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Nervous System Flashcards

1
Q

Meninges

A

Brian and spinal cord and the roots of peripheral nerves are enveloped by a series of connective tissue sheaths:
Dura mater: outermost (attached to skull)
Arachnoid: membrane attached to dura mater
subarachnoid space: contains CSF
pia mater: highly vascular, adherent to brain and spinal cord
Leptomeninges: Arachnoid + Pia Mater

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2
Q

Brain Divisions (embryonic)

A

Forebrain (telencephalon, diencephalon)
Midbrain (Mesencephalon)
Hindbrain (metencephalon, myelencephalon)

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3
Q

Forbrain

A

Cerebrum, Basal nuclei, Hippocampus, Amygdala

Thalamus and hypothalamus

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4
Q

Midbrain

A

Midbrain

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5
Q

Hindbrain

A

Pons and cerebellum

Medulla oblongata

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6
Q

CNS cells

A

Astrocytes, Oligodendroglia, Microglial Cells, Ependymal Cells

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7
Q

PNS cells

A

Schwann Cells

Satellite Cells

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8
Q

White Matter

A

Formed by dense accumulations of myelinated axons. The myelin sheath is rich in lipids and has a white appearance

Contains myelinated axons and glial cells, blood vessels. Peripheral in spinal cord, central in brain

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9
Q

Grey Matter

A

Rich in neuronal cell bodies, glial cells, and neuropil. The neuropil represents the axons, dendrites and cytoplasmic projections of glial cells that form the background matrix to neuronal cell bodies within the grey matter

Contains neurons, glial cells, and axons, blood vessels. Peripheral in brain, central in spinal cord

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10
Q

CNS: ectodermal origin

A

Sensitive to hypoxia: neurons, astrocytes, oligodendrocytes

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11
Q

CNS: Mesodermal origin

A

Not as sensitive to hypoxia: Microglia, vascular endothelium

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12
Q

Neurons

A

The functional cells of the nervous system in which two protoplasmic properties are highly developed:
Irritability (generation of an impulse) and
Conductivity (ability to transmit such an impulse from one locality to another
Neurons are dispersed throughout the CNS and grouped in specific areas in PNS

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13
Q

Neurons Structure

A

Cell body/perikaryon/soma

The cell body of the neuron contains the nucleus and the organelles. The axon and the dendrites branch off the cell body

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14
Q

Neuron Soma Structure

A

Euchromatic nucleus with prominent nucleolus
Basophilic cytoplasm = Nissl substance: RER and ribosomes
They are long living cells -> aging pigment=lipofuscin

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15
Q

Synapses

A

Specialized junctions with other cells that are along the length or at the end of an axon
Act as transmission points for electrical impulses
Can trigger the generation of an action potential in the postsynaptic cell; they can be excitatory or inhibitory
Synapses at end of an axon or axon branches are swollen into a club shape (boutons terminaux)
Those along the length of axon result in varicosities (swellings) in the axon (boutons en passant)

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16
Q

Synaptic Knob Structure

A 
Presynaptic part= termination of axon
Intersynaptic cleft
Postsynaptic part (dendritic thorn)
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17
Q

Synaptic Vesicles

A

Contain different types of neurotransmitters (Ach, Noradrenaline, and adrenaline, GABA, Dopamine, etc)

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18
Q

Neurons Synapse with:

A

Neuron
Muscle
Gland

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19
Q

Stimulatory Synsapse

A

Synaptic vesicles contain ACh

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20
Q

Inhibitory Synapse

A

Synaptic oval vesicles contain GABA

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21
Q

Oligodendrocytes

A

Provide support and the myelin sheath to axons within the CNS
Unlike schwann cells (PNS), these can form myelin sheaths for several axons at once (octopus)
Produce and can repair myelin sheath
Small dark nuclei (between myelin sheaths or around neurons)
Can be destroyed by viruses/toxins resulting in primary demyelination

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22
Q

Microglia

A

Private security system of CNS- CNS is very particular
Functions: Immunosurveillance, Immunoregulation, Reparative (phagocytic), Gitter cells (myelophages)
Derived from blood-borne monocyte
Resident macrophage of CNS

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23
Q

Gitter Cells

A

Microglial cells that are activated during necrosis or inflammation -> globular and swollen after having phagocytized debris from injured cells
Note the cytoplasmic vacuolation due to ingestion of cellular debris (foamy cytoplasm)

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24
Q

Astrocytes

A

Star shaped
CNS counterpart of the fibroblast
Involved in cell communication and the functioning of the BBB
2 types: protoplasmic (grey matter) and fibrillar (white matter)
Glial fibrillary acidic protein staining

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25
Astrocytes Functions
Transport of nutrients Part of BBB Antigen presentation
26
Ependymal Cells
Form an epithelium that lines ventricular cavities within the brain and the central canal of the spinal cord The cells are typically cuboidal or columnar with numerous motile cilia on their apical surfaces Central canal ependymal cells have cilia to help the circulation of the CSF
27
Ependymal Cells Function
Important barrier function that protects neural tissue from potentially harmful substances by mechanisms that are still incompletely understood Have only limited regenerative capacity and this typically do not undergo mitotic proliferation
28
Ventricular System
Ependymal cells line the inside of ventricles in the CNS, which also communicates with the subarachnoid space. Both circulate CSF
29
Cerebrospinal Fluid
Produced by choroid plexus by specific modified ependymal cell Produced and must be drained away at a constant rate The total volume of CSF is formed and renewed 3x a day can be sampled for clinical examination
30
CSF: roles
Medium for filtration system -> facilitates the removal of metabolic waste from the brain and exchange of biomolecules into and out of the brain (not glucose or O2, but will do hormones, vitamins etc) Helps maintain the delicate extracellular environment required by the brain to function optimally (homeostasis) Cushions the CNS in case of impacts
31
Choroid Plexus
CSF is formed as plasma and filtered from the blood through the choroid plexus ependymal cells Produced by a mechanism that involves active secretion of Na into the ventricles, then water follows the resulting osmotic gradient The ependymal cells are joined by tight junctions so it is impermeable to large molecules One choroid plexus in each ventricle
32
Choroid Plexus: Organization
Consists of a layer of cuboidal epithelial cells surrounding a core of capillaries and loose connective tissue The epithelium is specific modified ependymal cells, that have microvilli and are linked to adjacent cells by tight junctions (unlike ependymal) These tight junctions prevent the majority of substances from crossing the cell layer into the CSF- acts as a blood-CSF barrier Folds into many villi around each capillary, creating frond-like processes that project into the ventricles The villi, along with a brush border of microvilli, greatly increases the surface area of the choroid plexus
33
CSF circulation
Being secreted by choroid plexus in lateral and fourth ventricle go from lateral ventricle to third to fourth and then to the central canal or to the subarachnoid space where it travels around the brain. some goes through arachnoid villus to be resorbed back into venous circulation
34
Blood-CSF barrier
A pair of membranes separate blood from CSF and CSF from brain tissue blood-CSF boundary at the choroid plexus is a membrane composed of the ependymal cells and tight junctions that link them. (choroid plexus capillaries are fenestrated-no tight junctions) Brain-CSF boundary is the arachnoid membrane, which envelops the surface of the brain
35
Blood-CSF Barrier functions
prevents the passage of most blood-borne substances into the brain facilitates the transport of different substances into the brain due to the distinct structural characteristics between the two barrier systems (for a number of substances, the BCSFB is the primary site of entry into brain tissue) facilitates the removal of brain metabolites and metabolic waste into blood Modulates the entry of leukocytes from blood into the CNS Choroid plexus cells secrete cytokines which recruit monocyte-derived macrophages, among other cells, to the brain-this cell trafficking has implications in normal brain homeostasis and neuroinflammatory processes
36
Cerebellum
Cortex cerebelli- grey matter 1. Molecular layer-basket cells 2. Ganglionic cell layer- Pukinje cells 3. Granular cell layer- granule cells in stratum granulosum 4. White matter core- myelinated nerve fibers All layers communicate with each other in a complex fashion Fine tuning motion and maintaining body position in space not essential to survival but then all movements will need to be consious
37
Fetal Cerebellum
``` an additional exterior cortical lamina. These cells will populate the internal granular cell layer during early postnatal development External granular cell layer molecular layer ganglionic cell layer granular cell layer ```
38
Nucleus in CNS
A cluster of neurons in the CNS, located deep within the cerebral hemispheres and brainstem, performing a common function
39
Spinal Cord
In cross sections, white matter is peripheral and gray matter is centra, assuming H shape Horizontal bar of H is central canal, which is a remnant of the lumen of the embryonic neural tube Lined with ependymal cells. The grey matter of the legs of the H forms the anterior horns,. These contain motor neurons whose axons make up the ventral roots of the spinal nerves Grey matter also forms the posterior horns (arms of H) which receive sensory fivers from neurons in the spinal ganglia (dorsal roots) Spinal cord neurons are large and multipolar, esp in the anterior horns, where large motor neurons are found Dorsal and ventral roots will come together to forma trunk
40
Functional PNS division
Somatic Nervous System | Autonomic Nervous System
41
Somatic Nervous System
a one neuron system that innervates (voluntary) skeletal muscle or somatosensory receptors of the skin, muscles and joints
42
Autonomic Nervous System
a two neuron visceral efferent system, that innervates cardiac and smooth muscle and glands. It is involuntary and has two major subdivisions: Sympathetic (thoracolumbar) Parasympathetic (craniosacral)
43
Nerves
collection of axons/dendrites outside CNS consist of axons, dendrites, blood vessels, glial cells, and conective tissue investments Endoneurium, perineurium, epineurium. cells present in a nerve: endothelial cells, fibroblasts, schwann cells
44
Ganglia
Collections of Neuronal cell bodies and processes found outside the CNS Cells of a ganglion: neurons, neuroglial cells, amphicytes Schwann cells, endothelial cells. Axons are also present Two types of ganglia: sensory (craniospinal), autonomic
45
Satellite glial cells
(amphicytes) surround the neurosomas in ganglia of PNS provide electrical insulation around the soma regulate the chemical environment of the neurons
46
Schwann Cells
Envelope nerve fibers in PNS Wind repeatedly around a nerve fiber produces a myeline sheath similar to the ones produced by oligodendocytes in CNS Assist in the regeneration of damaged fibers
47
Schwann cells: Myeline sheath
AN insulating layer around a nerve formed by oligodendrocytes in CNS and schwann in PNS consists of the plasma membran of glial cells 20% protein, 80% lipid
48
Schwann cells: myelination
Production of the myelin sheath begins the 14th week of fetal development proceeds rapidly during infancy completed in late adolescence dietary fat is important to nervous system development
49
Myenteric Plexus
Situated between the inner and outer longitudinal layers of the tunica muscularis This structure helps to control peristaltic movement of the GI tract
50
Group or cluster of neurons in PNS called
Ganglion
51
Regarding Microglia
They have a reparative role through phagocytosis
52
What is contained in the area enclosed by the circle
Myelinated axons
53
Which is a cell of the PNS
Schwann cell
54
CSF produced by___
Choroid Plexus
55
Cytoplasmic projections of glial cells
are part of the neuropil
56
CT surrounding whole nerve is ___
epineurium
57
Regarding CSF
Filtered from plasma, acts as cushion, can be sampled for clinical evaluation
58
Large neuronal bodies within the ganglionic layer known as?
Purkinje Cells
59
Medulla Oblongata Nucleus
Nuclei are aggregates of neuronal cell bodies
60
Identify some of the small nuclei in medulla oblingata
Glial support cells: astrocytes, oligodendrocyts, microglia
61
Specialized glial cell that lines the central canal?
Ependymal cells | Create, absorb, and circulate CSF
62
Ventral horn
Innervates motor
63
Doral Horn
Innervates interneurons (recieves sensory afferents)
64
Lateral horn
Innervation of the autonomic nervous system
65
Granular substance in neurons?
Nissl substance. Represents the RER and ribosomes of the neuron
66
Satellite cells
Responsible for insulation and nutrition of the neurons
67
Endoneurium
Surrounds each individual myelinated neuron (nerve fiber)
68
Perineruium
Nerve fibers bundled to form fasicle surrounded by perineurium
69
Epineurium
Bundle of fasicles forms nerve and it is surrounded by epineurium

Microanatomy (21 decks)

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