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NEUR 101 > Midterm 1 > Flashcards

Midterm 1 Flashcards

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1
Q

How does natural selection affect the evolution of nervous systems?

A

Something about need to sense environment so can avoid predators, find food, reproduce. Talk about progression from simple to complex NS.

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2
Q

What is evolution?

A

Change in pop. gene pool over time

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3
Q

What is adaptation?

A

A feature that gives .org. better chance of survival and reproduction than if it did not have

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4
Q

What is natural selection?

A

Environment favors certain characteristics more than others

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5
Q

What is a selective pressure?

A

Any phenomenon in an environment that alters reproductive success of a pop.

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7
Q

Example of evolution

A

Peppered moth

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8
Q

Example of adaptation

A

DDT killing mosquitos with certain Na+ channels by causing hyperexcitability

Also modern-day RoundUp resistant plants and antibiotic resistant bacteria have certain features
RoundUp, antibiotics = selective pressures

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9
Q

Example of natural selection

A

Peppered moth in urban location = directional

Robins brood number: too few eggs, easy to all be killed by predators; too many, likely to die of starvation = stabilizing

Peppered moth = disruptive

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10
Q

Types of evolution (5)

A

1) mutation
2) genetic drifts
3) migration between populations
4) nonrandom mating
5) natural selection

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11
Q

Requirements for natural selection (4)

A

1) reproduction
2) heredity
3) variation
4) variation in fitness

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12
Q

Define fitness

A

A relative measure of reproductive success of an .org. in passing on its genes to the next generation

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13
Q

Types of natural selection (3/4) and differences between them

A

1) directional
2) stabilizing
3) disruptive
4) none

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15
Q

Contributions of Cajal

A

Drew networks of neurons
Theorized about synaptic gap = neuron doctrine

Proposed functional polarity

Used Golgi’s stain

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16
Q

Golgi

A

Thought all neurons were connected in continuous reticulum, breaking mandate of cell theory (reticular theory)

Made a stain

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17
Q

Outline progression from simple to complex NS through 5 phyla and describe differences and developments within

A

nerve net for reflexive movement (cnidaria)—>
bilateral symm. , centralization, segmentation for faster and more eff. comm. (flatworms/platyhelminthes) —>
cephalization, bilat. symm. and centralization (mollusca) —>
cephalization, bilat. symm., centralization, and segmentation (arthropoda) —>
CNS and spinal cord protected by vertebrae (chordata)

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18
Q

What is CNS?

A

Brain and spinal cord

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19
Q

What is PNS?

A

Nerves and ganglia outside CNS
Connects CNS to limbs and organs
Includes sensory neurons that link CNS receptors to processing circuits

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20
Q

Parts of CNS?

A 
BRAIN
Frontal lobe
Parietal lobe
Occipital lobe
Temporal lobe

SPINAL CORD

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21
Q

Parts of PNS?

A

AUTONOMIC NS
= automatic, involuntary
Cardiac muscles, glands
Sympathetic nervous system —> fight or flight
Parasympathetic nervous system —> rest and digest

SOMATIC NS
= voluntary
Sensory processing and motor control

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22
Q

What is autonomic nervous system?

A

AKA visceral nervous system

Automatic functions
Cardiac muscles, glands
Sympathetic nervous system —> fight or flight
Parasympathetic nervous system —> rest and digest

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23
Q

What is somatic nervous system?

A

Afferent nerves that carry info to CNS efferent fibers that carry neural impulses away

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24
Q

What components comprise the cytoskeleton? (3)

A

Microtubules
Neurofilaments
Microfilaments?

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25
Q

What is axoplasmic transport?

A

Movement of proteins from synapse to terminal and vv.

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26
Q

Types of axoplasmic transport (2)

A

1) fast (anterograde by kinesin, retrograde by dynein)

2) slow (either way by dynein)

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27
Q

Why are dendritic spines important?

A

Shape affects synapse strength, i.e. how good at making connections a neuron is
Have dynamic shape

Implicated in memory

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28
Q

Example of directional selection

A

Smaller salmon in PNW slip through fishers’ nets

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29
Q

Example of stabilizing selection

A

Robins’ nests eggs too few die by predation eggs too many die by starvation

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30
Q

Example of disruptive selection

A

Peppered moth melanin in urban areas, light in rural areas

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31
Q

What do microtubules do?

A

Transport tracks for organelles

MAPs normally form bridges

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32
Q

What is tau?

A

A microtubule-associated protein (MAP) whose malfunction in dissociating from MT’s is involved in Alzheimer’s

Review this!

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33
Q

What are neurofilaments for?

A

Support for atonal radial growth

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34
Q

What do microfilaments do?

A

Close association with membrane

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35
Q

What is the theory of functional polarity?

A

Dendrites and cell bodies of neurons receive info
Axons and collaterals transmit info to other cells

So we can predict direction of info flow through neuronal circuits
RECEIVE GENERATE TRANSMIT

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36
Q

Classifying neurons

A

NUMBER OF NEURITES
unipolar, bipolar, multipolar

DEBDRITES
stellate or pyramidal cells
spiny or aspinous

See also classification of glia

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37
Q

What do astrocytes do?

A

CNS

Regulate extracellular space and ion concentrations
Remove NT’s from synaptic cleft
Produce growth factors for survival

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38
Q

What do oligodendrocytes do?

A

CNS

Makes several sheaths (long sheets of glial membrane)
Usually can’t regenerate

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39
Q

What are nodes of Ranvier?

A

CNS and PNS

Breaks in between myelin sheaths

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40
Q

What are Schwann cells?

A

PNS

One cell makes one myelin sheath
If damaged, can regenerate

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41
Q

What is neurophysiology?

A

Physiology (study of normal function) of the nervous system

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42
Q

What is electrophysiology?

A

Study of electrical properties of cells and tissues

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43
Q

How does intracellular electrophysiological measurement work?

A

Electrode filled with conductive salt solution placed into soma
Amplifier measured voltage difference between electrode and ground

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44
Q

How does extracellular electrophysiological measurement work?

A

Electrode places just outside of cell close to neuronal membrane

Measures electrical activity without killing cell/org.

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45
Q

How are ion channels gated? (4+)

A

1) ligand-gated
2) voltage-gated
3) stretch activated
4) inactivation (special type)
5) no gating

46
Q

Properties of ion channels

A

Some are leak, some are gated

Balance of electrical force and concentration gradient

47
Q

What is Ohm’s Law (bio version)?

A

I = GV

48
Q

What is conductance?

A

G = 1/R

The rate at which ions pass through open ion channels

49
Q

How is membrane potential set up?

A

Leak channels balance high extracellular concentrations against charge difference as K+ flows into cell

Sodium-potassium pumps maintain it

50
Q

Why are ion pumps important?

A

Cell uses ATP so ion pumps can restore RMP after an action potential
Transport 2 K+ in 3 Na+ out, against concentration gradient

51
Q

Different types of glia (3)

A

1) astrocytes
2) myelinating glia
- a) oligodendrocytes in CNS
- b) Schwann cells in PNS
3) microglia

52
Q

What are microglia?

A

CNS

Responsible for immune system in brain
Some are phagocytes that remove debris
Secrete cytokines and growth factors

53
Q

How is RMP established?

A

SIMPLE-ish CELL

1) ion pumps establish conc. gradient: [K+]in = 125 mM, [K+]out = 5 mM
2) K+ associated with A- so anions enter cell too
3) make simple cell selectively permeable to K+ with K+ leak channels
4) K+ wants to flow down conc. gradient due to diffusionalforce but it leaves unbalanced negative charge inside cell
5) negative charge inside cell creates electrical force that attracts K+ to come back into cell
6) diffusional and electrical forces duke it out
7) eventually they balance at -80 mV equilibrium

54
Q

What is the Nernst equation?

A

Ex = (58 mV/z)*log([X]out/[X]in)

55
Q

What factors affect Ex?

A

1) concentrations

2) temperature: higher T, more diffusional force

56
Q

What is the GHK equation?

A

Vm = 58log((Pk[K]o + Pna[Na]o + Pcl[Cl]o)/(Pk[K]i + Pna[Na]i + Pcl[Cl]i))

57
Q

What factors affect GHK output, Vm?

A

1) permeabilities
2) concentrations
3) temperature

58
Q

How do you determine RMP?

A

Use GHK equation

59
Q

How do you determine driving force?

A

Vd = Vm - Ex

60
Q

What does driving force tell you?

A

How strongly an ion wants to diffuse (proportional to absolute value)

61
Q

What is an EPSP?

A

Excitatory postsynaptic potential

Influx of Na+ into the cell depolarizes it and brings neuron closer to threshold potential

62
Q

What is an IPSP?

A

Inhibitory postsynaptic potential

Influx of Cl- into the cell hyperpolarizes it and makes it harder for neuron to reach threshold potential

63
Q

What are the types of summation?

A

1) spatial

2) temporal

64
Q

How does spatial summation work?

A

PSPs on different dendrites and at different locations along a given dendrite are synthesized into a net change in potential

65
Q

How does temporal summation work?

A

Signals received over a period of time combine to produce a net signal

66
Q

What is lambda?

A

The length constant

ł = sqrt(Rm/Ri)

67
Q

What role did voltage clamp method play in determining ionic current responsible for AP?

A

Used to control or “clamp” the voltage across the cell membrane at the command voltage
Also measured current (flow of ions in and out of cell)

68
Q

What are passive (3) and active membrane properties?

A

PASSIVE
Signal decays over distance
Nothing to regenerate V
Travels in both directions

ACTIVE
No decay of V over distance
V-gated ion channels regenerate V
Only one direction

69
Q

What experiments did Hodgkin and Huxley conduct to understand AP?

A

Squid giant axon (400x diameter of mammalian axon)

A) V dependence
B) ionic currents
C) pharmacology (blocking)

70
Q

V dependence experiment

A

Used voltage clamp

Changed Vm in set interval up or down and observed if current resulted

Saw capacitative current but nothing else when 65 mV hyperpolarization
Saw capacitative current, transient inward current, and delayed outward current when 65 mV depolarization

71
Q

Ionic current experiments

A

Used voltage clamp

Changed Vm to -26, 0, +26, or +52 and compared results
Degree of inward current decreased as depolarization increased because got closer to Ena
Degree of outward current increased as got further from Ek

72
Q

General takeaways from HH experiments

A

Showed that Na+ and K+ are involved and that Na+ is responsible for inward current while K+ is responsible for outward current

Reminder: Outward current is treated as >0, inward current is negative in graphs

73
Q

Ionic current experiments part 2

A

Also took out Na from extracellular space and saw only outward early current (small bump as Na+ effluxed)

74
Q

Pharmacology experiments

A

Blocked Na+ with tetraethyl-ammonium and saw only inward current so they knew K+ is outward current

Blocked K+ with tetrodotoxin (puffer fish toxin) and saw (almost) only outward current so knew Na+ is inward current

75
Q

During action potential, what is relationship between voltage and current?

A

Membrane potential (Vm) follows iconic spike then dip

Current starts out as inward (neg.) then becomes positive with delayed K+ efflux

Small changes in ion concentration drive large changes in voltage

76
Q

What is measured during a voltage clamp experiment?

A

Ionic current

77
Q

How was pharmacology used to understand ionic basis of AP?

A

Selectively blocking ion channels allowed confirmation of which ion is responsible for which direction of current

78
Q

What is Na+ channel like structurally?

A

Six alpha helix subunits connected by loose coils
S4 = voltage sensor
S5-S6 pore loop = selectivity filter

Extra protein “ball” can block channel so even if conformation is activated it is also deactivated (occurs during hyperpolarization)

79
Q

What is K+ channel like structurally?

A

Created from 4 subunits
Each subunit has 6 alpha helices

S4 = voltage sensor
S5-S6 pore loop ==> selectivity filter

80
Q

Give the state of Na+ and K+ channels throughout AP

A

Look at worksheet

81
Q

How does conductance vary throughout AP?

A

See answer about Na+ and K+ ion channel states

82
Q

Compare and contrast structures of K+ and Na+ channels

A

Sense voltage change in the same way in same S4
Both have pore loop

Na+ channel is one long polypeptide with 4 domains

K+ is four subunits that make one opening total

83
Q

What are different phases of AP?

A 
Threshold
Rising phase
Overshoot
Falling phase 
Undershoot
Return to RMP
84
Q

How does the structure of V-gated Na and K channel inform us about action potential?

A

I don’t really know except maybe speeds of opening and also inactivation is cool

Absolute and relative refractory periods

85
Q

What are factors that influence AP conduction?

A

lambda and tau

86
Q

What is Rm?

A

Membrane resistance to flow of ions

87
Q

What is Ri?

A

Internal axonal resistance to flow of ions

88
Q

What factors can change Rm or Ri?

A

Number of pores in membrane

Diameter of axon

89
Q

Why do biological membranes have capacitance?

A

Phospholipid bilayer is thin enough that as charges collect inside and outside, they attract one another through membrane and end up very close to it and stick around because of mutual attraction

Also even though there are leak channels the RMP is not neutral

90
Q

What is saltatory conduction?

A

AP can “leap” between nodes of Ranvier much faster than it can travel down unmeyelinated cells

Only needs to open channels located in nodes and flow of AP is unilateral because of refractory periods

91
Q

What causes multiple sclerosis? What are symptoms?

A

MS symptoms are caused by demyelination of neurons at different sites throughout the body. As a consequence, Rm decreases, lambda decreases, and conductional velocity decreases. Thus, APs propagate more slowly and weakly, leading to weakness, lack of coordination, and impaired vision and speech.

92
Q

What are differences between electrical and chemical synapses?

A

ELECTRICAL SYNAPSES
3 nm between post and presynaptic cells
Cytoplasmic continuity across gap junction
Ionic current flows between cells
Almost instantaneous transmission but no variety
Involved in escape responses

CHEMICAL SYNAPSES
Synaptic cleft
Signals transmitted by NTs
Slower transmission but specialization by type of NT

93
Q

What are the steps in chemical synaptic transmission?

A

1) synthesize and store NT
2) AP arrives at terminal3) depolarize terminal and activate V gated Ca channels
3) Ca2+ influx into terminal
5) vesicle fusion
6) NT released
7) NT binds to receptors on postsynaptic side
8) receptor responds, e.g. opens ion channels
9) PSP creased

94
Q

How long does chemical synaptic transmission take?

A

2-5 ms

95
Q

What are classes of NY? (3)

A

Amino acids and amines (fast)

Peptides (slower, longer)

96
Q

What are experiments to test Ca2+ neurotransmitter release?

A

1) image Ca2+

2) block Ca2+

97
Q

Image Ca experiment

A

Use Ca sensitive dye in squid synapse

All color localized on presynaptic terminal

98
Q

Block Ca channels experiment

A

Control and added cadmium
Control is normal current and Vm change over time
Experimental no current or voltage change observed

99
Q

How are SNARE proteins involved in exocytosis?

A

Pull vehicle close to pbl so they fuse

100
Q

Proteins in exocytosis

A

Synaptobrevin
Synaptotagmin
Syntaxin
SNAP-25

101
Q

Synaptobrevin

A

Vesicular SNARE

Long straight high up on vesicles

102
Q

Synaptotagmin

A

Ca2+ bonding protein in vesicles
Has two clampy bits to catch ion
Middle of vesicles

103
Q

Syntaxin

A

pmb-bound SNARE
Short and smooth curve with tangled end
One set on outside of docking site

104
Q

SNAP-25

A

pmb-bound SNARE
Looks like crossed ends of jumping rope
One set on inside of docking site

105
Q

For NT receptors, what are differences between ligand gated ion channels and g-protein coupled receptors?

A

Fast vs. slow and long-lasting, acting by proxy

106
Q

What is Botox?

A

Neurotoxin that targets SNAREs so muscles can’t move because no Ca2+ released

107
Q

Outline how g-coupled protein receptor work?

A

Later

NEUR 101 (2 decks)

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