Structure of Neurones & Glia Flashcards
What are the 3 parts of a neuron?
Cell body/ soma
Dendrites- input
A single axon- ouput
What are dendrites and axons are sometimes called collectively?
Neurites
What is contained within the soma?
Nucleus
Perikaryon
What is perikaryon?
Cytoplasm of a neuron
What organelles of the cell body are found in the neuron?
Nucleus Ribosomes Golgi apparatus Microtubules Mitochondria Lysosomes Lipofucin bodies
What is the nucleus responsible for?
Contains DNA, replicate cells
Most adult neurons (after the age of 7) do not replicate- DNA involved only in protein synthesis
Protein made by transcription and translation (ribosomes)
What are ribosomes responsible for?
Translation
Most commonly associated with endoplasmic reticulum (ER)
Rough ER or Nissl bodies (making proteins and peptide sequences)
What is the golgi apparatus responsible for?
Protein assembly completed here
What are microtubules responsible for?
Cell body, dendrites and axon
Transporting packaged proteins
Forms part of the cytoskeleton (gives neuron some degree of rigidity)
How many neurons are in the mitochondria and what is it’s job?
Numerous in neurons
Supply energy
What are lysosomes responsible for?
Break down organelles
What are lipofucin bodies for?
Contain all neurons rubbish
Electron dense
Waste products in ‘old’ cells
What happens to lipofucin bodies as people get older?
As you get older your body obtains more lipofucin bodies
What is the role of dendrites?
Continuation of the cell body Contain free ribosomes and mitochondria Form branching patterns like trees Synapses are formed on dendrites Some synapses on spines
What is the role of axons?
Unique to neurons
Specialised for transmission of electrical impulses
Can be up to 1m in length
What are the part of the axon?
The axon hillock
Axon proper
Axon collaterals
Axon terminal
What does the axon hillock do?
Merges from soma
Generates electrical impulse
Causes neuron to fire
Where is the axon proper?
Long part of the axon
Emerges form axon hillock
Where are the axon collaterals?
Branch from the axon
What are the two cells that make up the brain and the spinal chord?
Neurons
glia
What are axons terminals?
Form swelling or boutons
Make synapses
What does an axon not contain?
Ribosomes
How do axons transport proteins?
Along microtubules
What are the ways of axonal transport in a neuron?
Axoplasmic transport (up to 1000mm/day)
Axoplasmic transport- both directions
Away from the cell body (anterograde transport)
Towards the cell body (retrograde transport)
What are the reasons for retrograde transport?
To get rid of things of no values
Some molecules can convey messages from axon terminals to cell body (i.e. enzyme requirement)
What is the composition of the nerve cell membrane?
Acts as a membrane
Consists of a phospholipid bilayer
Protein molecules embedded in the membrane confer unique properties
Allow ions to pass in or out of the cell selectively i.e. semi permeable membrane
How can neurons be classified?
Number of neurites Shape Connections Axons Neurotransmitters
What are the different number of neurites which can be classified in neurons?
Unipolar
Bipolar
Multipolar
What are the different shapes neurons can be?
Pyramidal
Sellate- star shape
What are the different connections for the classification of neurons?
Primary sensory neurons
Moto neurons
Interneurons
What are primary sensory neurons?
Connections with sensory neurons surfaces of the body
What are the moto neurons?
Connections with muscles
What are the interneurons?
Connections with other neurons
How can axons classify neurons?
Golgi type I- long axons
Golgi type II- local axons
How can neurotransmitters classify neurons?
E.g. cholinergic- contains acetylcholine
How much of cells in the brain are glia?
90%
What are the 3 principle classes of glia?
Astrocytes
Oligodendrocytes
Microglia
Astrocytes and oligodendrocytes= macroglia
What are astrocytes?
Star shaped
Most numerous type of glia
Few organelles
What is the function of astrocytes?
Function is not fully understood
Provide mechanical and metabolic support
Repair process (nervous system damaged, cause scar over and this is impenetrable, stops infection)
Regulate flow of ions and molecules in extracellular fluid
What are Oligodendrocytes?
Many organelles and microtrubules
What is the function of oligodendrocytes?
Make Myelin (fatty substance which rolls itself around axons, insulting it and allowing conduction of axons to be increased)
What is myelin?
Lipid sheath around axons
Electrically insulates axons, not continuous
Node of Ranvier
Peripheral nervous system- myelin formed by Schwann cell
What are microglia?
Microglia are really phagocytes, i.e. they remove waste.
About 100,000 neurons in your CNS die every day and microglia remove the debris.
