Chapter 4.3: Neurons

Question 1

Describe a multipolar neuron and its function

Answer 1

• the most common neuron
• single axon with many dendrites
• integrates lots of information

Question 2

describe a bipolar neuron and its function

Answer 2

• contains 2 extentsions: one dendrite and one axon with the cell body in the middle
• specialized sensory neurons such as the retina

Question 3

describe a unipolar neuron and its function

Answer 3

• either has an axon or dendrites but not both, with a cell body in the middle
• common in insects that have sensory neurons directly linked to the brain.

Question 4

_____ connect sensory and motor neurons. Do these cells contain axons?

Answer 4

Interneurons, no axon or very short axon.

Question 5

Input zone

Answer 5

dendrite

Question 6

trigger zone

Answer 6

hillock

Question 7

conducting zone

Answer 7

axon

Question 8

output zone

Answer 8

terminals

Question 9

3 important properties to neurons

Answer 9

1) they are electrically excitable
2) they conduct impulses through the axon
3) they deliver messages to target cells, usually chemically.

Question 10

2 Methods to increase speed of neural impulse conduction

Answer 10

1) myelin

2) axonal gigantism (larger diameter)

Question 11

how does myelin speed up impulse conduction?

Answer 11

acts as an insulator to prevent current leakage out of membrane. (INCREASES TRANSVERSE RESISTANCE ACROSS THE MEMBRANE) Allows for the the current to be propagated in a less-decremental fashion because the current remains inside the cell.

• also concentrates the voltage gated Na+ channels to the nodes of ranvier. Leads to faster depolarization and less area needing to be potentially maintained.
• decreases capacitance by separating the charges in the ECF and ICF even further apart, reducing transverse resistance.

Question 12

How does axonal gigantism speed up impulse conduction

Answer 12

larger diameter reduces inner resistance of the cell, allowing for the current to be easily propagated.

Question 13

Myelin is made from ____ cells in PNS and _____ cells in CNS

Answer 13

schwann in PNS and oligodendrocytes in CNS

Question 14

_____ is essential for myelin synthesis

Answer 14

cholesterol

Question 15

T/F: Multiple schwann or oligodendrocytes are used to form hundreds of myelin layers around a specific location of an axon

Answer 15

false. only one schwann cell can produce MULTIPLE layers of myelin. there are not multiple schwann cells in the same location.

Question 16

an increase in conduction speed is proportional to the _____ of the diameter

Answer 16

square root.

Question 17

what is a good method of speeding up axonal conduction if you are escaping a predator? downfall?

Answer 17

axonal gigantism is a good solution for time-critical pathways. it takes up a lot of space though/.

Question 18

Mauther neurons

Answer 18

seen in fish and amphibians who used large axons that run from brain stem to tail muscles that are used to escape predators.

Question 19

you can increase conduction speed either by ____ INTERIOR resistance or _____ trans-fiber capacitance.

Answer 19

you can increase conduction speed either by DECREASING interior resistance or DECREASING trans-fiber capacitance.