Neurons, Glia & Brain Tissue [1]

Question 1

Nucleus -Grey matter or white matter?

Answer 1

Grey

Question 2

Lemniscus -Grey matter or white matter?

Answer 2

White

Question 3

Ganglion -Grey matter or white matter?

Answer 3

Grey

Question 4

Peduncle -Grey matter or white matter?

Answer 4

White

Question 5

Cortex -Grey matter or white matter?

Answer 5

Grey

Question 6

Funiculus -Grey matter or white matter?

Answer 6

White

Question 7

Body -Grey matter or white matter?

Answer 7

Grey

Question 8

Fasciculus -Grey matter or white matter?

Answer 8

White

Question 9

Tract - Grey matter or white matter?

Answer 9

White

Question 10

Describe the function and distribution of astrocytes

Answer 10

Cells found within the brain and spinal cord; cell processes interdigitate with neurons and fill volume of brain

Keep neurons biochemically isolated by retrieving neurotransmitters that leak out of synapse

Helps maintain ionic equilibrium around neurons; soaks up potassium

Involved in blood flow regulation with the “end feet” of their processes (part of Blood Brain Barrier)

Involved in glial scar formation after CNS damage

Question 11

Describe the function and distribution of microglias

Answer 11

Mostly uniformly distributed throughout the brain. Also in spinal cord

Have processes like astrocytes,, but processes DONT overlap

Called “macrophages of the brain. Phagocytic, and remain in surveillance until they are activated by stimuli

Question 12

Describe the function and distribution of oligodendrocytes

Answer 12

Myelin-forming cell of the central nervous system.

Have several processes that contact axons of the CNS and insulate them with a myelin sheath.

When the CNS is damaged, these cells actively inhibit axonal regeneration by phagocytizing the myelin sheath of the neuron.

Question 13

Describe the function and distribution of Schwann cells

Answer 13

The myelin forming cell of the peripheral nervous system.

A single Schwanna cell can only myelinate a single axon.

When PNS neurons are damaged, these cells clear debris then line up along the endoneurium to give regenerating axons a path and growth substrate.

Question 14

What are the parts of the neuron?

Answer 14

dendrite, axon, axon terminal, Nissl substance

Question 15

Describe the relationship between cerebral blood flow and fMRI and PET scans

Answer 15

Blood flow to the brain can be regulated by autoregulation of the arterioles in the brain. Increases in blood pressure can be compensated for by an increase in vascular tone to maintain the diameter of the blood vessel. In functional hyperemia, local increase in neuronal activity results in an increased metabolic demand and thus increased local blood flow. This localized increase in blood flow to active neurons is the basis for fMRI and PET scans. PET uses an injected tracer in the blood stream while fMRI measures blood flow based off hemoglobin properties.

Question 16

Explain why substances in the circulatory system do not freely enter the brain extracellular space

Answer 16

The brain is separated from the rest of the systemic circulation by the Blood Brain Barrier (BBB). The BBB is created by endothelial cells forming tight junctions between each other, so there are no fenestrations in the capillaries of the brain. In order for a substance to enter the extracellular space of the brain, they must be actively transported across the endothelial cell or be capable of diffusing through the endothelial cell.

Question 17

Describe how astrocytes can regulate local blood flow in proportion to the neuronal activity in the area

Answer 17

Astrocytes extend their foot processes to blood vessels and help endothelial cells maintain their contacts that create the BBB. In addition, astrocytes can regulate vessel function through a glutamate pathway. When glutamate is absorbed by astrocytes, it causes the release of arachidonic acid within the astrocyte. This arachidonic acid undergoes an enzymatic reaction (by a P450 enzyme) which converts it to epoxy-eicosatrienoic acid (EET). The EET is released and acts on arterioles to hyperpolarize the cell membrane. This prevents smooth muscle constriction and reduces the vascular tone. The decreased tone results in vessel dilation and increased blood flow to areas of the brain that are actively releasing glutamate.

Question 18

Describe the differences in neural regeneration and glial response comparing the peripheral and central nervous systems

Answer 18

PNS nerve damage is repaired by regeneration of the damaged axons. The major glial cell involved with regeneration is the Schwann cell, which reacts to nerve damage by clearing myelin debris and also provides a “path” for regenerating synapses

Damage to CNS neurons does not frequently result in regeneration as PNS damage does. The oligodendrocytes destroy the intact myelin sheath and do not clear debris as Schwann cells do in the PNS. Thus, there is no good pathway for the axons to grow on and follow. Axons do no regenerate.

Question 19

Know the general function of the dendrite

Answer 19

These small processes passively conduct electrical signal (NOT and action potential) received from other neurons and act as areas of signal integration. There can be many dendrites per single neuron and all the dendrites may be receiving different information from their contacts

Question 20

Know the general function of the axon

Answer 20

Contains voltage-gated ion channels and is thus capable of generating an action potential. These processes can be branched and can be very long. In general, axons greater than 1 micron in diameter are myelinated.

Question 21

Know the general function of the axon terminal

Answer 21

The area of the axon that contacts the dendrites (or cell body, or axons, etc) of the next cell. A synapse forms between the axon terminal and the dendrite. These synapses are usually chemical synapses so the axon terminal. Influx of Calcium (in response to the action potential) allows the vesicles stored in the terminal to fuse to the membrane, which causes neurotransmitter release into the synaptic cleft.

Question 22

Know the general function of the Nissl substance

Answer 22

The dark staining endoplasmic reticulum and ribosomes in the cell bodies and dendrites. These indicate a high level of metabolic activity characteristic of neurons.

A Nissl stain is an RNA stain

Question 23

What is the role of the nucleolus?

Answer 23

Ribosome production! On a stain you will see the nucleolus and many ribosomes attached to the RER

Question 24

What is axoplasmic flow?

Answer 24

The continuous pulsing, undulating movement of the cytoplasm between the cell body of a neuron, where protein synthesis occurs, and the axon fiber to supply it with the substances vital for the maintenance of activity and for repair.

Bidirectional