Neurons: Design Principle Flashcards
Different neuron types have different ?
Number of processes extending from the soma, reflecting evolutionary and functional differences
What are some types of neurons ?
- Unipolar
- Bipolar (Information conveying)
- Multipolar
Neurons are just like other cells, but ?
With ‘specialisation’ for rapid communication
What are two particular specialisations that neurons have ?
- Morphological features
- An electrically excitable membrane
The contents of a neuron are contained within?
A plasma membrane
This plasma membrane is a lipid bilayer structure which forms a hydrophobic barrier. This is comprised of ?
Amphipathic lipids –eg.phospholipids - and proteins (~20% of membrane composition)
Is this plasma membrane stable ?
It is stable but fluid structure, where phosphate head groups face the aqueous environment and fatty acid tails face each other
What does this plasma membrane act as ?
The membrane acts as a barrier to water-soluble ions and charged molecules
What is the only way that they can cross the plasma membrane ?
Via membrane-spanning proteins
The cytoplasm is the contents of the inside of the cell. What can this be sub-divided into ?
- Cytosol
Aqueous component of the cytoplasm - Everything else:
Cytoskeleton, membranous organelles and vacuolar apparatus (Golgi, tubules, vesicles, lysosomes, endoplasmic reticulum).
The cytoskeleton determines?
Cell shape
What are three main components of cytoskeleton?
- Microtubules: long scaffolds involved in cell stability and transport mechanisms; dynamic
- Neurofilaments: bones of the cytoskeleton and structural support for axons – shorter; numerous and stable
- Actin: much shorter and concentrated at peripheral structures – for example, synapses where they can influence function; dynamic
Explain the processes of active transport for transporting proteins and organelles ?
SLOW: Cytoskeletal elements (e.g.actin), enzymes and some proteins move anterogradely at 0.2-2.5 mm/day. Involves mechanisms including microtubule slipping.
FAST: Membranous organelles (vesicles, mitochondria etc.) are moved both anterogradely and retrogradely at >400mm/day requiring ATP and molecular motors on microtubules
Name some transport proteins and explain ?
Ion channel:
Allows the passive flow of ions through the membrane
Ion pump:
Moves ions across the membrane against a concentration gradient
Other transporters:
Facilitates transfer of molecules across the membrane
What special proteins allows passive diffusion of ions ?
Ion channels
What is ion flow determined by?
Electrochemical driving forces
What are leakage channels ?
Some channels which are open all the time
Most channels are gated, meaning ?
They can be opened or closed
How is Gating achieved ?
By a conformational change in the structure of the protein
What is transport protein that uses energy to move ions across the membrane ?
Ion pumps
In Ion pumps, ions do not flow freely but ?
Can be actively transported against their electrochemical gradient and used to establish a high concentration of ions on one side of the membrane
Name some signalling proteins and explain ?
Receptors:
- Binds a signalling molecule and initiates a neuronal response
G Proteins:
- Initiates a cascade of biochemical reactions triggering a neuronal response when triggered by a signalling molecule
Other enzymes:
- Catalyses biochemical reactions associated with signalling
Name some binding proteins and explain ?
Adhesion proteins:
- Anchor the neuron to other cells
Cytoskeletal binding proteins:
- Anchor the cell membrane to the internal cytoskeleton
Explain how Glial cells are similar to neurons in a number of ways:
- Electrical potential across their membrane which can be varied
- Respond to various chemicals
- Some have a similar structure with a cell body and neurite branches
