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Neuroanatomy Exam 1 > Neurohistology > Flashcards

Neurohistology Flashcards

1
Q

Neuron

A

Nerve cell
The basic structural unit of the nervous system
Excitable and irritable

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2
Q

Cell body

A 
Spherical, ovoid or angular in shape
Trophic metabolic center of the cell
Receptve area of multipolar neurons
Most protein synthesis occurs in cell body
Sustains the cell
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3
Q

Organelles

A

Golgi Apparatus, mitochondira…

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4
Q

Cytoplasm

A

filled with basophilic clumps

Nissl bodies = stacks of RER

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5
Q

Nucleus

A

large, clear, euchromatic; encloses a spherical nucleolus

In adult –> no mitosis

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6
Q

Neurons and mitosis

A

in general neurons do not divide but in adult there may be some neural stem cells that can regenerate

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7
Q

Neurofilaments

A

contractile

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8
Q

Microtubules

A

form cytoskeleton, and tunnels for vesicle transport

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9
Q

Lipfuscin

A

yellowish-brown pigment
is lysosomal enzymatic residue
Cellular debris

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10
Q

Melanin granules

A

pigment present in certain neurons (substantia nigra)

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11
Q

Axon hillock

A

origin of axon, funnel shapedm no RER so is pale staining

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12
Q

most common type of neuron

A

multipolar neuron

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13
Q

Dendrites

A

radiate from soma
branch and taper
increase receptive area of neuron
like antennas that receive stimuli from receptors or other neurons
Multipolar neurons transmit information to cell body

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14
Q

Axon

A

cylindrical, variable in length
contains organelles
relays action potentials away from cell body to the axon terminal and then transmit them to other neurons, smooth or skeletal muscle cells, or gland cells

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15
Q

Initial Segment of Axon

A

Segment of axon distal to the axon hillock and proximal to where myelination begins
has numerous types of ion channels
AP is initiated here
in PNS following an injury, the proximal axon will regenerate whereas the distal axon that is disconnected from the cell body will degenerate

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16
Q

Terminal arborizations

A

terminal axonal branches

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17
Q

Terminal buttons

A

axon terminals
dilated ends of arborizatons
form synapses
some local protein synthesis occurs here

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18
Q

Axoplasmis transport

A

of macromolecules, organelles, vesicles

antero and retrograde

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19
Q

Anterograde

A

away from cell body

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20
Q

retrograde

A

towards cell body

Viruses and toxins that enter nerve endings travel to the CNS via retrograde transport

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21
Q

Anatomical classification of neurons

A

bipolar
unipolar
multipolar

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22
Q

Bipolar

A 
2 processes ( a peripheral process, the dentrite, and a central process, the axon)
Located in the retina and inner ear
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23
Q

Multipolar

A

numerous dendrites and a single axon, most common type of neuron

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24
Q

Unipolar

A

pseudounipolar
single process arising from cell body which then bifurcates into 2 processes and is t shaped
impulses are transmitted down the axon, bypassing the cell body
Located in sensory ganglia

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25
Functional classification of neurons
Motor Sensory Interneurons
26
Motor neurons
Efferent multipolar Skeletal motor = skeletal muscle fibers Visceral motor = smooth muscle, cardiac muscle or glands, autonomic
27
Sensory neurons
Afferent | receive sensory stimuli from the environment or from within the body
28
Interneurons
confined to CNS 99.9% of neurons multipolar
29
Synapses
1. Presynaptic Terminal 2. Synaptic Cleft 3. Postsynaptic Terminal 4. Types of synapses
30
Presynaptic terminal
synaptic vesicles, NTs | Presynaptic membrane
31
Synaptic cleft
space
32
Postsynaptic terminal
postsynaptic membrane | NT receptors
33
Types of synapses
axodendritic (common) axosomatic (common) axoaxonic dendrodendritic (electrical)
34
A synapse is a
junction between a neuron and a neuron, muscle cell, or gland cell It is the site where an AP is transmitted fromc ell to cell
35
Types of synapses (2)
Electrcal and chemical
36
Electrial Synapses
not common in mammals in cerebral cortex, brainstem, and retina have gap junctions impulse transmitted is rapid
37
Chemical synapses
most common type | associated with NTs
38
Neuroglia
``` provide both physical and physiological support protecting nerve cells more numerous than neurons 3-4 neuroglial cells for each neuron They do NOT conduct inpulses they CAN divide therefore form tumors ```
39
Astrocytes
exhibit processes with vascular feet that cover capillaries they use the feet too assist in formation of the BBB They moniotr ionic and chemical composition in extracellular space around nerve cells involved in tissue repair and form scar tissue folloowing nerve injury
40
Fibrous astrocytomas
make up about 80% of primary brain tumors in adults
41
Oligodendrocytes
each oligio myelinates one, or more than one axon | myelinate in CNS
42
Microglia
present in both gray and white matter and are phagocytic (CNS housekeepers)
43
Ependymal cells
line the ventricles of the brain and central canal of the spinal cord
44
Ependymoma
tumor growing into the fourth ventricle Compresses surrounding structures as it expands 5% of primary brain tumors
45
Nerve Fiber
A nerve is like a cable | a cable contains wires whereas a nerve contains axons
46
Unmyelinated axons are found in the
CNS and PNS
47
In the CNS unmyelinated axons
are not covered by glia (birthday suit)
48
In the PNS unmyelinated axons
no myelin sheath but are surrounded by schwann cells each axon occupies a groove of a schwann cell One schwann cell envelops many axons Schwann cells form a longitudinal uninterupted sheath along the length of the axon
49
Myelinated axons are present in
both CNS and PNS
50
Myelinated axons in the CNS are myelinated by
oligodenrocytes
51
Myelinated axons in the PNS are myelinated by
Schwann cells
52
Myelin
80% lipids lipprotein that is formed by concentric layers of cell membranes which have a high lipid content Myelin increases impulse conduction and insualtes the neurons NOT a substance that is secreted on the axon by a cell
53
Internodal Segment
insulated (myelinated) segments of axon
54
Nodes of Ranvier
uninsulated segments of axon
55
In PNS schwann cells
wrap their membrane repeatedly around one itnernode of a single axon forming the myelin sheath Each myelinated axon is covered by a series of schwannc ells
56
Guillain Barre Syndrome
the axons within a peripheral nerve are stripped of myelin
57
Schwannoma
a tumor in the PNS derived from schwann cells
58
Peripheral nerve covereings are associated with
nerves in the PNS only!
59
WHat are the peripheral nerve coverings>
``` Endoneurium = individual axons Perineurium = bundle of axons Epineurium = fibrous coat that covers several bundles which together make the gross nerve ```
60
A myelinated nerve cell axon in the PNS is covered by
1. myelin sheath (inner layer next to axon) 2. A basal lamina (middle layer) 3. Endoneurium (outer layer)
61
Receptors
scattered throughout the body at the peripheral terminals of sensory neurons They respons to mechanical stimuli and convert them into electrical impulses Named according to location in body and type of func that they carry or the stimulus they respond to
62
Exteroreceptors
close to body surface | olfactory, visual, taste, auditory, tactile
63
Proprioceptors
position sense in skin, muscles, tendons, ligaments, joint capsules, vestibular apparatus
64
Interoreceptors
detect stretch, BP, pH, O2 conc, Co2 conc, osmolarity
65
Nocireceptors
respond to noxious stimuli
66
Therorecetors
respond to temperature
67
Mechanoreceptors
respond to mechanical deformation
68
Chemoreceptros
for smell, taste
69
Photoreceptors
in retina
70
Extrafusal fibers
typical skeletal muscle cells contract to produce movement when they are stimulated motor innervation via alpha motor neurons Sensory innervation via pseudounipolar neuron endings
71
Muscle Spindles are
specialized mechanoreceptors unique to skeletal muscle that monitor muscle length They are oriented parallel to the longitudinal axis of the extrafusal muscle fibers
72
Structure of muscle spindle
Each muscle spindle is covered by a fibrous capsule and encloses 2-12 intrafusal fibers each of which is covered by a capsule
73
2 types of intrafusal fibers
1. Nuclear bag fibers | 2. Nuclear chain fibers
74
Nuclear Bag Fibers
have a noncontractile region with nuclei and a skeletal muscle contractile portion with myofibrils Static = sens to changes in muscle length Dynamic = sens to rate of change of muscle length
75
Nuclear chain fibers
have a noncontractile region with nuclei and a skeletal muscle contractile portion with myofibrils Mostly sensitive to changes in muscle length
76
Innervation of intrafusal fibers
Both sensory and motor innervation
77
Sensory innervation of intrafusal fibers
via annulospiral endings - become activated at the onset of msucle stretch or tension Via flower spray - become activated when stretch is in progress
78
Motor innervation of intrafusal fibers
via gamma motor neurons
79
Golgi Tendon Organ
1. Located where muscle inserts into tendon 2. Arranged in series 3. No contractile portion, no motor innervation 4. Monitor the amount of tension placed on a skeletal muscle
80
Retrograde reaction and regeneration (PNS)
proximal to site of injury 1. Chroatolysis (cell body swells, loss of nissl bodies, nucleus moves away from center of cell body) 2. Formation of free ribosomes, protein synthesis 3. Axon growns sprouts 4. Schwann cells guide axon growth downward toward target cell 5. growing axon grwos into endoneurium
81
Anterogrand changres (PNS)
distal to the site of injury (completely disconnected from cell body) 1 segment of axon distal to injury degenerates (wallerian degeneration) 2. Phagocytic cells derived from schwann cells and macrophages clean up debris 3. Schwann cells proliferate and along with external lamina they form tubes/tunnels to guide the axon sprouts to their targets

Neuroanatomy Exam 1 (9 decks)

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