1.3 The Neuron Flashcards
what is the cell body of the neuron called
the soma
what is the cytoplasm of the soma called
the perikaryon
What is the sole main purpose of the nucleus in the soma and what does it not do that most nuclei do
The main purpose is protein synthesis. The soma in the nucleus is not involved in any replication
Name the key organelles in the soma
-nucleus
-nucleolus
-rough ER
-free floating ribosomes
-golgi apparatus
-lipofuscin bodies
-mitochondria
What are lipofuscin bodies
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
What are nissl bodies
Nissl bodies are made mostly of RER and are involved in protein synthesis. There are many nissl bodies in the soma.
Where is the nucleolus found
Inside the nucleus
What are the 3 components of the neuronal cytoskeleton
microtubules, microfilaments and neurofilaments
What is the diameter of microtubules
25nm with a 15nm pore
What is the diameter of neurofilaments
10nm
What is the diameter of microfilaments
5nm
What are microtubules made of
Protein filaments made of alternating a and b tubulin arranged longitudinally. The tubulin heterodimers form 13 protofilaments surrounding the pore. Microtubules can have branches
How do microtubules change
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
What are the main roles microtubules
-structural support
-intracellular transport
Describe the structure of neurofilaments
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
What is the function of neurofilaments
To provide strength and stability
Which of the 3 cytoskeleton components are not active
Neurofilaments
Which of the cytoskeleton elements are biomarkers for neurodegenerative diseases like ALS, MS and Huntingdons
Neurofilaments
What do neurofibrillary tangles cause
Alzheimers
Describe the structure of microfilaments
Microfilaments are made up of 2 F-actin polymer filaments that are intertwined. Each F-actin polymer is made up of lots of G-actin monomers that combine to form trimers. The trimers are added to the growing side of the microfilament by ATP.
What is the key role of microfilaments
To change neuronal shape and motility to allow for synaptic plasticity. They form a dense network underneath the neuronal membrane
Out of the neurotransmitters glutamate and GABA, which is excitatory and which is inhibitory
Glutamate is excitatory and GABA is inhibitory
Describe the structure of dendrites
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
Why is axonal transport necessary
Since axons dont have ribosomes so cant synthesise proteins. Secretory proteins and organelles must be synthesised in soma and transported to axon
What is the difference between fast and slow axonal transport
fast transport (50-400nm/day) slow (<8nm/day)
fast axonal transport is bidirectional but slow axonal is anterograde only
fast axonal transport carries cargo like mitchondria, secretory vesicles, smoot ER and large dense core vesicles. slow axonal transport carries cargo like cytosolic and skeletal proteins
Describe the 2 directions of axonal transport and how they are carried out
Anterograde transport is carrying cargo (such as secretory proteins and organelles) from the soma to the axon terminal. This is done via kinesin motor proteins that walk along microtubules carrying the cargo, each step along the tubule by the kinesin requires the hydrolysis of an ATP.
Retrograde transport is carrying cargo (such as vesicles and growth factors) from the axon terminal to the soma. This is done via dyenin motor proteins that walk along microtubules carrying the cargo, each step along the tubule by the dyenin requires the hydrolysis of an ATP.
Describe how Herpes simplex virus 1 opperates
Herpes simplex virus type 1 (HSV-1) enters sensory nerves from epidermis and is transported to cell body by dynein where it remains latent
the viral capsids and their glycoprotein coats are transported separately along the axon by kinesin following reactivation so that the virus can reform, exit axon and trigger outbreak in epidermis
