Neurons, Glia, Brain Tissue

Question 1

What does Nucleus mean and is it white or grey matter?

Answer 1

Kernel, grey

Question 2

What does Ganglion mean and is it white or grey matter?

Answer 2

Swelling, grey

Question 3

What does Cortex mean and is it white or grey matter?

Answer 3

Rind, grey

Question 4

What does Body mean and is it white or grey matter?

Answer 4

Cell body, grey

Question 5

What does Lemniscus mean and is it white or grey matter?

Answer 5

Ribbon, white

Question 6

What does Peduncle mean and is it white or grey matter?

Answer 6

Little foot, white

Question 7

What does Funiculus mean and is it white or grey matter?

Answer 7

Small rope, white

Question 8

What does Fasciculus mean and is it white or grey matter?

Answer 8

Little bundle, white

Question 9

What is the function and distribution of astrocytes?

Answer 9

Astrocytes separate neurons, assist in cleaning up and recycling NT, transport nutrients from the blood to neurons, and their foot processes form the Pia Matter. They also provide signals to maintain the Blood Brain Barrier.

Question 10

What is the function and distribution of microglia?

Answer 10

Microglia are derived from the bone marrow and act as macrophages in the nervous system. Constantly form and degrade processes to touch local neurons, and act as “first responders” to neuron damage.

Question 11

What is the function and distribution of oligodendrocytes?

Answer 11

Oligodendrocytes myelinate axons in the CNS, one oligodendrocyte may myelinated unto 30 neurons of >1 micron in width.

Question 12

What is the function and distribution of schwann cells?

Answer 12

Schwann cells myelinate neurons in the PNS, only one neuron per schwann cell.

Question 13

What is the relationship between cerebral blood flow and fMRI and PET scans?

Answer 13

Functional Hyperemia is a local increase in blood flow due to increased neuronal activity, both fMRI and PET scans measure this change in blood flow to track brain activity. fMRI relies on intrinsic properties of hemoglobin and PET relies on an injected tracer (radioactive glucose commonly) to measure blood flow.

Question 14

Why do substances in the blood not freely enter the brain parenchyma?

Answer 14

The endothelial cells in the blood vessels of the brain are not fenestrated, and instead have tight junctions. Substances must either diffuse through the cells or be actively transported. Astrocytes do not directly form the BBB, but communication from them is necessary for the maintenance of the junctional complexes of the BBB.

Question 15

How do astrocytes regulate blood flow in an area?

Answer 15

Astrocytes are closely associated with neutropils (areas of dense terminals, dendrites, and axons) and take up glutamate from the synapses. Glutamate causes release of arachidonic acid in the astrocyte, which is converted to epoxy-eicosatrienoic acid (EET) by P450 enzyme. EET is released and hyper polarizes arteriole membranes (smooth muscle?) resulting in relaxed muscle tone, dilation, and increased blood flow.

Question 16

What is the order of neural regeneration and glial response in the PNS?

Answer 16

Schwann cells clear myelin debris and line up along the endoneurium to form a substrate for the outgrowth of the neuron. The remaining end of the neuron emits substances (incl. ATP) which activate microglia. Microglia divide and express cytokines that activate astrocytes. Microglia also strip synapses and reorganize the neural networks serving the affected area, sometimes causing neuropathic pain states.

Question 17

What is the order of neural regeneration and glial response in the CNS?

Answer 17

Oligodendrocytes do not clear myelin debris or assist regrowth of the affected neurons. They express chemical signals that inhibit neuron growth. Microglia activate local astrocytes which also proliferate to form a glial scar that physically and chemically inhibits neuron growth.CNS neurons are capable of regrowing, but are actively prevented by this process.