Lecture 1 - How does the brain work? Excitability of membrane: resting & action potential

Question 1

How complex is the human brain connectome?

Answer 1

100 billion neurons; 10^15 synapses

Question 2

What are the 3 different functions of neurons?

Answer 2

Sense changes in environment (sensory)
Communicate changes to other neurons (interneurons)
Command body’s responses to sensations (motor)

Question 3

What is the function of glia?

Answer 3

Insulate, support and nourish neurons

Question 4

What are neurites?

Answer 4

Axons and dendrites

Question 5

Soma/cell body/perikaryon:
~__ ___ diameter
__-rich cytosol
contains organelles

Answer 5

~20 μm diameter
K+-rich cytosol
contains organelles

Question 6

Vesicles enclose materials for transport from soma to terminals
- on ______/______ along microtubule “_____”
- ___-dependent process

___________: from soma to terminal, use ______
___________: from terminal to soma, use ______

Answer 6

Vesicles enclose materials for transport from soma to terminals
- on kinesin/dynein along microtubule “tracks”
- ATP-dependent process

Anterograde: from soma to terminal, use kinesin
Retrograde: from terminal to soma, use dynein

Question 7

Axon Terminal
* also called terminal ______
* site axon contacts another neuron
* point of contact called ______
* terminal _____ - axon form many branches
* ___________: when neuron makes synaptic contact

Answer 7

Axon Terminal
* also called terminal bouton (“button”)
* site axon contacts another neuron
* point of contact called synapse
* terminal arbor - axon form many branches
* innervation: when neuron makes synaptic contact

Question 8

Axon Terminal
*terminal cytoplasm different:
- ___________ do not extend into terminal
- numerous _______ _______ (50 nm across)
- dense _______ covering at membrane facing synapse
- numerous ____________

Answer 8

Axon Terminal
*terminal cytoplasm different:
- microtubules do not extend into terminal
- numerous synaptic vesicles (50 nm across)
- dense protein covering at membrane facing synapse
- numerous mitochondria

Question 9

Dendritic spine
* receive some ________ ______
* hang from dendrite
* consist of _____ and ______ ____

Answer 9

Dendritic spine
* receive some synaptic inputs
* hang from dendrite
* consist of stalk and spine head

Question 10

What forms the chemical signal in the synapse?

Answer 10

Neurotransmitters (stored in synaptic vesicles)

Question 11

What is the site for nerve gas and psychoactive drugs?

Answer 11

The synapse

Question 12

What is the transformation of information from pre-synaptic to post-synaptic neuron?

Answer 12

electrical to chemical to electrical

Question 13

Concepts of Brain Function
The Brain as a LUMP of wet clay?

Answer 13

L: Localisation or distribution of function
U: Use It or Lose It
M: Magnification
P: Plasticity

Question 14

Long-term potentiation
What is Hebb’s postulate on plasticity?

Answer 14

Neurons that fire together, wire together

Question 15

What are the mechanisms underlying the formation of LTP?

Answer 15

Glutamatergic excitory synapse
Addition of postsynaptic AMPA receptors
Enlargement or maturation of spines after LTP

Question 16

What is the posterior hippocampus known for?

Answer 16

Episodic memory, spatial information

Question 17

What is the Vm (membrane potential) in a neuron and in a skeletal muscle?

Answer 17

In neuron
Vm = -65mV

In skeletal muscle
Vm = -80 mV

Question 18

What are the characteristics of an action potential?

Answer 18

• also called spike, nerve pulse or discharge
• generated by a cell is similar in size and duration
• does not diminish down axon
• code: frequency and pattern
• lasts 2 msec

Question 19

What are sensory receptors?

Answer 19

Specialised structures - contain ion channels that are involved in generating electrical signals to be decoded as specific sensations

Question 20

The nervous system has to ______, _________ and _______ information

Answer 20

The nervous system has to collect, distribute and integrate information

Question 21

Axon
* not like a telephone copper wire
* MORE like a ______ _______ _____
Passive electrical currents
* do not conduct very ___
* ____ out
Action Potentials
* do not diminish over _______
* fixed in ____
Excitable membrane
* capable of generating &
conducting APs

Answer 21

Axon
* not like a telephone copper wire
* MORE like a leaky garden hose
Passive electrical currents
* do not conduct very far
* leak out
Action Potentials
* do not diminish over distance
* fixed in size
Excitable membrane
* capable of generating &
conducting APs

Question 22

What are the 3 main players affecting resting membrane potential?

Answer 22

Salts
Membrane
Channels and pumps

Question 23

Ion Channels
* _____membrane
* require - subunits to form _______ pore
* important property specified by ________ of pore & pore ______

Answer 23

Ion Channels
* transmembrane
* require 4-6 subunits to form aqueous pore
* important property (ion selectivity, gating) specified by diameter of pore & pore lining

Question 24

sodium-potassium pump
Na+/K+ ATPase
*breaks down ___ in the presence of ___
•expends ___% of total ATP used by brain

Answer 24

sodium-potassium pump
Na+/K+ ATPase
*breaks down ATP in the presence of Na+
•expends 70% of total ATP used by brain

Question 25

What are ion transporters responsible for?

Answer 25

Generating concentration difference of ions

Question 26

What are ion channels responsible for?

Answer 26

Generating electrical signals

Question 27

What does amount of current flow depend on?

Answer 27

Electrical potential (V, volts)
Electrical conductance, g (S, siemen) = 1/R

Question 28

What does equilibrium potential, Eion, depend on?

Answer 28

The ratio of concentration of ions in the outside vs inside of the cell (Nernst equation)

Question 29

How is the resting potential determined?

Answer 29

Goldman-Hodgkin-Katz equation

Resting potential is determined predominantly by K+ permeability, but is also influenced by Na+ and Cl- permeabilities

Question 30

What is the voltage clamp method used for?

Answer 30

Recording currents at specific voltages

Question 31

Generation of multiple APs
* depolarise just to __________ - rate is ~ 1 hertz (1 per sec)
* higher ______________
- frequency _________, say to ___ Hz or _____ Hz (max)
- once an AP is initiated, impossible to initiate another for about _ ___ (_________ refractory period)
- ________ refractory period: after refractory period difficult to initiate another action potential

Answer 31

Generation of multiple APs
* depolarise just to threshold - rate is ~ 1 hertz (1 per sec)
* higher depolarisation
- frequency increases, say to 50 Hz or 1000 Hz (max)
- once an AP is initiated, impossible to initiate another for about 1 msec (absolute refractory period)
- relative refractory period: after refractory period difficult to initiate another action potential