D4H3 Nervous System

Question 1

3 basic divisions of the nervous system

Answer 1

1) central nervous system
2) peripheral nervous system
3) special senses

Question 2

gray matter in CNS

Answer 2

• consists mostly of nerve cell bodies, dendrites, and axons (together called neuropil) and glial cells
• eg: cerebral cortex, or central horns of the spinal cord

Question 3

white matter in CNS

Answer 3

• made up of axons of the neurons in the gray matter

- eg: corpus callosum of the cerebrum, tracts of the spinal cord

Question 4

3 basic cell types in the nervous system

Answer 4

1) neurons
2) glia and support cells
3) non-neural cells

Question 5

definition of neurons

Answer 5

• electrically excitable cells
• highly polarized structure (dendrites, cell body/soma/perikaryon, axon)
• can communicate signals by means of action potentials propagated along long extensions (axons)
• transmit message to other neurons and other cells at special junctions called synapses by releasing neurotransmitters

Question 6

cell body/soma of neurons

Answer 6

• neuron cell bodies w/ large, rounded nucleus w/ prominent nucleolus
• have lots of rough ER to make lots of protein

Question 7

dendrites of neurons

Answer 7

• processes that receive stimuli from other neurons, then send the message to the cell body
• usually highly branched, like a tree (dendrite = tree)
• often covered in spines (small projections on surface); synaptic contact often happens at spines

Question 8

axons of neurons

Answer 8

• processes that conduct action potentials away from the cell body
• arises from the cell body at the axon hillock, where action potentials are initiated
• are smooth processes (w/o spine)

Question 9

axoplasmic support

Answer 9

• axons don’t have ribosomes (so don’t have protein synthesis)
• axoplasmic transport is a way to get cellular components from the cell body (point of synthesis) to the axon
• 2 components:
  1) fast transport (mostly vesicles moving along microtubule tracks, mediated by kinesin in anterograde direction; dynein in retrograde)
  2) slow transport (for larger cell components, cytoskeleton, cytoplasm)

Question 10

synapses

Answer 10

• sites of chemical communication usually found between the end of an axon and a cell body or dendrites of another neuron
• can also be found between dendrites, between axons

Question 11

glial cells

Answer 11

• aka “neuroglia” (= nerve glue)
• occupy the space between neurons, separating neurons from each other and from blood vessels
• 3 types of neuroglial cells in CNS:
  1) astrocytes
  2) oligodendrocytes
  3) microglia

Question 12

astrocytes (what are they/what are the basic types?)

Answer 12

• type of neuroglial cells in CNS
• star-shaped cells (“astro”naut in the stars)
• 2 basic types:
  1) protoplasmic (in gray matter of brain and spinal cord)
  2) fibrous (in white matter)

Question 13

function of astrocytes

Answer 13

• transport materials between neurons and blood vessels
• give structural rigidity to the CNS
• regulate the composition of the extracellular space around neurons
• store energy (mainly glycogen)
• secrete growth factors

Question 14

What is astrocyte cytoskeleton made up of?

Answer 14

astrocyte cytoskeleton is mostly microtubules and intermediate filament proteins made up of “glial-fibrillary acidic protein” (GFAP)

Question 15

oligodendrocytes

Answer 15

• type of neuroglial cell in CNS

- most abundant in the white matter of the CNS, where they form the myelin sheaths of axons

Question 16

ependymal cells (what are they?)

Answer 16

-epithelium-like layer lining the cavities (ventricles) of the brain and the central canal of the spinal cord (these cavities contain the cerebrospinal fluid)

Question 17

Why do ependymal cells have cilia on their apical surfaces?

Answer 17

-cilia on surface helps to circulate the CSF (cerebrospinal fluid)

Question 18

choroid plexus

Answer 18

• the folds of ependyma (choroidal villi) extending into the ventricles of the brain
• has many blood vessels
• is covered by cuboidal epithelium that secretes the CSF

Question 19

microglia

Answer 19

• “micro” (small), dense, highly branched cells w/ processes covered in thornlike projections
• are migratory and phagocytic, serve a “white blood cell” type of role: “brain macrophages”
• are derived from circulatin macrophages
• more abundant after damage (so they can clear dying neurons)

Question 20

meninges

Answer 20

-fibrous, connective tissue coverings of the CNS

• 3 layers:
  1) outer dura mater
  2) middle arachnoid layer (has subarachnoid space b/n arachnoid layer and pia mater, bridged by arachnoid trabeculae, filled w/ CSF)
  3) inner pia mater (thin layer of tissue that coats the outer surface of the CNS, fuses w/ arachnoid trabeculae)

Question 21

Nissl bodies/Nissl substance

Answer 21

..

Question 22

why is gray matter gray?

Answer 22

-darker b/c made up of clusters of cell bodies

Question 23

why is white matter white?

Answer 23

-lighter b/c made up of axons (of neurons), which have myelin, which is fatty (and fat is white)

Question 24

GFAP (glial-fibrillary acidic protein)

Answer 24

• intermediate filament proteins

- ..?

Question 25

BBB (blood brain barrier)

Answer 25

• due to zonula occludens between capillary endothelium cells
• restricted permeability for capillaries in the brain
• essential metabolites in blood are transported across, but other things (ex: antibiotics) kept out of brain
• certain regions of brain have permeable BBB so can “sample” blood for regulatory molecules

Question 26

glymphatic system

Answer 26

-brain’s version of trying to do what the lymphatic system does elsewhere

…

Question 27

satellite cells in PNS

Answer 27

• act as supportive cells around neurons
• are the glia in ganglia
• act like Schwann cells (provide wrappings)

Question 28

Schwann cells

Answer 28

myelinate neurons

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