Cells of the Nervous System

Question 1

what is the basic structural and functional unit of the nervous system?

Answer 1

Neurone

Question 2

how is neurone cell diversity of morphology achieved?

Answer 2

different number and shape of processes, determined by function and location.

note this makes neurones more vulnerable to degenerative disorders like alzheimers.

Question 3

features of a neurone

Answer 3

• large nucleus
• prominent nucleolus
• lots of RER and Golgi
• lots of mitochondria
• highly organised cytoskeleton

Highly organised and very metabolically active secretory cell (lots of protein trafficking)

Question 4

what do Dendrites do?

Answer 4

• input information
• branch frequently allowing integration of signals
• contain many spines which is where synapses occur

Question 5

describe the structure of a pyramidal cell

Answer 5

4 points of cell body. 3 primary dendrites off which secondary dendrites arise. One long axonal projection.

Question 6

most plastic area of a neurone?

Answer 6

dendrites as can make many different spines hence synaptic pathways

Question 7

spines synapse with?

Answer 7

many other neurones

Question 8

what are purkinje cells?

Answer 8

cells of the cerebellum, look like a tree, planar cells, heavily branched but linear when looked from side

Question 9

what is an axon?

Answer 9

output impulses away from cell body and axon hillock

it contains prominent microtubules and neurofilaments

Question 10

why are axons the same diameter throughout?

Answer 10

to maintain the same speed of impulse throughout

Question 11

why are microtubules and neurofilament needed in an axon?

Answer 11

neurofilament for strength

microtubules for vesicular transport

Question 12

the axon has nodes of ranvier made by myelination, what is the structure of the node?

Answer 12

the node itself contains only sodium ion channels.
next to it is the paranode where the schwan cell attaches
next to that is the juxtanode where there are potassium ion channels.

Question 13

types of axon terminals

Answer 13

boutons (bulge at the end of an axon)

varicosities (bulges along axon where neurotransmitter released)

Question 14

how are different impulses integrated?

Answer 14

different transmitters cause different amounts of depolarisation of the dendrites. these signals are summated and processed by the post synaptic neurone

Question 15

types of synapse?

Answer 15

• axo-dendritic (excitatory)
• axo-somatic (inhibitory)
• axo-axionic (modulatory)

Question 16

how long can axons be?

Answer 16

micrometers to a metre

Question 17

what makes the neurofilament cytoskeleton strong?

Answer 17

many cross bridges, the more neurofilament, the better the axon calibre.

Question 18

what types of transport is there within an axon?

Answer 18

retrograde: vesicles transported towards cell body
anterograde: movement towards the synapse (away from cell body)

to differentiate, they are morphologically and biochemically different to allows recognitions by only certain compartments

Question 19

what happens in multiple sclerosis?

Answer 19

demyelinating neuropathy

Question 20

types of morphology of neurone

Answer 20

• unipolar
• bipolar (retinal)
• psuedunipolar (dorsal root ganglion)
• Golgi Type I multipolar
• Golgi type II multipolar

Question 21

features of golgi type I cells (purkinje and pyramidal)

Answer 21

• highly branched dendritic tree
• long axons
• most vulnerable to degradation eg ataxia

Question 22

features of golgi type II cells (stellate cells of cobra cortex and cerebellum)

Answer 22

• highly branched dendritic tree

- short axons

Question 23

function of interneurones

Answer 23

responsible for:
• modification
• integration
• facilitation
• coordination
• inhibition 

of sensory inputs

Question 24

what are neuroglia?

Answer 24

non excitable support cells of the nervous system needed for correct functioning of neurones.

Question 25

what are immature progenitors neuroglia for?

Answer 25

regeneration

Question 26

what are astroglia?

Answer 26

fibrous astroglia in white matter
proteoplasmic astroglia in grey matter

They signal eachother through Gap junctions in continuity in reaction and signalling

involved in homeostasis as foot processes scan microenvironment and react specifically.

Question 27

function of astroglia?

Answer 27

• scaffold for neuronal migration and growth
• formation of BBB (glia limitans)
• transport substances from blood to neurones
• create synapses
• removal of excess ions or neurotransmitter and water
• glial scar formation
• synthesis of neurotrophic factors

Question 28

what are oligodendroglia?

Answer 28

production and maintenance of myelin sheath of many neurones in the CNS

Question 29

what are microglia?

Answer 29

• derived from bone marrow
• immune function (inflammation)
• acts as a macrophage and is first to respond in brain infection
• changes morphology from processes to blob when activated
• needed for tissue remodelling
• synaptic stripping

Question 30

what are peripheral glia?

Answer 30

schwann cells, each produces only one myelin sheath in PNS. they are also needed for axon regeneration.