Electrical Signaling

Question 1

Describe the Structure of a Neuron

Answer 1

Cell body (soma) = control centre, produces proteins and chemicals for normal functions

Axon = projections from the soma, SENDS signals to other neurons

Dendrites = projections that RECEIVE signals, there are many but they are short

Question 2

Features of electrical signaling

Answer 2

1. Instantaneous
2. Essential for survival
3. Responds to danger fast

Question 3

How does a neuron generate electrical impulses

Answer 3

Need a difference in electrical charge between inside/outside

Cellular fluid is full of IONS, goes through ion channels

The way in which these ions are moved across the plasma membrane underlies the production of electrical impulses

Question 4

Define Resting Membrane Potential

Answer 4

Difference in charge inside and outside of the neuron

At rest, the potential is POLARIZED (-70 millivolts). The aim is to keep sodium out of the neuron and keep potassium inside the neuron. There is a concentration gradient from high to low. Passively, potassium is driven out and sodium is driven in. Actively, potassium is pumped in and sodium is pumped out in order to maintain EQUILIBRIUM

Question 5

Define depolarize

Answer 5

Decrease the charge of the membrane to make it MORE POSITIVE (aka fire) linked to EPSP

Question 6

Define Hyperpolarize

Answer 6

Increase the charge of the membrane to make it MORE NEGATIVE (aka not fire) linked to IPSP

Question 7

Define EPSP

Answer 7

Excitatory post synaptic potentials, increase likelihood that the neuron will fire

Question 8

Define IPSP

Answer 8

Inhibitory post synaptic potentials, decrease likelihood that the neuron will fire

Question 9

Define Action Potential

Answer 9

How neurons respond to input. Has a threshold. Excitation occurs at –65 millivolts and lasts 1 millisecond. ALL OR NOTHING. Reversal of membrane from –70 to +50

Question 10

Define Summation

Answer 10

The net effect of activity, it is integrated over space and time

Question 11

Define Integration

Answer 11

Neurons can add together all the EPSP and IPSP into one signal

Question 12

Explain Depolarization (up down graph… time on x axis… membrane potential on y axis)

Answer 12

Rising phase/depolarization = influx of sodium through sodium gated channels

Repolarization = continued efflux (means out) of potassium ions

Hyperpolarization = when too many potassium ions have flowed out

Question 13

Define ABSOLUTE Refractory Period

Answer 13

Periods after action potential where no more action potential can be initiated (1-2 milliseconds after, in the green area)

Question 14

Define RELATIVE refractory period

Answer 14

When an action potential is possible BUT only by very high stimulation

Question 15

Describe Myelination

Answer 15

Conduct nerve impulses very fast (430km/hr)

Nerve conduction velocity can be increased by insulating the axons

Insulated by a layer of oligodendrocytes (myelin sheath)

Action potential occurs in unmyelinated gaps between the glial cells (Nodes of Ranvier)

Question 16

Describe Saltatory Conduction

Answer 16

The nodes are close enough together such that the rising phase and one node can produce voltage-gated rising phase at an adjacent node

Action potential therefore JUMPS from node to node

This increases the rate at which an action potential can travel along an axon

Question 17

Describe how Demyelination causes Multiple Sclerosis

Answer 17

Disease of demyelination

Neurodegenerative autoimmune disorder: the body’s own immune system attacks and damages myelin sheath cells, replacing them with scar tissue

Axons can no longer conduct signals as effectively

Conduction finally stops when sodium ions can’t enter neurons at all because of the scar tissue