Neurohistology

Question 1

neurons

Answer 1

-basic cell unit of the nervous system
-consist of a cell body with projections called dendrites which help with synaptic activity as well as an axon that facilitates long distance communication and est. contact with nerve terminals
-axon is wrapped with myelin

Question 2

neuroglia

Answer 2

-derived from the ectoderm with the exception of microglia (derived from the mesoderm)
-astrocytes, microglial cells, oligodendrocytes, and peripheral neuroglial cells

Question 3

embryogenesis of the CNS

Answer 3

-basic structure of the CNS originates in the neural plate, which comes from the ectoderm
-neural plate gives origin to neural groove that gives origin to microscopic structures of the CNS

Question 4

astrocytes

Answer 4

associated with axons and neurons and blood vessels —> in recent years we have realized the importance of them in neuronal function

Question 5

oligodendrocytes

Answer 5

-cells that produce myelin
-heavily myelinated axons have rapid conduction vs less myelinated have slower conduction

Question 6

how is the neural tube divided?

Answer 6

divided into three parts:
-forebrain
-midbrain
-hindbrain

Question 7

what does the interior of the neural tube give rise to?

Answer 7

the interior gives rise to the brain, midbrain, and spinal cord

Question 8

adult brain mimics what we see in embryogenesis

Answer 8

brain contains all the physiological functions associated with cognition and behavior

Question 9

major components of brain

Answer 9

-frontal lobe- largest portion of the brain and critical for many functions like motor organization (motor cortex) and cortical regions with topographic distribution
-prefrontal cortex- controls executive functions, behavior, and personality
-premotor cortex- organizes motor info and organization
-occipital lobe- has cerebral cortex that processes visual info that comes from optic nerves

Question 10

what happens if you lose the frontal lobe?

Answer 10

-in the 20th century, people with severe mental health disorders would have their frontal lobes removed and they would be calmer since they would lose their personalities and behaviors
-football players who repeatedly get concussions and hit their frontal lobe tend to experience issues with their personalities and behaviors later in life

Question 11

brain organization

Answer 11

-gray matter- high density of neurons and neuroglia
-white matter- high density of myelinated axons

Question 12

spinal cord

Answer 12

-contained in the spine, which is the body compartment
-carries sensory info from body to brain and impulses from the brain to the body —> bilateral pathways
Ex. damage to the spinal cord or trauma in neck can cause issues with paralysis since this communication is interrupted

Question 13

descending info: motor function

Answer 13

Ex. if you want to use your right hand, need to know where your right hand is first (sensory input) —> signal is generated in premotor cortex —> goes to primary motor cortex —> signal goes in white matter down to the spinal cord

Question 14

left brain —> right side of body

Answer 14

-90% of fibers controlling right hand come from left side of brain
-signals come from the prefrontal cortex but primary motor cortex is on the left side —> signals come down to portion of brainstem where they cross @ pyramidal decussation

Question 15

corticospinal tract

Answer 15

-one of the most important tracts of the spinal cord
-package of axons with backup function on the same side of hand

Question 16

symptoms of motor disfunction

Answer 16

weakness, paralysis, stiffness (spasticity), and cramps

Question 17

ascending info: sensory function

Answer 17

-if you have or need to execute a function the brain needs to know everything about the function
-nerves carrying sensory info from hands and legs —> spinal cord —> carries info to the brain and the first stop is the thalamus

Question 18

thalamus

Answer 18

distributes info to the frontal lobe and facilitates movement

Question 19

symptoms of sensory disfunction

Answer 19

pain, lack of sensation, abnormal sensation, and lack of balance

Question 20

CNS histology

Answer 20

in CNS we frequently include neurons but alone it doesn’t work —> need microglial cells, blood supply, myelin, and astroglial cells

Question 21

astroglial cells

Answer 21

close contact with neurons and blood vessels

Question 22

microglia

Answer 22

-microglia and macrophages originated in the mesoderm
-representatives of the immune system in the brain
-no immune privilege in the CNS —> in the CNS microglia and astroglia are part of the innate immunity along with the blood vessels that connect the CNS and bloodstream

Question 23

what is the main excitatory neurotransmitter?

Answer 23

glutamate

Question 24

what is the main inhibitory neurotransmitter?

Answer 24

GABA

Question 25

what happens during embryogenesis?

Answer 25

-during process the brain acquires neurons and neuroglial cells
-during the first year to two years of life, there is not a lot of stimulation so the organization is on the lower side
-after the baby is born, important to provide stimulation otherwise they may have a deficiency in synaptic connectivity
Ex. kids with autism may not have enough stimulation during this time

Question 26

important factors for development of cerebral cortex

Answer 26

-function of glia like astrocytes that facilitate movement of neurons
-immune system is important —> pregnant women need to be careful not to get sick since it can cause the embryo’s immune system to react

Question 27

when is the critical period of synaptic development?

Answer 27

in utero to two years of age

Question 28

when is the adaptation period of synaptic development?

Answer 28

after two years of age
Ex. language imprinted during first two years of life is stronger than a second language acquired as a teenager

Question 29

adaptation period

Answer 29

-strain on synaptic connectivity
-more susceptible to change
Ex. learn algebra in high school then come to college and stop using it —> synaptic connectivity goes away but you do not lose your primary language

Question 30

subtypes of glial cells

Answer 30

-astrocytes- help blood vessels and issue long processes called glial processes
-blood vessels- critical for the blood brain barrier, which has macrophages and endothelial cells
-microglia- derived from mesoderm and interact with neurons

Question 31

how do glial cells help synapses?

Answer 31

-for neurotransmitter to be released, glial cell is controlling the traffic of the neuron and exchange of the neurotransmitter
-synapses are formed or taken away
-synaptic removal is dependent on microglial cells
-synaptic structures use compliment factors and microglia phagocytyse the synaptic structure —> constant process of synaptic modeling

Question 32

perivascular astrocyte

Answer 32

-healthy tissue that went through injury —> glial cells come to injury and produce growth factors (cytokines and chemokines) for recovery
-some glial cells facilitate regeneration

Question 33

cajal

Answer 33

-pioneer in histology of CNS
-used photography in the 19th century and exposed film for hours
-he used microscope photography and paint to expose histology
-believed in neurocentric theory that the neuron was the main cell of the CNS

Question 34

pio del rio-hortega

Answer 34

-instead of drawing neurons, he drew other cells surrounding the neurons
—> found that many neurons were attached to microglia
-fired from lab since he went against what cajal believed

Question 35

importance of microglia

Answer 35

-main cell mediator of innate immunity in the CNS
-critical for metabolic processes structure of synaptic formation, and direction of transcriptomic function of different areas of the brain
-sensory of injury and disfunction, director of phagocytosis, and necessary for healthy and normal synaptic plasticity

Question 36

microglia derivation from mesoderm

Answer 36

-1st wave is stem cells from yolk sac that populate brain and liver
-2nd wave is macrophages past embryogenesis —> monocytes are represented in different organs as macrophages throughout life

Question 37

brain and CNS have lymphatic drainage system

Answer 37

-elements of the CNS are drained into lymphatic drainage system
-facilitates communication between brain and lymphatic chain