Chapter 2 Neurons and the Action Potential

Question 1

Components of a neuron

Answer 1

dendrites, a cell body, an axon, and synaptic terminals

Question 2

The functional subdivision of the structure of a neuron.

Answer 2

receiving, integrating, and transmitting compartments.

Question 3

Polarization

Answer 3

a concept which describes that the dendrite receives, the cell-body integrated, and the axons transmit.

Question 4

the outer membranes of the neurons

Answer 4

made of fatty substances, are draped around a cytoskeleton.

Question 5

cytoskeleton

Answer 5

built up of rods of tubular and filamentous proteins that extend out into dendrites and axons alike.

Question 6

dendritic spines

Answer 6

tiny protuberances that stick out from the dendrites

Question 7

growth factors

Answer 7

molecules that the end-points of the axons also respond to. these factors are taken up inside and then transported to the cell body where they influence the expression of neuronal genes and hence the manufacture of new proteins.

Question 8

synapses

Answer 8

the junctional spots of dendrites and neurons. most of the synapses on cells in the cerebral cortex are located on the den dendritic spines that stick out like little microphones searching for faint signals

Question 9

synaptic transmission

Answer 9

communication between nerve cells at these contact points

Question 10

excitation

Answer 10

currents that come into the cell

Question 11

inhibition

Answer 11

currents that move out of the cell

Question 12

action potentials

Answer 12

the electrical pulses that axons of neurons transmit

Question 13

ion channels

Answer 13

contained in the axonal membrane, can open and close to let through electrically charged ions.

Question 14

electrical depolarisation

Answer 14

When channels open, the Na+ or K+ ions flow down opposing chemical and electrical gradients, in and out of the cell

Question 15

resting membrane potential

Answer 15

The Na+-K+ pump open, sodium and potassium channels closed. The resting membrane potential is -70. It is negative because 3 sodiums went out and 2 potassium moved in, and they are both positive ions, which causes there are more positive ions outside than inside

Question 16

Failed initiations

Answer 16

initiation of action potential failed, unable to go to the depolarization, go back to the resting state.

Question 17

Action potential - Depolarization

Answer 17

Start of the action potential, sodium channel opened, a pulse of sodium ions flashes into the cell and a new equilibrium is established within a millisecond. This stage is positive because there are more positive ions inside than outside.

Question 18

Action potential - Repolarization

Answer 18

Potassium channel open. the other two are closed. There are more positive ions outside.

Question 19

the refractory period

Answer 19

a brief period of silence

Question 20

all-or-nothing

Answer 20

the distinctive characteristics of the action potential, they don’t vary in size, only in how often they occur. Thus, the only way that the strength or duration of a stimulus can be encoded in a single cell is by variation of the frequency of action potentials.

Question 21

myelin sheath

Answer 21

In many axons, action-potentials move along reasonably well, but not very fast. In others, action potentials really do skip along the nerve. This happens because long stretches of the axon are wrapped around with a fatty, insulating blanket, made out of the stretched-out glial cell membranes,