Studying the Nervous System Flashcards
What was the very first way of studying the nervous system?
Dissection of the brain and drawing diagrams, first done by vesalius (1543)
After dissection what was the next step in methods to investigate the nervous system?
Light microscope methods (1900)
What did using light microscope techniques allow visualisation of?
Features and connections of the cell groups in the CNS
What accompanied light microscope in order to see features of the CNS?
Staining
Light microscope and golgi staining allows visualisation of?
Cell bodies and dendrites
LM and Nissl staining allows visualisation of?
Cell bodies
LM and Myelin staining allows visualisation of?
Myelinated axons
What did staining and light microscopes allow the determination of?
The 6 layers of the cerebral cortex
How were the connections of the CNS studied using light microscopy?
The axons of tracts were cut and could tell what they the connection went depending on what degenerated
If by cutting the axon the cell body degenerates, what kind of degeneration is that
Retrograde degeneration
If by cutting the axon the axon degenerates, what kind of degeneration is that?
Anterograde degeneration
After dissection and light microscopes what method came next?
Electron microscopy (1950s)
What elements of the CNS could be studied with electron microscopy?
Subcellular elements of neurons e.g. synpases
After dissections, light microscopy and electron microscopy what was the next method used to study the CNS?
Lesion studies
What are the two types of lesion studies?
- Observation of functional changes after inducing lesions in animals
- Relating disorders in man to lesions in brain areas
How is observation of lesion studies not that accurate?
Because lesions arent normally specific and compensation can occur
After dissections, light microscopy, electron microscopy and lesion studies was the next method used to study the nervous system?
Electrical stimulation
Where is electrical stimulation applied in the CNS?
The tracts or nuclei (collection of neurons) of the CNS
What is an example of how electrical stimulation can show CNS function?
Stimulation of the motor cortex results into contraction of muscles on the opposite side of the body
What did the electrical stimulation show existed in the sensory and motor regions of the cortex?
That the body is represented by maps in these areas called homunculus (that weird thing with all the body parts)
What are three modern anatomical techniques in studying the CNS?
- Tract tracing
- Immunocytochemistry
- In situ hybridsation
How are tracer substances in tract tracting transported?
By axonal transport
How is tract tracing initiated?
Tracers are placed in the CNS close to the cell bodies or axon and are taken up and transported along the axon
What kind of tracing is used to identify axon terminals?
Anterograde tracing
Where are tract tracers taken up in anterograde tracing and where do they accumulate?
They are placed by and taken up by the cell bodies and transported along the axon where they accumulate in the axon terminals
What kind of tracing is used to identify cell bodies?
Retrograde tracing
Where are the tract tracers taken up in retrograde tracing and where do they accumulate?
They are placed by and taken up by the axon terminals and they are transported along the axon where they accumulate in the cell body
Name a tracer used in both retrograde and anterograde tracing?
Radio active amino acids
How are radio active amino acids detected in tracing?
Using autoradiography which involved using photographic emulsion on histological slides
Name a good retrograde tracing tracer?
Horseradish peroxidase (HRP)
Name an anterograde tracing tracer?
PHAL (a lectin extracted from red kidney beans)
What is involved in immunocytochemistry?
Antibodies with a bound flourescent probe of HRP bind to molecules in the CNS like neurotransmitter receptors
What type of microscopy can be used with immunocytochemistry?
Both light and electron
What is insituhybridation?
Producing DNA probes complementary to mRNA sequences (obtained from a library) in the CNS and the probes are then identified by autoradiography
What are three kinds of electrical recording methods?
- Extracellular recording
- Intracellular recording
- Patch clamping
What is electrical recording techniques used to study in the CNS?
The electrical activity of the CNS
What is involved in extracellular recording methods?
A metal electrode placed on the nerve connected to an ampflier and a screen displayed the electrical activity (cathode ray tube)
What is involved in intracellular recording methods?
Glass micropipettes containing an electrolyte solution are inserted into the neuron or axon attached to an amplifier and screen
What is an advantage of intracellular recording methods?
You can label recording neurons by injecting dye through the micropipette
What is involved in the patch clamping method?
Follow through ion channels is recorded by a piece of the membrane clamped by a micropipette
What are three computer imaging methods used to study the CNS?
- Computerized tomography (CT)
- Magnetic resonance imagine (MRI)
- Positron emission tomography (PET)
What is involved in CT scans?
X-ray beams are targetted at many angles at the head and the absorance of radiation in areas can be detected to determine the density of the tissue
What is involved in MRI scans?
Magnetic field used to generate signals from protons in tissues
What are three advantages of MRI scans?
- Good spatial resolution of the brain
- Non-invasive (no drugs or x-rays)
- Safe for humans
What is involved in PET scans?
Tracers/drugs containing positron-emitting radio nucleotides
How are the tracers/drugs in PET scans administered?
Injected into the blood supply or inhaled
What is example of a tracer/drug that is inhaled in pet scans?
Radioactive oxygen
What areas of the brain take up the tracers/drugs involved in PET scans?
The active areas of the brain
What happens to the positrons of the drugs/tracers in PET scans when they are taken up?
Converted to photons which can be detected by the PET scanner and the active areas of the brain can be visualised
Give an example of when you would use PET scans?
To see the active language areas during reading or spoken tasks
