Neuro Block I- Synapses and Spinal Cord and Brainstem

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1

electrical vs. chemical synapses

electrical: current flows freely through open gap junctions

chemical: NTs are released from the presynaptic cell, traverse the cleft and bind to receptors on the post synaptic cell

2

what can pass easily through gap junction pores

ions and small molecules (no proteins)

3

describe the flow of ion and current through gap junctions

ion flow bidirectionally; current is rectifying (only flows on direction)

4

gap junctions can be excitatory or inhibitory

in the inferior olive, thalamus, and hippocampus, are either excitatory or inhibitory

what about in the cerebral cortex

1. excitatory

2. inhibitory

5

what are the key benefits to using gap junctions opposed to the chemical synapse

we get synchronozation of activity in a network of interconnected neurons

fast and synchronized

6

what is functional role of glial cells in membrane potentials

help to regulate extracellular potassium concentration

note: some epilepsies are due to breakdown in this regulation causing depolarizations

7

two major classes of chemical synapses

1. ionotropic (channel linked)- the channels and receptor are part of the same protein

2. metabotropic (G protein linked)- receptor is GPCR whose response opens nearby channels

8

4 variations of boutons terminoux

1. axodendritic
2. axoaxonic
3. axosomatic
4. dendrodendritic

9

explain boutons en passage

where is this commonly found

when we see several connections on a single postsynaptic cell

commonly found on autonomics of smooth muscle

10

light vs. dark core NT vesicles

light core
- small molecular NTs (epi and norepi)
-made in soma, but some may be recyclced in the axon terminal

dark core
-peptide (larger molecules)
-always made in soma and brought to the terminal via transport along the MTs

11

why are 80% of deaths due to diabetes actually the result of atherosclerosis

each of the 3 major problems with diabetes leads back to vascular problem

(vasoconstriction, atherosclerosis, hyperplasia blood vessel endothelial cells)

12

one advantage and disadvantage to using G linked metabotropic synapse systems

adv: amplification of singla within the cell

disad: too many pieces of puzzle can go wrong and energetically expensive

but the advantages must outweigh the disad because this is a common mechanism in the body

13

explain how axoaxonic synapses can be used to regulate the final outcome

the first axon synapses on the second axon to modulate whether the signal the second axon sends willl be excitatory or inhibitory

14

temporal vs spatial summation

when multiple signals are sent to the same neuron, they can combine spatial (as a function of distance to one another) or spatially (as a function of time in between separate signals)

15

give an example of how neuronal integration works

say you grab a mug of hot coffee and it begins to burn; brain says hold ont the mug, but withdrawal refelex may tell same neurons to let go

excitatory and inhibitory potentials combine in neuron of focus and summartion is detected at initial segment to determine AP or not

16

what is missing from axon terminal that may otherwise allow for APs to possibly jump the synaptic cleft

Na-channels (NOT IN THE AXON TERMINAL)

17

for each junction, indicate type of receptor

1. NMJ
2. Preganglionic AM
3. postganglionic parasympathetic
4. brain stem and basal forebrain

1. nicotinic (PNS)
2. nicotinic (PNS)
3. muscarinic (PNS)
4. muscarinic (CNS)

18

catecholamines are important NTs

outline the sequence of biosynthesis for both epi and serotonin

tyrosine->DOPA->dopamine->norepi->epi

tryptophan->sero

19

name the 2 AAs that often act as NTs

excitatory or inhibitory

1. glutamate
2. aspartate

both excitatory

20

most glutamate receptors are ionotropic. a special type of Glu channel is the NMDA channel; compare the conventional to the NMDA glutamate receptor

conventional receptors work as normal ionotropic receptor

NMDAs have a Mg2+ ion that block the channel. this means that you need a larger depolarization to activate this channel, but once activated it leads to lasting changes in the synapse

21

NMDAs may lead to

1. long term potentiation
2. excitotoxicity

explain each

LTPs are involved in learning and memories. the NMDA can be activated to cause LTPs to lead to long term changes in how the membrane responds to potential changes

excitotoxicity- this is when excitation occurs too much for too long causing damage or even killing the neuron

22

inhibitory NTs

GABA
glycine

23

reaction to get GABA

glutamate->(glutamic acid decarboxylase)->GABA

24

peptide NTs

substance P

endogenous opioids

25

gas NT

NO (nitric oxide)

26

five fates of NTs

1. interact with receptor
2. breakdown
3. re-uptake (back into cell from which it was secreted)
4. uptake (it's a different cell; usually glial)
5. diffusion-it simply diffuses out of synaptic cleft

27

what is the main task of the nervous system? where do nerve cells make this happen?

communication

synapses

28

how does the change in membrane potential activity proceed at that region

...

29

what are the types of synapses

electrical and chemical synapses

30

what is the structure of electrical synapses

opposed plasma membranes of cells in near contact

proteins acting like membrane spanning pores align in adjacent cells from multiple

6 connexins, forming a connexon

31

what passes through gap junction pores?

ions
small molecules

32

what direction can current go in?

bidirectional or rectifying (only allows in one direction and not the other

33

where are gap junctions found? where are they excitatory and inhibitory?

PNS and CNS

excitatory: inferior olive, thalamus, hippocampus
inhibitory: cerebral cortex

34

how do gap junctions communicate?

rapidly through no neurotransmitters, no synaptic delay; at most direct level, straightforward effects

35

where is activity of gap junctions synchronized?

in the network of interconnected neurons

36

what is the neuron doctrine

says the individual nerve cells comprise the nervous system instead of a syncitium

37

how do gap junctions help with glial cells

they are the functional link between glial cells

play a role in helping astrocytes regulate EC K because they are linked by gap junctions; epilepsy could be from this

they also play a role in intracellular transport within Schwann cells

38

how are Schwann cells linked in a useful function by gap junctions?

if something goes nucleus to membrane to get there, it would have to go around, but it can take shortcuts through membranes to get there quickly

39

what are some consequences of malfunctioning connexin proteins in Schwann cells?

CMT disease family

CMT X chromosome is gene, conduction of APs break down

probably most common cause of peripheral neuropathy
- high foot arch, paresthesis, arched foot, atrophy of muscle in legs, inverted champagne bottle leg

40

what is true about chemical synapses compared to electrical synapses

more common
seemingly better understood

41

why are chemical synapses considered "chemical"

involvement of chemical molecule to carry signal from one signal from one cell to next

42

what are the two major classes of chemical synapses

channel linked chemical synapses- ionotropic
G protein linked chemical synapses- metabotropic

43

what are some variations in chemical synapses (boutons terminaux)

axodendritic
axoaxonic
axosomatic
dendrodendritic
boutons en passage (multiple boutons on postsynaptic cell; when one works, they all exert effect)- typical of how postsynaptic autonomic cells synapse on smooth muscle cell

44

what is the basic sequence of function in a chemical synapse

AP in presyn neuron
depol of axon terminal
entrance of Ca ions into axon terminal
exocytosis of NT
diffusion of NT across synaptic cleft
binding of NT to receptor molecules of postsyn cell
initiates response in postsyn cell
-hyperpol: inhibitor
-depol: excitatory
removal of released NT

45

what triggers NT vesicles to dock with plasma membrane?

Ca entrance due to Ca channel opening due to depolaritzation of terminal

46

what docking proteins are on the presynaptic cell that help bring vesicles closer to synaptic cell

synapta bregmen and synapta tagin on vesicle
synaptataxon and synap 25 on synaptic cleft

47

what are light core NT vesicles containing?

small clear vesicles with small molecule NTs, ACh, GABA, glutamate, glycine

48

what are dense core vesicles containing?

amines
dopamine
epi
norepi
serotonin

49

what are in larger dense core vesicles?

peptide NTs
endogenous opiates
beta endorphin
enkephalins
neuropeptide Y
can be found many places because made many places

50

what is the general orientation of a G protein receptor complex?

NT in ECF in synaptic cleft
receptor on membrane
G protein with alpha, beta, gamma subunits with GDP on alpha
adenylate cyclase in membrane

51

what happens when receptor binds NT?

Galpha switches GDP for GTP and it goes to activate adenylate cyclase, which produces cAMP and can amplify response

52

why are chemicals needed at cehmical synapses?

ions will not be able to cross synaptic cleft

53

where is ACh present in the body? what types of receptors are at each point?

ACh, present in PNS at NMJ (nicotinic), pregang autonomic motor receptors (nicotinic), postgang parasym receptors (muscarinic)

in CNS: brain stem and basal forebrain receptors (muscarinic)

54

what are catecholamines derived from?

epi and norepi from tyrosine

serotonin from tryptophan

enzyme: dopa decarboxylase takes DOPA dihydroxyphenylalanine to dopamine

55

what are some AAs that are NTs

glutamate and Asp

56

what types of channels are normally there for glutamate?

channel linked with receptor site and ion channel that works fast as an excitatory NT; if it goes, it lets Na into cells and cells depolarize

but there

57

what is the special type of glutamate receptors?

NMDA receptor with a narrow throat with Mg lodged in it; if a glutamate does bind, it still does not allow things in because of Mg; if there is a big depolarization with the normal glutamate receptors, then the NMDA receptors change and they allow Ca ions through which changes cells in a way that a regular glutamate channel depolarization does not

58

what is long term potentiation

excitation of this cell when Ca comes in can last a longer time than when just regular glutamate cells come open

downside of these is excitotoxicty: when Ca ions come in it is risky because high Ca levels are bad, cells can go through self induced suicide and they can be excited to death

59

how is GABA produced?

from glutamate, which via glutamic acid decarboxylase becomes GABA (gamma amino butyric acid)

60

are GABA and glycine usually involved in inhibition or excitation

inhibition

61

what are some peptide hormones?

substance P
endogenous opioids

62

what is the function of NO as a neurotransmitter?

dilation of BVs

63

what are the fates of neurotransmitters?

inactvation
reuptake
uptake
diffusion
interaction of NT and receptors

64

what are the two types of changes in membrane potential of postsynaptic cells? where do these affect the cell? how can these types of things be modulated?

excitatory postsynaptic potential (EPSP)
inhibitory postsynaptic potential (IPSP)

affect at initial segment on the axon

axoaxonic or axodendritic or axosomatic summation

65

why are the membarne potentials at the initial segment important?

this is where VG Na channels are most concentrated

66

what that we did in class is a good example of neuronal integration

motor centers in brain have inhibitory synaptic input from descending spinal tract and sensory input from the hand has a withdrawal reflex on muscle, these combine and you can override the reflex for a while

67

what portion of the neural tube does the spinal cord develop from?

caudal portion of neural tube

68

what parts of spinal cord give rise to sensory and motor regions, respectively

alar plate to sensory
basal plate to motor

69

where are the nerves located in cervical spine C1-C7? T1 and below?

C1-C7 above corresponding vertebral bone
T1 and below all below corresponding vertebral bone

70

where are the spinal cord enlargements?

cervical enlargement is C5-T1

lumbosacral enlargement is L2-S3

71

what is the progression of location of conus medullaris in the developing spinal cord? why?

first it is present at the coccygeal vertebral level
next it is present at S3
at birth it is present at L2-L3
a few months after birth it is present at about L1-L2
bones grow at a faster rate than the spinal column, so they take spinal nerves with it

72
card image

side 1: posterior
side 2: anterior
a. dorsal root
b. ventral root
c. dorsal ramus
d. ventral ramus
e. gray rami communicantes
f. white rami communicantes
g. sympathetic ganglia

73

what cord segment innervates the upper arm?

C5

74

what cord segment innervates the thumb and lateral forearm

C6

75

what cord segment innervates the middle finger

C7

76

what cord segment innervates the little finger

C8

77

what cord segment innervates the nipple

T4

78

what cord segment innervates the umbilicus

T10

79

what cord segment innervates the big toe

L5

80

what cord segment innervates the heel

S1

81

what cord segment innervates the back of the thigh

S2

82
card image

what spinal cord level is this

thoracic

83
card image

what spinal cord level is this

lumbar

84
card image

what spinal cord level is this

cervical

85
card image

what spinal cord level is this

sacral

86
card image

a-d

a. Lissauer's tract
b. posterolateral sulcus
c. posterior intermediate sulcus
d. posterior median sulcus

87
card image

e-h

e. gracile fasciculus
f. cuneat fasciculus
g. dorsal funiculus
h. lateral funiculus

88
card image

i-k

i. ventral funiculus
j. anterior median fissure
k. anterior white commissure

89

where do dorsal and dorsal root ganglion neurons come in and synapse on the dorsal horn? at the respective level, above, or below?

can be any of the three, travel elsewhere in Lissauer's tract

thin diameter axons more likely to go up or down

90
card image

a-e

a. cuneate fasciculus
b. gracile fasciculus
c. lateral corticospinal tract
d. dorsal spinocerebellar tracts
e. ventral spinocerebellar tracts
f. anterolateral system

91
card image

a. substantia gelatinosa
b. nucleus propria
c. Clarke's nucleus
d. dorsal horn
e. lateral horn
f. intermediate gray horn
g. ventral horn

parasympathetic nucleus is only in the cervical and sacral

92

what is Rexed lamina IX

always at anterior horn, lower motor/alpha motor neurons that innervate muscle cells

93

what are the most important tracts within the spinal cord?

Dorsal Column Pathway
anterolateral system
corticospinal tract
dorsal spinocerebellar tract also considered

94

what types of axons are involved in the dorsal column pathway?

Ia, Ib, II
large diamater heavily myelinated sensory afferent axons

95

what is somatotopic organization

organization that reflects that of the body

96
card image

a. what levels of the spinal cord run in a and which ones are on which side
b. what levels of the spinal cord run in b and which are on which side
c. what is c
d. where are we in the spinal cord

a. S5-T6
b. T5-C1
c. substantia gelatinosa
d. above T5

97
card image

a. what levels of the spinal cord terminate here
b. what is this

a. S5-T6, running outward
b. substantia gelatinosa

98

Dorsal column pathway
- ascending/descending?
- location of tract?
- origin of tract?
- termination of tract?
- "laterality"?
-"somatotopicity"?

ascending pathway
located in dorsal funiculus
origin: primary and sensory afferent neurons with cell bodies in dorsal root ganglion
terminate in dorsal column nuclei
ipsilateral organization
somatotopic organization within the tract with the lower body control being more medial and the upper body control being more lateral

99
card image

a. what is this
b. what is this
c. what is this
d. what is this
e. what is this

a. gracile nucleus
b. cuneate fasciculus
c. gracile fasciculus
d. gracile fasciculus

100
card image

e. what is this f. what is this
g. what spinal cord level is this
h. what spinal cord level is this
i. what spinal cord level is this

e. cuneate fasciculus f. cuneate nucleus
g. cervical
h. thoracic (lateral horn) below T6
i. sacral/lumbar

101

what is the functional role of the DCP?

carry proprioceptive
fine touch and vibration sense
pallesthesia: vibration

102

Anterolateral system
- ascending/descending?
- location of tract?
- origin of tract?
- termination of tract?
- "laterality"?
-"somatotopicity"?

ascending
location is in ventral-lateral funiculus
originates in substantia gelatinosa and nucleus proprius
terminates in thalamus
contralateral
lower body is more dorsal and lateral while upper body is more ventral and medial

103

what is another name for the anterolateral system

spinothalamic tracts

104

what is the functional role of the anterolateral system?

pain, temperature, crude touch

105

what types of axons are in the anterolateral system?

Adelta and C

106
card image

label
what does e represent?
where in g would arm innervations lie?

a. nucleus proprius
b. Lissauer's tract
c. substantia gelatinosa
d. still substantia gelatinosa
e. lissauer's tract can synapse either in substantia gelatinosa or nucleus proprius
f. thalamus
g. anterolateral system
h. anterior white commissure

more ventral and medial
legs more dorsal and lateral

107
card image

a. cerebral cortex
b. motor decussation
c. no difference between arm and leg
d. no difference between arm and leg
ARM MORE MEDIAL, LEG MORE LATERAL

108

Lateral Corticospinal Tract
Dorsal column pathway
- ascending/descending?
- location of tract?
- origin of tract?
- termination of tract?
- "laterality"?
-"somatotopicity"?

descending pathway
origin in pyramidal cells in cerebral cortex
termination: spinal cord gray matter
contralateral: R side cortex controls L side
somatotropic: to upper body is more medial, lower body more lateral

109

what is the function of the lateral corticospinal tract

1. carry motor instructions down to spinal cord
2. modulate sensory processing in cord- can tone down reflex

110
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a. how does a get to go straight up?
b. what is this
c. what is this

a. due to inferior cerebellar peduncle
b. cerebellum
c. Clarke's nucleus

111

Posterior Spinocerebellar Tract
- ascending/descending?
- location of tract?
- origin of tract?
- termination of tract?
- "laterality"?
-"somatotopicity"?

ascending
in margin of lateral funiculus (posterior part)
origin: cells of Clarke's nucleus
terminate in cerebellum
ipsilateral

112

what is the functional role of the posterior spinocerebellar tract?

convey proprioception from the lower body

113

what type of axons run in the posterior spinocerebellar tract?

Ia, Ib, II

large diameter, heavily myelinated sensory afferent axons

114
card image

what is affected in the depiction? what is depicted?

anterior cord syndrome (at cervical cord)
fine touch, proprioception, vibration sense
- not affected because the dorsal columns are not affected by the anterior spinal artery

pain and temperature
- bilateral at and below level of lesion, clinically it is one or two levels below

motor
- flaccid paralysis at the level
- spastic paralysis at lower levels

115
card image

what is affected in the depiction? what is depicted?

Brown Sequard Syndrome (at any level)
fine touch, proprioception, vibtration sense
- same side lost

pain and temperature
- opposite side loss

motor
- flaccid at level, same side
- spastic at levels below, same side

116
card image

what is affected in the depiction? what is depicted?

syringomyelia/syringomyeliac syndrome (cervical cord takes place more than others)

fine touch, proprioception, vibration sense
- no effect

pain temperature
- cavitation at anterior white commissure
- loss only at level of injury

motor
- maybe some flaccidity but paresis (weakness) first and possible paralysis later if lesion works itself over

117
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what is the depicted ailment? what can cause this? what are the manifestations of this type of lesion?

tabes dorsalis

tertiary syphillis

loss of fine touch, vibration sense, proprioception, which can be shown through a positive Romberg test (swaying) because together with visual and vestibular input coordinates balance

118
card image

what is the depicted ailment? what can cause this? what are the manifestations of this type of lesion?

polio

viral infection of poliovirus

loss of alpha motor neurons at the particular level, which leads to either paresis or flaccid paralysis with time

119
card image

what is the depicted ailment? what can cause this? what are the manifestations of this type of lesion?

ALS

combination of flaccidity or spasticity depending on whether upper MNs or lower MNs are affected; if you lose lower motor neurons, you have a more immediate problem

120
card image

a. medulla
b. pons
c. midbrain
d. tegmentum
e. tectum
f. tectum
g. tectum
h. cerebral peduncles (crus cerebri) that contain pyramidal tract axons and corticospinal axons
i. red nuclei
j. substantia nigra
k. corticospinal and corticobulbar axons
l. pontine nuclei
m. inferior olive (inferior olivary nucleus)
n. pyramids (pyramidal tract axons), corticospinal axons
o. tegmentum
p. tegmentum

121
card image

what is each layer?

a. upper midbrain
b. lower midbrain
c. pons
d. high medulla
e. low medulla

122
card image

what are the labeled areas?
what is this tract useful for? what do all these things do?

a. diencephalon
b. CN III
c. CN IV
d. vestibular nuclei
e. CN VI
f. spinal cord
g. MLF

axons can drop in, go with spinal cord, and get off the track at a particular place

they can also cross the midline
these things communicate across the MLF to make eye movements compensate for head movements

123

what do CN III, CN IV, and CN VI have in common?

they help innervate the movement of the eye

124

what do the vestibular nuclei do?

receive information from vestibular apparatus about head movements

125

what happens when we turn our head

every time we move our head, we make eye movements that compensate for head movement, and eyes will move in the opposite direction of the turn to help stabilize the visual world

126

if MLF breaks for some reason, what happens to our eyes when we move our head

coordination breaks down like in MS

127

what is nystagmus

when you see repeated movements in the eye but then they flip back really fast to the direction you move, slowly move usually then flip when their eyes cant move the right way any more

always named for the direction of fast eye movement

can be pathological

128
card image

what pathway is this?
a. what is this
b. what is the somatotopic organization here
c. what is this
d. what is the somatotopic organization here and WHAT is the pink area
e. what is this
f. what is here
g. what is this
h. what is this

Lateral Corticospinal tract
a. cerebral cortex
b. LTA lateral to medial
c. dorsal column nuclei
d. LTA lateral to medial and it is the pyramid
e. spinal cord
f. motor decussation
g. cerebral peduncles
h. pontine nucleus

129
card image

what tract is this
a. what is this
b. what is the somatotopic organization here
c. what is the somatotopic organization here
d. what is the somatotopid organization here
e. what does this path's axons originate from

medial lemniscus
a. thalamus
b. ATL medial to lateral
c. ATL medial to lateral
d. ATL posterior to anterior
e. dorsal column nuclei

130
card image

what tract is this
a. what is this
b. what is the somatotopic organization
c. what is the somatotopic organization
d. what is this

Anterolateral system
a. thalamus
b. LA post to ant
c. LA post to ant
d. spinal cord

131

where is the reticular formation located on the brainstem?

nondescript part of center of brainsteam

132

what are the three regions of the reticular formation

lateral (mostly in medulla)
medial
raphe (gets most mention, in midline)

133

what do control centers in the brainstem have control over? where are they?

breathing, swallowing, cardiovascular control, coughing, gagging, vomiting

in or around reticular formation

134

where is the brainstem in reference to the forebrain and spinal cord?

a place that takes input from spinal cord and forebrain and also passes through the brainstem and the bulk of a cranial nerves run out of brainstem and thus relay response

135

what is ascending reticular actvation's role

send projections ramified throughout the forebrain and correlate arousal or excitement; they set this level

some brainstem neurons are extensive in their projections

136

what are the monoamine systems of the reticular formation?

norepinephrine
dopamine
serotonin

137

what are two important regions in the norepinephrine monoamine systems?

famous in having cell bodies in one spot: locus ceruleus (blue spot, more important) and lateral reticular nuclei (near medulla)

138

where is locus ceruleus

below and lateral to ventricles

139

why is the norepinephrine monoamine system important?

sets wakefulness, elevates level of attention to fit current situation

140

what are the dopamine monoamine systems? where are they located?

substantia nigra (pars compacta is the important part of SN to remember) and ventral tegmental area

midbrain

141
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what is depicted in dark areas?

locus ceruleus

142

where is substantia nigra located? ventral tegmental area?

just deep to cerebral peduncles in midbrain

VTA is ventral to that

143

what are the dopamine monoamine systems important?

parkinson's and motor problems

mostly movement, cognition, and pleasure related

144

what is important with mesolimbic or mesocortical systems?

discussing projections from ventral tegmental area using dopamine to limbic areas in cerebral hemispheres or just cerebral hemispheres altogether

145

where is the raphe? what type of monoamine system does it hold and use in its neurons

midline of brainstem reticular formation

serotonin

146

what does the serotonin monoamine system control?

general level of arousal (morning vs. evening) not moment to moment

part of pain control pathway in nervous system (makes life more bearable), also called descending pain control pathway

147

where is the cholinergic monoamine system?

basal forebrain, basal ganglia

148

where do the vertebral arteries supply the brain?

most of medulla except posterior lateral section

149

where does the basilar artery supply in the brain?

most of pons
anterior medial midbrain

150

what does the posterior cerebral artery supply in the brain?

much of midbrain, except anterior medial part