Psych 261 Midterm2 Ch4

The production of new cells

Cells that are continuing to divide

Human neurons continue to proliferate longer.

Immunoglobulins and chemokines

Impaired migration, decreased brain size, decreased axon growth, and mental retardation.

Forming its axon and dendrites

The axon

After the migrating neuron has reached its destination

The formation of the synapses.

1) The olfactory receptors - because they are exposed to the outside world and its toxic chemicals.

2) Stem cells in the nose - periodically divide with one cell remaining immature while the other differentiates to replace a dying olfactory receptor

3)The hippocampus - new supply of neurons keeps it "young" to learn new tasks. Blocking the formation of new neurons impairs new memories.

Using measurements of a radioactive isotope of carbon, carbon14.

That each axon would find its way to the correct muscle in the extra limb. Later evidence supports this statement.

A growing axon follows a path of cell surface molecules, attracted by some chemicals and repelled by others, in a process that steers the axon in the correct direction. They follow a gradient of chemicals.

Eg. The axons with the lowest concentration connect to the tectal cells with the lowest concentration

If he cut a newt's eye and inverted it, axons grew back to their original targets, even though the connections were inappropriate to their new positions on the eye

We start with more neurons and synapses than we can keep. Synapses form with approximate accuracy, and then a selection process keeps some and rejects others.

The axons would attach based on a chemical gradient but could not fine-tune their adjustment based on experience. Connections would be less precise.

A protein delivered by the muscle when a neuron forms a synapse on it, that promotes the survival and growth of the axon.

The axon degenerates and its cell body dies.

The process by which a neuron kills itself if its axon does not make contact with an appropriate postsynaptic cell by a certain age.

A chemical that promotes the survival and activity of neurons. Essential for growth of axons and dendrites, formation of new synapses, and learning.

Neurons within the brain.

They regulate the expression of other genes and control the start of anatomical development, including such matters as which end is the front and which is the rear.

A condition marked by hyperactivity, impulsiveness, difficulty maintaining attention, varying degrees of mental retardation, motor problems, heart defects, and facial abnormalities.

Interferes with neuron proliferation, impairs neuron migration and differentiation, and impairs synaptic transmission.

1) Alcohol inhibits receptors for glutamate, the brain's main excitatory transmitter, and enhances receptors for GABA, the main inhibitor. Because of the decrease in net excitation, many neurons undergo apoptosis.

2) Further harm occurs because neurons try to compensate by building more glutamate in response to being inhibited, which brings excess Na and Ca into the cell and poisoning the mitochondria once the alcohol leaves, which leads to increased cell death.

Developed a thicker cortex, more dendritic branching, and improved learning.

Somatosensory cortex (postcentral gyrus) of the right hemisphere.

When people play instruments for a long time, the representation of the fingers in the somatosensory cortex could spread out to have each finger overlap its neighbour. It would be hard to clearly feel the difference between one finger and another, therefore, it is more difficult to move them independently.

"Musician's cramp". One or more fingers may go into constant contraction.

In the presence of peer pressure.

Many neurons lose some of their synapses and the remaining synapses change more slow than before in response to experiences. Also, the prefrontal cortex becomes less able to maintain a high level of firing while storing a working memory.

Many of them compensate by activating additional brain areas.

A sharp blow to the head that does not puncture the brain.

1) The rotational forces that drive brain tissue against the inside of the skull.

2) Blood clots that interrupt blood flow to the brain.

Temporary interruption of normal blood flow to a brain area.

The result of a blood clot or other obstruction in an artery.

The result of a ruptured artery.

In ischemia, the neurons deprived of blood lose much of their oxygen and glucose supplies.

In a hemorrhage, they are flooded with blood and excess oxygen, calcium, and other chemicals.

The accumulation of fluid, which increases pressure on the brain and the probability of additional strokes.

The sodium-potassium pump, leading to an accumulation of sodium inside neurons.

Excess release of the transmitter glutamate, which damages both neurons and synapses.

It breaks up blood clots.

Refers to the decreased activity of surviving neurons after damage to other neurons.

1) A cut in the nervous system causes a scar to form, creating a mechanical barrier. Scar tissue is beneficial immediately after the damage, but blocks regrowth of axons later.

2) Neurons on the two sides of the cut pull apart.

3) The glia cells that react to CNS damage release chemicals that inhibit axon growth.

New branches that take over vacant synapses. They are formed by other axons when a cell secretes neurotrophins after losing input from a particular axon.

Depends on whether the sprouting axons convey information similar to those that they replace.

Helps compensate for decreased input by enhancing responses to other synapses (more responsive, more easily stimulated).