physiological psychology chapter 4

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1.              What is the difference between a sex-linked gene and a sex-limited gene?

A sex-linked gene is primarily related to x-linked genes or chromosome specific genes, and a sex-limited gene is present in both sexes but will only impact one sex (so a male may have sex-limited genes for breast size, but those genes will not be expressed). 

2.              Name and describe the five major stages in the development of neurons in the CNS.

1.     Proliferation

a.     Production of new cells and neurons

b.     Cells lining the ventricles divide

c.     Some become stem cells and continue dividing

d.     Others remain where they are or become neurons and glia that migrate to other locations.

2.     Migration

a.     Neurons and glia move to their locations in a variety of directions

b.     Some don’t reach their locations until adulthood

c.     Immunoglobins and chemokines guide neuron migration

3.     Differentiation

a.     Axon and dendrites differentiate from each other

b.     After migration

4.     Myelination

a.     Glia produces myelin

b.     First in spinal cord, then hindbrain, midbrain, and forebrain

c.     Occurs gradually over decades

5.     Synaptogenesis

a.     Synapses form between neurons

b.     Throughout life as neurons are constantly finding and discarding connections

c.     Slows significantly later in life

3.              In what brain areas have new neurons been found in adulthood?  What are stem cells and where are they found?

4.              What did Sperry observe when he damaged the optic nerve of newts?  What happened when he rotated the eye by 180 degrees?  What conclusion did these results suggest?

Sperry found that when the optic nerve regrew, it regrew in the correct direction and found the correct location. When he rotated the eye by 180 degrees the newt’s connections still regrew to the same locations, but they now saw the world upside down and reversed. These results suggested that there was a chemical trail that guided the regrowth of neurons to the correct location every time.

5.              How do neurons “find their way” to form the appropriate connection?

Neurons are attracted by some chemicals and repelled by others, so that they follow a kind of chemical trail that leads them to the right place.

6.              What is apoptosis?  What type of chemical can prevent apoptosis?

Apoptosis is the process of getting rid of unnecessary neurons. A chemical that prevents apoptosis is a neurotrophin.

7.              What does the “ferret experiment” tell us about how the cortex can rewire itself?

In the ferret experiment, the researchers rerouted the optic nerve of the brain to connect to the auditory cortex. The ferret’s auditory cortex developed the ability to process visual information which tells us that the brain is highly adaptable depending on the challenge presented to it.

8.              How does experience and training affect the structure and organization of neurons?

Experience and training can affect one’s ability to learn, the development of the brain, and dendritic branching. Particularly special experiences can make the brain adapt. For example, the blind person occipital lobe will begin to process tactile stimuli.

9.              In what two ways does a stroke kill neurons?  What are some current strategies used to minimize the effects of a stroke?

An Ischemic stroke can kill neurons by depriving neurons of oxygen and blood, and a hemorrhage can kill neurons by flooding them with excess blood, calcium, oxygen, and other chemicals. To minimize the effects of the stroke, a drug, tPA, breaks up blood clots. This treatment is useful directly after a stroke. Cooling the brain can also help because it reduces overstimulation, apoptosis, and inflammation.

10.           Describe how damaged neurons regrow new axons?

Damaged neurons regrow new axon through a process called axon sprouting where new branches form on an axon to attach to vacant receptors on the postsynaptic neuron. The cells that have lost their innervation release neurotrophins to induce the axons to form collateral sprouts.