Lec 12 - Brain cells Flashcards
What does the CNS mainly consist of?
Tissues of the brain (Cerebellum) and spinal cord
What is the brain composed of?
Neurones and glia
What are neurons?
Excitable nerve cells that transmit electrical signals
What are glia cells?
Supporting cells of the brain
How are neurons connected and communicate?
Synapse that transmit signals to other cells
Neurons can be categorized into 3 types
Sensory - taste, feel
Inter - think, see, percieve
motor - muscular contraction
What is a soma?
A substance which contains the nucleus of a neuron where the protein synthesis occurs
Whare are the 4 cell types of the central nervous system (CNS)?
Oligodendrocytes:
Produce myelin sheathe (conduction)
Microglia:
Immune defence
Astrocytes:
Most numerous, metabolism and synapse formation
Ependymal cells:
Line the CSF-filled cavities (ventricles) of CNS
Cerebrospinal fluid : CSF
Outline the lineage of astrocyte, oligodendrocyte and neuron cells
Neural stem cell > NRP > Neuron
Neural stem cell > GRP > OPC > Oligodendrocyte
Neural stem cell > GRP > ARP(spinal)/APC(optic) > Astrocyte
Outline the lineage of microglia cells
Haematopoietic stem cell > Myeloi progenitor cells > Microglia
What is the purpose of oligodendrocytes?
Myelination of nerve fibers by myelin sheathe
This ensures cast conduction by axons
When does myelination predominantly occur?
first 18 months of life
Why is myelination important?
vital for co-ordinated movement
What are the steps in development of oligodendrocytes in vivo?
Perinatal progenitor > Late progenitor > Pre-myelinating oligodendrocyte > Myelinating oligodendrocyte
How many axons can oligodendrocytes myelinate?
40-50 axons
What diseases are associated with oligodendrocytes?
Cerebral palsy
heterogeneous group of movement disorder with various causes, movement and posture impairment. Non-progressive pathology that formed in utero (
Give a profile on astrocytes
Star-shaped
Divided into protoplasmic and fibrous forms (grey/white matter) and the radial glial cells
Radial glial cells are fundamental to brain development as they generate first neurons
What is a unique feature of radial glial cells?
Retain neural stem cell capabilities into adulthood
What is the difference between protoplasmic astrocyte and fibrous astrocyte?
Protoplasmic are in close connection with neuron and capillary (neurovascular unit). Found at synapse as required for proper synaptic transmission.
Fibrous are in a white matter tract where it may interact with oligdendrocytes to promote myelination
What do astrocytes regulate?
Extracellular K+ homeostasis
Remove excess glutamate (neurotoxic)
Supply glutamine for glutamateric neurotransmission
Synaptogenesis and synaptic maintenance
Neurotransmission
Control local blood flow and metabolic support for neurons
Which cells form the blood brain barrier?
Both protoplasmic and fibrous astrocytes
What are diseases associated with astrocytes?
Neuromyelitis optica (Devic's disease): Loss of vision and paralysis
Cause: inflammation and demyelination in optic nerve and spinal cord
NMO:
Autoimmune disease causing death to astrocytes (aquaporin-4)
What is the role of mircoglia cells?
Defenders of the brain
Acts as a macrophage of the CNS
Acounts as 15% of brain cells
Removes cellular debris
Monitors extracellular environment
Sense homeostatic disturbances
Occupy own spatial territory
Interacts with other cells
What receptors do microglia cells have?
Cytokine Pattern recognition Fc Complement Chemokine
What do pattern recognition receptors do?
Foreign entities - viruses, bacteria, parasite
i.e pathogen associated molecular patterns (PAMPS)
Stimulation of phagocytosis
induction of cytotoxic mechanisms
Activates immune response
What do Fc (immunoglobulin) and complement receptors do?
Promotes production of damaging cytokines and reactive oxygen species (ROS), both are antibody dependant
Also mediates phagocytosis through recognition of antibody bound to microbes
What are unique features of microglia cells?
upon phagocytosis, it undergoes antigen presentation to other cells by using MHC class II
Activation upregulates MHC class II
interacts with T-cells and stimulate CD4-T cells to produce cytokines
How is microglia activity measured?
PET (position emission tomography)
Radio-ligand PK11195 binds to activated but not to resting microglia
What are diseases associated with microglia cells?
Huntingdon’s disease
Parkinson’s disease
Outline how microglia cells take part in Alzheimer’s disease
Accumulation of amyloid beta plaques and tangles P-tau protein
Damage begins in temporal and parietal lobes of cortex, progress to hippocampus and amygdala
What is the function of satellite cells found exclusively in peripheral nervous system?
Surround neuron cell bodies in ganglia
Regulate O2, CO2 nutrient
What is the function of schwann cells found exclusively in peripheral nervous system?
Surround axons in PNS
Myelination of peripheral axons
Repair process after injury
