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Cellular and Molecular Neuroscience > Slides 3 > Flashcards

Slides 3 Flashcards

1
Q

Where does integration of sensory information typically occur?

A

Mostly in the pre-frontal cortex

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2
Q

What are the 3 things the brain needs to do in order to produce behaviour?

A
  1. Receive info about the world
  2. Integrate info to create a sensory reality
  3. Produce commands to control the movement of muscles
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3
Q

What are the brain’s 3 primary functions?

A
  1. Create a sensory reality
  2. Integrate information
  3. Produce behaviour
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4
Q

How are white matter tracts detected in the brain?

A

Tractography

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5
Q

Sensory receptors:

A

specialized cells that transduce (convert) sensory energy (like light) into neural activity

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6
Q

Energy for vision

A

Light –> chemical

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7
Q

Energy for audition

A

air pressure –> mechanical

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8
Q

Energy for somatosensation

A

Mechanical energy and sometimes chemical energy

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9
Q

Energy for taste and olfaction

A

Chemical molecules

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10
Q

Is our perception an exact replication of the real world?

A

Not really, it is a subjective construction of reality that is manufactured by the brain

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11
Q

How does the brain distinguish between the different senses?

A

They are processed in different parts of the brain

Learn to distinguish the senses through experience

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12
Q

Which is our primary sense?

A

Vision

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13
Q

3 layers of the eye

A

Cornea: clear outer covering
Lens: focuses light
Retina: where light energy initiates neural activity q

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14
Q

Retina vs Fovea

A 
Retina = light sensitive surface at the back of the eye consisting of neurons and photoreceptor cells 
Fovea = center of the retina, the receptive field at the senteer of the eye's visual field
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15
Q

what is the function of the bipolar cells?

A

They connect the rods and cones to the ganglion cells

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16
Q

What cells make up the optic nerve?

A

The axons of the ganglion cells

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17
Q

Retinohypothalamic tract

A

Axons of ganglion cells that go to the hypothalamus and contribute to circadian rhythms and pupil size

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18
Q

Characteristics of rods

A
  • More numerous than cones
  • Sensitive to dim light
  • Used for night vision
  • No colour perception
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19
Q

Characteristics of cones

A
  • Responsive to bright light
  • Colour and high visual acuity
  • Located in the fovea
  • Colour vision
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20
Q

2 layers of a photoreceptor

A

Outer: stacks of membranes that contain visual pigment molecules (rhodopsin)
Inner: organelles and opsin molecules

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21
Q

Geniculostriate visual pathway

A

Retina –> visual cortex

Main pathway that allows you to form images

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22
Q

Tectopulvinar visual pathway

A

retina –> superior colliculus
Allows you to detect motions
Visually guided movements

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23
Q

Retinohypothalamic visual pathway

A

Synapse at the suprachiasmatic nucleus of the hypothalamus

Regulates circadian rhythm and pupillary reflex

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24
Q

Is an image formed at V1?

A

No, thats where all of the information (colour, motion, depth, form) is integrated
Images are put together in V2, V3, and V4

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25
Q

Dorsal Visual Stream

A

Occipital –> parietal

How: visually guided movements

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26
Q

Ventral Visual stream

A

Occipital –> temporal

What: visual identification of objects

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27
Q

Pinna:

A

Funnel-like external structure of the ear designed to catch sound waves and direct them to ear canal

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28
Q

External ear canal:

A

Amplifies sound waves and directs them to the eardrum

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29
Q

Middle ear:

A

An air filled chamber with 3 bones:

  • Hammer
  • Anvil
  • Stirrup
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30
Q

The inner ear has what 3 components?

A

Cochlea
Basilar membrane
Hair cells

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31
Q

Cochlea:

A

Fluid filled stricture that have the auditory receptor cells

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32
Q

Basilar membrane:

A

Receptor surface in the cochlea that transduce sound waves into neural activity
- Where the hair cells are embedded

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33
Q

Hair cells

A

Sensory cells that when stimulated by waves in the cochlear fluid, push up against the tectorial membrane and make action potentials in the auditory nerve

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34
Q

Fast vs slow wave sound frequencies

A

Fast: max displacement at base of membrane
Slow: max displacement at apex of membrane

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35
Q

Process of sound wave to NT release

A
  • Sound makes waves in the cochlear fluid which moved the basilar membrane
  • Hair cells are anchored in the basilar membrane, so they get pushed up against the tectorial membrane
  • Displacement of hair cells changes the membrane potential and leads to NT release
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36
Q

Inner vs outer hair cells

A

Inner: afferent and make up 90% of auditory nerve
Outer: both efferent and afferent

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37
Q

What direction of movement of the hair cells causes a depolarization?

A

Movement towards the tallest cilia
K+ entry
Causes Ca+ to enter and NT to be released

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38
Q

What direction of movement causes the hair cells to hyperpolarize?

A

Movement towards the shortest cilia

Causes less NT release

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39
Q

Where do the inner hair cells synapse to?

A

spiral ganglion axons that make the auditory nerve (cranial nerve 8)

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40
Q

What brain region helps you detect where sounds are coming from?

A

Superior Olivary complex

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41
Q

What brain region mediates sound guided movements?

A

Inferior colliculus

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42
Q

Left vs right temporal lobe in sound processing

A 
Left = language processing 
Right = spatial dynamics and emotion
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43
Q

Humans have which two types of skin?

A

Hairy and glabrous

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44
Q

Nociception

A

Perception of pain, temperature and itch

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45
Q

Hapsis

A

perception of fine touch and pressure

Identify objects through touch

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46
Q

Proprioception

A

Perception of the location and movement of the body

- sensitive to the stretch of muscles and tendons and movement of joints

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47
Q

What sense to free nerve endings respond to?

A

Chemical signals for pain

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48
Q

Rapidly adaptive reception

A

responds briefly at the beginning and at the end of a stimulus
- touch, fluttering sensations and vibration

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49
Q

Slowly adapting receptor

A

responds as long as a sensory stimulus is on the body

- pain, temperature, skin indentation

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50
Q

Root ganglion neurons

A

Axons that carry sensory information from the skin to CNS

- May synapse with other neurons in the spinal cord or go straight to the brain

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51
Q

Proprioceptive and haptic neurons

A

Large, well myelinated axons –> fast

Ipsilateral in spinal cord and cross at brain stem

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52
Q

Nociceptive neurons

A

Small, not well myelinated axons –> slow

Cross in brain stem

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53
Q

Primary somatosensory cortex (Broadmans area 3-1-2)

A

Receives projections from the thalamus

Begins the process to constructing perceptions from somatosensory information

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54
Q

Secondary somatosensory cortex

Brodman’s area 5 and 7

A

Refines the construction of perceptions

Projects to the frontal cortex

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55
Q

Integrating vision with somatosenses

A

The dorsal stream projects to the secondary somatosensory cortex and then to the frontal lobe

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56
Q

Movement planning in the frontal lobe

A

Prefrontal: planning movements
Premotor: organizes motor sequences
Primary motor: produces specific movements

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57
Q

Axon projections of one eye

A

Half stay on the ipsilateral side and go to the contralateral side

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58
Q

Which receptors are furthest away from the lens?

A

Photoreceptors

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59
Q

What cells are the interneurons of the visual system?

A

Amacrine and horizontal cells

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60
Q

Which cells does light reach first in the eye?

A

Ganglion cells

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61
Q

Which eye cells produce action potentials?

A

Ganglion and amarine cells

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62
Q

What eye cells produce graded potential

A

Photoreceptors, horizontal cells and bipolar cells

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63
Q

What NT do photoreceptors release?

A

Glutamate

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64
Q

How are pigments arranged in rods and cones?

A

Rods: in disks that do not contact the membrane
Cones: comb-like structures that are continuous with the membrane

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65
Q

How many disks are replaced each hour?

A

3, it requires a lot of energy

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66
Q

What is rhodopsin made of?

A

A complex of a large opsin protein and a light absorbing retinal

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67
Q

What does the opsin protein look like?

A

A large protein with 7 hydrophobic trans-membrane helices

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68
Q

What happens to retinal when it absorbs light?

A

It changes shape = photoisomerization

It goes from 11-cis retinal to all trans retianl

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69
Q

What happens to rhodopsin when retinal changes shape?

A

The whole protein changes shape

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70
Q

What molecule is crucial for phototransduction?

A

Metarhodopin II

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71
Q

All-trans retinal is the precursor for what?

A

11-cis retinal

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72
Q

What nutrient is needed from our diet to make all-trans retinal

A

Vitamin A

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73
Q

What is the confirmation of retinal at rest>

A

11-cis retinal

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74
Q

Because all-trans retinal is more straightened out, what happens to the rhodopsin protein when activated by light

A

The opsin gets pushed open

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75
Q

What is different between photoreceptors that capture different colour wave lengths

A

the amino acid sequences are slightly different

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76
Q

How do invertebrates’ photoreceptors respond to light?

A

Depolarization

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77
Q

How to photoreceptors in vertebrates respond to light?

A

Hyperpolarization

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78
Q

What does photoactivated rhodopsin (meta II) do when stimulated?

A

It activates the G-protein transducin, initiating the phototransduction cascade

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79
Q

What is the activity of photoreceptors in the dark?

A

Na+ and Ca++ enter ion channels and cause depolarization and glutamate is released

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80
Q

What happens to the activity of the photoreceptor when stimulated by light?

A

The sodium channels close due to reduced levels of cGMP

Rod becomes hyperpolarized and reduces glutamate release

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81
Q

Levels of cGMP and sodium channels

A 
High = channel open 
Low = channel closed
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82
Q

The g-protein transducin has 3 subunits. What happens to the alpha subunit during transduction?

A

Alpha exchanges GDP for GTP

It break off and activates the membrane bound phosphodiesterase. It hydrolyzes cGMP to GMP –> reducing levels of cGMP

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83
Q

What happens when there is decreased cGMP?

A

It is less able to bind to Na channels, so they close and the rod hyperpolarizes

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84
Q

What dictates the specific wave length that will stimulate a rod?

A

The amino acid sequence of the opsin molecule

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85
Q

The amount of of NT released from the rods is related to what?

A

The amount of light

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86
Q

Is there a blood brain barrier on the nose?

A

No

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87
Q

Sequence of olfactory cells

A

Receptors to Glomerulus to Mitral cells (which make up the olfactory projection)

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88
Q

What are the inhibitory cells in olfaction

A

Periglomerular cells (connest the glomerulus together)
Tufted cells
Granule cells

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89
Q

Odour applied to the soma makes what type of response?

A

A short rapid response

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90
Q

Odour applies to the dendrites of cilia produce what type of response

A

A large, long lasting response

|&raquo_space; Due to second messengers

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91
Q

What receptors are involved in smell and where are they located?

A

Golf receptors

In the cilia

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92
Q

What happens to the Golf receptor when an odour binds?

A
  1. Alpha subunit dissociates
    2a. Activates adenylyl cyclase and increases cAMP
    3a. Opens Na and Ca channels influx
    2b. Also a activates phospholipase 3
    3b. Converts PIP2 to IP3
    4b. Opens Ca channels
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93
Q

What happens when the olfactory cilia become depolarized (influx of Na and Ca)

A

Ca causes the chloride channels to open, and Cl effluxes, causing further depolarization

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94
Q

What happens when the olfactory cilia become depolarized (influx of Na and Ca)

A

Ca causes the calcium-activated chloride channels to open, and Cl effluxes, causing further depolarization

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95
Q

What does it mean to say that odour receptors are more general?

A

More than one odourant type can bind to each receptor

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96
Q

Why do odour receptors need to be constantly replenished?

A

Because they are constantly being killed off, maybe from all the calcium

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97
Q

Are receptor types evenly spaced in the nose/

A

No, particular odourant receptors are found in restricted areas of the olfactory epithelium

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98
Q

Where do olfactory receptors project to?

A

To the olfactory bulb

Which mainly projects to the amygdala

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99
Q

What is the significance of lots of olfactory projections to the amygdala

A

It makes unconscious emotional assessment of odour

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100
Q

What other sense enhances taste?

A

Smell

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101
Q

Which flavours have g-protein receptors?

A

Umami
Salty
Bitter
Sweet

102
Q

Where are taste buds located?

A

Mainly within small bumps on the tongue called papillae

But they are all throughout the mouth

103
Q

Do taste cells have axons?

A

No, they form chemical synapses with afferent neurites

104
Q

What is the signal transduction pathway for all G-coupled taste receptors

A
  1. Alpha subunit activate phospholipase 3
  2. Phospholipase 3 make PIP2 into IP3 and DAG
  3. IP3 release calcium from ER 4. Increased calcium levels make NT release
105
Q

What is the scala media?

A

It is the fluid in the cochlea that has a high concentration of potassium and low concentration of sodium that the hair cells are in

106
Q

Fast waves = ______ pitch

A

High pitch/frequency

107
Q

The scala media has a high concentration of K and low Na, so what ion rushes in when the hair cell channels open?

A

Potassium

108
Q

After K rushes into the hair cell, what happens?

A

There is a calcium influx which causes NT release

109
Q

What is another name for the hair cells?

A

Stereocilium

110
Q

What connects the stereocilium?

A

Tip links - a coiled protein

111
Q

How do the tip links open ion channels on hair cells?

A

When the hair cells move, they tension in the tip links increase and this promotes the opening of K channels

112
Q

What protein opens the gates of the ion channels when there is tension in the coil between hair cells

A

myosin

113
Q

How do hair cells adapt to sound?

A

The myosin protein slides down the kinocilium, which reduces tension in the coil and closes the gates

114
Q

What type of calcium channel is in hair cells?

A

Potassium gated calcium channel

115
Q

What important function does calcium play in hair cells?

A

Stimulates the release of NT

116
Q

How are nocioceptive, hapsis, and proprioceptive receptors stimulated?

A

Nociception : free nerve endings activated by chemicals
Hapsis : activated by mechanical stimulation of the hair or tissue
Proprioception: sensitive to stretch and tension of muscles

117
Q

Rapidly adapting receptor

A

responds breifly to the beginning and the end of a stimulus on the body

118
Q

Slowly adapting receptor

A

responds as long as sensory stimulus in on the body

119
Q

Stretch receptor (weak vs strong)

A

sense the stretch of the muscle
Weak: produces grated potential
Strong: produces action potential

120
Q

Fast vs Slow adapting stretch receptor

A

Slow adapting = persisting firing

Fast adapting = declining firing

121
Q

What is the muscle spindle made of?

A

small intrafusal fibers that are embedded in the bulk of the muscle

122
Q

What two types of neurons innervate the muscle spindle?

A
  1. Large muscle fibers are supplied by alpha-motorneurons

2. Intrafusal fibers are supplied by gamma efferent fibers

123
Q

Group 1A of the afferent neurons of the muscle spindles

A

Large diameter, fast conducting that from the primary nerve ending

124
Q

Group 2 of the afferent neurons of the muscle spindles

A

Smaller and conduct more slowly, that form the secondary nerve endings

125
Q

Primary nerve endings of the muscle spindle

A

Sensitive to the rate of change of the stretch (rapidly adapting)
> connected to group 1A axons

126
Q

Secondary nerve endings of the muscle spindle

A

Sensitive to the level of static tension (slow adapting)

> connected to the smaller group 2 axons

127
Q

What are 3 ways that mechanoreceptor channels can be opened?

A
  1. Through forces conveyed through tension in the membrane
  2. Forces affecting coiled proteins linked to the channel gate
  3. Indirectly activated by a second messenger
128
Q

What ion enters the muscle when it contracts

A

Sodium

129
Q

What are the two main receptors involved in pain perception?

A

G protein coupled receptors (GPRC) - metabotropic

Transient receptor potential (TRP) - ionotropic

130
Q

TRPs have different thermal activation ranges, what does that mean?

A

Different chemicals produce sensations of temperature that are not necessarily painful (menthol)

131
Q

How do GPCR affect TRP?

A

The activation of GPCR can increase the sensitivity of TRPs

132
Q

GPCR - TRP axis

A

When the GPCR and stimulated, they can lead to the activation of different kinases which phosphorylate the TRP and activate them –> TRP gets sensitized to pain

133
Q

What is the mechanism of the GPCR - TRP axis

A
  1. GPRC stimulates phospholipase C (PLC)
    2 PLC stimulates PKC
    3 PKC activated TRP

There are many different mechanisms, but the important component is that a Kinase phosphorylates TRP

134
Q

What part of the spinal cord are the pain receptors located?

A

Dorsal horn

135
Q

What can make nociceptors hyper-reactive

A
  • more transducers
  • more GPCR
  • more signalling
  • more Na channels
136
Q

What role does inflammation play in pain sensitivity

A

Inflammation can phosphorylate TRPs and alter the thresholds of activation

137
Q

What causes the delay between stimulation of a pre-synaptic neuron and a post synaptic response?

A

The time it takes the NT to travel across the cleft

138
Q

What causes the delay to increase and decrease

A

Temperature

Warmer = less delay

139
Q

What is required for an action potential to occur?

A

A depolarization of the cell

140
Q

Do depolarizations always result in action potentials?

A

No

but action potentials are the strongest depolarization

141
Q

What causes the delay between the end of an action potential and the release of NT?

A
  1. The time required to open calcium channels

2. The time it takes Ca entry to trigger NT release

142
Q

Depolarization leads to the increase of what ion in the cell?

A

Calcium

143
Q

High levels of Ca trigger the release of NT. Where are Ca channels mostly located?

A

Concentrated in the active zones of the terminal membrane

144
Q

In terms of the active zone and calcium channels, what increased the chance that NT will be released

A

If there is a bigger active zone with more calcium channels

145
Q

What is the readily releasable pool?

A

The collection of vesicles that are bound to the pre-synaptic membrane at the active zone that are able to be rapidly released

146
Q

What is the reserve pool?

A

Vesicles in the middle of the terminal button that are bound to each other by actin filaments that are ready to be put into the readily releasable poo;

147
Q

What is the quantum of transmitter?

A

The amount of NT contained in one vesicle = there is a set number of NT per vesicle

148
Q

What are the names of the 3 steps of vesicle NT release?

A
  1. Docking
  2. Priming
  3. Exocytosis
149
Q

What does HVA stand for in terms of calcium channels?

A

High voltage activated

150
Q

Which subunit in calcium channels forms the pore?

A

The alpha-1B subunit

151
Q

Which subunit in calcium channels forms the pore?

A

The alpha subunit

152
Q

Which type of calcium channel do we focus on in this course?

A

N-type

153
Q

What is the composition of the calcium channel protein?

A

Alpha in the middle, flanked by beta and gamma subunits

  • beta in intracellular
  • gamma has 4 transmambrane segments
  • alpha2 is extracellular
154
Q

Is there just one type of each subunit in the calcium pore?

A

No, there are many different isoforms

155
Q

In calcium channels, the alpha subunit is the largest, and it incorporates (4):

A
  1. Conduction pore
  2. Voltage sensors
  3. Gating apparatus
  4. Ligand binding sites
156
Q

How many segments are there in the alpha subunit of the calcium channel? What do they do

A

6
S1-S4 are the voltage sensor molecules
S5&6 form the pore

157
Q

How does the calcium channel open?

A

As the S5 and S6 subunits are activated, they twist and open the pore

158
Q

What are the 3 different stages of voltage gated ion channels?

A 
Activation = pore open 
Deactivation = pore closed 
Inactivation = pore closed and unable to open
159
Q

There are two types of SNARE proteins embedded in membranes that form a complex:

A

V(esicle) SNARE

T(plasma membrane) SNARE

160
Q

What is the name of the v-SNARE?

A

Synaptobrevin

161
Q

What are the names of the two t-SNAREs

A

SNAP-25

Syntaxin-1

162
Q

What is the function of synaptotagmin?

A

A Ca binding protein in the synaptic vesicle membrane

163
Q

What happens to synaptotagmin when there is a calcium influx due to a depolarization?

A

Calcium will bind to synaptotagmin and will change the conformation from a trans to a cis state

164
Q

What happens when synaptotagmin goes from a trans to a cis state?

A

It binds to the plasma membrane and pulls the vesicle closer to it, which allows it to dock and fuse

165
Q

Primed vs non-primed excitosome

A

Primed: a docked vesicle-SNARE complex that is ready to be released
Non-Primed: a docked vesicle-SNARE complex that is not ready to be released because it is not close enough to the membrane

166
Q

What does the non-primed excitosome complex unit consist of?

A
  • A calcium channel
  • Syntaxin 1
  • SNAP 25
  • trans synaptotagmin
167
Q

What keeps the non-primed complex away from the membrane?

A

The electrostatic repulsion of the negative charge of trans synaptotagmin

168
Q

What happens to the non-primed complex when there is a depolarization?

A

Ca concentration increases and binds to synaptotagmin which inserts itself into the membrane

169
Q

Once the excitosome is primed, it is ready for what?

A

Fusion

170
Q

What is the process of fusion?

A

Calcium binds to synaptotagmin which binds to the SNARE complex. Complexin leaves and an omega figure is formed

171
Q

In the docking phase, what protein is holding syntaxin in its native conformation?

A

Munc

172
Q

The SNARE complex that is formed by the tangling of synaptobrevin, syntaxin and SNAP 25 is stabilized by what during priming?

A

A protein called complexin

173
Q

Once the NT are released, the synaptic vesicle is recycled by ______

A

Endocytosis = a bubble comes off the plasma membrane

174
Q

Neurotransmitter release is regulated by what two things?

A
  1. Rate of neuron firing

2. Probability that vessicles will undergo exocytosis

175
Q

What NT is used in all neuromuscular synapses?

A

Acetylcholine

176
Q

What other synapse is ACh used in?

A

Parasympathetic terminals

177
Q

How is the precursor to ACh, Acetyl CoA made?

A

During glycolysis when pyruvate is broken down, acetyl groups are transferred to the coenzyme A

178
Q

Where does choline come from?

A

Our diets

179
Q

What are the two components that make up ACh?

A

Acetyl CoA and Choline

180
Q

How are Acetyl CoA and Choline combined to make ACh?

A

the enzyme Choline Acetyltransferase

181
Q

What puts NT into vessicles and what else does it determine?

A

Vesicular Neurotransmitter Transporters

they determine how many NT are in each vesicle

182
Q

What energy source drives the vesicular neurotransmitter transporters?

A

the proton electrochemical driving force gradient

183
Q

What happens to the concentration of receptors as you move away from the post-synaptic density?

A

There are fewer receptors

184
Q

How many subunits are in the nicotinic ACh receptor?

A

5 subunits around a central pore

185
Q

Which subunit has the binding site in ACh receptors

A

Alpha

186
Q

How many alpha subunits are there in ACH receptors?

A

At least 2 `

187
Q

What ion rushes in when ACh receptors open?

A

Sodium

188
Q

Different subunit combinations of the ACh receptor dictate what?

A

The different functional properties of that receptor

189
Q

How many trans membrane domanes does each subunit have in the ACh receptor and what are they labeled?

A

4

M1-M4

190
Q

In which ACh subunit domain is the binding site located?

A

The larger M1 amino terminal domain

191
Q

What does the ACh M2 domain do?

A

determines the ionic selectivity of the receptor and faces the inside of the channel pore

192
Q

What is the secondary structure of the ACh subunits that span the membrane?

A

Non-polar (hydrophobic) alpha helixes

193
Q

Where specifically on the ACh receptor does ACh bind?

A

To the cys-loops on the beta pleated sheets on the extracellular side

194
Q

What happens to the ACh receptor when ACh binds?

A
  1. The beta sheets rotate
  2. This causes M2 to move outward
  3. This opens the pore
195
Q

What is the precursor molecule to GABA?

A

Glutamate

196
Q

What are the two main Glutamate receptors?

A

AMPA and NMDA

197
Q

How do the AMPA and NMDA receptors work together?

A

When AMPA is stimulated it lets sodium in.

The sodium will activate NMDA and calcium will enter

198
Q

How many subunits are there in the AMPA receptors and what are they called?

A

4

GluA1 to GluA4 (or Glur1-4 or GluR-A - D)

199
Q

Each AMPA subunit can exist in what two forms? Caused by what?

A

“Flip” and “flop”

Caused by alternative splicing

200
Q

What is different about the flop GluA2-GluA4 AMPA subunits?

A

They desensitize faster but recover slower

201
Q

AMPA receptors usually only allow sodium to flow in, but in what case does to allow Calcium in as well?

A

If the GluA2 receptor is (Q) instead of (R)

> (R) is due to a post-transcriptional modification

202
Q

Is GluA2 (R) or (Q) caused by a modification?

A

(R)

203
Q

How many subunits in the GABA receptor?

A

5

204
Q

GABA binds to which sub unit and how many of these subunits are there?

A

Alpha

There are 2

205
Q

When the GABA pore is open, which ion rushes in?

A

Chloride

206
Q

Barbituates, ethanol etc have their ___ binding sites on the GABA receptor

A

Own

207
Q

What is the function of tonic inhibition?

A

It is baseline inhibition that makes sure there is not random excess excitation

208
Q

Desensitization of the GABA receptor

A

Even when GABA is bound the pore will not open, it is in a constant in between state
> caused by over use (alcoholism)

209
Q

What is the difference between the GABA(A) receptor and the GABA(B) receptor?

A

GABA(A): direct acting - has a pore

GABA(B): indirect acting - opens a channel through second messengers

210
Q

What receptors are direct acting and which are indirect acting

A 
Direct = ionotropic 
Indirect = metabotropic
211
Q

What are the 4 main G-proteins?

A

Gs
Gq
Gi
Go

212
Q

What is the effector of the Gs protein?

A

More adenylyl cyclase –> more cAMP –> more PKA

213
Q

What is the effector of the Gq protein?

A

More PLC –> IP3 –> Ca Diacylglycerol –> PKC

214
Q

What is the effector of the Gi protein?

A

Less adelylyl cyclase –> less cAMP –> more K channels open –> inhibition

215
Q

What is the effector of Go protein?

A

less Ca channels shut –> less NT release

216
Q

What is the composition of G-protein coupled receptors

A

7 transmembrane domains
Extracellular amino terminals
Intracellular carboxy terminals

217
Q

Which intracellular loops are the binding cites?

A

2nd and 3rd

218
Q

What can lead to the desensitization of the G-protein?

A

Phosphorylation

219
Q

Which domains do ligands bind to in G-proteins?

A

TM3,5,6,7

220
Q

What happens when a ligand binds to the G-protein?

A

The subunits twist and the alpha and beta/gamma subunits break off

221
Q

When the G-protein is stimulated, what happens to the alpha subunit?

A

It exchanges GTP for GDP and the alpha subunits becomes activated

222
Q

What on the receptor determines what G-protein configuration will bind?

A

C-terminus

223
Q

Once the alpha and beta/gamma subunits are freed from the G-protein, what do they do?

A

They modulate the activity of target proteins

224
Q

What protein turns GTP back into GDP

A

GTPase-activating proteins

225
Q

Once GTP is turned back into GDP, what can happen?

A

The trimer can reassemble and attach back to the G-protein

226
Q

Is the beta/gamma subunit complex membrane bound?

A

yes

227
Q

What does the G-protein beta/gamma subunit do once activated?

A

It can interact directly with an ion channel to open or close it

228
Q

What does the G-protein alpha subunit do once activated?

A

It can activate one or more enzymes that can alter ion channel activity through second messengers

229
Q

How to the Gi beta/gamma subunit open a potassium channel?

A

Directly

Induces a post-synaptic hyperpolarization

230
Q

How do the Gi beta/gamma subunits open channels

A

Possibly by causing a rotation in the sub units

231
Q

Which NT can bind to autoreceptors?

A

Norepinephrine

232
Q

What happens what Go protein autorecepots are stimulated?

A

It causes the a,b,g subunits to release and bund to N-type calcium channels, inhibiting calcium influx and reducing NT release

233
Q

Gs pathway

A

Alpha subunit is activated –> activates adenylyl cyclase –> turns ATP into cAMP –> activates PKA –> phosphorylates CREB –> initiates transcription

234
Q

What does the Gq protein do when stimulated?

A

Phospholipase C –> turn PIP2 into IP3 –> Activate ER to release Ca++ –> Ca++ does many things

235
Q

Why does intracellular calcium need to be very well regulates?

A

Because it is very cytotoxic

236
Q

A neuron can make how many connections?

A

50 000

237
Q

EPSPs are associated with the opening of what channels?

A

Sodium: influx

238
Q

IPSPs are associates with the opening of what channels?

A

Potassium: efflux
Chloride: influx

239
Q

Within the plane of the membrane, what forms a selective filter for cations/anions?

A

Negative and positive charges

240
Q

What is the main difference between sodium and potassium channels?

A

the 4 subunits of the sodium channel are all linked up

the 4 subunits of the potassium channel are all separate

241
Q

In a voltage gated sodium channel, there are __ domains each with ___ transmembrane segments

A

4

6 (S1-S6)

242
Q

Which segment in the voltage gated sodium channel is responsible for voltage sensing?

A

S4

243
Q

Which segments in the voltage gated sodium channel form the pore that ions flow through?

A

S5 and S6

244
Q

In a voltage gated potassium channel, there are __ domains each with ___ transmembrane segments

A

4

6

245
Q

How many subunits form the pore in a voltage gated potassium channel?Expressed with accessory ___ subunits

A

4

Beta

246
Q

What makes the sodium channels selective

A

the ring of 4 glutamic acids that line the insides of the pore

247
Q

What makes the potassium channels selective?

A

backbone carbonyl oxygens

248
Q

How many binding sites are there within the potassium pore and what binds to the,?

A

4 (s1-s4)

Two water molecules and two potassium molecules

249
Q

Potassium channels are often ____ at rest

A

open

250
Q

Sodium channels are often ____ at rest

A

closed

251
Q

How do the voltage gated potassium channels open once stimulated?

A

It causes a rotation of the S4 domain, which intereacts with S6 segments to open the gate

Cellular and Molecular Neuroscience (4 decks)

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