3 Cells of the Nervous System Flashcards
Q: What is the basic structural and functional unit of the nervous system? role? (2)
A: neuron- information processing and responsible for generation and conduction of electrical signals
Q: How many inputs can a neuron take and how many outputs can they have?
A: can have many inputs but only one output
Q: How is neuronal structure diversity achieved?
A: differences in number and shape of processes
Q: What are the features of a neuron? (6) Summarise.
A: -Large nucleus
- Prominent nucleolus
- Abundant rER (since it’s a secretory cell)
- Well developed Golgi (because of need to transport proteins over long distances)
- Abundant mitochondria
- Highly organised cytoskeleton
HIGHLY ORGANISED METABOLICALLY ACTIVE SECRETORY CELL
Q: What is the role of a dendrite? Structure? (3) How many __ can a large pyramidal neuron have?
A: major area of reception of incoming information
- spread from cell body
- branch frequently
- often covered in protrusions called spines (dendritic spines receive the majority of synapses)
may have 30,000/40,000 spines
Q: Draw diagrams for purkinje cells and pyramidal neurons. Where are there a large number of Purkinje Cells? what are they?
A: REFER
cerebellum- inhibitory
Q: Describe the structure of pyramidal neurons. (4)
A: You get primary dendrites coming off the vertices of the pyramid
There are secondary dendrites branching off the primary
Tertiary dendrites branch off the secondary
Single axon coming from a straight side
Q: What’s the role of an axon? Where are they? How many per cell? Branching? (2)
A: -conduct impulses away from cell body
- emerge at axon hillock
- usually 1
- may branch after leaving cell body in 2 places forming axon collaterals: just after leaves cell body or when closer to target cell so it can innovate multiple targets
Q: Diameter of axon changes? result? Can be? (2)
A: -After leaving the axon hillock it maintains the same diameter the whole way down (thereby maintaining the same speed)
-myelinated or not where axonal membrane of a myelinated fibre is only exposed at the Nodes of Ranvier
Q: Benefit of myelination?
A: can get faster conduction without needing larger axon diameter
Q: What do axons contain? (2) Include 2 roles.
A: -abundant microtubules and neurofilaments (play critical role in determining axon caliber/quality)
-intermediate filaments = needed for tensile strength as the cells can be very long
Q: How is the molecular composition of the axon organised? (3)
A: into domains: juxta-paranode -> paranode -> node (where are Na+ channels concentrate)
PARANODE - the area where the ends of the myelin is bound to the axon to form tight junctions - this prevents leakage of current under the myelin sheath
JUXTAPARANODE - an area with dense myelin where you find potassium channels
Q: What are the forms of axon terminals that exist? (2) Describe them.
A: -boutons= basic synapse with a bulb
-varicosties= multiple swellings containing neurotransmitter when axons synapse with many smooth muscle cells as it passes
axon variscosity (synaptic bouton)
Q: What do synapses contain? (3) Length?
A: -abundant mitochondria - 45% of total energy consumption is required for ion pumping and synaptic transmission - this is why neurons are sensitive to oxygen deprivation
- synaptic vesicles
- specialised mechanisms for association of synaptic vessels with membrane
length can vary between mm and m
Q: How are competing inputs from axons organised?
A: integrated in the postsynaptic neuron - NEURONAL INTEGRATION -> produce sigle AP (on/ off signal)
Q: What are the 3 types of synapse? What are the names based on?
A: 1. Axo-dendritic = often excitatory
- Axo-somatic = often inhibitory
- Axo-axonic = often modulatory
Names are based on which parts of the two neurons synapse (e.g. axo-somatic = axon and soma)
Q: What does fast axonal transport involve? Daily? How? (2)
A: -Transport of membrane associated materials ANTEROGRADE
-Vesicles with associated motors are moved down the axon at 100-400mm per day
-Proteins are packaged into a vesicle and then the vesicle is targeted down towards the presynaptic membrane (vesicle have adhesion proteins -> attach to microtubules and motor proteins that need ATP to allow vesicle to move)
Q: What is retrograde transport? What determines direction of axonal transport movement?
A: moving vesicles containing various molecules back to the cell body
The microtubules are polarised (positive and negative) so the vesicles can only move in one direction (Transport goes in two directions but down two different microtubules)
Q: Describe axonal damage in multiple sclerosis. (2)
A: If there is a restriction to the axon (e.g. traumatic injury or inflammatory disease) you begin to see SWELLINGS
SWELLINGS - vesicles of neurotransmitter keep being transported down the axon and they accumulate because they have no where to go
Q: Name 4 morphological subtypes of neurons.
A: -Pseudounipolar
- bipolar
- Golgi Type I Multipolar
- Golgi Type II Multipolar
Q: What do pseudounipolar neurons tend to be? Structure? Signal conduction?
A: -Tend to be sensory neurons
- They have two fused processes which are axonal in structure
- The signal received passes directly to the axon terminal without going through the soma
Q: What are bipolar neurons involved in? Structure? Example.
A: -white matter of the cerebral cortex
-1 dendron and 1 axon
retinal bipolar cells
Q: What is the structure of Golgi Type I Multipolar? (2) 4 examples including location.
A: -Highly branched dendritic trees
-Axons extend long distances
- Pyramidal Cells of the cerebral cortex
- Purkinje Cells of the cerebellum
- Anterior Horn/ motor Cells of the spinal cord
- Retinal Ganglion Cells
Q: What is the structure of Golgi Type II Multipolar? (3) 1 example including location.
A: -Highly branched dendritic trees
- Short axons that terminate quite close to the cell body of origin
- dendritic tree is not as uniform and cell body is not typical of a pyramid shape
Stellate Cells of the cerebral cortex and cerebellum
Q: What are the 3 functional classifications of neurons?
A: -Sensory Neurons
- Motor Neurons
- Interneurons
Q: What are interneuons responsible for? (5)
A: modification, coordination, integration, facilitation and inhibition of sensory input
Q: What are neuroglia? Essential for? 7 examples. Most numerous cell type in brain?
A: support cells of nervous system
-correct functioning of neurons
- Astroglia **
- Oligodendroglia
- Microglia
- Immature progenitors
- Ependymal cells
- Schwann cells
- Satellite glia
Q: What are oligodendroglia? (2) 2 main types? Structure? Function? (2)
A: myelin forming cells of the central nervous system = Metabolically highly active hence needs lots of NRG
- Interfascicular
- Perineuronal
- Small spherical nuclei
- Few thin processes
- Prominent ER and Golgi
- Production and maintenance of myelin sheath
- Each cell produces 1-40 myelin sheaths
Q: What is myelin? structure? What’s visible at EM level? Name 2 diseases that can affect it (loss of myelin).
A: lipid rich insulating material -> can have up to 50 layers
dark and light bands seen at EM level
- Multiple Sclerosis (loss of myelin due to autoimmune reaction)
- Adrenoleukodystrophy/ALD (leads to progressive loss of myelin)
Q: What are microglia? (3) Where do they develop from? Function? (5)
A: -Immune cells of the CNS
-Resident macrophage population of the CNS
-Developed from bone marrow during early development - the only cells that are NOT derived from the brain
- Involved in immune surveillance
- Present antigens to invading immune cells
- First cells to react to infection or damage
- Role in tissue remodelling
- Synaptic stripping
Q: Describe microglial morphology. In relation to MS?
A: When they respond to a change, the cell shape changes and if the stimulus is strong enough it becomes phagocytic (starts off as relay neurone looking -> phagocytic cell)
MS - microglial cells could be the ones destroying the myelin sheath
Q: What are peripheral glial cells also called? Functions? (2) Structure? Conduction?
A: -schwann cells
- Each schwann cell produces one myelin sheath
- Promote axon regeneration
Wrap themselves around the nerve axon rather than just wrapping a process around the axon
AP conduction is not as fast as conduction involving oligodendroglial insulation
Q: What’s the structure of astroglia? Contains? What suggests astroglia-astroglia signalling?
A: -Multi-processed - star shape
- numerous intermediate filament bundles in the cytoplasm of fibrous astroglia (give high tensile strength)
- gap junctions
Q: What are the functions of astroglia? (7)
A: 1. Scaffold for neuronal migration and axon growth during development
- Formation of blood-brain barrier
- Transport of substances (nutrition) from blood to neurons
- Removal of neurotransmitters (by controlling levels of K+ and water)
- Synthesis of neurotrophic factors (allows neurons to survive)
- Potassium ion buffering
- Glial scar formation
Q: Describe astrocyte/astroglia interaction with blood vessels. (2)
A: -have ordered arrangement of astrocytes with minimal overlap
-each cell forms a specific territory that interfaces with microvasculature
Q: Summarise astrocytes.
A: sample their own microenvironment and interact with other cell types
