1.3 The Neuron

Question 1

what is the cell body of the nucleus called

Answer 1

the soma

Question 2

what is the cytoplasm of the soma called

Answer 2

the perikaryon

Question 3

What is the sole main purpose of the nucleus in the soma and what does it not do that most nuclei do

Answer 3

The main purpose is protein synthesis. The soma in the nucleus is not involved in any replication

Question 4

Name the key organelles in the soma

Answer 4

-nucleus
-nucleolus
-rough ER
-free floating ribosomes
-golgi apparatus
-lipofuscin bodies
-mitochondria

Question 5

What are lipofuscin bodies

Answer 5

Lysosomal waste of cell debris that build up in granules of yellow/brown pigmented waste. Older cells have more of the waste hence the pigments are known as wear and tear pigments

Question 6

What are nissl bodies

Answer 6

Nissl bodies are made mostly of RER and are involved in protein synthesis. There are many nissl bodies in the soma.

Question 7

Where is the nucleolus found

Answer 7

Inside the nucleus

Question 8

What are the 3 components of the neuronal cytoskeleton

Answer 8

microtubules, microfilaments and neurofilaments

Question 9

What is the diameter of microtubules

Answer 9

25nm with a 15nm pore

Question 10

What is the diameter of neurofilaments

Answer 10

10nm

Question 11

What is the diameter of microfilaments

Answer 11

5nm

Question 12

What are microtubules made of

Answer 12

Protein filaments made of alternating a and b tubulin arranged longitudinally. The tubulin heterodimers form 13 protofilaments surrounding the pore. Microtubules can have branches

Question 13

How do microtubules change

Answer 13

New tubulin proteins are added at the + end of the microtubule using a polymerisation reaction where GTP is converted to GDP. Tubulin proteins can also be removed from the negative end via depolymerisation. Tubulin is either in a growing, stable or shrinking phase

Question 14

What are the main roles microtubules

Answer 14

-structural support
-intracellular transport

Question 15

Describe the structure of neurofilaments

Answer 15

2 neurofilament monomers twist together to form a dimer, and then 4 dimers twist to form a protofilament, then 2 protofilaments twist to form a protofibril, then 3 protofibrils combine to form a neurofilament

Question 16

What is the function of neurofilaments

Answer 16

To provide strength and stability

Question 17

Which of the 3 cytoskeleton components are not active

Answer 17

Neurofilaments

Question 18

Which of the cytoskeleton elements are biomarkers for neurodegenerative diseases like ALS, MS and Huntingdons

Answer 18

Neurofilaments

Question 19

What do neurofibrillary tangles cause

Answer 19

Alzheimers

Question 20

Describe the structure of microfilaments

Answer 20

Actin monomers are called G actin and are bound to ATP. 3 G actins combine to form a trimer. The trimer then joins the + end of the growing filament (called F actin polymer)

Question 21

What is the key role of microfilaments

Answer 21

To change neuronal shape and motility to allow for synaptic plasticity. They form a dense network underneath the neuronal membrane

Question 22

Out of the neurotransmitters glutamate and GABA, which is excitatory and which is inhibitory

Answer 22

Glutamate is excitatory and GABA is inhibitory

Question 23

Describe the structure of dendrites

Answer 23

Dendrites can either be thin, mushroom shaped or stubby. On each dendritic branch, there are dendritic spines and each one forms a synapse. The spines are dynamic and can change shape due to microfilaments. The more spines the greater the connectivity