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

lec 2 - nervous system histology Flashcards

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
Q

Epineurium:

A

around entire nerves

Epineurium wraps one entire nerve (e.g., epineurium surrounds the femoral nerve)

loose CT layers

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26
Q

Neuroglia in the CNS only:

A

astrocytes
ependymal cells
microglia
oligodendrocytes

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27
Q

Astrocytes:

A

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)

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28
Q

___ create a regulated microenvironment for neuronal cell bodies, synapses, and capillaries in the CNS

A

astrocytes

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29
Q

Ependymal cells:

A

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

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30
Q

Microglia:

A

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

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31
Q

___ are the only glial cell derived from mesoderm.

A

Microglia

32
Q

Oligodendrocytes:

A

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
Q

Cells in gray matter:

A

Neuronal cell bodies and dendrites (most abundant)

Astrocytes

Microglia

34
Q

Cells in white matter:

A

Neuronal axons (most abundant)
Oligodendrocytes (most abundant)
Astrocytes
Microglia

35
Q

spinal cord - gray matter =

A

Composed of neuronal cell bodies

Divided into dorsal, ventral, and lateral horns (T1-L2, S2-S4)

Synapses happen here

36
Q

spinal cord - white matter =

A

Composed of neuronal axons

Divided into dorsal, ventral, and lateral columns

37
Q

Spinal cord enlargements

A

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
Q

___ line the central canal of the spinal cord

A

Ependymal cells

> Ciliated simple cuboidal to columnar epithelium

39
Q

cerebellum gray/white matter =

A

Gray matter: external
> Cerebellar cortex (3 layers)

White matter: internal
> cerebellar medulla

40
Q

From superficial to deep, the cerebellar cortex is composed of:

A

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
Q

cerebrum gray/white matter =

A

Gray Matter: external
> Cerebral cortex (6 layers)

White Matter: internal

42
Q

From superficial to deep, the layers of the cerebral cortex:

A

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
Q

Molecular/Plexiform layer (layer I):

A

> most superficial layer
composed predominantly of processes of neurons from deeper layers and their synapses (lots of dendrites from pyramidal and fusiform cells)

44
Q

Small pyramidal/External granular layer (layer II):

A

consists primarily of stellate cells (small neurons)

45
Q

Medium pyramidal/External pyramidal layer (layer III):

A

consists primarily of pyramidal cells

46
Q

Granular/Internal granular layer (layer IV):

A

consists mainly of stellate cells and some pyramidal cells

major sensory input center of the cerebral cortex

47
Q

Large pyramidal/Internal pyramidal layer (layer V):

A

consists predominantly of pyramidal cells

most prominent in motor cortex (major motor output tracts)

48
Q

Polymorphic/Multiform layer (layer VI):

A

deepest layer, composed of fusiform cells primarily

49
Q

CNS Connective Tissue: Spinal Meninges

A

dura mater

arachnoid mater

pia mater

50
Q

Dura mater:

A

> 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
Q

Arachnoid mater:

A

> middle layer
Loose connective tissue
Arachnoid granulations/villi allow CSF to drain into dural venous sinuses

52
Q

Arachnoid trabeculae =

A

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
Q

Pia mater:

A

> deep, delicate layer
lines the brain tissue directly
goes into every sulcus of the brain
loose connective tissue
Denticulate ligament
Filum terminale

54
Q

dural sac =

A

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
Q

denticulate ligament =

A

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
Q

filum terminale =

A

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
Q

filum terminale internus =

A

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
Q

Spaces within spinal meninges:

A

epidural space
subdural space
aubarachnoid space

59
Q

Epidural space:

A

> 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
Q

spinal meninges vs cranial meninges:
epidural space

A

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
Q

Subdural space:

A

> (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
Q

Subarachnoid space:

A

> 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
Q

Lumbar punctures (spinal taps) =

A

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
Q

There are several layers of skin, connective tissue, and bone that are superficial to the dura mater

From superficial to deep:

A

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
Q

The dura mater in the skull separates into 2 distinct layers

A

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
Q

Ventricular System

A

> Lateral ventricles
Interventricular foramina (of Monro)
3rd ventricle
Cerebral aqueduct (of Sylvius)
4th ventricle

67
Q

Lateral ventricles

A

> 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
Q

Ventricles =

A

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
Q

Interventricular foramina (of Monro)

A

Connects each lateral ventricle to 3rd ventricle

70
Q

3rd ventricle

A

The 3rd ventricle is located in the region of the diencephalon, between the 2 thalami

The 3rd ventricle is a single, midline structure

71
Q

Cerebral aqueduct (of Sylvius)

A

Courses through midbrain and connects 3rd and 4th ventricles

72
Q

4th ventricle

A

The 4th ventricle is located in the pons and medulla

leads down to the central canal of the spinal cord

73
Q

Median and lateral apertures are in 4th ventricles

A

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
Q

Once in the subarachnoid space, CSF enters arachnoid granulations, then drains into ___

A

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
Q

Choroid Plexus

A

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
Q

The typical total CSF volume in adults is about ___

A

150cc

CSF is produced by the choroid plexus at a rate of 20cc/hour (500cc/day)

77
Q

Blood Brain Barrier (BBB)

A

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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