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48 Cards in this Set

  • Front
  • Back

What is proliferation?

The production of new cells

What are stem cells?

Cells that are continuing to divide

What is one major difference between human brains and chimpanzee brains?

Human neurons continue to proliferate longer.

What chemicals guide neuron migration?

Immunoglobulins and chemokines

What happens if there is a deficit in immunoglobulins and chemokines?

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

What is neuron differentiation?

Forming its axon and dendrites

Which part of the neuron develops first?

The axon

When do dendrites begin to form?

After the migrating neuron has reached its destination

What is myelination? Is it a slow or fast process?

When glia produce the insulating fatty sheaths that accelerate transmission in many vertebrate axons. It is a slow process.

what is synaptogenesis?

The formation of the synapses.

What are some exceptions to the belief that the brain could not develop new neurons?

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.

What is one way to test for newly formed neurons?

Using measurements of a radioactive isotope of carbon, carbon14.

Which idea did Paul Weiss dismiss when he did his experiment with the graft of the frog leg?

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

How does an axon find its target?

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

What was Sperry's evidence that axons grow to a specific target instead of attaching at random?

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

What is neural Darwinism?

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.

If axons from the retina were prevented from showing spontaneous activity during early development, what would be the probably effect on development of the thalamus?

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

What is the nerve growth factor?

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

What happens if an axon does not receive NGF?

The axon degenerates and its cell body dies.

What is apoptosis?

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

NGF is a neurotrophin. What does that mean?

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

Although neurotrophins are essential to the survival of motor neurons in the periphery, what neurons are they not responsible for the survival of?

Neurons within the brain.

What is the purpose of homeobox genes?

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.

What is fetal alcohol syndrome?

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

How does alcohol damage the brain?

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

How does alcohol kill neurons?

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.

How does a stimulating environment affect neuronal changes? (Rats)

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

Which brain area shows expanded representation of the left hand in people who began practicing stringed instruments in childhood and continued for many years?

Somatosensory cortex (postcentral gyrus) of the right hemisphere.

Give an example of when the expansion of a relevant brain area is not always a good thing?

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.

What is focal hand dystonia?

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

Under what circumstances are adolescents most likely to make an impulsive decision?

In the presence of peer pressure.

Why do old people's memory and reasoning begin to fade?

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.

What is one way in which older adults compensate for less efficient brain functioning?

Many of them compensate by activating additional brain areas.

What is a closed head injury?

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

What are causes of damage after a closed head injury?

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

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

What is a stroke?

Temporary interruption of normal blood flow to a brain area.

What is ischemia?

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

What is a hemorrhage?

The result of a ruptured artery.

What happens with the neurons in ischemia and what happens to the neurons in a hemorrhage?

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.

What is an edema?

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

what do both ischemia and hemorrhage impair?

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

What does a combination of an edema and excess sodium provoke?

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

What does the drug tissue plasminogen activator (tPA) do?

It breaks up blood clots.

What is diaschisis?

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

What are some problems that limit axon regeneration?

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.

What are collateral sprouts?

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.

Is collateral sprouting helpful or harmful?

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

What is denervation supersensitivity?

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