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OS9.1 - Neuro > Terms > Flashcards

Terms Flashcards

1
Q

Nissl body

A
  • basophilic masses, primarily rough ER and ribosomes
  • concerned with protein synthesis
  • only exist in the soma and extend into proximal dendrites but not in axon hillock or beyond
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2
Q

Neuroglia: types and locations

A

CNS: astrocytes, oligodendrocytes
PNS: Schwann cells, satellite cells

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3
Q

How many axons per neuron?

A

one

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4
Q

How many internodes are formed by one Schwann cell?

By one oligodendrocyte?

A

Schwann cell –> 1 internode

Oligodendrocyte –> many internodes, but only 1 internode per process per axon

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5
Q

Axon hillock

A

start of the axon, is free of Nissl bodies, organelles, and myelin

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6
Q

Axon initial segment

A

portion of the axon that extends from the axon hillock to the first bit of myelin; generally the site of action potential initiation

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7
Q

Axon collaterals

A

major branches of an axon

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8
Q

Pseudounipolar

A

Ex: DRG neurons; they only have one projection from the soma, but then it has 2 projection, one to the periphery and the other to central

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9
Q

Bipolar

A

2 primary neurites leaving opposite ends otf the cell

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10
Q

Multipolar

A

several primary dendrites leaving the soma

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11
Q

Silver stain

A
  • aka Golgi stain

- usually stain only a subset of neurons, but it will stain the entire neuron

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12
Q

Golgi type I cells

A
  • projection neurons, or principal cells, that integrate information and send a long axon to another brain area
  • ex: pyramidal cells
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13
Q

Golgi type II cells

A
  • interneurons that have short axons (or no axon) which don’t leave the local brain area
  • ex: chandelier, basket cells
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14
Q

Neuromuscular junction (NMJ)

A

defined as the synapse between a motoneuron and muscle; a motoneuron is a neuron whose axon contacts muscle or glands

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15
Q

Post-synaptic density

A

an electron dense part of the post-synaptic membrane which appears dense due to the many proteins present

  • excitatory = PSD is much denser than pre-synaptic density
  • inhibitory = PSD is equally dense as pre-synaptic density
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16
Q

What are the NTs and receptors for excitatory synapses?

A
  • ACh –> Nicotinic receptors

- Glutamate –> AMPA and NMDA receptors

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17
Q

What are the NTs and receptors for inhibitory synapses?

A
  • Glycine

- GABA –> GABA(a) receptors

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18
Q

What are the NTs and receptors for modulatory synapses?

A
  • DA
  • NE
  • ACh –> M receptors
  • GABA –> GABA(b) receptors
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19
Q

Gray’s type 1 and 2 synapses

A

Type 1 = excitatory synapse; post is much denser than pre; mostly found on dendrites
Type 2 = inhibitory synapse; equal density pre and post; mostly found on the soma

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20
Q

Gap junction

A
  • 6 connexins (TM protein molecule) –> 1 connexon
  • 2 connexons in each cell membrane –> pore/gap junction

Electrical synapses, since gap junctions allow for passive electrical flow, can be bi-directional

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21
Q

Engines of MT-based axonal transport

A

Dynein –> retrograde

Kinesin –> anterograde

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22
Q

Neuroglia

A
  • Schwann cells - myelin for PNS
  • Oligodendrocytes - myelin for CNS
  • Astrocytes - 2 types, general support and BBB
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23
Q

Other supporting cell types

A
  • Microglia - phagocytosis, inflammation, “CNS immune cells”
  • Satellite cells - act as astrocytes in the ANS
  • Ependymal cells - line central canal
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24
Q

Astrocytes

A
  • types: fibrous (in white matter; have perivascular feet) protoplasmic (in gray matter), and radial (in development)
  • serve to move metabolic products to/from neurons, maintain ideal ionic concentrations (by taking up excess ions/NTs)
  • contact vessels (perivascular feet for BBB), neurons (perineural feet) and myelin
  • facilitate anigiogenesis, synaptogenesis, and BBB maintenance
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25
Q

Schmidt-Lanterman cleft

A

small folds of cytoplasm that remain when the Schwann cell has squeezed most all its cytoplasm out in order to myelinate an axon

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26
Q

Endoneurim

A

thin CT that surround each nerve fiber

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27
Q

Perineurim

A

CT that surrounds a fascicle/bundle of nerves

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28
Q

What nerves are myelinated?

Unmyelinated?

A
  • myelin: vibration and motor

- no myelin: pain and temperature

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29
Q

Radial glia

A
  • a type of astrocyte
  • present mostly in development for neural migration
  • oriented on axis of pia to ventricle, perpendicular to ventricle
  • Mueller cells (retina) and Bergmann glia (cerebellum) are radial glia that persist into adulthood
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30
Q

Satellite cells

A
  • neural crest origin
  • function as astrocytes in peripheral ganglia
  • they are modified Schwann cells (in PNS), oligodendrocytes (in CNS)
  • surround the entire soma of ganglion cells but can only see the nucleus in H&E, they stain darker than the adjacent ganglion cells
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31
Q

Ependymal cells

A
  • ciliated cells that line the ventricles of the brain and central canal of spinal cord
  • they don’t have tight junctions allowing for free exchange of CSF and nerve tissue
  • basal surface is in close contact with astrocytes
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32
Q

Myotatic stretch reflex

A

sensory input from muscle spindle stretch synapses in spinal cord on:

  1. motoneuron - this stimulates extensor muscle to contract
  2. interneuron - this sends inhibitory signal to flexor muscle motoneuron which then does not stimulate the flexor muscle to contract
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33
Q

Examples of gates in gated channels, and selectivity filters

A
  • charged amino acid for voltage sensor
  • ligand binding site for ligand-gated channel
  • selectivity filter could be charged aa in the pore, or a physically small pore
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34
Q

How do ion channels act like variable resistors?

A

channel gating controls resistance

35
Q

The membrane is like a ____ circuit.

Describe time constant and RC circuit

A

Parallel/resistor-capacitor circuit.

  • consequently, electrical signals are slowed by the storage of charge in the capacitator
  • this means the membrane has a characteristic time constant (lambda; time it takes the membrane potential to decay)
  • this property limits the time period over which electrical signals can be integrated
  • time constant is longer for larger diameter cable
  • both time constant and amplitude decrease with distance because of 2 things: charging the capacitor (membrane) and charge leakage through the membrane
36
Q

Nernst equation -

GHK equation -

A

Nernst - predicts the membrane potential when at equilibrium and only permeable to a single ion species
GHK - predicts the membrane potential when at equilibrium and takes into account all permeant ion species

37
Q

Difference between electrotonic propagation and action potential

A
  • electrotonic = passive propagation (seen in graded potentials); ex include sensory receptor potentials and synaptic potentials
  • action potential = an active response which boosts the passive propagation by voltage-gated Na channel
38
Q

What is the threshold for AP determined by?

A

the voltage at which inward/depolarizing current is balanced by outward/hyperpolarizing current; further depolarization achieves the all-or-none response

39
Q

What is the ionic basis for the membrane depolarization going beyond 0mV in an AP?

A

the fact that membrane permeability selectivity is maintained but by a different ion (no longer K as is the case at resting membrane potential)

40
Q

Why the delay to open K channels when a potential first appears?

A
  • slower kinetics of K channels

- K channels require greater depolarization

41
Q

Functional states of the Na+ channel

A
  1. Closed - activation gate closed; inactivation gate open; can be opened by voltage
  2. Activated/Open - both gates open
  3. Inactivated - activation gate still open, inactivation gate closed; can’t be opened by voltage
Activation = Closed --> Open
Inactivation = Open --> Inactivated
Repolarization = Inactivated --> Closed
Deactivation = Open --> Closed
42
Q

Functional states of the K+ channel

A
  • there is no inactivation over time scales relevant for an AP, so only two states: closed and activated/open
  • at resting potential most channels are closed
  • it takes longer to respond to depolarization, and the depolarization must be higher, than Na+ channels for opening
43
Q

Na+ and Ca+ channel structure

A
  • alpha subunit + auxiliary subunits
  • alpha subunit has 4 domains which arrange to form the pore
  • each domain consists of 6 TM regions
44
Q

Generalized epilepsy with febrile seizures (GEFS)

A

point mutation in the Na channel that causes it to be open too long which leads to hyperexcitability and seizures

45
Q

Periodic paralysis

A

Na+ channel mutations in skeletal muscle

46
Q

Familial hemiplegic migraine

A

mutation in the P/Q-type Ca channel

47
Q

Congenital stationary night blindness (CSNB)

A

truncated L-type Ca channels in the retina

48
Q

Lambert-Eaton [Myasthenic] syndrome

A

SCC produces antibodies to P/Q-and pre-synaptic L-type (and other) Ca channels which alters their function; clinical manifestations include NMJ dysfunction (weakness)

49
Q

Benign familial neonatal seizures (BFNC)

A

mutation of voltage-gated K channel

50
Q

Myotonia

A

Hyperexcitability of muscle.

  • can be caused by mutations in Na+ or Cl- channels in skeletal muscle
  • ->Cl channels because they are very permeable in skeletal muscle at rest, so the muscle normally has a very negative resting potential; if the Cl channels can’t establish this potential then they are depolarized compared to normal
51
Q

Episodic ataxia Type I

A

attacks of generalized ataxia induced by emotion or stress, with myokymia both during and between attacks; symptoms last SECONDS to MINUTES; appears in infancy; due to point mutation of Kv1.1-type K+ channels in basket cells and interneurons that form GABAergic synapses on Purkinje cells in cerebellum, thus affecting all motor output from the cerebellum

52
Q

Episodic ataxia Type II

A

attacks of ataxia with or without migraine, maybe also progressive cerebellar atrophy, nystagmus, vertigo, visual disturbances and dysarthria; symptoms last from HOURS to DAYS; attacks can be precipitated by emotional/physical stress, coffee, alcohol; due to truncated mutants of P/Q-type voltage-gated Ca++ channels

53
Q

Difference between paralysis and ataxia

A 
paralysis = weakness of muscle with normal coordination
ataxia = discoordination of muscle with normal strength
54
Q

Fast neurochemical transmission is mediated by…

A

ligands binding to their ligand-gated receptor-channel

55
Q

Neuromodulatory effects

A
  • effects that are not depolarization or hyperpolarization per se, but rather biochemical changes in the cell which alter function and/or excitability
  • these are mediated by G-protein coupled receptors
  • the GPCRs then interact directly with a channel or do something else indirectly their second messengers
56
Q

Diseases of the pre-synaptic terminal

A
  • Botulinum toxin - cleaves SNAREs, no ACh release at NMJ

- Tetanus toxin - cleaves synaptobrevin, no GABA release

57
Q

Myasthenia Gravis

A

autoimmune disorder with antibodies that attack/destroy ACh Muscarinic receptors at the NMJ

58
Q

Excitatory post-synaptic potential

A
  • a graded potential that results from the opening of cation channels and influx of positive charge into the neuron, thereby depolarizing the membrane and increasing the chance of reaching AP threshold
  • in the CNS, excitatory NTs include glutamate and aspartate
59
Q

Inhibitory post-synaptic potential

A
  • a graded potential that results from the opening of anion channels and influx of negative charge into the neuron, or shunting of excitatory current, thereby decreasing the chance of reaching AP threshold
  • mainly GABA in the brain, glycine in the spinal cord
60
Q

Summation

A

the occurrence of more than one PSP that happen close enough in time and/or space that the previous PSP haven’t decayed yet, and together they can reach threshold for an AP

61
Q

Reuptake of glutamate and use of glucose

A

done by astrocytes at the synaptic cleft

  • occurs via Na transporters that bring in 3 Na+ ions with 1 glutamate
  • the increase in IC Na activates the ATPase to normalize the IC Na concentration
  • the increased use of ATP by Na/K-ATPase stimulates glycolysis (which uses glucose brought to astrocyte from circulation)
  • the lactate produced by glycolysis is given to the neuron for conversion back to pyruvate with generation of ATP
62
Q

Why is ATP needed in the resting neuron?

The active neuron?

A

ATP is always and predominantly needed for maintaining the ion concentration in the cell via the Na/K-ATPase and other energy-dependent ion pumps

63
Q

Forebrain

A

cerebrum, thalamus, ventricles, hypothalamus

- Telencephalon + Diencephalon

64
Q

Midbrain

A
  • superior/inferior colliculi

- Mesencephalon

65
Q

Hindbrain

A
  • reticular formation, pons, cerebellum, medulla

- Metencephalon + Rhombencephalon

66
Q 
Brain segments:
Telencephalon
Diencephalon
Mesencephalon
Metencephalon
Rhombencephalon
A 
Tel - cerebral hemispheres
Di - thalamus, hypothalamus
Mes - midbrain
Met - pons, cerebellum
Rhom - medulla
67
Q

Basal Ganglia

A
  1. Caudate nucleus
  2. Putamen
  3. Globus pallidus external
  4. Globus pallidus internal

+Lenticular nucleus includes the putamen, GPe, GPi
+Caudate and Putamen form the striatum.

68
Q

Brainstem

A

-midbrain
-pons
-medulla
“Braintem-p-m”

69
Q

Spinal cord:

  • number of cord segments
  • where does adult cord end?
A
  • cervical 8, thoracic 12, lumbar 5, sacral 5
  • adult cord ends at T12/L1
  • Note that all spinal nerve roots exit below the same-numbered vertebra except for C1-7 which exit above (switches at C8)
70
Q

Corticospinal tract

A
  • carries motor signals from cortex to muscles*
  • aka pyramidal because the tract forms the pyramids
  • Betz cells M1 - corona radiata - posterior limb IC - crus cerebri - pons - pyramids; 85-90% decussate to lateral CST, rest form the anterior CST - anterior horn LMNs; anterior tract fibers cross then synapse at target level
71
Q

Spinothalamic tract

A
  • carries pain and temperature to sensory cortex*

- DRG - Lissauer tract - synapse - decussate, anterior white commissure - anterolateral tract - VPL - S1

72
Q

Posterior/Dorsal Column

A
  • carries proprioception*
  • DRG - ipsilateral fasciculus gracilis (medial) and fasciculus cuneatus (lateral) - synapse nucleus gracilis/cuneatus -decussate, internal arcuate fibers - medial lemniscus - VPL - internal capsule - corona radiata - S1
73
Q

Muscle spindle nerves

A
  • 2 types: annulospiral endings and flower spray endings
  • annulospiral carry information about muscle length/stretch and velocity in type Aalpha Ib fibers
  • flower spray carry information about muscle length/stretch in type Abeta II fibers
74
Q

Golgi tendon organ nerves

A
  • free nerve endings in the GTO sense the force applied to the muscle; carried in Aalpha IIb fibers
  • free nerve endings in joint GTO sense the torque applied to joint; carries in Abeta II
75
Q

Paciniain corpuscle

A
  • rapidly adapting mechanoreceptor
  • located in subcu skin and joint (as well as muscle and mesentery)
  • carried by Abeta II fibers
  • skin–>gross pressure and vibratory skin sense ~250Hz
  • joint–>joint movement
  • Epicritic pathway*
76
Q

Ruffini organ

A
  • slowly adapting mechanoreceptor
  • located in deep glabrous skin and joint
  • carried by Abeta II fibers
  • skin–>sustained pressure, skin stretch, slippage (position sense)
  • joint–>joint angle
77
Q

Meissner’s corpuscle

A
  • rapidly adapting mechanoreceptor
  • located in subepidermal (glabrous) skin
  • carried by Abeta II fibers
  • skin–>light touch, vibration
78
Q

Merkel’s disc

A
  • slowly adapting mechanoreceptor
  • located in skin and mucosa (right beneath basal epithelial cells)
  • carried by Abeta II fibers
  • skin –> light touch
79
Q

Free nerve endings

A
  • typically respond to pain and nociceptive stimuli
  • sharp pain, cool/cold carried by A delta fibers
  • dull/aching pain, warmth, or touch carried by C fibers
80
Q

Motor nucleus of V

A

cell bodies of motoneurons to masticatory muscles and a few others

81
Q

Mesencephalic nucleus of V

A
  • cell bodies of primary afferents for muscle spindles and GTOs from masticatory muscles
  • analogous to DRGs (for these afferents only)
  • special because these afferents don’t have bodies in trigeminal ganglion (like all the other sensory afferents)
  • monosynaptic stretch reflex is mediated by projections from here to the motor nucleus of V
82
Q

Clarke’s nucleus

A
  • cell bodies located in intermediate medial gray matter of spinal cord (layer VII) btw T2-L2 (peak @ T9)
  • involved in unconscious proprioception (for cerebellar tracts)
  • this is where lower body proprioception afferents synapse and the axons that leave this nucleus ascend in what begins the dorsal spinocerebellar tract
83
Q

Rexed laminae (layers I-IX)

A

Layers I-VI = intermediate sensory neurons
Layers VII-VIII = local circuit, autonomic, commissural neurons
Layer IX = LMNs

OS9.1 - Neuro (8 decks)

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