Neurophysiology Fundamentals

Question 1

Is the cell membrane a good conductor of electrical signals?

Answer 1

No!
It is a double-lipid structure, charged particles (e.g. ions) can’t pass through it
Therefore, ion channels are needed instead

Question 2

Two types of ion channel

Answer 2

Voltage-gated: activated through electrical changes

Ligand-gated: activated by the binding of a neurotransmitter

Question 3

How is the resting membrane potential reached?

Answer 3

At rest, K+-channels are open, which allow K+ ions to diffuse out of the cell, according to the gradient. Cl- ions have no way of leaving the cell. This leads to an increasing intracellular negative charge, which pulls the K+ ions against the gradient. The electrochemical equilibrium is obtained when there is a balance between the gradient pull and the electric pull. For K+ ions in the neurons, the equilibrium potential is -65 Mv.

Question 4

Neuron with nothing to say

Answer 4

(Inside of cell is) negatively charged: working hard to stay silent

Question 5

Neuron with something to say

Answer 5

(Inside of cell is) positively charged: hard work stops and (Na+) ions flood in

Question 6

Hyperpolarization vs Depolarization

Answer 6

Incoming signals, mostly through neurotransmitter binding that have an effect on the membrane potential.
Hyperpolarization = more negative
Depolarization = more positive

Hyperpolarization is inhibitory (IPSP) as moves membrane potential further from the action potential threshold (-50Mv), and depolarization is excitatory (EPSP) as it moves the membrane potential closer to the threshold.

Question 7

Explain whats going on

Answer 7

When threshold is reached at -50Mv, voltage-gated Na+-channels open, causing an influx of Na+, creating self-reinforcing sharp increase in membrane positivity up to a peak of approx. +60 mV.

voltage-gated Na+-channels self-inactivate, ending the surge, and voltage-gated K+-channels briefly open, causing an “undershoot” below resting membrane potential

Question 8

RMP is _____ driven; AP is _____ driven [Which ions?]

Answer 8

RMP is potassium-driven (K+); AP is sodium-driven (Na+)

Question 9

Passive axonal conductance

Answer 9

Axonal conductance = how the action potential goes from postsynaptic dendrites down to the cell body and further on to the axon terminals.

Fluctuations in membrane potential, e.g. from action potentials, travel a brief distance
along the membrane and dissipate

The process is fast but leaky, just like my ass.

Question 10

Active axonal conductance

Answer 10

Nearby voltage-gated Na+-channels are activated from an action potential, restarting the whole action potential cycle in adjacent parts of the membrane.

This process is energy-costly and slow

Question 11

Describe the pic

Answer 11

Increasing the distance between clusters of ion channels and thoroughly insulating
the intermediate segment with myelin (inert membrane from oligodendrocytes)
combines robust active and fast passive conductance.

Lightning fast pew pew

Question 12

Answer 12

Question 13

Answer 13

Question 14

Short term synaptic plasticity.

Explain synaptic facilitation, synaptic depression, synaptic augmentation/potentiation

Answer 14

synaptic facilitation: rapid successions of action potentials lead to accumulation of
Ca2+ in synaptic terminal, causing release of larger transmitter quantities after each
action potential

synaptic depression: in persisting high-frequency stimulation, transmitter releases
surpasses synthesis rate, decreasing quantities released after each action potential

synaptic potentiation/augmentation: lesser understood processes (e.g. calciumdependent enzymatic activations) that lead to a somewhat delayed release of higher
neurotransmitter amounts (as compared to baseline) after high-frequency activations