Midterm 1 Flashcards
How does heroin enter into the brain?
Heroin crosses the blood-brain barrier quickly because it is a very lipid soluble.
Very strong opiate
How does morphine enter into the brain?
Morphine crosses the blood-brain barrier a bit slower than heroin because it is a less lipid soluble.
How does Imodium Anti-Diarrheal enter into the brain?
It does not enter into the brain because it does not cross the blood-brain barrier.
What do barbiturates do?
They have a sedative and depressive effect. The sedative effect shows tolerance, but the depressive effect does not.
Name the concept:
- It occurs when a drug becomes more and more effective through repeated use.
Sensitization
How do you study the brain and get to know what each part of the brain does?
You study people who have damage in that specific area of the brain you are trying to research.
What does CT scan stand for?
Computerized Tomography
Why are CT scans a good option to photograph the brain?
They are relatively cheap and fast.
What are the cons of CT scans?
The resolution of the photographs is not great for soft tissues like the brain.
What is the mechanism of CT scans?
An X-ray beam, is projected through the head of the patient to an X-ray detector. The X-ray beam is delivered from all angles.
A computer then translates the information received from the X-ray detector into a series of pictures of the skull and brain.
What does MRI stand for?
Magnetic Resonance Imaging
What happens when a strong magnetic field is applied to the body?
The spin of very hydrogen atom proton assumes a particular direction inline with the magnetic field.
Radio frequency waves are administered to the body. This energy is absorbed by protons, changing the direction of their spin. These protons then emit their own radio waves when their spin immediately flips back to that determined by the magnet.
What is the mechanisms used by MRIs?
A strong magnetic field is applied to the body, which changes the direction of the spin of hydrogen atom protons.
By triangulating where the emitted radio waves are coming from, the scanner provides an estimate of the relative density of protons in each area of the body.
What do MRI scans primarily reveal?
The density of lipid molecules
What stands for DTI?
Diffusion Tensor imaging
What is DTI?
A variation of the MRI technique that measures the direction and speed of the diffusion of water molecules instead of hydrogen atom protons
What is DTI used to identify?
It is used to identify axon tracts in the brain.
What does fMRI stand for?
Functional magnetic resonance imaging
- Of spontaneous human brain activity.
How do fMRI scans function?
The oxygenated blood slightly distorts the magnetic field. We can infer the movement of oxygenated blood around the brain by rapidly collecting a series of images and measuring the movement of these magnetic field distortions over time.
Wha mechanism do fMRI scans use?
A rapid series of MRI scans.
It’s possible to detect changes in blood oxygenation, which reflects blood flow and correlates with neural activity. When a brain region is active, blood flow to that region quickly increases.
Why is fMRIs popular?
It’s popular because it doesn’t involve needles, surgery or radioactivity. It provides both structural and functional information with decent spatial resolution and temporal resolution.
What do PET scans stand for?
Positron Emission Tomography
What are the mechanisms of PET scans?
It involves injecting a person with radioactive compound. Radioactive sugar molecules are commonly used to detect changes in energy use in the brain.
The scanner identifies where radioactive molecules are located over time.
What molecules do PET scans use?
Radioactive sugar molecules
- Similar to glucose, but it does not break down as easily as sugar, do it stays around for hours.
What do PET scans measure?
It is used as a general measure of neural activity.
Also used to measure changes in the expression levels of neurotransmitter receptors across weeks.
What are macroelectrodes?
Metal discs that are attached to the scalp
What does an EEG measure?
It measures the electrical activity in the brain that uses macroelectrodes attached to the scalp.
It records the summed population-level activity of millions of neurons.
What can an EEG be used for?
It can be used as a diagnostic tool, since specific patters of EEG activity are associated with different states of consciousness, stages of sleep and types of cerebral atrophy.
What does EEG stand for?
Electroencephalogram
What is an experimental ablation?
It’s a lesion study. It involves the removal or destruction of a portion of the brain. Presumably, the functions that can no longer be performed following the surgery are the ones the brain region normally controls.
How can radio frequency be used to create lesions in the brain?
Small lesions can be made by passing radiofrequency current through a metal wire that is insulated everywhere but the tip.
This electric current produces heat that burns cells around the tip of the wire.
Size and shape of lesion determine by duration + intensity of burn
What is the downside of radio frequency lesions?
Axons just passing through will also be burned.
What is an excitotoxic lesion?
It’s a brain lesion produced by intracerebral injection of a glutamate rejector agonist. These drugs cause so much excitation that the affected neurons often undergo apoptosis, while axons passing through are usually spared.
What is a sham lesion?
“Placebo” procedure that duplicates all steps of producing brain lesion except for one that actually causes extensive brain damage.
What is a reversible lesion?
A temporary lesion can be achieved by injecting drugs that block or reduce neural activity in a given region.
What are some of the common drugs used to create reversible lesions?
- Voltage-gated sodium channel; blockers (stops all action potential)
- GABA receptor agonists (which hyperpolarize cell bodies
What are microelectrodes?
Thin metal wires with a fine tip that can record the electrical activity of individual neurons.
What can microelectrodes be used as?
They can be used in behaving animals to record every action potential from a given neuron. And with the newest microelectrodes, it is possible to record from hundreds of single neurons simultaneously.
During which surgery are microelectrodes implanted in the brains of animals?
Stereotactic surgery
What is the difference between chronic electrical recordings and acute recordings?
chronic electrical recordings are made over an extended period of time.
Acute electrical recordings are made over a relatively short period of time.
What do we use electrical stimulation for?
To know how the activity of specific receptors or cell populations influences behaviour.
How does electrical stimulation work?
It involves passing an electrical current through a wire inserted into the brain.
This will affect everything in the area.
Some electrical stimulation patterns counterintuitively, tend to produce the same behavioural effects as lesioning the brain area.
How do chemical stimulations work?
Is achieved with drugs. They are administered through a guide cannula implanted into a particular brain region.
What are ontogenetic?
It refers to the use of light to control neurons which have been made sensitive to light though the introduction of foreign DNA. This foreign DNA encodes light-sensitive proteins known as opsins. Opsins are proteins that are sensitive to light.
What are opsins?
Opsins are proteins that are sensitive to light.
What are the steps to ontogenetics?
1) a light-sensitive protein from algae
2) Take the gene for this protein
3) Insert the DNA into specific neurons in the brain
4) Neurons communicate by firing. This is an electrical signal created by opening and closing ion channels
What can opsins be used for?
It can be used to either pulse light or leave it on to drive action potential activity. It can also be used to inhibit action potential activity in animals.
What are the steps to Viral-Meditated Gene delivery?
1) You take a light-sensitive protein from algae. It’s a protein that is an ion channel and opens in response to blue light.
2) You take the gene for this protein and insert it into the DNA of a hollowed-out virus.
3) You insert the virus into the brain
What is a virus?
It’s a type of DNA delivery system. Viruses normally replicate by injecting viral DNA into a host organism. Virus DNA contains instructions on how to make more virus.
It’s a small infectious agent that replicates inside the cells of other organisms.
We can target opsin expression to specific neurons in the brain according to?
1) where their soma are located
2) Where their axons are located
3) The proteins they express
4) Whether they recently had more action potentials than normal
Why is monitoring GCaMP protein fluorescence a good way to measure neural activity?
Researchers modified it to bind to calcium and fluoresce much brighter when it does. Since a little calcium influx always occurs during action potentials, the cells will fluoresce bright and we can measure neural activity this way.
What is retrograde labeling?
Tracing afferent axons
- It is used to label the cells that innervate (project to) a given region.
What is anterograde labeling?
Tracing efferent axons
- It is used to label where the axons from a particular region go to.
What is stereotactic surgery?
It’s a surgical intervention that uses a stereotactic apparatus. That is a device that permits a surgeon to put something into a very specific part of the brainé
It is used to inject things into the brain, such as drugs, viruses, or tracer molecules.
It can be used to permanently implant things, like cannula, electrodes or fibre optic cable.
What is the Bregma?
It’s the junction where pieces of skull fuse together. It is often used as a reference point for a stereotactic brain surgery.
What are the common reasons stereotactic surgery is used for?
- Lesion a brain area
- Lesion a specific type of cell in a particular brain area
- To change gene expression
- To implant a guide cannula to allow for later infusions of drugs
- To implant microelectrodes for stimulation or recording experiments
- To implant fibre optic cables to allow for imaging or stimulation using ontogenetic techniques
What can microdialysis be used for?
It can be used in behaving animals to measure changes in neurotransmitter levels in a given brain region.
Name the technique:
- Refers to the use of a semipermeable membrane to either deliver molecules to or measure the amount of molecules in some solution or brain area.
Dialysis
What is a microdyalisis probe?
Small metal tube that holds dialysis tubing. These can be places in the animal’s head.
Name the method:
- A histological method that is used to label proteins and peptides in biological tissue.
Immunohistochemistry