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Module 8 > Cellular Anatomy of CNS > Flashcards

Cellular Anatomy of CNS Flashcards

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1
Q

what are the cells of nervous tissue

A
  1. neurons (nerve cells)
  2. neuroglia (astrocytes, oligodendrocytes, microglia)
  3. ependymal
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2
Q

what are neurons

A

comminication network

excitable

receptive to stimuli

conduct impulses

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3
Q

what are neuroglia

A

supportive cells

regulate environment

help neurons function

immune function

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4
Q

what are ependymal cells

A

specialized epithelial cells

involved in CSF production

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5
Q

what are the parts of the neuron

A
  1. cell body
  2. dendrite
  3. axon
  4. axon terminal
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6
Q

what are the features of the neuron cell body

A

supply centre of neurons

contain nucleus and cytoplasmic organelles

nissi body has concentration of ribosomes for protein synthesis

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7
Q

what are the features of dendrites

A

processes that ramify from the other cell body

provide large surface area for contact with other neurons

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8
Q

wgat are axons

A

a prominent dendrite extends from the cell body

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9
Q

what are the axon terminals

A

point of synapse

contact with other neurons

communicate by chemicals

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10
Q

what are the morphological variations of neurons

A
  1. multipolar
  2. bipolar
  3. unipolar
  4. pseudounipolar
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11
Q

what are mutlipolar neurons

A

several dendrites

most dominate type

throughout the brain and spinal cord

single axon

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12
Q

what are bipolar neurons

A

one main dendrite receiving stimuli

one axon delivering impulse to target site

olfactory, inner ear and retinal

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13
Q

what are unipolar neurons

A

sensory neurons

short extension from cell body

one dendrite and one axon

fused together

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14
Q

what are pseudounipolar neurons

A

begin as bipolar and fuse with development to give the unipolar neuron

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15
Q

what are the functional classification of neurons

A
  1. sensory or afferent neurons
  2. motor or efferent
  3. interneurons
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16
Q

what are sensory or afferent neurons

A

receive sensory input directly (dendrites) or from adjacent cells

conveys sensory stimuli as impulse (action potential) to the CNS via cranial or spinal nerves

mostly unipolar

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17
Q

what are motor or efferent neurons

A

convey impulse from CNS to target (muscle, glands) via cranial or spinal nerves

mostly multipolar

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18
Q

what are interneurons

A

located with CNS

connection between sensory and motor

mostly multipolar

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19
Q

what are olfactory cells

A

detect odour on chemical receptors on bipolar neurons

chemoreceptors are located on cilia that project from dendrites

cilia covered by mucs from supporting cells and olfactory glands

required to solubilize the odour for receptor association

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20
Q

what are the types of sensory neurons

A
  1. meissners corpuscles: touch receptor, mass of dendrite ending
  2. merkel: touch, free nerve endings
  3. pacinian: pressure, laminated capsules
  4. nociceptor: pain, free nerve endings
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21
Q

what are the most abundant neuron in the CNS

A

multipolar neurons

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22
Q

what are the types of multipolar neurons

A
  1. dendritic tree
  2. purkinje neuron
  3. pyramidal neuron
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23
Q

what are dendritic tree neurons

A

pattern can vary

greatly enhances number of synapses

dendritic spine can alter and gives a level of plasticity

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24
Q

what are the features of purkinje neurons

A

found in cerebellum

controls gait

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25
what are the features of pyramidal neuron
found in cortex thought processing
26
what is a depolarizing graded potential
makes the membrane less polarized inside is less negative reduced potential difference between the inside and outside of the membrane
27
what is hyperpolarized graded potential
makes the membrane potential more polarized inside is more negative greater potential difference between inside and outside
28
what are the effects of myelin
1. insulates segments of the axons (internodes) --\> nodes of ranvier is gap between internodes, has high concentration of ion channels 2. action potential jumps (saltatory conduction) 3. greatly enhances speed of conductance 4. reduced the need for large diameter axons
29
what are the variable arrangements of neuron connections
1. simple series circuit 2. divergent series 3. convergent series 4. reverberating 5. parallel after discharge
30
what are simple series circuit
single presynaptic (before synapse) stimulates a single postsynaptic (after synapse) ex. reflex arc
31
what are divergent series
single presynaptic stimulates several post synaptic ex. nerve impulse from a single neuron can influence many spinal neurons for complex movement
32
what are convergent series
several neurons stimulate single neuron ex. a neuron that connects to a specific neuromuscular junction recieves input from many cells in the brain
33
what are reverberating circuit
feedbacks to stimulate neurons at early points in cascade thought to be involved in memory formation
34
what are parallel after discharge circuits
different number of neurons in a cascade that converge on a common neuron ex. complex cognitive processing such as math
35
what does the gray matter in the brain contain
neuronal cell bodies dendrites astrocytes neurons arranged in specific layers and form complex networks
36
what does the white matter contain
myelinated axons oligodendrocytes microglia
37
what is the spinal cord composed of
gray and white matter
38
how is the organization of the spinal cord different from the brain
white matter on outside with gray matter forming a horn
39
what does gray matter in the spinal cord contain
cell bodies and dendrites sensory neuron input (cell body in ganglion) in dorsal nerve root interneuron mediator motor output from ventral nerve root connects to ascending (sensory) and descending (motor) white matter tracks
40
how is white matter organized in the spinal cord
tracks of myelinated axons arranged into specific bundles called tracts
41
how is the PNS organized
arranged in bundles of nerve fibres nerves enclosed in 3 layers
42
what are the 3 layers that enclose nerves in the PNS
1. epineurium 2. perineurium 3. endonurium schawnn cells myelinate axons in the PNS
43
what is the epineurium
thick, tough connective tissue
44
what is the perineurium
tough CT surrounding bundle
45
what is the endonurium
loose delicate CT surrounds each axon
46
how many schawnn cells per axon
1 cell per axon
47
what are the labels
48
what are the cells that support the cells of the CNS
1. astrocytes 2. oligodendrocytes 3. microglia
49
what are astrocytes and their function
star shaped protoplasmic (gray) and fibrous (white) involved in blood brain matter and remove neurotransmitters from synaptic cleft
50
what are oligodendrocytes and their function
found mainly in white matter smaller than astrocytes produce myelin around axons
51
what are microglia
ovoid shape change morphology on activation resident immune cells, remove debris + bacteria (lipid laden macrophages gitter cells)
52
what are the structures
53
what are the important roles astrocytes play
associates with blood vessel to form barrier --\> association with pericytes to regulate gene expression reactive in many neurodegenerative disorders and extend processes produce trophic substances and can upatake glutamate and potassium can form scar tissue to block formation of neuronal tracks (spinal cord injury)
54
what is the blood brain barrier and the blood CSF barrier
CNS needs a consistent environment cannot be subjected to gross fluctuations of ionic chemical and hormonal levels energy source needs replenished and waste needs to be removed
55
what is the function of the choroid plexus
produces CSF lateral, third and 4th ventricle CSF enters subarachnoid space --\> between pia and arachnoid meninges then enters spinal canal --\> circulates around the CNS
56
what are ependymal cells of the choroid plexus
cuboidal or columnar epithelial cells line the vesicles of the brain and spinal cord ciliated to regulate CSF movement and turnover
57
what is the funciton of ependymal cells of the choroid plexus
ependymal tight junction act to filter blood CSF is clear solution
58
59
how is CSF absorbed
in arachnoidal villus into venous sinus
60
what are arachnoid villi
project into the sinus through the dura matter (grouped arachnoid villi termed arachnoid granulations)
61
what are arachnoid villi covered in
thin layer of epithelium from sinus
62
what occurs when pressure in subarachnoid space is higher than sinus
CSF moves into sinus higher pressure closes the tubules of the arachnoid villa
63
what can abnormality of arachnoid villi lead to
abnormality in regulation can lead to hydrocephalus
64
how does communication via neurotransmitters (NT) occur
synaptic cleft --\> gap between presynaptic and postsynaptic membranes APs can't jump the cleft --\> NT cause either excitatory or inhibitory gradient on postsynaptic sites
65
what are excitatory NTs
depolarizes post synaptic membranes so resting potential nearer the threshold for AP excitatory postsynaptic potential (EPSP) ex. glutamate, aspartate stimulate influx of +ve ions or efflux of -ve ions
66
what are inhibitory NTs
hyperpolarization of post synaptic membrane so resting potential further from threshold inhibitory postsynaptic potential (IPSP) GABA, glycine stimulates influx of -ve ions or efflux of +ve ions
67
what are the events at the synapse (7)
1. nerve impulse travels along axon to the presynaptic terminal 2. impulse causes depolarization that activates and opens calcium channels 3. calcium activates a series of protein events on synaptic vesicles (proteolytic and phosphorylation events) 4. synaptic vesicles fuse with membrane and release the NTs into synaptic cleft 5. Nts bind to receptors on postsynaptic membrane ion channels (dendrites) 6. initates post synaptic depolarization 7. clearance of NTs from the synaptic cleft occurs by various methods (diffusion, enzymatic breakdown, reabsorption)
68
what are ionotropic receptors
ligand binding site ligand modulates opening probablity and ion flux GABA
69
what are metabotropic receptors
has a ligand binding site couples to a G protein site production of 2nd messenger modulates ion channels alters opening probability ex. acetylcholine
70
what are the classes of neurotransmitters
1. amino acids 2. monoamines 3. soluble gases 4. acetylcholine (excitatory, inhibitory, both)
71
what are the features of glutamate
simple amino acid excitatory transmitter in CNS
72
what is NMDA
a subtype of glutamate receptor
73
what is a feature of NMDA
has a pore containing a Mg2+ binding site --\> binding block the channel and is removed following depolarization
74
what is GABA
g-aminobutyric acid inhibitory NT
75
how is GABA generated
by conversion of glutamate by GAD
76
what are the two types of receptors
1. GABA A: ionotropic, located post synaptically and permeable to Cl- ions 2. GABA B: metabotropic, located pre and post synaptically and modulated calcium and potassium channels
77
what are biogenic amines
removal of carboxy groups of certain amino acids generate biogenic amines most act via metabotropic receptors
78
what is a class of biogenic amines
catecholamines norepinephrine, epinephrine, dopamine
79
what are the receptors of acetylcholine
ionotropic (nicotine) and metabotropic (muscarinic) mainly excitatory
80
what are purines
ATP and adenosines ATP acts on P2 ionotropic receptors and can be excitatory adenosines: A1-3 receptors
81
what is nitric oxide
lipid soluble free radical no receptor, passes membrane by diffusions influences blood pressure
82
what are neuropeptides
G-protein coupled receptors powerful analgesics

Module 8 (43 decks)

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