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Year 2: NeuroBiology > Lecture 6: Chemical/Electrical Signals > Flashcards

Lecture 6: Chemical/Electrical Signals Flashcards

1
Q

characteristics of neurons

A

terminally differentiated epithelial cells

most have lost replicative capactities

different morphologies

communicate via electric and chemical signals

sensory = afferent, motor = efferent, and interneurons = integration and coordination

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2
Q

what cellular organs are contained in the soma

A

nucleus
rough ER
smooth ER
golgi apparatus
lysosome/peroxisome
mitochondria
cytoskeleton structures
cell membrane

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3
Q

describe the nucleus of a neuron

A

condensed

no replicative functions = no centrioles

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4
Q

function of rough endoplasmic reticulum and where in the neuron this takes place

A

protein and peptide synthesis in the Nissl body

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5
Q

smooth ER function

A

lipid synthesis

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6
Q

golgi apparatus function

A

modification of synthesized proteins and peptides and lipids for sorting

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7
Q

lysosome/peroxisome function

A

degrade metabolic waste

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8
Q

mitochondria function

A

power

produce ATP

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9
Q

function of cytoskeleton

A

made of neurofilaments

give shape to neuron

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10
Q

functions/purposes of the soma of a neuron

A

holds all cellular organs

synthesizes most molecules a neuron needs to survive

reception and summation of signals

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11
Q

what cellular organs can be found in the axon of a neuron as well as the cell body

A

mitochondria

lysosome/peroxisome

enzymes for synthesis/activation of neurotransmitters

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12
Q

what happens at the axon hillock

A

initiation of action potentials

APs are initiated by peripheral process in pseudounipolar neurons

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13
Q

how does the axon form synapses with target cells

A

release of neurotransmitters

transformed from electrical to chemical

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14
Q

what defines the type of neuron morphologically

A

number and location of the dendrites

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15
Q

multipolar neuron

A

multiple dendrites from the soma

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16
Q

bipolar neuron

A

dendrites mainly on one end of the soma

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17
Q

unipolar neuron

A

one hillock with dendrites on the axon

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18
Q

pseudounipolar neuron

A

one hillock then divides axon to 2 branches (1 branch like dendrites)

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19
Q

what type of neuron are most sensory neurons and their unique characteristics

A

pseudounipolar

unique characteristics = limited cellular organs, like axons, but has golgi apparatus extension

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20
Q

describe rapid delivery of molecules in the neuron and the 2 subtypes

A

active transportation

anterograde transportation = FROM soma TO dendrites/axons

retrograde = FROM dendrites/axons back TO soma

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21
Q

what proteins are involved in retrograde and anterograde transportation in the neuron

A

anterograde = kinesin

retrograde = dynein

viral and bacterial toxins can hijack these transportation mechanisms

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22
Q

the neuron cellular membrane is selectively permeable. What are some examples of this

A

water transporation across water channels facilitated aquaporin proteins

leaking and gated ion channels can be found in the membrane

sodium and potassium channels, controlled by ATP, found in the membrane as well

other molecules can enter only via transporters, receptors, etc

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23
Q

what is osmotic potential

A

numbers of ions and molecules

ratio

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24
Q

what is electric potential

A

positive and negative charges

ratio

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25
what is the resting membrane potential of the neuron
negative
26
describe a ligand gated channel
neurotransmitter acts as a "ligand" (key) ion channel acts as the receptor (key hole) activation of channel causes a change in membrane potential
27
describe a voltage gated channel
opened when resting membrane potential increases to the threshold no ligands needed
28
describe modality gated ion channels
can open or close via touch, heat, pressure, cold, light, sounds, etc
29
what ion is in charge of the resting membrane potential and how can it "freely" cross the cellular membrane
K+ can freely cross through leaking channels
30
what are the 5 phases of initiation of an action potential
**numbers/thresholds vary, just using these as example values** resting potential (-70mv) slow depolarization (>-70mv, mv increased via activation of modality/ligand gated Na+ channels; forms a graded potential) fast depolarization (>-55mv, at threshold, result of voltage gated Na+ channel; action potential) repolarization (back to -70mv; voltage gated K+ and pumps) hyperpolarization (<-70mv; voltage gated K+ and pumps)
31
definition of an action potential
phase of potential above the threshold lasts ~ 1mSec
32
what are the 3 stages of voltage gated sodium channels
resting state activated state inactivated state never an instance where both gates will be closed at the same time
33
describe the resting state of voltage gated sodium channels
below threshold potential activation gate closed inactivation gate open
34
describe the activated state of voltage gated sodium channels
fast depolarization both gates are open
35
describe the inactivated state of voltage gated sodium channels
repolarization and hyperpolarization activation gate is open inactivation gate is closed
36
what is the absolute refractory period related to voltage gated sodium channels
at both the activated and inactivated states where you can not induce another AP
37
what is the relative refractory period related to voltage gated sodium channels
when some channels have returned to resting state but not all slightly earlier than hyperpolarization phase can induce another AP with higher stimulation but increased threshold
38
what defines the unidirectional conduction of APs
the refractory period
39
describe repolarization of neurons
back to restong membrane potential there is a compromised balance of electric and osmotic potentials not just K+ that is flowing out of cell
40
describe how sodium potassium pumps work
maintain the Na+ and K+ gradients 3 Na+ out and 2 K+ in dependent on ATP; accounts for 20-40% of the energy consumed by the brain
41
if an AP is produced in the middle of the axon, why might it spread bidirectionally when conduction of APs is generally unidirectional
both afferent and efferent tracts on one axon. if coming from the middle it can send both ways
42
how do the voltage gated sodium channels aid in the unidirectional conduction of an AP
activated and then inactivated voltage gated sodium channels block backflow absolute refractory period = unidirectional spread q
43
what happens if there are multiple action potentials along one axon
the intensity of the stimuli is represented by frequency of the action potentials repolarization follows the absolute refractory period
44
what is a node of ranvier and what happens here in relation to AP conduction
small gap in the myelin sheath only voltage gated sodium channels there is no hyperpolarization secondary to an outflow of potassium (because there are no K+ channels present here) only need regeneration of AP in the nodes; this gives a fast pass in the internodes (parts covered by myelin)
45
where are potassium channels located on an axon
internodes- covered by myelin
46
what is saltatory conduction
AP conduction jumping from one node to another excitation occurs only at the nodes of ranvier
47
what type of axons are fastest
larger diameter, myelinated less resistance occurs
48
`describe the giant axon of a squid
nonmyelinated, 800 micrometer diameter aids in water jet propulsion; escape mechanism diameter is almost 400 folds of 1 myelinated vertebrate axon
49
describe the myelin sheath of most axons in the CNS
oligodendrocytes covers multiple axons for the few nonmyelinated axons in the CNS - astrocytes wrap around
50
describe the myelin sheath in most axons of the PNS
schwann cells only cover a single axon nonmyelinated axons are bundled together and wrapped in schwann cells without myelin sheath
51
describe communication between layers of myelin
gap junctions used for signal and molecule transportation local ions replenish fast during repolarization
52
what is multiple sclerosis
autoimmune injury sporadic lesion (sudden/unpredictable) affects the oligodendrocyte myelin in the CNS causes problems/damage to olfactory bulb/tract and CN II (optic) in the diencephalon
53
what guillain barre syndrome
autoimmune injury affects schwann cell myelin of the PNS
54
how do signals from neurons travel to target cells
neuron synapses with dendrites, soma or axons/terminals signals sent to terminal functional cells of muscles, glands, etc
55
components of electrical synapse
gap junction AP bidirectional conduction
56
components of a chemical synapse
presynaptic axon terminal contains vesicles with neurotransmitters synaptic cleft (gap in between pre and post) postsynaptic membrane contains receptors for neurotransmitters (logand gated and G protein coupled receptors)
57
synapse definition
relat or transformation of electrochemical signals
58
how is an electric signal turned into a chemical signal
AP arrives at presynaptic terminal of chemical synapse depolarization opens the Ca2+ voltage gated channel inflow of Ca2+ facilitates docking of vesicles on the presynaptic membrane fuse vesicles with presynaptic membrane neurotransmitters are released and then diffuse across synaptic cleft and bind to post synaptic membrane
59
after neurotransmitters bind to the post synaptic membrane, what 2 responses can take place
excitation: excitatory postsynaptic potential (EPSP) - depolarization of postsynaptic membrane - doesnt necessarily mean AP initiation inhibition: inhibitory posy synaptic potential (IPSP) - hyperpolarize postsynaptic membrane - doesnt mean AP will necessarily be inhibited
60
what are ionotropic receptors of the postsynaptic membrane
ligand gated ion channels fast, point to point, and specific one AP is enough small vesicles with different neurotransmitters sent to synaptic gap causes depolarization or hyperpolarization of postsynaptic membrane
61
what are metabotropic receptors of the postsynaptic membrane
GPCR, 2nd messenger system slow, can be point to area, nonspecific need multiple APs (longer Ca2+ opening) small vesicles with different neurotransmitters sent to synaptic cleft large vesicles release neurotransmitters through exocytosis binding of neurotransmitters release G protein subunit initiates multiple responses
62
describe single postsynaptic membrane potentials
graded potentials either EPSP or IPSP dissipate due to distance and time (spatiotemporal effects)
63
what is temporal summation
stimuli from same lcation or locations with different time frame
64
what is spatial summation
stimuli from different locations simultaneously
65
what are the results of AP summation
if over resting potential but lower than threshold = no AP over threshold = AP initiated lower than resting potential = inhibitory; hyperpolarized and refractory to be activated
66
what is NMJ
neuromuscular junction specialized button shaped synapes
67
describe what takes place at the NMJ
APs arrive at motor neuron acon terminal depolarization; opem terminal voltage gate Ca2+ channel vesicle fuses with presynaptic membrane Aacetylcholine is released ACh binds to receptor on aplha subunit this causes Na+ channels to open depolarization of postsynaptic membrane if above threshold, AP initiated result = muscle contraction
68
what are NMJ channelopathies
disorders that impair channels around the synapses autoimmune antibodies can block or initiate degradation of channel molecules
69
what is lambert eaton syndrome
voltage gated calcium channels affected diminshed Ca2+ channel function = impaired fusion of ACh vesicles with membrane result = weakness and flaccidity
70
what is isaacs' syndrome
affects voltage gated potassium channels blocked K+ channel = impaired depolarization result = continuous release of ACh = spasm
71
what causes myasthenia gravis
directly affects ACh receptor involved in sodium channels indirectly affects ACh receptor localization (ACh must be concentrated in the postsynaptic membrane by stabilizers MuSK and LRP4)
72
what is myasthenia gravis/S&S
most common NMJ pathology weakness; eye muscles often effected the worst treatment = block acetylcholinesterase
73
possible "fates" of neurotransmitters
reuptake degradation diffusion away endocytosis by postsynaptic membrane
74
two types of ACh receptors
nicotinic: ionotropic - in PNS; fast EPSP - point to point, specific, fast Muscarinic: metabotropic, GPCR based - in PNS: slow IPSP in smooth and cardiac muscle; point to point, specific, slow - in CNS: modulating functions; point to area, nonspecific, slow
75
what is muscarine
agonist of ACh receptors in brain/PNS (parasympathetic); deadly poison
76
describe anterograde transportation of neurotransmitters for small molecular neurotransmitters
enzymes needed are synthesized in the soma transport to terminals synthesize small molecular neurotransmitters in terminal
77
describe anterograde transportation of neurotransmitters for peptide neurotransmitters
prepeptide synthesized in soma transport with enzymes to terminal degrade to form active neurotransmitter
78
describe retrograde transportation of neurotransmitters
molecules are recovered from terminals transported back to cell body for reuse
79
4 categories of neurotransmitters
amines amino acids neuropeptides other small molecules and ions
80
medication for agonist of Leukotriene
aspirin
81
medication for antagonist of ACh
curare
82
how do receptors on the postsynaptic membrane define functions of neurotransmitters
fast vs slow excitatory vs inhibitory (depends on receptor and transmitter) - i.e. glutamate can be either for different bipolar neurons in the visual system
83
what are the 3 amines that overlap in their function of maintaining arousal and alert status via the ARAS
norepinephrine seratonin dopamine
84

Year 2: NeuroBiology (10 decks)

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