prof maxwell: neurons and glia Flashcards
cells of the nervous sysem
nerons
glia
neurons
conducting electrical information and processing information
glia
mechanic and metabollic support
neuron parts
cell body (soma
dendrites
axon
axon terminals
dendrites
1.the inputpart of the neuron
2.fine processes which emerge from the cell body and receive information from
other neurons
3.dendrites are an extension of the cell body
4.contain many free ribosomes and mitochondria
5. formelaborate branching patterns like trees
6.Numerous synapses (connections from other neurons) are formed with dendrites these are sometimes made onto specialised structures called spines
axon
- the output part of the neuron
2.They are specialised for transmission of electrical impulses over long distances- can be up
to 1m in length. - unique to neurons
neurites
axons and dendrites
organelles of the cell body: nucleus
contins DnA
DnA serces as blueprint for receptor enzymes etc
used for transcription an transcription an translation
most adult neutrons do not replicate
organelles of the cell body; ribosomes
known as cells factory
site of translation
• Although single free ribosomes are present in the perikaryon, more commonly they are associated with endoplasmic reticulum (ER). This combination of ER and ribosomes is often referred to as ‘rough’ ER or Nissl Bodies.
perikaryon
the cytoplasm surrounding the nucleus in neutron
organelles in neutron: the golgi apparatus
Protein molecules enter the Golgi apparatus where protein assembly is completed and is enclosed in membranes for transport (The finishing shop and packaging department).
organelles in nwuron: microtubules
- Found in the cell body, dendrites and axon- responsible for transporting packaged protein (the railway system).
- Also form part of the cytoskeleton- provides support for the neuron
organelles in cell body: mitochondria
Numerous in neurons- supply energy (power stations)
organelles of the cell body:lysosomes
Contain enzymes which break down organelles (breaker’s yard)
organells in the cell body: lipofucin bodies
contain waste products in old cells: the scrapyard
parts of the axon; axon hillock
(the part of the axon which emerges from the cell body) which tapers to form the initial axon segment.
parts of the axon; AXON PROPER
THE MAIN APRT OF THE AXON
parts of the axon; axon collaterals
branches of the axon
parts of the axonaxon terminals
these form swellings or boutons
boutons are what synapses are made of
axonal transport
- axons have no ribosomes and cannot produce protein so must transport protein along microtubules. this is known as axoplasmic transport
axoplasmic transport
1.transporting of protein through microtubules to axon
this can be fast, around 100mm/day
2.• can occur in both directions. Away from the cell body (anterograde transport) or towards the cell body (retrograde transport).
the nerve cell membrane
- acts as a barrier and encloses the cytoplasm
- like other cell membranes it consists of a phospholiid bilayer
- The protein molecules embedded in the membrane confer unique properties upon it. They
allow molecules to pass in or out of the cell selectively i.e. the membrane is semi- permeable.
classification of neutrons depends on:
- number of neutrites:
- shape:
- connections
- axons
- neurotransmitters
calssification: number of neutrinos
unipolar, multipolar, bipolar
classification: shape
eg
pyramidal, stellate (star shaped). Neurons may also be classified as spiny if
spines are present e.g. spiny stellate.
classification: connections
- Primary sensory neurons- form connections with the sensory surfaces of the body, e.g. skin, retina etc.
- Motoneurons- form connections with muscles.
- Interneurons- Form connections with other neurons
classification: axons
Golgi Type I- cells with long axons Golgi Type II- cells with local axons
axons: golgi type I:
cells with long axons
:axons: golgi tpe II
cells with local axons
classification: neurtransmitters
e.g. cholinergic neurons contain the neurotransmitter acetylcholine
Glia (neuroglia)
- about 90% of cells in brain are glia
- 3 types of gla: astrocytes, oligodendrocytes and microglia
- someties oligodendrocytes and astrocytes are called microglia
Macroglia
astrocytes and olligodendrocytes
Glia: astrocytes
- most numerous type of glia
- contain few organelles
3.
astrocyte functions
- function is not fully understood
- probably have a few functions
- provide mechanic and metabolic support for neutrons
- involved in reapir processes in damaged CNS
- they regulate the flow of ions and various there molecules in extracellular fluid
Glia: Oligodendrocytes structure and function
- contain many organelles
- make myelin in the CNS
- • The sheath electrically insulates axons but is not continuous and the axonal membrane is
exposed. The region where the sheath is interrupted is known as the Node of Ranvier. This arrangement increases the speed of electrical conduction of the axon.
nodes of ranvier
part of axon where myelin sheath is interupted and axon is exposed
this increases the speed of the electrical impulses
Schwann cell.
produce myelin in the peripheral nervous system
Glia: 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.
modern anatomical methods: tract tracing method
1,Tracer substances are transported by axonal transport. 2.Tracers are placed in the CNS close to the cell bodies or axon termimals of cells and are selectively taken up and transported along the axon.
• Anterograde tracing is used to identify axon terminals, i.e. the tracer is placed in
the vicinity of cell bodies, is taken up, transported along the axon and accumulates
in axon terminals.
• Retrograde tracing is used to identify cell bodies, i.e. the tracer is placed in the
vicinity of axon terminals, is taken up, transported along the axon and accumulates in cell bodies.
tract tracing method: types of tracers
• Radio active amino acids are made into protein and detected by
autoradiography. A technique which employs the use of photographic emulsions
on histological slides (anterograde and retrograde tracing).
• Horseradish peroxidase (HRP) is a very good retrograde tracer.
• Few substances are good anterograde tracers but Phaseolus vulgaris
leucoagglutinin (PHAL), a lectin extracted from red kidney bean, is an excellent anterograde tracer.
modern anatomical methods: immunocytochemistry
Antibodies are used to detect molecules in the CNS, (e.g. neurotransmitters, receptors). Bound antibodies in tissue are detected by attaching a fluorescent probe or an HRP molecule to the antibody.
• This method can be used with light or electron microscopy
modern anatomical methods: insituhybridisation
In situ hybridisation is used to detect mRNA sequences produced in neurons, e.g. for peptides or receptors.
• Complimentary DNA probes used to detect mRNA (probes are identified by
autoradiography).
• RNA sequences are obtained from a library.
electrical recording methods: extracellular recording
A metal electrode is placed on the surface of nerve or in the CNS and is connected to amplifier and cathode ray tube. Electrical activity can be observed on the screen of the cathode ray tube.
electrical recordig methods: intracellular reording
Glass micropipettes containing an electrolyte solution are inserted into a neuron or axon. These are also connected to an amplifier and a cathode ray tube. Markers, such as dyes, may also be injected through micropipettes to label recorded neurons.
electrical recording metods: patch camping
In this method a small piece of cell membrane is attached to a micropipette and current flow through ion channels in the membrane is recorded, e.g. ion channels in a rod of the retina responding to a flash of light.
computer imaging methods:
These methods are used widely in a clinical setting but are also providing new and important information about the structure and function of the brain.
computer imaging techniques: computer tomography
X-rays are beamed at many angles through the head and the amount of radiation absorbed is measured by a detector. A computer determines the density of tissue and a CT scan is produced.
computer imaging technique: magnetic resoance imaging
Magnetic fields are used to generate signals from protons in tissue. This method provides good spatial resolution of the brain (i.e. ‘anatomical’ images). It is also non- invasive (i.e. drugs, X-rays etc. are not used) and is considered to be very safe for human subjects. 3-D images of the brain can be generated with modern computer technology.
computer imaging techniques: positron emission tomography
Tracers or drugs containing positron-emitting radio nucleotides are injected into the blood supply or are inhaled as a gas (e.g. radioactive oxygen). These substances are taken up by active regions of the brain. Positrons are converted into photons which are detected by the PET scanner and active regions of brain can be visualised e.g. language areas during reading or spoken tasks.
