Module 1: Cell/ Molecular Overview and Electrical Signals

Question 1

characterize the “functional microanatomy” of neurons

Answer 1

soma (cell body), dendrites (branches that receive signals from other neurons), axon (specialized for rapid conduction of nerve signals

Question 2

Describe structural and functional classifications of neurons and the significance of variations in neuron structure

Answer 2

can be short to one axons or dendrites

types of structural classifications:
unipolar (axon and dendrites from same side)
biolar (axon and dendrites from opposite sides)
pseudo-unipolar (kind of a mix)
multipolar (axons and dendrites coming from every side of soma)

types of neurons:
afferent neurons: info going to brain
efferent neurons: signals coming from brain
interneurons: cellular communication between neurons

Question 3

recall commonly used neural circuit motifs (convergence, divergence, feedforward and feedback excitation, lateral inhibition, and disinhibition)

Answer 3

convergence: diversity in input

divergence: diversity in output

feedforward: signals galvanize forwards

feedback excitation: exciting step earlier in process.

recurrent (lateral) excitation: excites other lines of excitation

lateral inhibition: inhibition of lateral excitation.

disinhibition: series of inhibitory signals

Question 4

distinguish between the CNS and PNS and recall the basic functions of the major types of glial cells found in the CNS and PNS

Answer 4

CNS: brainstem and spinal cord
PNS: everything else

glial: support cells of the NS

CNS glial cells:
- astrocytes - maintain appropriate chemical environment (ex. support BBB).
- microglia - support immune function (macrophages, cytokines, etc.).
- oligodendrocytes - myelinate CNS axons (increase speed of transmission).

PNS glial cells:
- schwann cells - (oligodentrocyes of PNS) myelinate peripheral NS axons

Question 5

describe types of neuronal electrical signals, how ion movements produce electrical signals, and the forces that create membrane potentials

Answer 5

types of signals:
1. receptor potential (external stimulation, ex. light)
2. synaptic stimulation (ex. neurotransmitter)
3. robust stimulation (action potential)

resting potential formed by negative potassium state, action potential makes it more positive, this is maintained by potassium leak channels and sodium-potassium pump

Question 6

distinguish between the nernst and goldman equations, as well as voltage, current, resistance, and conductance

Answer 6

nernst: only accounts for potassium, so its note entirely accurate bc it doesn’t account for the other ions affecting the resting potential.

goldman equation: accounts for potassium, sodium, and chloride and takes into account their P values (permeability)

voltage: electrical current difference

current: flow of ions

resistance: opposite to charge

conductance: ability to carry an electrical current from one place to the other

Question 7

describe the ionic basis for the resting membrane potential and the action potential

Answer 7

resting membrane potential: high concentration of potassium in the cell is responsible for the highly negative environment, voltage gated channels are done

action potential: as Na+ enters from an adjacent region, the voltage-gated Na+ channels open –> sodium to rush in and depolarize the membrane –> propagation of ap to next node –> Na+ undershoots a bit and then the channels close and become inactive

Question 8

describe current flow across a membrane during a voltage clamp experiment and the relationship between current amplitude and membrane potential

Answer 8

voltage clamp technique sets electrical voltage into cell to see how neuron would react, small changes in voltage had little effect, but a strong positive voltage –> strong depolarization of the membrane, but little clarity on what ions were responsible.

the method measures the amount of current required to maintain the membrane at a particular voltage, can add pharmacological toxins to separate sodium and potassium and see the effects

sodium declines quickly bc closed after ap and moves on to next node quickly, potassium fluctuates over a longer period

higher the current and higher the membrane potential, more likely to get an action potential
current = permeability x voltage

Question 9

characterize saltatory action potential conduction, and how myelin increases conduction speed

Answer 9

myelin (oligodendrocytes) insulate the electrical charge in the axon and allow it to go down the axon without losing charge. between each node is the nodes of ranvier, where another action potential occurs, then its propagated through the glial cell until the next space

saltatory action potential: action potential jumps from node to node