PSYC201 Week 2

Epigenetics

Gene expression. Experiences can produce epigenetic changes which then alter gene expression within the brain. 

Adding an acetyl group to a histone tail…

Loosens its grip on the DNA therefore allowing the expression of genes.

Removing an Acetyl group…

tightens the histone’s grip on the DNA preventing the gene from being expressed. 

Adding a methyl group to the beginning of a gene…

turns the gene off.

removing a methyl group to the gene…

turns the gene on

Proliferation is…

the production of new cells

Synaptogenesis

the formation of synapses which begin before birth and continue throughout life. 

Myelination is…

the process of glia producing fatty sheaths around the axons, myelin first is formed in the spinal cord then the hindbrain, then midbrain, and then the forebrain.

Each ganglion in the sympathetic nervous system has…

just enough axons to supply the muscles in its areas with none left over. 

In the sympathetic nervous system, it originally forms a lot more neurons than needed. When any of the neurons form a synapse onto a muscle, the muscle then delivers the protein…

Nerve growth factor (NGF). Any axon that does not receive this protein does not survive and dies off this is called apoptosis. NGF cancels apoptosis from occurring. 

Neurotrophin is…

A chemical that promotes the activity and survival of neurons. They are essential for the growth of axons, dendrites and formation of synapses.  

Once a neuron loses input from an axon it…

releases neurotrophins which prompt other axons to form new branches or collateral sprouts. Areas sounding the damage form new synapses and sprouting at a higher rate than usual.

Denervation supersensitivity

when some synapses may become inactive, possibly due to damage, the remaining synapses become more responsive and easily stimulated. Occurs within dendritic receptors. 

Spacial resolution

how close together can we identify two different things

Temporal resoultion

How close together in time can we measure changes 

Neurogenesis…

The birth of new neurons starts after about five weeks. Neurons start to migrate to where they need to go.

Glycogenesis…

Glial cell development/birth

Synaptic pruning…

The brain strengthens the important connections and eliminate the connections that you are not using

The terminal region tells axons…

where to go through the release of chemicals. Once the axons are in place the chemicals are gone and therefore in adulthood / end of development the connections cannot regrow. 

Neurons are post-mitotic meaning…

They can’t divide and so cells cannot replicate when they die.

Collateral spouting is where…

If an axon dies and deaerates, other axons will form a secondary set of synapses to take up the action of axon 2 (the previous axon that was attached to the dead axons. 

Central Nervous System (CNS)

The brain and the spinal cord, The spinal cord communicates with muscles and sense organs. 

Peripheral Nervous System (PNS)

What connects the brain and the spinal cord to the rest of the body. The PNS has two categories, the somatic nervous system and the autonomic nervous system. 

Sympathetic nervous system

heightened physical arousal would be something that this system would do (survival related activates) (fighting, fleeing, feeding, mating).   

Parasympathetic nervous system

Reduce arousal (redirect blood to other parts of the body) and returns the body to a resting state.   

Transcranial Magnetic stimulation (TMS)

This produces magnetic stimulation to the scalp, causing the neurons to be inactive. 

Electroencephalograph (EEG)

Records electrical signals of the brain through electrodes on the scalp, non invasive. It can record an individual’s response to a stimulus which is called  evoked potentials or evoked responses. 

Magnetoencephalography (MEG)

Measures faint magnetic responses that are generated by brain activity. 

Positron-emission tomography (PET)

Produces an image of brain activity, the individual receives an injection of glucose containing radioactive atoms. When radioactive atoms decay, they release a positron which then collides with an electron creating gamma rays, which are picked up by the gamma ray detectors surrounding the individual’s head.  

Functional Magnetic resonance imaging (fMRI)

Safe and non invasive procedure that detects the changes in the flow of blood, Increases in blood flow are correlated with neuronal activation. You cannot infer causality from an fMRI. 

EEG and MEG both result in…

precise information about the timing, but not as accurate about the location. 

PET and fMRI are able to provide…

more comprehensive detail on location of brain activity however, they are not as accurate with the timing. They both also require a lot more time and effort. 

Computerized axial tomography (CT or CAT scan)

used for observing brain anatomy. Dye is injected into the blood, X-rays are then passed through the head.

How do neurons know where to mirgate to? 

The terminal region tells the axons where to go through the release of chemicals. 

Once the axons are in place the chemicals are gone and therefore in adulthood / end of development the connections cannot regrow. 

The nerve growth factor (NGF) produced by terminal regions…

allows for the nerve cell to remain and strengthen however if the target does not release NGF, the axon degenerates and the cell dies via natural cell death and process called apoptosis. 

Apoptosis

Any axon that does not receive the NGF protein does not survive and dies off.

If a lesion occurs in the brain it cannot create new cells to take over other the dead cells. The brain compensates by…

causing surrounding brain cells become more active

Collateral spouting is where…

if an axon dies and degenerates, other axons will form a secondary set of synapses to take up the action of axon 2 (the previous axon that was attached to the dead axons).