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2020 Winter > Neurobio 2 > Flashcards

Neurobio 2 Flashcards

1
Q

Explain what the spike threshold is.

A

The amount of depolarization that a membrane potential must cross to initiate an action potential
– When crossed → action potential MUST happen!

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2
Q

What are 3 advantages of communicating with electrical synapses? And a disadvantage?

A

Fast, reliable, and allow for spike synchronization

Disadvantage: less flexible - signals cannot be modified (stronger/weaker)

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3
Q

If you have electrodes in two cells that are connected by a synapse. How can you determine whether the synapse is electrical or chemical?

A

Electrical if… spikes are synchronized in both the cells

Chemical if… there’s a millisecond delay

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4
Q

Where does chemical synapses delay of about 1 msec come from?

A

Calcium channels are opening slowly

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5
Q

Where does a spike start

A

in the axon hillock

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6
Q

Difference between ELECTRICAL synapses and CHEMICAL

A

electrical – gap junctions

chemical – neurotransmitters

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7
Q

Gap junctions

A

Direct transfer of current from one cell to the next

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8
Q

Spike synchronization

A

Causes spikes to happen at same time in both cells

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9
Q

Steps of chemical synapses

A

1- action potential depolarizes axon terminal
2- calcium channels open
3- Ca++ gushes in
4- Ca++ binds to protein
5- synaptic vesicle binds to post synaptic membrane
6- vesicle fuses with membrane
7- neurotransmitter crosses synaptic cleft
8- NT diffuses across cleft
9- NT binds to channel
10- channel opens (or closes)
11- current in or out (post-synaptic potential)

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10
Q

depol/hyper

PSPs

A

depolarization: epsp
hyperpol: ipsp

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11
Q

NEUROTRANSMITTERS

A

AMINO ACIDS (not synthesized at terminals)

  • GLU: most common, excitatory NT (CNS)
  • GABA, GLY: inhibition (Cl-)

AMINES

  • Acetylcholine (ACh): excites muscles
  • Norepinephrine (NE): symp post-ganglion

PEPTIDES (synthesized @ cell body)

  • substance P: co-released along w/ other NT
    • B-endorphine: binds opiate receptors
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12
Q

What are dense core vesicles? How do they get to the presynaptic terminal? Under what circumstances are they released?

A

Dense core vesicles: secretory granules that get released when they are super excitatory; vesicle full of peptide
– Co-released with transmitters
Don’t get released in active zone (full of mechanism of clear transmitters); released in terminal

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13
Q

What happens to the extra membrane that is added to the presynaptic terminal as vesicles fuse with the membrane?

A

Vesicle opens and empties its neurotransmitters into the synaptic cleft; & becomes a vesicle again (recycles)

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14
Q

Why is the neuromuscular junction (nmj) the most thoroughly studied vertebrate synapse? What is an important difference between the nmj and synapse in the CNS?

A
  • motor end plate
  • Easily accessible, the most powerful, and least invasive
  • HUGE release of (200) vesicles released at nmj
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15
Q

axo-dendritic
axo-somatic
axo-axonic

A

axo-dendritic: more often excitatory (synapse @ dendrite of cell 2)
axo-somatic: synapse @ cell body of cell 2
axo-axonic: (pre-synaptic inhibition): synapse @ axon of another cell

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16
Q

Peptide neurotransmitters are generally released

A

with high frequency trains of spikes

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17
Q

Postsynaptic potentials (PSPs) generally last much longer than action potentials. Why is that adaptive, i.e. what function does that serve?

A
  • Allow for signals to be modified (stronger/weaker)
  • Action potential is a momentary event
  • Principle of summation - More likely to overlap (both for temporal and spatial)
  • -spatial is more likely to add together
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18
Q

Why does opening chloride channels, with glycine or GABA for example, inhibit a neuron even if the chloride equilibrium potential is the same as the resting potential? If a single inhibitory synapse is activated in such a neuron, would you see an ipsp?

A
  • chloride equilibrium usually same as resting potential; will always try to go back
  • if sodium depolarizes - chloride will try to balance it out
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19
Q

EPSP

A

-always depolarizing direction

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20
Q

ionotropic

metatrobic

A

iono: DIRECT action of neurotransmitter on an ion channel
meta: INDIRECT postsynaptic response, mediated by g-proteins
- direct action of g-protein: can directly act on channels or rev up an enzyme
- indirect action of g-protein: 2nd messenger

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21
Q

Ecl always ___ threshold

A

below

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22
Q

Synapses with post synaptic receptors that open channels that are equally permeable to sodium and K+ ions… what’s true?

A

Synapse would be excitatory because more current flows in than out through channels

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23
Q

We know that the nicotinic acetylcholine receptor opens a nonspecific cation channel (i.e. positive ion can pass through). Explain why opening this channel causes a depolarization. In other words, why is the inward sodium current greater than the outward potassium current? Which way would calcium flow, in or out?

A
  • Depolarization caused by more sodium goes in and potassium comes out
  • driving force is greater on sodium
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24
Q

What is meant by the term “shunting inhibition?” Describe the spatial arrangement of excitatory versus inhibitory synapses onto the neuron.

A

Shunting inhibition: stopping epsp from getting to soma - usually done by chloride
- Chloride CANCELS OUT EXCITATION by activating
excitatory : on periphery of dendrites
Inhibitory : cell body or basis of dendrites

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25
Q

What are two different ways to increase the length constant of a dendrite. Why is the length constant important functionally?

A
  1. close ion channels
  2. increase diameter - evolution - decreases resistance

Important because positive current leaks out / amplitude falls off with distance

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26
Q

Graded potentials

A

vary in amplitude

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27
Q

Spatial summation
v
Temporal summ

A

Spatial- different location

temporal- same location, different times

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28
Q

Synaptic potentials are:

A

LOCAL

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29
Q

Characteristics of synaptic potentials

A
  • length constants vary w/ resistance (membrane and internal)
  • -decrement over distance (they change)
  • -positive current travels both ways (leaks out)
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30
Q

What would happen if activated synapse on neurons w/ GABA, which opens chloride channels?

A

PSP would be flat (nothing would happen)

-chloride happy at equilibrium

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31
Q

Explain 2 different general ways that activated G-proteins can exert their effects in a postsynaptic neuron?

A
  • Go straight to a channel

- Go straight to an enzyme (longer turn responses/effects, more powerful, affects multiple channels)

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32
Q

Metatrobic

A

indirect postsynaptic response, mediated by g-proteins (Guanine nucleotide binding proteins)

  • -GPCR: g-protein binding receptor
  • -activates g-protein by trasnmitter binding to receptor: moves through cell and does something else

has BETA and ALPHA segments
GDP attached
if activates: segments fall off into 2 pieces and both get activated

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33
Q

What are 2 potential advantages of metabotropic synapses over ionotropic synapses? What is a disadvantage in using metabotropic synapses?

A
  • Lasts longer & amplify the signal

- Slower to respond

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34
Q

2nd messenger

A

-nicotinic ACh receptor generalized cation Ch
(on skeletal muscle)
-muscarinic ACh receptor
(muscarinic)

35
Q

What does the term “decussate” mean? Where do the somatosensory pathway of large sensory neurons such as Meissner’s corpuscles decussate? Where do the somatosensory pathway of small sensory neurons such as pain receptors decussate?

A

DECUSSATE: cross from one side of the brain to the other (crossing midline)

  • large/fast sensory neurons pathway – Dorsal column nuclei
  • small/slow – spinal cord
36
Q

What are two important differences between the responses of Pacinian corpuscles and Merkel’s disks?

A

Pacinian corpuscles: fast-adapting, deep receptive fields that respond to deep pressure and high-frequency vibration

Merkel’s disks: slow-adapting, unencapsulated receptors that respond to light touch at the upper layer of skin

37
Q

What is the function of lamellar capsule of the Pacinian corpuscle? What is the usefulness of having receptors such as Pacinian corpuscles and Meissner’s corpuscles that respond best to vibration?

A

To detect vibration

Because it’s important for analysis of texture

38
Q

At the skin receptor level, what are we measuring when we measure a 2-point threshold? Where in the body do you find 2-point thresholds at very close spacing?

A

Measuring a neuron’s receptive field

Fingertips!

39
Q

Precisely where are the 3 synapses in the somatosensory pathway extending from a Pacinian corpuscle and resulting in an epsp in a cortical neuron in S1?

A

Big/Fast
Dorsal column nuclei (in medulla)
VP Nucleus in the thalamus
S1

Small
First in spinal cord (where they come in)
Crosses midline and goes PAST MEDULLA to VP nucleus
S1

40
Q

In simple words, what is lateral inhibition and what does it accomplish?

A

Lateral inhibition is when neighboring cells inhibit one another
- ACCOMPLISHES: edge detector that amplifies edges.

41
Q

What is meant by the term somatosensory map? Why is the somatosensory map distorted?

A

Somatosensory maps: areas of the brain that are spatially organized and respond to sensory stimuli.
-“Distorted” - based on a neurological “map” of the areas and proportions of brain dedicated to processing motor functions

42
Q

What 2 properties do neurons share that are in the same cortical column of Area 3b (the touch area)?

A

Same area on body - overlapping receptive fields

Share same submodalities (touch, pressure, vibration)

43
Q

Describe the organization of synaptic connections within a cortical column.

A

talk to each other in the column

44
Q

What are 2 ways to increase the size of the cortical representation of a single finger?

A

Increase usage of that finger

Cut off neighboring finger(s)

45
Q

Define the term motor unit. Why is it called a motor “unit”?

A

Motor unit: motor neuron and all the muscle fibers it innervates
It’s a unit because all the components work together

46
Q

What are 2 ways to increase tension in a muscle?

A

Increase fire rates

Fire more motor neurons

47
Q

What is the size principle, and why is it functionally adaptive?

A

Small motor units are recruited before large motor units

Makes contractions smoother (picking small objects vs big ones)

48
Q

What does calcium do to cause the muscle to contract? What is the basis for rigor mortis.

A

Calcium binds to troponin, shifting tropomyosin, exposing myosin binding sites
RIGOR MORTIS:
ATP gets depleted
ATP needs to be active but it’s not so myosin heads don’t released

49
Q

Please give a step-by-step description of the events underlying the stretch reflex.

A

Tapping stretches the tendon (detected by muscle spindles in quadriceps)
Fire 1a axon (sends signal to brain = alpha motor neuron)
Enters dorsal horn
Synapses motor neuron on ventral horn
Excites motor neuron → muscle contracts
NEG FEEDBACK LOOP

50
Q

4 Mechanoreceptors

A

shallow: better at localizing stimulators/touch
- Merkel’s disk (FAST)
- Meissner’s corpuscle (SLOW)

deep

  • Pacinian corpuscle (FAST)
  • Ruffini’s ending (SLOW)
51
Q

Pacinian corpuscle react to…

A

1-2 in the beginning and 1-2 at the end

52
Q

vibration sensations important for…

A

analysis of texture; different amounts of stimulation

53
Q

Lateral inhibition

A

edge detector - amplifies the edge; neighboring pathways inhibit each other

54
Q

lateral inhibition likely to happen in

A

dorsal column nucleus (in medulla)

55
Q

4 maps of body

A

touch, texture, muscle/limbs, complex features

56
Q

columnar arrangment

A
  • 100 nuerons

- share location/receptive field

57
Q

important concepts ch 12

A 
>lateral inhibition
>maps
>columnar arrangment
>receptive field
>plasticity
58
Q

plasticity

A

area in brain corresponding with body

59
Q

asterognosia

neglect syndrome/hemmineglect

A
  • unable to recognize objects by touch

- can’t recognize own part of body/world

60
Q

flexors vs

extensor

A

flex: limb going TOWARDS body
exten: AWAY from body

61
Q

synergists

antagonists

A

syn: 2 flexors
ant: flexor + extensor

62
Q

upper motor neuron…

lower motor neuron….

A

brian

spinal cord

63
Q

motor neurons controlling FLEXORS are …

A

dorsal to extensors

64
Q

motor neurons controlling AXIAL MUSCLES are …

A

medial to those controlling distal muscles

65
Q

motor neuron pool

A

all alpha motor neurons that innervate a single muscle

66
Q

motor neuron pool

A

all alpha motor neurons that innervate a single muscle

67
Q

motor neuron is the __ site of integration before movement

A

final

68
Q

muscle fiber

A

very large cell with amazing internal structure

69
Q

syncytium

A

fusion of cells to form one

70
Q

excitation-contraction coupling

A

1- action potential in alpha motor neuron
2- release of ACh
3- ACh open cation channel
4- EPSP big
5- muscle action potential
6- spike breads down t-tubules
7- Ca++ release from sarcoplasmic reticulum
8- Ca++ and ATP cause contraction (sliding filaments)
9- Ca++ resequestered
10- fiber relaxes

71
Q

thick and thin filaments

A

thin- actin

thick- myosin

72
Q

sliding filament model

A

Ca++ causes a shift in actin filament
- BINDS TO TROPONIN
Tropomyosin moves off actin binding sites
Myosin heads now able to bind to sites (forming cross bridge)
Muscle contraction happens!

73
Q

What is sarcoplasmic reticulum

A

extensive intracellular sac containing calcium ions

74
Q

ends of muscle spindle get info from…

A

gamma motor neuron

75
Q

muscles and spindles are :

A

parallel

76
Q

what do gamma motor neurons do

A
  • innervate “intramural” fibers inside muscle spindle

- take up slack of gamma motor neuron

77
Q

intrafusal

extrafusal

A

in-gamma

ex-alpha

78
Q

golgi tendon organs

A

monitor how much muscle is pulling on tendon

-1b fibers increase firing rate with increased muscle tension

79
Q

functions of golgi tendon organs

A

1- protect tendon connection

2-control muscle tension

80
Q

golgi tendon organs vs

muscle spindles

A
  • regulates muscle tension

- regulates muscle length

81
Q

reciprocal innervation

A

contraction of one muscle set accompanied by relaxation of antagonist muscle
- biceps/triceps

82
Q

flexor withdrawal reflex

A
  • mediated by sensory receptors (step on a tack)
  • always GOES TO flexors
  • flexor motor neurons get excited (lift foot away)
83
Q

crossed-extensor reflex

A

flex one leg –> extend the other

  • activation of extensor
  • inhibition of flexor

2020 Winter (4 decks)

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