Chapter 2

Question 1

What are Neurons?

Answer 1

-they are the building blocks of the nervous system
-they allow you to sense/interact with the world
-neurons are about communicating information
-how they communicate information explains how we think and behave

Question 2

What are the basic parts of a neuron?

Answer 2

-soma/cell body
-axon
-dendrites
-synapses

Question 3

What is Soma/Cell body?

Answer 3

-20um (microns) wide
-contains cell nucleus
-fluid filled (cytoplasm)

Question 4

What is Nucleus?

Answer 4

-5-10um wide
-contains entire DNA (deoxyribonucleic acid)

Question 5

What is Cytoplasm?

Answer 5

-makes up much of the cell
-salty substance high in potassium
-organelles float within it

Question 6

How does DNA turn into protein?

Answer 6

-DNA is transcribed into mRNA via RNA polymerase and mRNA is then translated into proteins (protein synthesis) via ribosomes

Question 7

What is the proteins influence?

Answer 7

-interactions with other neurons (receptors)
-changes in the activity of enzymes (long-lasting enzymatic activity - kinases)
-structural changes in the neuron (more synaptic/dendritic connections)

Question 8

What is in the neuronal membrane?

Answer 8

-cell membrane (5 nm lipid bilayer) containing proteins that communicate with outside the cell
-proteins in the membrane vary across soma, dendrites and axon

Question 9

What do the proteins in cell membrane do?

Answer 9

-act as transporters or pumps
-act as channels or pores
-interact with chemicals outside the cell to produce intracellular changes
-crucial for the transfer of electrical signals

Question 10

What is the axon?

Answer 10

-unique to neurons and specialized for information transfer
-transmits signals known as an AP
-axon hillock: first part of axon
-contains no ribosomes
-width varies but same width throughout single cell
-thicker axon = faster nerve impulse travels
-often branches (axon collaterals)
-length varies from less than a millimeter to over a meter

Question 11

What is the Synapse?

Answer 11

-also known as terminal bouton or axon terminal
-point of ‘contact’ with other neurons
-information typically flows only in one direction (unidirectional)
-synapse is the site of action of many toxins and psychoactive drugs

Question 12

What happens to an electrical signal going down an axon?

Answer 12

-electrical signal coming down the axon is converted into a chemical signal that crosses the synapse/synaptic cleft, and is then turned back into an electrical signal

Question 13

What happens to the NTs in the synapse?

Answer 13

-NTs are the chemical signal
-packaged inside synaptic vesicles (50nm) and released via exocytosis
-NTs diffuse across the synapse and excite or inhibit post-synaptic cell

Question 14

What are Dendrites?

Answer 14

-tree-like structures that extend from the soma (branches)
-variety of shapes and sizes
-receive incoming signals (info)
-covered in post-synaptic ends containing receptor proteins
-these receptors interact with NTs in the synapse

Question 15

How do we categorize neurons?

Answer 15

-connections (origin/end of info)
-number of neurites (dendrites + axon; unipolar, bipolar, multipolar)
-axon length (projection vs local circuit neurons)
-shape of dendrites or cell body (stellate or pyramidal)
-signalling system (NT used)

Question 16

How are messages/information transmitted by neurons?

Answer 16

-info conveyed by a neuron is simple
-many neurons = many simple (often parallel) messages
-messages can be: refined, summated, combined, coordinated

Question 17

What is Convergence & Divergence and Reverberatory?

Answer 17

-convergent: many signals are coming in
-divergent: splitting the signal
-reverberatory: fires in a loop back to themselves

Question 18

What is the role of Glia?

Answer 18

-primary role is to support neuronal function (known as neuroglia)
-astrocytes
-myelination

Question 19

What are astrocytes (glia)?

Answer 19

-provide physical support (fill the space between neurons) in the CNS
-regulate K+ level outside cell (important for neuronal comm.)
-surround synapses (restrict/regulate spread of NTs)
-micoglia are the most common type of glial cell

Question 20

What are the 2 main types of myelinating glia?

Answer 20

-Oligodendroglia (CNS)
-Schwann Cell (PNS)

Question 21

What is Myelination (myelin)?

Answer 21

-protects neurons & speeds up the propagation of nerve impulses
-forms white matter (cell bodies form grey matter)
-myelin forms a tube (sheath) surrounding the axon
-series of segments with small spaces in between along the axon
-gaps between myelin sheath are known as Nodes de Ranvier