Lec 12 - Brain cells

Question 1

What does the CNS mainly consist of?

Answer 1

Tissues of the brain (Cerebellum) and spinal cord

Question 2

What is the brain composed of?

Answer 2

Neurones and glia

Question 3

What are neurons?

Answer 3

Excitable nerve cells that transmit electrical signals

Question 4

What are glia cells?

Answer 4

Supporting cells of the brain

Question 5

How are neurons connected and communicate?

Answer 5

Synapse that transmit signals to other cells

Question 6

Neurons can be categorized into 3 types

Answer 6

Sensory - taste, feel
Inter - think, see, percieve
motor - muscular contraction

Question 7

What is a soma?

Answer 7

A substance which contains the nucleus of a neuron where the protein synthesis occurs

Question 8

Whare are the 4 cell types of the central nervous system (CNS)?

Answer 8

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

Question 9

Outline the lineage of astrocyte, oligodendrocyte and neuron cells

Answer 9

Neural stem cell > NRP > Neuron
Neural stem cell > GRP > OPC > Oligodendrocyte
Neural stem cell > GRP > ARP(spinal)/APC(optic) > Astrocyte

Question 10

Outline the lineage of microglia cells

Answer 10

Haematopoietic stem cell > Myeloi progenitor cells > Microglia

Question 11

What is the purpose of oligodendrocytes?

Answer 11

Myelination of nerve fibers by myelin sheathe

This ensures cast conduction by axons

Question 12

When does myelination predominantly occur?

Answer 12

first 18 months of life

Question 13

Why is myelination important?

Answer 13

vital for co-ordinated movement

Question 14

What are the steps in development of oligodendrocytes in vivo?

Answer 14

Perinatal progenitor > Late progenitor > Pre-myelinating oligodendrocyte > Myelinating oligodendrocyte

Question 15

How many axons can oligodendrocytes myelinate?

Answer 15

40-50 axons

Question 16

What diseases are associated with oligodendrocytes?

Answer 16

Cerebral palsy
heterogeneous group of movement disorder with various causes, movement and posture impairment. Non-progressive pathology that formed in utero (

Question 17

Give a profile on astrocytes

Answer 17

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

Question 18

What is a unique feature of radial glial cells?

Answer 18

Retain neural stem cell capabilities into adulthood

Question 19

What is the difference between protoplasmic astrocyte and fibrous astrocyte?

Answer 19

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

Question 20

What do astrocytes regulate?

Answer 20

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

Question 21

Which cells form the blood brain barrier?

Answer 21

Both protoplasmic and fibrous astrocytes

Question 22

What are diseases associated with astrocytes?

Answer 22

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)

Question 23

What is the role of mircoglia cells?

Answer 23

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

Question 24

What receptors do microglia cells have?

Answer 24

Cytokine
Pattern recognition
Fc
Complement
Chemokine

Question 25

What do pattern recognition receptors do?

Answer 25

Foreign entities - viruses, bacteria, parasite
i.e pathogen associated molecular patterns (PAMPS)

Stimulation of phagocytosis
induction of cytotoxic mechanisms
Activates immune response

Question 26

What do Fc (immunoglobulin) and complement receptors do?

Answer 26

Promotes production of damaging cytokines and reactive oxygen species (ROS), both are antibody dependant

Also mediates phagocytosis through recognition of antibody bound to microbes

Question 27

What are unique features of microglia cells?

Answer 27

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

Question 28

How is microglia activity measured?

Answer 28

PET (position emission tomography)

Radio-ligand PK11195 binds to activated but not to resting microglia

Question 29

What are diseases associated with microglia cells?

Answer 29

Huntingdon’s disease

Parkinson’s disease

Question 30

Outline how microglia cells take part in Alzheimer’s disease

Answer 30

Accumulation of amyloid beta plaques and tangles P-tau protein

Damage begins in temporal and parietal lobes of cortex, progress to hippocampus and amygdala

Question 31

What is the function of satellite cells found exclusively in peripheral nervous system?

Answer 31

Surround neuron cell bodies in ganglia

Regulate O2, CO2 nutrient

Question 32

What is the function of schwann cells found exclusively in peripheral nervous system?

Answer 32

Surround axons in PNS
Myelination of peripheral axons
Repair process after injury