L33: Neural Architecture Flashcards
1
Q
Basic components of nervous system
A
- Neurones: functional unit, cannot divide
- Soma: nucleus + organelles: protein-producing
- Dendrite (towards soma)
- Axon (away from soma)
- Synapse - Glial cells / neuroglia: supporting cells, can divide
- Central vs peripheral glial cells
2
Q
3 physiological properties of neurone
A
- Excitability
- Conduction
- Secretion
3
Q
Development of nervous system
A
Neuroepithelial cells
- Ependymal cell —> Cerebral ventricle surface
- Glioblast —> Oligodendrocyte (CNS myelin sheath), Astrocyte (Fibrous + Protoplasmic: BBB)
- Apolar neuroblast —> bipolar —> multipolar
Mesenchyme —> Microglia (phagocytes)
4
Q
Organisation of CNS and PNS
A
CNS:
- Gray matter (information process, sensory, synaptic integration): cell bodies, neuropil, glial cells, capillaries
- White matter (signal transmission): Glial cells, myelinated axons
(Brain: 外gray內white, Spinal cord: 外white內gray)
PNS:
- Ganglia: Nerve cell bodies, with supporting cells
- Nerve: Myelinated/unmyelinated axons, with supporting cells
5
Q
Structure of nerve fibre
A
Axon and myelin sheath (surrounded by endoneurium)
—> Nerve fascicle (surrounded by perineurium)
—> Nerve trunk (surrounded by epineurium)
6
Q
Classification of neurones
A
- Morphology (no. of processes connecting to cell body)
- Pseudounipolar —> sensory
- Bipolar —> sensory
- Multipolar —> motor - Functional
- Sensory (Pseudounipolar, Bipolar): detect stimuli
- Motor (Multipolar): Spinal motor, Pyramidal cell: respond to stimuli
- Interneurones: Integration, process, store, make decision
7
Q
Describe Cell body
A
Rough ER: Nissl body
Intermediate filament: Neurofilament: structural support for axon
CELL BODY DO NOT PROCESS INFORMATION
8
Q
Describe Dendrite
A
- Extension of soma cytoplasm: also contain organelles
- Unmyelinated
- Dendritic tree —> increase receptor SA
- Receive stimuli
- Larger diameter than axon
9
Q
Describe Axon
A
- Single extension from soma, may branch in axon end
- Myelinated / Unmyelinated
- Cytoplasm: No Golgi, rER, ribosome, mRNA
- Axon hillock: between soma and axon
- Initial segment: beginning of myelin sheath and action potential generation
- Antrograde vs Retrograde transport
10
Q
Describe Synapse
A
- Junction between axon and neurone/muscle/gland
- Chemical vs Electrical
—> Chemical: electrical —> chemical —> electrical, neurotransmitter release via synaptic cleft, only one direction, SLOW
—> Electrical synapse: gap junction, connexons, ions directly moved, no synaptic cleft e.g. cardiac, smooth muscle, electrical transmission in both direction, RAPID - Axodendritic (80%) vs Axosomatic vs Axoaxonic (control other synapses) synapse
- One-way transmission (depolarisation of pre-synaptic membrane)
11
Q
Central vs Peripheral glial cells
A
Central:
- Astrocytes:
- Largest, do not form myelin
- (FW) Fibrous: white matter, long unbranched
- (PG) Protoplasmic: gray matter, short branched - Oligodendrocytes: myelin sheath in CNS
- Microglia: phagocytes
- Ependymal cells: cerebral ventricle surface
Peripheral:
- Perineuronal satellite cells: do not form myelin sheath, surrounding cell body controlling microenvironment, electrical insulation
- Schwann cells: myelin sheath in PNS
12
Q
Function of astrocytes
A
- Form BBB: processes stretch from blood vessel to neurones, covering them
- Astrogliosis: phagocytose neuronal debris —> glial scar: maintain and repair
- Physical and metabolic support
- Trophic factors
- Keep extracellular K+ low (K+ buffering), Neurotransmitter buffer, Electrolyte buffer
- Guidance for migrating neurones
13
Q
Function of myelin sheath
A
- Accelerate transmission of action potential
- Electrical insulation
- Protection
- Track for axon regeneration
14
Q
Describe myelin sheath
A
- Interrupted at nodes of Ranvier
- Schwann cell: mesaxon wrap only one internodal segment of one axon
- Oligodendrocyte: Multiple processes wrapping several internodal segments of up to 50 axons
- Nerve impulse: saltatory
- Wrap around axon in a spiralling motion, cytoplasm squeezed out —> concentric layer
- Decreased capacitance, Increased resistance
15
Q
Unmyelinated axons in CNS and PNS
A
CNS: Bare, lack basal lamina and CT
PNS:
- groups of axons fit into a groove/grooves of Schwann cells (axons嵌入Schwann cell)
- no nodes of Ranvier
- series of Schwann cells cover entire length of axons
