Chapter 5: Protecting and Maintaining the Adult Nervous System

Question 1

adult post natal neurogenesis in the ___ and ___ are largely seen

Answer 1

olfactory bulb and hippocampus

Question 2

radioactive carbon studies show that:

Answer 2

most neurons are created before you are born, but the adult brain is capable of producing neurons in certain regions, glia, and endothelial cells.

Question 3

baby _____ at the intersections of the major skull bones allows for skull and brain expansion

Answer 3

frontanelles.

Question 4

cranial vault

Answer 4

the body cavity housing the brain.

Question 5

the meninges is between the ___ ___ and the ___

Answer 5

cranial vault and brain

Question 6

outermost layer of meninges

Answer 6

dura mater

Question 7

innermost of the meninges

Answer 7

pia mater

Question 8

the subarachnoid space holds ___

Answer 8

CSF

Question 9

density of CSF is ___ to that of nervous tissue

Answer 9

identical. allows for the brain to float in CSF, decreasing the force with which the brain slams against the cranial wall when you bang your head against a hard surface.

Question 10

the left and right ventricles are the

Answer 10

lateral ventricles.

Question 11

the lateral ventricles are connected through a narrow tube (___ of ____) which lead into a small ____ ventricle.

Answer 11

the lateral ventricles are connected through a narrow tube (FORMAINA of MONRO) which lead into a small THIRDventricle.

Question 12

caudal of the third ventricle is the ___ ___, which passes to the ___ ventricle. This ventricle extends down another tube called the ____ ___ to reach the spinal cord.

Answer 12

caudal of the third ventricle is the CEREBRAL AQUADUCT, which passes to the 4th ventricle. This ventricle extends down another tube called the CENTRAL CANAL to reach the spinal cord.

Question 13

the ____ ____ lines regions of the ventricles and produces CSF

Answer 13

choroid plexus.

Question 14

blood vessels course mainly though th e___ ___

Answer 14

subarachnoid space

Question 15

The CSF is produced mainly by the ___ ____, circulates through the ventricles, and is eventually recycled into the ____.

When does hydrocephalus result?

Answer 15

The CSF is produced mainly by the choroid plexus, circulates through the ventricles, and is eventually recycled into the blood.

Hydrocephalus results when CSF drainage is blocked.

Question 16

after circulating through the ventricles, CSF leaves the subarachnoid space through ___ ___ which protrude into ___ ___ that drain blood from the brain

Answer 16

after circulating through the ventricles, CSF leaves the subarachnoid space through ARACHNOID GRANULATIONS which protrude into VENOUS SINUSES that drain blood from the brain

Question 17

CSF tends to flow from the ___ to the ___. Why?

Answer 17

Because the choroid plexus is largest in the lateral ventricles (LV), the CSF tends to flow from the forebrain toward the hindbrain.

Question 18

How to you treat hydrocephalus/ prevent CSF blockage

Answer 18

can reduce pressure using a one way valve into the peritoneal. Cerebral shunts are also used in adult brains if CSF outflow is blocked.

Question 19

What is a subdural hematoma? How is it caused?

Answer 19

a brain bleed/ rupturing blood vessels and neural death.

severe blow to the head tears BRIDGING VEINS that course from the cerebral surface to the dural veins and venous sinuses. Results in blood accumulating in the brain because the veins cannot drain the blood away from the brain.

Question 20

general syndrome caused by repeated head trauma

Answer 20

chronic traumatic encephalopathy. Involves substantial inflammation of the brain, neurodegeneration, and progressive dementia.`

Question 21

purpose of CSF

Answer 21

1) cushion brain
2) metabolic support/ remove waste
3) maintain chemical homeostasis.

Question 22

The blood–brain barrier is formed by ___ ___ between capillary ____ cells

Answer 22

The blood–brain barrier is formed by TIGHT JUNCTIONS between capillary ENDOTHELIAL cells.

Question 23

tight junctions are formed by special proteins called ___ and ___

Answer 23

claudins and occludens.

Question 24

some things can get past the blood brain barrier, what are they? How is water transported?

Answer 24

lipophillic substances and small molecules. Larger molecules/hydrophillic substances requires transporters. water is transported on a mass scale using aquaporins.

Question 25

the blood-CSF barrier has tight junctions between the ___ ___ ___ that face the ventricle

Answer 25

CHOROID EPITHELIAL CELLS that face the ventricle

Question 26

CSF from the ventricles ultimately collects in the subarachnoid space around the brain. It is transported from there into veins through “___ ___ that can move through the arachnoid membrane.

Answer 26

CSF from the ventricles ultimately collects in the subarachnoid space around the brain. It is transported from there into veins through “giant vacuoles” that can move through the arachnoid membrane.

Question 27

the innate immune response generates ___, which consists mainly in the release of ___ and ___, and prompts some white blood cells to kill damaged cells and devour debris.

Answer 27

the innate immune response generates INFLAMMATION, which consists mainly in the release of CYTOKINES and CHEMOKINES, and prompts some white blood cells to kill damaged cells and devour debris.

Question 28

What is the adaptive immune system?

Answer 28

its cells bind to pathogens, migrate to the lymph nodes, and present the pathogens to lymphocytes. Some lymphocytes then release cytokines or make antibodies.

Question 29

which type of lymphocyte is responsibly for making antibodies? what do these antibodies do?

Answer 29

B-cells. when these antibodies bind to their matching antigetns, macrophages and special killer cells derived from bone marrow ar stimulated to remove the threat.

Question 30

_____ can be used as “Trojan horses” to deliver substances across the BBB into the brain

Answer 30

Nanoparticles can be used as “Trojan horses” to deliver substances across the BBB into the brain

Question 31

T/F: B cells, macrophages and killer cells are capable of crossing the blood brain barrier

Answer 31

true. even though the nervous system is immune privileged and has a very tight barrier, certain immune system components can enter the brain.

Question 32

What happens to white blood cells when they enter the parenchyma? (normal brain tissue)

Answer 32

they get converted to either MICROGLIA (macrophages of the brain), or they get killed by ASTROCYTES.

Question 33

Why do the blood brain and blood CSF barriers get leaky when the brain or ites meninges are under attack? Isn’t this counter productive?

Answer 33

leaky barriers allows white blood cells to enter the CSF, and from there, the brain parenchyma (because the ependymal cells that line the ventricles are pretty permeable to CSF in the brain).

Even if the white blood cells in the parenchyma are transformed to microglia, this still boosts the supply of cells available to fight the threat. thus, opening the barriers strengthens the brain’s immune response.

Question 34

____ migrate towards brain injurym where they engulf and remove cellular debris and occasionally release cytokines

Answer 34

microglia

Question 35

what is excitotoxicity? How is it induced?

Answer 35

cell death as a result of an excessive calcium influx, resulting in uncontrolled rapid firing. Often induced by excessive glutamate.

Question 36

explain the role of potassium buffering astrocytes

Answer 36

some astrocytes possess K+ channels that tend to be open at the astrocyte’s resting potential and let K+ flow into the cell rather than out of it.

through these specialized K+ channesl, astrocytes ABSORB much of the K+ that builds in the extracellular space around highly active neurons.

Without K+ being lower in the ECM, the highly active neurons will become ever more depolarized (because K+ would not be able to efflux if ECM concs are high), thus making them more likely to die from excitotoxicity.

Question 37

Which type of astrocytes form glial scars?

Answer 37

REACTIVE astrocytes. when called to action, reactive astrocytes proliferate and move to the site of injury, and soak up flutamate and other substances released through necrosis. This protects the remaining neurons.

Question 38

regeneration of damaged axons is due to ___. How?

Answer 38

schwann cells.

when an axon is experiencing degeneration, the schwann cells DE-DIFFERENTIATE and re-enter the cell cycle, and secrete a variety of moelcuels that promote axonal regneration. Once the axons have successfully re-innervated their target, the schwann cells re-differentiate and start to myelinated the regenerated parts of the axons.

Question 39

Why do peripheral axons regenerate after an injury, whereas central axons do not?

Answer 39

because glial scars tend not to form in the Peripheral nervous system. Astrocytes in glial scars impede axonal regeneration because axons cannot grow over a glial scar, which is why CNS axons cannot regenerate over a site of injury.

Question 40

T/F: Oligodendrocytes (mylin secreting in CNS) can act like schwann cells and repair axons in the CNS

Answer 40

FALSE. they actually do the opposite of schwann cells.

Oligodendrocytes secrete NOGO, which INHIBITS axon growth by collapsing axonal growth cones.

Question 41

Braille alexia reveals significant brain rewiring. Explain

Answer 41

braille alexia as a result of occipital lobe damage suggests that the occipital lobe in a blind person was functionally reqired to receive inputs from the somatosensory system (to read and visualize braille).

Question 42

General rule of compensating for a lost sensory system

Answer 42

the earlier a disruption occurs, the greater the ability of the nervous system to compensate for the damage. the brain systems have “invaded” the brain regions that lost hteir normal inputs on account of the early damage (ex/ being born blind). the nervous system’s degree of palsticity tends to decrease with age.

Question 43

constraint-induced movement therapy

Answer 43

recovery from damage is improved if the organism is forced to use the damaged limb

Question 44

Explain how cortical remapping after injury can cause phantom limb pain

Answer 44

ex/ after losing an arm, the somatosensory input from the FACE migrates and rerouts into the cortical region that used to process info coming from the arm. This means that touches to the face will be perceived at least sometimes, as stimulation of the missing arm, which would be perceived as pain.

The greater the extent of this rerouting, the greater the phantom pain.

Question 45

Neurons rely mainly on ___ from the blood for energy

Answer 45

glucose

Question 46

glucose can go through ___ or ___ ___ to generate ATP

Answer 46

glycolysis or oxidative phosphorylation

Question 47

T?F: neurons can synthesize glucose from ketone bodies or protein or fat

Answer 47

false. unlike other organs, neurons cannot synthesize glucose, or store glycogen (but astrocytes can). Must obtain all glucose from environment.

Question 48

The pyruvate created through glycolysis either enters the oxidative phosphorylation pathway or is converted to ____

Answer 48

lactate, which can be converted back to pyruvate with the help of NAD+.

Question 49

the ___ ___ ___ protects the brain against arterial blockages. How?

Answer 49

circle of willis. this arterial ring forms because the major arteries that feed the brain are linked by small communicating arteries.

Question 50

How do the communicating arteries of the circle of willis connect the major arteries?

Answer 50

the anterior cerebral arteries are connected across the mid line, and the posterior cerebral arteries are connected to the middle cerebral arteries.

there are three communicating arteries

Question 51

most humans do not have all the communicating arteries in the circle of willis. what problems will they face?

Answer 51

not having all the communicating arteries increases the chances of having an ischemic stroke because the brain isn’t as protected against arterial blockage.

Question 52

lactate shuttle hypothesis

Answer 52

the “lactate shuttle hypothesis,” astrocytes convert glucose to lactate and then shuttle some of it across to neurons, which can use the lactate to drive oxidative phosphorylation.

Question 53

how do astrocytes recycle glutamate released by neurons?

Answer 53

astrocytes convert this glutamate to glutamine and ship it over to neurons, which then convert it back to glutamate.

Question 54

3 main vessel adaptations thatprovide a defense against blocked blood vessels

Answer 54

1) communicating arteries between major arteries
2) collateral branches also linking major arteries
3) anastomoses: small arterioles on the SURFACE

Question 55

_____ are arterioles on the ___ while ____ arterioles are on the deep portions of the brain.

Answer 55

ANASTOMOSES are arterioles on the SURFACE while PENETRATING arterioles are on the deep portions of the brain.

Question 56

____ arterioles are bottlenecks in the brain’s blood supply

Answer 56

penetrating arterioles. Because they do not anastomose with each other (variably connect).
Therefore, if one penetrating arteriole is blocked, there is no safety net because no other arteriole can supply that exact location.

blocking a penetrating arteriole removes the blood flow to that area.

Question 57

Why are the deeper locations of the brain blood bottle necks, while arterioles on the surface of the brain are filled with anastomoses?

Answer 57

the outer cortex has most of the cell bodies and are the most metabollically active. the harder the neurons work, the more blood flows to them. therefore, it is more beneficial for the arterioles to be interconnected in this region.

Question 58

fMRI records ___ signals

Answer 58

BOLD (blood oxygen level dependent) signals.

Question 59

What is the BOLD method of fMRI? What info does it convey?

Answer 59

method compares the ratio of oxygenated Hb to deoxygenated Hb across various regions of the brain across multiple time points. WHen arterial blood flow into a brain region increases, the BOLD signal increases because there is more oxygenated Hb. Therefore, the BOLD signal is generally interpreted as an increase in neuronal activity.

Question 60

How is arteriole diameter controlled?

Answer 60

by smooth muscle (constriction = less blood flow, dilation = more blood flow)

Question 61

How are smooth muscles controlled to dilate/constrict?

Answer 61

ASTROCYTES!!

the end feet of astrocytes help maintain the blood-brain barrier, but they also control regional blood flow. Ca2+ levels in the end feed correlate with arteriole diameter. Ca2+ levels within an astrocyte end foot causes the adjacent blood vessel to dilate.

Question 62

explain the mechanism behind blood vessel dilation in a neural area of high activity.

Answer 62

1) glutamanergic synapses are active, allows glut to be released out of cells
2) extrasynaptic glutamate binds to METABOTROPIC GLUT RECEPTORS on astrocytes
3) Ca2+ influx in the astrocytes occur, and the end feet of the astrocytes experience increased levels of Ca2+.
4) a rise in Ca2+ in the astrocyte end feet increase the dilation of the arterioles surrounding it.

Question 63

Hemodynamic response

Answer 63

diameter of the vessel close to the activated neurons.

The induced increase in blood flow overcomes the need for oxygen supply.

Question 64

BOLD signalling eseentially measures the ___ response

Answer 64

hemodynamic

Question 65

Why does deoxy Hb produce weaker signals on fMRI?

Answer 65

Has an odd number of protons
This disturbs the local magnetic field
Which causes the transverse magnetization signal to decay more rapidly
This is the basis for fMRI recording