2 - Neurons & Glia Flashcards
Extracellular space has high concentration of which ions?
Na+ and Cl-
Intracellular space has low ….. and high …..
Low [Na+] and high [K+]
Why is [Ca2+] kept low in neurons?
Because it’s a critical signalling ion
True or false - neurons have low amounts of mitochondria
FALSE - lots of mitochondria because neurons consume lots of energy
What are secretory vesicles?
Specialised packages that contain neurotransmitter
Define neurotransmitter
Specialised chemical used to communicate info between neurons
What are some important parts of a neuron?
- neuronal membrane -> separates intra and extracellular spaces
- ribosomes -> protein synthesis
- rough ER (aka Nissl bodies)
- mitochondria -> provide energy for membrane-bound ion pumps
What makes a neuron special?
- Neural processes that extend away from cell body
2. Mechanisms for electrical and chemical communication
What’s a neurite?
A neuronal process (ie: axons and dendrites)
Which direction do axons and dendrites transmit info?
Axons transmit info away from soma and dendrites transmit towards soma
What are the 3 protein structures in the neuronal cytoskeleton?
- microtubules
- neurofilaments
- microfilaments
Microtubules
Run longitudinally down neurites
Mediate intracellular transport
Microtubule associated proteins regulate their assembly and function
Neurofilaments
Structural support
Regulate axon diameter
Microfilaments
Linked to microtubules and membrane
Comprised of actin
What are the 3 important parts of axon?
Axon hillock, axon proper and axon terminal
Does the ER extend into the axon?
No - protein synthesis mainly happens in cell body
What is transported within an axon?
Proteins, neurotransmitters and metabolites
What are 2 methods of axon transport?
- Fast axoplasmic transport
2. Slow axoplasmic transport
Fast axoplasmic transport
- proteins synthesised in soma actively transported towards synapse
- metabolic waste from synapse transported to soma
Slow axoplasmic transport
- mechanisms unclear
- active transport
- real slow
What are the 2 transport directions in an axon?
- anterograde via kinetic (towards synapse)
- retrograde via dynein (away from synapse)
Do axon terminals have microtubules?
No
True/false - axon terminals have protein-dense membrane and lots of mitochondria
TRUE
What does the pre-synaptic neuron release?
Neurotransmitter
Synaptic cleft
Small gap between membranes of 2 neurons
Where does neurotransmitter bind after being released?
Binds to proteins in post-synaptic membrane and then converted into electrical signal
Spines
Small extensions of cell membrane where axon of another neuron comes in close proximity
Density and length of dendritic spines depends on what?
Environment and development
What can occur when spines don’t develop properly?
Mental retardation
T/F - a neuron’s dendritic arbor limits its function
True
Why do neurons vary in structure?
Because structure begets function
How do neurons vary?
- number of neurites
- shape and dendrites
- connections
- axon length
- neurotransmitter
What is a unipolar neuron?
Neuron with one primary axon/dendrite projecting from soma
Stellate cells
Collate info locally within a brain region
Pyramidal cells
Send info to other brain regions
Do stellate cells have long axons?
No they have very short axon
Glia
Support neuronal function and may be involved in info transmission
Main types of glia
- myelinating glia
- astrocytes
- Microglia
- ependymal cells
What are the 2 types of myelinating glia?
Oligodendroglia (CNS) and Schwann cells (PNS)
What do myelinating glia produce?
Myelin - electrically insulating sheath around axons
What are the gaps in myelin called?
Nodes of Ranvier
Why are nodes of ranvier important?
Provide connection between cytoskeleton in axon and extracellular fluid
What’s the primary function of myelin?
Increase axonal conduction velocity
Astrocytes support and influence what?
Support synaptic signalling, influence neurite growth and regulate chemical content of extracellular space (eg: K+ buffering)
More roles of astrocytes
- regulate neurotransmitter in synapse
- neuronal communication
- ensheath small arterioles and capillaries
Microglia
Fight inflammation and form specialised immune system in brain
Ependymal cells
Line fluid-filled ventricles
Produce CSF so brain floats
Control fluid release between brain tissue and CSF in ventricles
