Week 3 Recitation Review

Question 1

Please define the membrane potential?

Answer 1

This is the voltage (potential difference) across the neuronal membrane.

Question 2

What are the 3 most important players in neuronal communication & the membrane potential?

Answer 2

1) Ions - Na+, Cl-, Ca2+, K+, etc
2) Phospholipid bilayer - ions cannot flow freely across the membrane due to the phospholipid bilayer
3) Proteins - form/affect the channels/pores which allow ions/molecules to cross the phospholipid bilayer

Question 3

What is the neuronal membrane potential at rest?

Answer 3

-65mV with it being most permeable to K+, so strong K+ concentration inside the cell

Question 3

When it comes to neuronal communication, what is the cytosol (inside the cell concentration of ions) vs outside the cell (extracellular fluid)?

Answer 3

Inside the cell: K+ and A- (anions)
Outside the cell: Na+, Ca2+, Cl-

Question 4

What are some of the important proteins/channels involved in neuronal communication and membrane potential?

Answer 4

Na+ leak channels (not gated)
K+ leak channels (not gated)
Voltage gated Na+ channels
Voltage gated K+ channels
Na+/K+ pumps

Question 5

Describe the 9 steps involved with a membrane potential at rest creating an action potential

Answer 5

1) EPSP depolarizes (spike-initiation zone) with Na+ flowing into the axon
2) Axon membrane gets depolarized to -45/40mV
3) Voltage gated Na+ channels allows more Na+ to flow in
4) Membrane gets depolarized enough to create an action potential (positive/depolarized gets spread to adjacent membrane)
5) Na+ channels close and inactivate, thus halting Na+ influx (~1ms)
6) Voltage gated K+ channels open with K+ flowing out, thus starting the falling phase (just passing the crest)
7) Membrane hyperpolarizes, creating an absolute refractory period where a new signal cannot occur
8) K+ flows slow down to balance things out, Na+ channels reactivate, thus still in a relative refractory period
9) Membrane depolarizes (back up from bottom) to resting membrane potential

Question 6

What are the two types of post-synaptic potential summation?

Answer 6

Temporal - one cell produces multiple actions potentials (over time) to the same neuron
Spatial - more than one cell produces an action potential onto the same neuron

Question 7

Describe the 7 steps for sensory system stimulus and flow

Answer 7

1) receptor stimulated in the periphery
2) signal transduction (chemical or mechanical to electrical transduction of external stimuli to action potential)
3) This signal is sent to relay nuclei (spinal cord -> brain stem)
4) Then sent to the Thalamus
5) Which sends info to the primary sensory cortices
6) Which sends the signals to the secondary sensory cortices
7) Which sends the signal to the association cortices

Question 8

What are the two types of post-synaptic action potential receptors?

Answer 8

Ionotropic - whereby the ligand activates the receptor and thus PSP
Metabotropic - GPCR’s whereby the ligand starts a secondary process which eventually (through steps) activates the receptor response