Bill Wisden - Neuroscience Flashcards
Why do we want to study the brain?

What are the different levels one can study the brain?

From an evolutionary standpoint why would we need neurons?
Hypothetical multicellular organism with sensory cells (S) that control motor cells (M) (e.g., cilia) by releasing a chemical transmitter or hormone into the common fluid space – diffusion like this takes time…
Direct connections between sensory and motor cells by means of nerve axons speed up this communication
Communication is quicker and more specific – Wired in speed and specificity
Note - the ultimate action on the motor cells is still chemical
Hence, a sensible speculation could be that the nervous systems evolved to hardwire and improve the specificity of communication (Sensor direct connects to motor cell)

Why can’t we rely on diffusion?
Simple organism could rely on this but this would hinder communication in larger/more complex organisms…
On what timescale does diffusion normally occur?

What is Stokes-Einstein law?

How long would it take for a molecule to diffusion along 1 cm of axon (rough calculation)?
Why 6D?

How was axonal movement studied?

What were the three types of movement identified from pulse-chase radiolabeling?
Discovered three types of movement – faster than passive diffusion but not fast (hours – days) –> facilitate movement along these long axonal regions
Fast - 50-400 mm/d –> 3 hours for movement from cell body to terminal
Slow b - 2-8 mm/day
Slow a - 0.2-1 mm/day
How is material moved inbetween the cell body and axon terminal?

What are the two main cytoskeletal elements?

What are the different motor proteins and what do they transport?

Outline the general process by which signals are transferred from one dendrite of one nueron to the dendrite of another

Why are membrane channels needed in neurons?
Movement of ion through the lipid bilayer would require a lot of energy – thermodynamically not favourable
Membrane - Negatively charged phosphate on head + hydrophobic environment

What is the basic idea that allows for electrical signal creation in neurons?
Basic idea of electrical signals – Driven by differences of ion conc. on opposite sides of membrane
What is the role of pumps in neurons?
Active pumping –> The action of the pumps is crucial for the maintenance of ionic concentration differences within membranes (essential for the creation of electrical signals)
There are many different kinds of pumps - Most use ATP as an energy source to build up a gradient of ions.
A large proportion of the energy intake of a human is devoted to the operation of ion pumps - explains the increase of mitochondria in neurons
How does a sodium pump work?

What are the distribution of ions across neuronal membranes at a resting state?
Distribution of ions across neuronal membranes
Different animals, varied numbers for the exact concentrations.
But the relative concentrations, high K in, low K out, high Na out, low Na in, are always the same - High K+inside and High Na+ outside
Other things to note…
A- –> anions of other ions e.g. Carboxylate groups (COO-) of amino acids, sugars, etc.
Chloride is high on the outside and low on the inside
Other important ion for signalling is Ca2+ - tends to be higher outside
Balancing out the charges of all ions…
we get an electrochemical gradient where the inside of the cell is more negatively charged relative to the outside – between -60 to -75 mV

Using the example attache below (K+ permeable membrane), outline what is meant by electrochemical equilibrium

All systems move towards equilibrium – this case electrical & chemical equilibrium
Setup - membrane permeable only to K+ ions + high concentration of K+ and A- in one cell
- K ions start to diffuse down their concentration gradient from one side to the other – left to right down chemical gradient
- This results in a build up of charge (Negative - left + positive - right) - electrical potential difference builds up
- Chemical forces causing a net diffusion of K from left to right are now countered by a growing electrical force which opposes the flow of K+
- Eventually an electrochemical equilibrium potential is reached where the electrical force equals the chemical (or diffusional) force, and no exchange occurs

How can we calculate membrane potential at equilibrium for a given ion species?

What kinds of stimuli can open channels?

In relation to neurons, what are changes in membrane potential/voltage used for?

Definition of depolarization and hyperpolarization?

What happens to voltage as an electrical signal passes through an axon?

































































































