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Neuroscience - spring 2024 > lec 2 - nervous system histology > Flashcards

lec 2 - nervous system histology Flashcards

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1
Q

Cells of the Nervous System

A

Neurons

Neuroglia/Glia/Glial cells

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2
Q

Neurons =

A

Excitable cells, capable of carrying electrical signals

Functional unit of the nervous system

use property of excitability to produce and move an action potential (nerve impulse) along an axon to excite another neuron or a different type of effector cell (e.g., skeletal muscle)

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3
Q

neuron communication

A

> occurs via synapses

> neurotransmitters are released at the presynaptic membrane and bind to receptors on the postsynaptic cell

> initiates a new action potential at the postsynaptic cell

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4
Q

Neuroglia/Glia/Glial cells =

A

Supporting cells of the nervous system

Non-conducting cells of the nervous system

Glial cells are essential cells of the nervous system that support neurons

There are six major types of glial cells
> ependymal cells
> oligodendrocytes
> satellite cells
> astrocytes
> microglia
> schwann cells

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5
Q

Neuronal Structure

A

dendrites
cell body/ soma/ perikaryon
axon
axon terminal

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6
Q

Dendrites:

A

receive information

numerous extensions off the cell body

specialized to receive stimuli from other neurons at synapses

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7
Q

Cell body/Soma/Perikaryon:

A

processes and integrates information

Contains nucleus and other organelles

Nissl substance/body: dark-staining portions of the cell body formed by ribosomes on the rough endoplasmic reticulum and free ribosomes

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8
Q

Axon:

A

transmits action potentials

single long process that extends from the cell body and reaches other cells (e.g., other neurons, muscle cells, etc.)

specialized to generate and conduct nerve impulses (action potentials) to other cells

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9
Q

Axon terminal:

A

site of synapse with other cells and neurotransmitter release into the synaptic cleft

site of synapse of neurotransmitter release

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10
Q

Various types of synapses can occur, but the most common is ___, in which an axon of one neuron synapses on a dendrite of another neuron

A

axodendritic

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11
Q

Axonal cell bodies =

A

contain a large euchromatic nucleus with a prominent nucleolus and surrounding cytoplasm

cytoplasm reveals abundant rough ER (rER) and free ribosomes

ribosomes on the rER and the free ribosomes appear as small bodies called Nissl bodies/substance that stain intensely with basic dyes and metachromatically with thionine dyes

each Nissl body corresponds to a stack of rER

cytoplasm also contains mitochondria, Golgi apparatus, lysosomes, microtubules, neurofilaments, transport vesicles

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12
Q

Neuron types

A

multipolar neurons
bipolar neurons
pseudounipolar neurons

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13
Q

Multipolar neurons:

A

motor neurons and interneurons

multiple dendrites extending from cell body

single axon

most common neurons

carry somatic and visceral motor output from the ventral and lateral horns to skeletal and smooth or cardiac muscle, respectively.

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14
Q

Interneurons =

A

multipolar neurons that help integrate information

allow information to cross from one side of the spinal cord to the other side of the spinal cord

allow information to travel up and down the spinal cord)

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15
Q

Bipolar neurons:

A

special sensory neurons

Single dendrite extending from cell body

Single axon

neurons carry special sensations (sight/vision, smell/olfaction, hearing/audition, balance/equilibrium)

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16
Q

Pseudounipolar neurons:

A

general sensory neurons

Peripheral process with dendrites in periphery

Central process relaying into CNS

single axon that bifurcates close to the cell body into a peripheral process that goes to the body periphery and has dendrites at its end and a central process that enters the CNS

carry all general sensations (touch, temperature, proprioception, vibration, pressure, pain, etc.) from the entire body

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17
Q

Neuroglia in the PNS only:

A

Satellite cells = Located in peripheral ganglia

Schwann cells/ Neurolemmocytes/ Mantle cells = Located in peripheral nerves and peripheral ganglia

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18
Q

Functions of Satellite Cells

A

electrically insulates PNS cell bodies

Regulates nutrient and waste exchange for cell bodies in ganglia

also called mantle cells

they are modified Schwann cells that surround the cell body of neurons in PNS ganglia

provide anchoring and support to the cell body and help control the chemical environment (regulate microenvironment of PNS ganglia)

Derived from neuroectoderm, specifically, the neural crest

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19
Q

Functions of Neurlemmocyte/Schwann cells

A

surround and insulate PNS axons and myelinate those hacing large diameters

allows for faster propagation along an axon in the PNS

create the myelin sheath in the PNS

Injured in Guillain-Barre syndrome

One Schwann cell can only wrap the axon of one neuron

Derived from neuroectoderm, specifically, the neural crest

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20
Q

Connective Tissue in the PNS

A

myelin sheath
endoneurium
perineurium
epineurium

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21
Q

Myelin sheath:

A

around axons

Formed by Schwann cells in PNS
Formed by oligodendrocytes in CNS

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22
Q

Nodes of Ranvier:

A

gaps in the myelin sheath, allowing for Saltatory conduction

where voltage gated ion channels are located on the axon

allow for faster conduction of action potentials (saltatory conduction, where conduction of action potentials occurs from node to node)

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23
Q

Endoneurium:

A

wraps around individual nerve fibers

just superficial to the myelin sheath

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24
Q

Perineurium:

A

Perineurium wraps around groups of nerve fibers

A group of nerve fibers is called a fascicle, thus perineurium wraps around fascicles

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25
Epineurium:
around entire nerves Epineurium wraps one entire nerve (e.g., epineurium surrounds the femoral nerve) loose CT layers
26
Neuroglia in the CNS only:
astrocytes ependymal cells microglia oligodendrocytes
27
Astrocytes:
in white and gray matter and at blood-brain-barrier most abundant glial in CNS = most common glial cells in the CNS and may also be called macroglia derived from neuroectoderm, specifically, the neural tube provide physical and structural support, repair processes > perform phagocytosis of non-functioning synapses > scar formation in the CNS after cerebral infarction > maintain a constant internal milieu in the CNS > extracellular potassium buffer > remove excess neurotransmitters > glycogen fuel reserve buffer = responsive gliosis after neural injury)
28
___ create a regulated microenvironment for neuronal cell bodies, synapses, and capillaries in the CNS
astrocytes
29
Ependymal cells:
in brain ventricles and central canal of spinal cord ciliated simple cuboidal to columnar cells apical surfaces of ependymal cells are lined by cilia, which help circulate cerebrospinal fluid (CSF) Specialized ependymal cells in the choroid plexus produce CSF Derived from neuroectoderm, specifically, the neural tube
30
Microglia:
evenly distributed in gray and white matter phagocytic scavenger cells of the CNS activated in response to tissue damage specialized cells for phagocytosis and antigen processing (i.e., they are brain macrophages, part of the mononuclear phagocyte system) secrete cytokines and growth factors mediate immune defense activity within the CNS
31
___ are the only glial cell derived from mesoderm.
Microglia
32
Oligodendrocytes:
surround CNS axons and are predominantly in white matter create the myelin sheath in the CNS one oligodendrocyte wraps and creates the myelin sheath around multiple axons damaged in multiple sclerosis Derived from neuroectoderm, specifically, the neural tube
33
Cells in gray matter:
Neuronal cell bodies and dendrites (most abundant) Astrocytes Microglia
34
Cells in white matter:
Neuronal axons (most abundant) Oligodendrocytes (most abundant) Astrocytes Microglia
35
spinal cord - gray matter =
Composed of neuronal cell bodies Divided into dorsal, ventral, and lateral horns (T1-L2, S2-S4) Synapses happen here
36
spinal cord - white matter =
Composed of neuronal axons Divided into dorsal, ventral, and lateral columns
37
Spinal cord enlargements
The spinal cord widens and increases in gray matter volume to accommodate the neuronal cell bodies controlling the upper and lower limbs Cervical enlargement Lumbar enlargement
38
___ line the central canal of the spinal cord
Ependymal cells > Ciliated simple cuboidal to columnar epithelium
39
cerebellum gray/white matter =
Gray matter: external > Cerebellar cortex (3 layers) White matter: internal > cerebellar medulla
40
From superficial to deep, the cerebellar cortex is composed of:
Molecular layer: consists of unmyelinated granule cell axons, Purkinje cell dendrites, and interneurons. Purkinje layer: contains large Purkinje neurons, which are a type of multipolar neuron that receive impulses from the granular cells, which is important for controlling motor movement Granular layer: tightly packed with small granule cells (granule neuron cell bodies) > in contact with the cerebellar medulla
41
cerebrum gray/white matter =
Gray Matter: external > Cerebral cortex (6 layers) White Matter: internal
42
From superficial to deep, the layers of the cerebral cortex:
Molecular (plexiform) layer Small pyramidal (external granular) layer Medium pyramidal (external pyramidal) layer Granular (internal granular) layer Large pyramidal (internal pyramidal) layer Polymorphic (multiform) layer
43
Molecular/Plexiform layer (layer I):
>most superficial layer > composed predominantly of processes of neurons from deeper layers and their synapses (lots of dendrites from pyramidal and fusiform cells)
44
Small pyramidal/External granular layer (layer II):
consists primarily of stellate cells (small neurons)
45
Medium pyramidal/External pyramidal layer (layer III):
consists primarily of pyramidal cells
46
Granular/Internal granular layer (layer IV):
consists mainly of stellate cells and some pyramidal cells major sensory input center of the cerebral cortex
47
Large pyramidal/Internal pyramidal layer (layer V):
consists predominantly of pyramidal cells most prominent in motor cortex (major motor output tracts)
48
Polymorphic/Multiform layer (layer VI):
deepest layer, composed of fusiform cells primarily
49
CNS Connective Tissue: Spinal Meninges
dura mater arachnoid mater pia mater
50
Dura mater:
> tough outer covering > Dense irregular connective tissue > Dural/Thecal sac: from C1 to S2 vertebral levels Composed of 2 layers: > Periosteal layer: superficial > Meningeal layer: deeper
51
Arachnoid mater:
> middle layer > Loose connective tissue > Arachnoid granulations/villi allow CSF to drain into dural venous sinuses
52
Arachnoid trabeculae =
form as fibers that connect deeper down to the pia mater span from the arachnoid mater to pia mater = located in the subarachnoid space Arachnoid granulations occur as outpocketings of the arachnoid mater and subarachnoid space that project into the dural venous sinuses > important for allowing CSF (which fills the subarachnoid space) to drain into the dural venous sinuses
53
Pia mater:
> deep, delicate layer > lines the brain tissue directly > goes into every sulcus of the brain > loose connective tissue > Denticulate ligament > Filum terminale
54
dural sac =
surrounds the spinal cord and contains the spinal cord and cerebrospinal fluid (CSF) ends at the level of the 2nd sacral vertebra CSF ends at the S2 vertebra as well
55
denticulate ligament =
forms as lateral extensions of pia mater that attach into the arachnoid and dura mater provide lateral support/anchoring for the spinal cord and separate the ventral and dorsal rootlets
56
filum terminale =
forms as pia mater collapses off the cauda equina of the spinal cord provides longitudinal/vertical support/anchoring for the spinal cord by attaching to the coccyx travels with the cauda equina appear more white (like connective tissue) and will extend off the very tip of the conus medullaris
57
filum terminale internus =
part of the filum terminale that is still within the dural sac dural sac ends at the S2 vertebral level, yet the filum terminale internus continues and becomes the filum terminale externus after it leaves the dural sac filum terminale externus is continuous with the filum terminale internus and becomes the externus after the dural sac ends and the arachnoid and dura mater collapse onto it
58
Spaces within spinal meninges:
epidural space subdural space aubarachnoid space
59
Epidural space:
> between dura and vertebral column > contains fat, blood vessels, and lymphatic vessels > between the dura mater and the periosteum of the vertebral canal, superficial to dura mater > filled with loose connective and adipose tissue as well as vasculature
60
spinal meninges vs cranial meninges: epidural space
In the spinal meninges, the epidural space is a fat-filled space that contains arteries, veins, and lymphatic vessels In the cranial meninges, the epidural space is a potential space between the periosteal layer of dura mater and the skull The epidural space in the skull is only filled when there is a pathology (e.g., epidural hematoma)
61
Subdural space:
> (not visible) > between dura and arachnoid > potential space (only filled with a pathology) The subdural space is a potential space in the cranial and spinal meninges
62
Subarachnoid space:
> between arachnoid and pia > Contains CSF The subarachnoid space is a space between the arachnoid and pia mater that contains CSF in both the spinal and cranial meninges
63
Lumbar punctures (spinal taps) =
performed to draw CSF from the subarachnoid space in order to diagnose various disorders (meningitis, encephalitis, cancer, etc.) usually performed between L4 and L5 vertebrae.
64
There are several layers of skin, connective tissue, and bone that are superficial to the dura mater From superficial to deep:
skin (epidermis and dermis) subcutaneous connective tissue epicranial aponeurosis loose connective tissue periosteum bone dura mater, periosteal layer dura mater, meningeal layer arachnoid mater subarachnoid space pia mater brain tissue
65
The dura mater in the skull separates into 2 distinct layers
periosteal dura = layer that is applied to the bones of the skull meningeal dura = more internal aspect that is in contact with the arachnoid mater
66
Ventricular System
> Lateral ventricles > Interventricular foramina (of Monro) > 3rd ventricle > Cerebral aqueduct (of Sylvius) > 4th ventricle
67
Lateral ventricles
> There are 2 lateral ventricles: right and left > right and left lateral ventricles are located in the right and left cerebral hemispheres > right and left lateral ventricles do not communicate with each other > each lateral ventricle drains into the 3rd ventricle via right and left interventricular foramina (of Monro)
68
Ventricles =
cavities/spaces in the brain that are filled with cerebrospinal fluid (CSF) contain and produce CSF choroid plexus is present in all ventricles of the brain, but it is most abundant in the lateral ventricles > cells of the choroid plexus produce CSF and the ependymal cells that lines the ventricles contain cilia that help transport CSF through the ventricular system
69
Interventricular foramina (of Monro)
Connects each lateral ventricle to 3rd ventricle
70
3rd ventricle
The 3rd ventricle is located in the region of the diencephalon, between the 2 thalami The 3rd ventricle is a single, midline structure
71
Cerebral aqueduct (of Sylvius)
Courses through midbrain and connects 3rd and 4th ventricles
72
4th ventricle
The 4th ventricle is located in the pons and medulla leads down to the central canal of the spinal cord
73
Median and lateral apertures are in 4th ventricles
openings in the 4th ventricle that allow CSF to leave the ventricular system and enter the subarachnoid space allow CSF to enter the subarachnoid space There is one median aperture at the midline There are two lateral apertures Median aperture = foramen of Magendie Lateral apertures = foramina of Luschka
74
Once in the subarachnoid space, CSF enters arachnoid granulations, then drains into ___
dural venous sinuses (venous filled spaces in the meninges of the skull that drain blood from the brain and skull) Blood from the dural venous sinuses drains back into the internal jugular vein
75
Choroid Plexus
ependymal cells line the ventricles of the brain and the central canal of the spinal cord formed by specialized ependymal cells and vascularized pia mater that secrete CSF CSF is produced in the ventricles, but we need to get it into the subarachnoid space, which is accomplished via the median and lateral apertures in the fourth ventricle
76
The typical total CSF volume in adults is about ___
150cc CSF is produced by the choroid plexus at a rate of 20cc/hour (500cc/day)
77
Blood Brain Barrier (BBB)
functional barrier that allows for greater regulation over the passage of substances moving from the blood into CNS tissue compared to other tissues in the body The main components of the BBB include: > tight junctions of capillary endothelium > basement membrane > astrocytes (foot processes) protects neurons and glia from > bacterial toxins > infections agents > exogenous substances helps maintain stable composition and constant balance of ions in the interstitial fluid

Neuroscience - spring 2024 (10 decks)

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