1.6 Microstructure Flashcards
A protein is produced in a neuron. How does its fate differ if it is translated at a free ribosome vs RER ribosome?
Free: Cytosolic protein
RER: Proteins destined for cellular/organelle membrane
Why do neurons have so much rough endoplasmic reticulum compared to other cells?
Proteins translated by RER ribosomes are used for membranes. Neurons need many of these proteins, such as channels, and so they have lots of RER.
Which organelles are present in high amounts in neurons?
- Mitochondria (energy)
- RER (protein production)
- Golgi body (protein transport)
- Cytoskeleton
The thicker an axon of a neuron, the _____ the impulse travels
Faster
What organelles/structures can be found in an axon terminal?
- “Bubbles” of synaptic vesicles (containing neurotransmitters)
- Mitochondria (active vesicle transport)
Which protein is responsible for anterograde/retrograde vesicle transport along axons?
Anterograde: Kinesin
Retrograde: Dynein
What is the most abundant cell type in the brain?
Astrocytes
Describe the function of astrocytes
- Recycle neurotransmitters
- Structural support
- Regulate concs in environment, like ions, nutrients and dissolved gases
How do astrocytes help in metabolism of neurons?
- Well positioned to access glucose from the bloodstream
- Convert glucose into lactate
- Neurons can use lactate to produce energy (perhaps even preferred during periods of activity…)
Astrocytes regulate homeostasis of the CNS by ensuring concentrations of ions, neurotransmitters, and water. What channels do they use to regulate water conc?
Aquaporins (specifically, aquaporin 4, or AQP4)
What is astrogliosis?
The proliferation of astrocytes to form a scar in response to CNS injury
Describe the benefits and drawbacks of astrogliosis
Good: walls of area
Bad: prevents new connection, slows recovery
What is the PNS equivalent of astrocytes?
Satellite cells
What is the function of oligodendrocytes?
Myelinating axons
Citing a specific kind of microglial cell, explain why neurons in the CNS cannot be regenerated in response to injury
In response to injury, oligo’s release inhibitory factors
What are the two types of conduction?
Saltatory: myelin + nodes of ranvier
Continuous: no myelin
What is the PNS equivalent of oligodendrocytes? What is their biggest difference to their CNS alternatives?
- They are called Schwann cells
- They can only myelinate one axon, whereas oligos can myelinate 15
What is the function of microglia?
- Roaming phagocytes
- Synaptic pruning
- Neurodegenerative disease
Describe the activation of microglia
- Injury detected
- Processes retracted
- Motility increased
- Gather around injury site, and perform phagocytosis
True or false: microglial phagocytosis promotes inflammation
True
Describe the structure of the blood brain barrier
- Endothelial cells (held together with tight junctions)
- Pericytes
- Basement membrane
- Astrocytes (and their “podocyte” feet processes)
In most capillaries, transport of substances is paracellular (i.e., between cells). is this the case in the blood brain barrier?
- No
- Instead, transport mostly happens through cells
Outline the different ways in which substances can be transported across the blood brain barrier
- Passive diffusion
- Carrier mediated transport (i.e. channel proteins)
- Receptor mediated transport (i.e. in an endosome)
- ABC transporters allow substances to go the other way (brain to blood)
Give some examples of substances that cross the blood brain barrier via transport proteins
- Glucose
- Amino acids
- Peptides
- Choline
Describe, fundamentally, how substances cross the BBB through transport proteins.
- Bind to first transport protein, undergoes conformational change, allowing passage into cell
- Bind to second transport protein, undergoing conformational change, and allowing passage into brain
Receptor mediated vs adsorptive transcytosis
RM: Ligand must bind to receptor
Adsorptive: Binds to negative membrane charge
Is transport via ABC transporters active or passive? What kind of substances does it remove?
- Active
- Removes toxins
