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Midterm 1 Flashcards

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
Why are dendritic spines important?
Shape affects synapse strength, i.e. how good at making connections a neuron is Have dynamic shape Implicated in memory
28
Example of directional selection
Smaller salmon in PNW slip through fishers’ nets
29
Example of stabilizing selection
Robins’ nests eggs too few die by predation eggs too many die by starvation
30
Example of disruptive selection
Peppered moth melanin in urban areas, light in rural areas
31
What do microtubules do?
Transport tracks for organelles | MAPs normally form bridges
32
What is tau?
A microtubule-associated protein (MAP) whose malfunction in dissociating from MT’s is involved in Alzheimer’s Review this!
33
What are neurofilaments for?
Support for atonal radial growth
34
What do microfilaments do?
Close association with membrane
35
What is the theory of functional polarity?
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
36
Classifying neurons
NUMBER OF NEURITES unipolar, bipolar, multipolar DEBDRITES stellate or pyramidal cells spiny or aspinous See also classification of glia
37
What do astrocytes do?
CNS Regulate extracellular space and ion concentrations Remove NT’s from synaptic cleft Produce growth factors for survival
38
What do oligodendrocytes do?
CNS Makes several sheaths (long sheets of glial membrane) Usually can’t regenerate
39
What are nodes of Ranvier?
CNS and PNS Breaks in between myelin sheaths
40
What are Schwann cells?
PNS One cell makes one myelin sheath If damaged, can regenerate
41
What is neurophysiology?
Physiology (study of normal function) of the nervous system
42
What is electrophysiology?
Study of electrical properties of cells and tissues
43
How does intracellular electrophysiological measurement work?
Electrode filled with conductive salt solution placed into soma Amplifier measured voltage difference between electrode and ground
44
How does extracellular electrophysiological measurement work?
Electrode places just outside of cell close to neuronal membrane Measures electrical activity without killing cell/org.
45
How are ion channels gated? (4+)
1) ligand-gated 2) voltage-gated 3) stretch activated 4) inactivation (special type) 5) no gating
46
Properties of ion channels
Some are leak, some are gated Balance of electrical force and concentration gradient
47
What is Ohm’s Law (bio version)?
I = GV
48
What is conductance?
G = 1/R The rate at which ions pass through open ion channels
49
How is membrane potential set up?
Leak channels balance high extracellular concentrations against charge difference as K+ flows into cell Sodium-potassium pumps maintain it
50
Why are ion pumps important?
Cell uses ATP so ion pumps can restore RMP after an action potential Transport 2 K+ in 3 Na+ out, against concentration gradient
51
Different types of glia (3)
1) astrocytes 2) myelinating glia - a) oligodendrocytes in CNS - b) Schwann cells in PNS 3) microglia
52
What are microglia?
CNS Responsible for immune system in brain Some are phagocytes that remove debris Secrete cytokines and growth factors
53
How is RMP established?
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
What is the Nernst equation?
Ex = (58 mV/z)*log([X]out/[X]in)
55
What factors affect Ex?
1) concentrations | 2) temperature: higher T, more diffusional force
56
What is the GHK equation?
Vm = 58log((Pk[K]o + Pna[Na]o + Pcl[Cl]o)/(Pk[K]i + Pna[Na]i + Pcl[Cl]i))
57
What factors affect GHK output, Vm?
1) permeabilities 2) concentrations 3) temperature
58
How do you determine RMP?
Use GHK equation
59
How do you determine driving force?
Vd = Vm - Ex
60
What does driving force tell you?
How strongly an ion wants to diffuse (proportional to absolute value)
61
What is an EPSP?
Excitatory postsynaptic potential Influx of Na+ into the cell depolarizes it and brings neuron closer to threshold potential
62
What is an IPSP?
Inhibitory postsynaptic potential Influx of Cl- into the cell hyperpolarizes it and makes it harder for neuron to reach threshold potential
63
What are the types of summation?
1) spatial | 2) temporal
64
How does spatial summation work?
PSPs on different dendrites and at different locations along a given dendrite are synthesized into a net change in potential
65
How does temporal summation work?
Signals received over a period of time combine to produce a net signal
66
What is lambda?
The length constant ł = sqrt(Rm/Ri)
67
What role did voltage clamp method play in determining ionic current responsible for AP?
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
What are passive (3) and active membrane properties?
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
What experiments did Hodgkin and Huxley conduct to understand AP?
Squid giant axon (400x diameter of mammalian axon) A) V dependence B) ionic currents C) pharmacology (blocking)
70
V dependence experiment
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
Ionic current experiments
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
General takeaways from HH experiments
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
Ionic current experiments part 2
Also took out Na from extracellular space and saw only outward early current (small bump as Na+ effluxed)
74
Pharmacology experiments
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
During action potential, what is relationship between voltage and current?
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
What is measured during a voltage clamp experiment?
Ionic current
77
How was pharmacology used to understand ionic basis of AP?
Selectively blocking ion channels allowed confirmation of which ion is responsible for which direction of current
78
What is Na+ channel like structurally?
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
What is K+ channel like structurally?
Created from 4 subunits Each subunit has 6 alpha helices S4 = voltage sensor S5-S6 pore loop ==> selectivity filter
80
Give the state of Na+ and K+ channels throughout AP
Look at worksheet
81
How does conductance vary throughout AP?
See answer about Na+ and K+ ion channel states
82
Compare and contrast structures of K+ and Na+ channels
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
What are different phases of AP?
``` Threshold Rising phase Overshoot Falling phase Undershoot Return to RMP ```
84
How does the structure of V-gated Na and K channel inform us about action potential?
I don’t really know except maybe speeds of opening and also inactivation is cool Absolute and relative refractory periods
85
What are factors that influence AP conduction?
lambda and tau
86
What is Rm?
Membrane resistance to flow of ions
87
What is Ri?
Internal axonal resistance to flow of ions
88
What factors can change Rm or Ri?
Number of pores in membrane | Diameter of axon
89
Why do biological membranes have capacitance?
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
What is saltatory conduction?
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
What causes multiple sclerosis? What are symptoms?
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
What are differences between electrical and chemical synapses?
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
What are the steps in chemical synaptic transmission?
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
How long does chemical synaptic transmission take?
2-5 ms
95
What are classes of NY? (3)
Amino acids and amines (fast) | Peptides (slower, longer)
96
What are experiments to test Ca2+ neurotransmitter release?
1) image Ca2+ | 2) block Ca2+
97
Image Ca experiment
Use Ca sensitive dye in squid synapse | All color localized on presynaptic terminal
98
Block Ca channels experiment
Control and added cadmium Control is normal current and Vm change over time Experimental no current or voltage change observed
99
How are SNARE proteins involved in exocytosis?
Pull vehicle close to pbl so they fuse
100
Proteins in exocytosis
Synaptobrevin Synaptotagmin Syntaxin SNAP-25
101
Synaptobrevin
Vesicular SNARE | Long straight high up on vesicles
102
Synaptotagmin
Ca2+ bonding protein in vesicles Has two clampy bits to catch ion Middle of vesicles
103
Syntaxin
pmb-bound SNARE Short and smooth curve with tangled end One set on outside of docking site
104
SNAP-25
pmb-bound SNARE Looks like crossed ends of jumping rope One set on inside of docking site
105
For NT receptors, what are differences between ligand gated ion channels and g-protein coupled receptors?
Fast vs. slow and long-lasting, acting by proxy
106
What is Botox?
Neurotoxin that targets SNAREs so muscles can’t move because no Ca2+ released
107
Outline how g-coupled protein receptor work?
Later

NEUR 101 (2 decks)

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