries
Why do we need the blood brain barrier?
is a protective mechanism that helps maintain a stable environment for the brain
and prevents harmful amino acid and ions present in the bloodstream and blood cells from entering the brain
A = endothelium - tight junction
B = foot process of astrocytes
How do ions, WBC and gases move in and out of capillaries?
fenestrations
Are capillaries in the brain fenestrated?
no
What junctions lie between the capillaries in the brain?
tight junctions
What do the papilla cells of the capillaries sit?
basement membrane
thick basal lamina
What are the 3 layers forming the blood brain barrier?
- endothelium - tight junction
- thick basal lamina
- foot processes of astrocytes
In the brain, what substances can pass through the capillaries?
lipid soluble
What are the lipid soluble substances?
O2, H2O
How does glucose and amino acids pass through the blood brain barrier?
pump mediated
What circumventricular organs in the brain do not have a blood brain barrier?
hypothalamus
posterior pituitary
Why do the hypothalamus and posterior pituitary not have a BBB?
they are endocrine organs
allows it to function properly
What is the role of the cerebrum?
seat of consciousness
A = cerebrum
B = cerebellum
C = brainstem
D = diencephalon
A = midbrain
B = pons
C = medulla
D = spinal cord
A = thalamus
B = hypothalamus
What are the 3 sections of the brain?
midbrain
pons
medulla
Where does the lower end of the medulla sit?
foramen magnum
What are the vital centres of the brainstem?
cardiorespiratory, pathway for fibre tracts
