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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
Q

Functional classification of neurons

A

Motor
Sensory
Interneurons

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26
Q

Motor neurons

A

Efferent
multipolar
Skeletal motor = skeletal muscle fibers
Visceral motor = smooth muscle, cardiac muscle or glands, autonomic

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27
Q

Sensory neurons

A

Afferent

receive sensory stimuli from the environment or from within the body

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28
Q

Interneurons

A

confined to CNS
99.9% of neurons
multipolar

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29
Q

Synapses

A
  1. Presynaptic Terminal
  2. Synaptic Cleft
  3. Postsynaptic Terminal
  4. Types of synapses
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30
Q

Presynaptic terminal

A

synaptic vesicles, NTs

Presynaptic membrane

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31
Q

Synaptic cleft

A

space

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32
Q

Postsynaptic terminal

A

postsynaptic membrane

NT receptors

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33
Q

Types of synapses

A

axodendritic (common)
axosomatic (common)
axoaxonic
dendrodendritic (electrical)

34
Q

A synapse is a

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
Q

Types of synapses (2)

A

Electrcal and chemical

36
Q

Electrial Synapses

A

not common in mammals
in cerebral cortex, brainstem, and retina
have gap junctions
impulse transmitted is rapid

37
Q

Chemical synapses

A

most common type

associated with NTs

38
Q

Neuroglia

A 
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
Q

Astrocytes

A

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
Q

Fibrous astrocytomas

A

make up about 80% of primary brain tumors in adults

41
Q

Oligodendrocytes

A

each oligio myelinates one, or more than one axon

myelinate in CNS

42
Q

Microglia

A

present in both gray and white matter and are phagocytic (CNS housekeepers)

43
Q

Ependymal cells

A

line the ventricles of the brain and central canal of the spinal cord

44
Q

Ependymoma

A

tumor growing into the fourth ventricle
Compresses surrounding structures as it expands
5% of primary brain tumors

45
Q

Nerve Fiber

A

A nerve is like a cable

a cable contains wires whereas a nerve contains axons

46
Q

Unmyelinated axons are found in the

A

CNS and PNS

47
Q

In the CNS unmyelinated axons

A

are not covered by glia (birthday suit)

48
Q

In the PNS unmyelinated axons

A

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
Q

Myelinated axons are present in

A

both CNS and PNS

50
Q

Myelinated axons in the CNS are myelinated by

A

oligodenrocytes

51
Q

Myelinated axons in the PNS are myelinated by

A

Schwann cells

52
Q

Myelin

A

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
Q

Internodal Segment

A

insulated (myelinated) segments of axon

54
Q

Nodes of Ranvier

A

uninsulated segments of axon

55
Q

In PNS schwann cells

A

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
Q

Guillain Barre Syndrome

A

the axons within a peripheral nerve are stripped of myelin

57
Q

Schwannoma

A

a tumor in the PNS derived from schwann cells

58
Q

Peripheral nerve covereings are associated with

A

nerves in the PNS only!

59
Q

WHat are the peripheral nerve coverings>

A 
Endoneurium = individual axons
Perineurium = bundle of axons
Epineurium = fibrous coat that covers several bundles which together make the gross nerve
60
Q

A myelinated nerve cell axon in the PNS is covered by

A
  1. myelin sheath (inner layer next to axon)
  2. A basal lamina (middle layer)
  3. Endoneurium (outer layer)
61
Q

Receptors

A

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
Q

Exteroreceptors

A

close to body surface

olfactory, visual, taste, auditory, tactile

63
Q

Proprioceptors

A

position sense in skin, muscles, tendons, ligaments, joint capsules, vestibular apparatus

64
Q

Interoreceptors

A

detect stretch, BP, pH, O2 conc, Co2 conc, osmolarity

65
Q

Nocireceptors

A

respond to noxious stimuli

66
Q

Therorecetors

A

respond to temperature

67
Q

Mechanoreceptors

A

respond to mechanical deformation

68
Q

Chemoreceptros

A

for smell, taste

69
Q

Photoreceptors

A

in retina

70
Q

Extrafusal fibers

A

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
Q

Muscle Spindles are

A

specialized mechanoreceptors unique to skeletal muscle that monitor muscle length
They are oriented parallel to the longitudinal axis of the extrafusal muscle fibers

72
Q

Structure of muscle spindle

A

Each muscle spindle is covered by a fibrous capsule and encloses 2-12 intrafusal fibers each of which is covered by a capsule

73
Q

2 types of intrafusal fibers

A
  1. Nuclear bag fibers

2. Nuclear chain fibers

74
Q

Nuclear Bag Fibers

A

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
Q

Nuclear chain fibers

A

have a noncontractile region with nuclei and a skeletal muscle contractile portion with myofibrils
Mostly sensitive to changes in muscle length

76
Q

Innervation of intrafusal fibers

A

Both sensory and motor innervation

77
Q

Sensory innervation of intrafusal fibers

A

via annulospiral endings - become activated at the onset of msucle stretch or tension
Via flower spray - become activated when stretch is in progress

78
Q

Motor innervation of intrafusal fibers

A

via gamma motor neurons

79
Q

Golgi Tendon Organ

A
  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
Q

Retrograde reaction and regeneration (PNS)

A

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
Q

Anterogrand changres (PNS)

A

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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