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NESC 3670: Genes, Brain & Behaviour > Lec 9: Fundamentals of NS (neurons & neural transmission within a cell) > Flashcards

Lec 9: Fundamentals of NS (neurons & neural transmission within a cell) Flashcards

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1
Q

cells are specialized to perform specific ___

A

functions

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2
Q

human NS is comprised of what 2 types of cells

A

neurons

glia

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3
Q

neurons are specialized for _____

  • 2 roles
A

communication

1) information transmission (e.g. about detected event or requirement movement)
2) information processing (e.g. to interpret a pattern of visual info as being a human face)

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4
Q

what did Cajal do?

A

first to demonstrate that the individual cells comprising the NS remained separate

  • showed they did not grow into each other as previously believed
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5
Q

neurons contain which 5 structures?

A

1) membrane (separate inside from outside)
2) nucleus (contain chromosomes)
3) mitochondria (perform metabolic activities, provide energy the cell requires)
4) ribosomes (synthesize new proteins)
5) endoplasmic reticulum (new protein packaging system)

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6
Q

movement of afferent vs efferent???

A

afferent= towards CNS, from receptor in PNS

efferent= from CNS to muscles/glands

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7
Q

are sensory neurons afferent/efferent?

A

afferent

  • sensory rec in PNS –> CNS
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8
Q

are motor neurons afferent/efferent?

A

efferent

  • CNS–> muscles/glands
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9
Q

a sensory neuron is _____ at one end to b highly ____ to a particular type of _____

A

specialized

highly sensitive

stimulation (e.g. touch, temperature, odour)

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10
Q

motor neuron has its ____in the spinal cord and receives ____ from other neurons and conducts impulses along its ___ to a muscle

A

soma in spinal cord

receives excitation

axon to muscle

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11
Q

name 5 components similar in all neurons

A

dendrites

soma/cell body

axon

myelin sheath

presynaptic terminals

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12
Q

what are dendrites?

A

branching fibres with a surface lines with synaptic receptors responsible for bringing in information from other neurons

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13
Q

some dendrites contain ____ ___

A

dendritic spines

  • further branch out and inc the surface area of the dendrite
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14
Q

what is contained within the soma?

A

nucleus
mitochondria
ribosomes
other structures found in other cells

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15
Q

what is the function of the soma?

A

responsible for the metabolic work of the neuron

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16
Q

what is an axon?

A

thin fiber of a neuron responsible for transmitting nerve impulses away to other neurons, glands or muscles

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17
Q

some neurons are covered with an insulating material called ____ ____

A

myelin sheath

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18
Q

interruptions in the myelin sheath are called __________

A

nodes of Ranvier

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19
Q

what are presynaptic terminals?

A

end points of an axon responsible for releasing chemicals to communicate with other neurons

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20
Q

what is an afferent axon?

A

bringing info INTO a structure

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21
Q

what is an efferent axon?

A

carry info AWAY from a structure

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22
Q

what are interneurons???

aka..?

A

aka intrinsic neurons

  • dendrites/axons are completely contained within a structure
  • responsible for the gating activity of other cells
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23
Q

T/F the function is closely related to the shape of a neuron?

A

TRUE

  • shape determines its connection with other neurons
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24
Q

which type of neurons branch extremely widely within a single plane?

A

cerebellum purkinje cells

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25
Q

name 5 types of glia

A 
astrocytes
microglia
oligodendrocytes
schwann cells
radial glia
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26
Q

what is the function of astrocytes?

A

help synchronize the activity of the axon by wrapping around the presynaptic terminal and taking up chemicals released by the axon

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27
Q

what is the function of microglia?

A

remove waste material and other micro-organisms that could prove harmful to the neuron

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28
Q

at what stage in development are microglia important?

A

during period of apoptosis in early development (where there is synaptic pruning)

  • aid in cells being degraded
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29
Q

what is the function of oligodendrocytes and Schwann cells?

A

build the myelin sheath that surrounds the axon of some neurons

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30
Q

what is the function of radial glia?

A

guide the migration of neurons and the growth of their axons and dendrites during embryonic development

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31
Q

describe active transport in the NS

A

protein mediated process by which useful chemicals are brought into the brain

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32
Q

which 4 materials are transported via active transport int he brain?

A

glucose
hormones
amino acids
vitamins

  • brought INTO brain via active transport
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33
Q

glucose is a ____ sugar, it is the primary source of ____ for neurons

A

simple sugar

nutrition

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34
Q

name a chemical that is necessary for the use of glucose in the brain

A

thiamine

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35
Q

what is the blood-brain barrier?

A

mechanism that surrounds the brain and blocks most chemicals from entering

  • block incoming viruses, bacteria, and harmful material from entering b/c neurons do not regenerate
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36
Q

** where does neurogenesis occur in the adult brain? (3)

A

olfactory bulb
dentate gyrus
hippocampus

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37
Q

what are terminal buttons of axons?

A

form junctions with other cells and release NT

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38
Q

name the 3 main functions of a neuron

A

1) reception
2) conduction
3) transmission

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39
Q

during an AP, what is the direction of neural impulse?

A

toward axon terminals

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40
Q

describe neuron communication

A
  • impulse releases NT from vesicles
  • NT enters synaptic gap
  • NT binds to receptors on the receiving neuron
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41
Q

information must be transmitted in 2 ways

A

1) WITHIN each neuron

2) BETWEEN neurons

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42
Q

neuron membrane is composed of ____ & _____

A

lipid & protein

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43
Q

what is embedded in the membrane? why?

A

protein channels

permit certain ions to cross through the membrane at a controlled rate

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44
Q

ion channels are what type of proteins?

A

pore-forming membrane proteins

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45
Q

what is the function of ion channels?

A

establish a resting membrane potential and shape AP by gating the flow of ions across the cell membrane

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46
Q

why is ACh important?

A

neuromuscular junctions

  • association with ACh receptor to open the channel (= influx of Na)
  • blocked by Na ions
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47
Q

What are the 2 types of ion channels?

A
  • ligand gated (NT)

- voltage-gated

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48
Q

how do voltage-gated ion channels work?

A

open and close in response to small voltage changes across the plasma membrane

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49
Q

what is the resting potential?

A

electrical charge across the membrane, it is ~70mV differentce between inside and outside

-70mV

50
Q

the membrane is ____ permeable which means

A

selectively permeable

  • allowing some chemicals to pass more freely than others
51
Q

what are ions?

A

electrically-charged molecules

e.g. Na, K, Cl

52
Q

why does a resting potential exist?

A

because ions are concentrated on different sides of the mmebrane

53
Q

which ions are inside the cell?

A

Na and Cl

54
Q

which ions are outside the cell

A

K and organic anions

55
Q

electical voltages and concentration gradients across the membrane exert ____ on the ions

A

forces

56
Q

explain the forces exerted on ions

A
  • K and Cl: forces of voltage and concentration are balanced
  • organic anions are too large to pass through membrane
  • BOTH voltage & concentration forces lead to Na entering the cell
57
Q

list 2 ways that the resting potential is maintained

A
  • Na ions are actively transported to maintain resting potential
  • Na/K pump exchanges 3Na for 2 K
58
Q

how many molecules of Na and K are exchanged using a Na/K pump?

A

3Na

2K

59
Q

what is the Na/K pump?

A

protein complex that continually pumps 3Na out of the cells, while drawing 2K ions into the cell

60
Q

main purpose of the Na/K pump?

A

help maintain electrical gradient

61
Q

** 4 steps of the Na-K exchange pump

A

1) 3Na and ATP bind to the carrier molecule
2) ATP breaks down to ADP+P, and release energy. Carrier molecule changes shape, Na are transported across the membrane
3) Na diffuse away from the carrier, 2K bind to carrier, P is released
4) carrier molecule resumes original shape, transporting K across membrane, K diffuse away from carrier. Carrier can again bind to Na and ATP

62
Q

in basic terms, what is an AP

A

rapid depolarization of the membrane

63
Q

stimulation of the neuron past the threshold of excitation triggers ____ or ____

A

nerve impulse

AP

64
Q

where does AP start?

A

axon hillock

  • passes quickly along axon
65
Q

following AP, the membrane is quickly ____ to allow subsequent firing

A

repolarized

66
Q

describe the 4 main events that occur during the course of an AP

A

1) AP begins with partial depolarization
2) excitation threshold is reached, sudden large depolarization
3) followed rapidly by repolarization
4) then brief hyperpolarizaiton

67
Q

what is the excitation threshold?

A

tells us what the membrane potential is that is required to be changed to commit to the depolarization

68
Q

what are voltage-activated channels?

A

membrane channels

permeability depends upon the voltage different across the membrane

69
Q

explain what happens during rapid depolarization

A
  • when partial depolarization reaches activation threshold, voltage-gated Na channels open
  • Na rush into
  • nerve pulse occurs
  • mem potential changes from =70mV to +40mV
  • net pos charge inside, net neg charge outside= depolarization
70
Q

what is depolarization?

A

decreasing the polarization towards 0

71
Q

explain what happens during repolarization

A
  • Na channels close, become refractory
  • depolarization triggers opening of voltage-gated K channels
  • K rush out of cell, repolarizing, then hyper-polarizing
  • net neg inside, net pos outside
72
Q

explain how the resting potential is resumed

A
  • K channels closed
  • repolarization resets Na channel
  • ions diffuse away from the area
  • Na/K transporter maintains repolarization
  • membrane is ready to “fire” again
73
Q

what is the function fo local anesthetic drugs on gated-ion channels

A

block Na channels

prevent AP

e.g. Novocain

74
Q

what is the All-or-None response?

A
  • AP
  • always the same size
  • either it is not triggered at all (membrane refractory) OR triggered completely
75
Q

what is a refractory period?

A
  • sensitivity of area to further stimulation decreased for a time
76
Q

2 different types of refractory periods

A

absolute

relative

77
Q

what is an absolute refractory period?

A
  • complete insensitivity exists to another stimulus

- from beginning of AP until near end of repolarization

78
Q

what is a relative refractory period?

A

stronger-than-threshold stimulus can initiate another AP

79
Q

what does ‘propagation of AP’ mean?

A

transmission of AP down the axon

80
Q

passive conduction ensures….

A

adjacent membrane depolarizes, so AP travels DOWN axon

81
Q

transmission by continuous AP is relatively ____ (fast/slow) and energy consuming because _____

A

slow

b/c of Na/K pump

82
Q

what is the faster, more efficient mechanism for conduction of AP

A

saltatory conduction

83
Q

saltatory conduction is facilitated through….

A

myelination (wrapping of myelin)

84
Q

what is a myelin sheath?

A

fatty material made by glial cells (oligodendrocytes/Schwann cells)

85
Q

function of myelin sheath?

A
  • insulate the axon
  • prevent passage of ions over the membrane
  • allow for rapid movement of electrical impulses along axon
86
Q

what is a Node of Ranvier?

A

gaps in myelin sheath where AP are transmitted

  • at each Node, the AP is regenerated by a chain of positively charged ion pushed along by the previous segment
87
Q

what is the speed of a neural impulse?

A

2-200+ mph

88
Q

explain saltatory conduction

A
  • myelinated regions of axon are electrically insulated

- electrical charge moves ALONG the axon (vs across the membrane)

89
Q

during saltatory conduction, where does AP occur?

A

only at unmyelinated regions

–> Nodes of Ranvier

90
Q

benefit of “jumping” of AP in saltatory conduction

A

jumping of AP from node to node

  • provides rapid conduction of impulses
  • conserves energy of the cell
91
Q

(saltatory conduction)

AP at node triggers ____ to the next node, where the membrane ____

A

AP at node triggers flow of current to the next node

membrane regenerates the AP

92
Q

what would happen if there were no myelin sheaths?

A

a lot of current leakage

93
Q

T/F there are nerves in the CNS

A

FALSE

94
Q

in the CNS the groups/bundles of nerve fibres are called what???

A

tracts

e.g. spinothalamic tract

95
Q

what is the definition of a nerve?

A

a distinct peripheral extension of the CNS conducting electronic messages (AP) to and from the CNS

96
Q

every spinal/cranial nerve is surrounded and protected by ____ tissue

A

connective tissue

97
Q

what is the endonerium?

A

wraps each neuron

98
Q

what is the perineurium?

A

covers nerve bundles (fascicles)

99
Q

what is the epineurium?

A

covers fascicles

100
Q

intensity of AP is expressed as what?

A

impulses/second

IPS: 0-1000

101
Q

conduction velocity is expressed as?

A

0.2- 120m/s

102
Q

an AP is a rapid ____ electrical change that is ___, not graded. it obeys the ____ law

A

rapid reversible

maximal

all or none

103
Q

what are NTs?

A

chemical messengers that traverse the synaptic gaps between neurons when released by the sending neuron

  • travel across synapse, bind to receptor sites on receiving neuron
  • influence whether it will generate neural impulse
104
Q

what is ACh?

what is it involved in?

A

acetylcholine

  • 1st substances identified as NT
  • link motor neurons and muscles (contract/relax)
  • involved in memory, learning, sleep, dreaming
105
Q

what are endophins?

A
  • bound like NT

- released during pain and discomfort

106
Q

main functions of ACH

A

enables muscle action, learning, memory

107
Q

examples of ACh malfunctions

A
  • alzheimers disease

ACh- producing neurons deteriorate

108
Q

main functions of DA?

A

influence movement, learning, attention, emotion

109
Q

examples of DA malfuctions

A
  • excess DA= schizophrenia

- lack DA= tremors, dec mobility, Parkinsons

110
Q

main functions of 5-HT?

A

affects mood, hunger, sleep, arousal

111
Q

examples of 5-HT malfunctions

A
  • linked to depression
112
Q

main functions of NE?

A

control alertness and arousal

113
Q

result of lack of NE

A

depress mood

114
Q

what is a major inhibitory NT?

A

GABA

115
Q

undersupply of GABA linked to?

A

seizures, tremors, insomnia

116
Q

what is a major excitatory NT?

what is it involved in?

A

glutamate

memory

117
Q

oversupply of glutamate results in??

A
  • can overstimulate brain

- migraines, seizures

118
Q

what are effects of drugs on the brain?

A
  • alter amount of NT released at synapses
  • mimic/facilitate action of NT
  • block action of NT
119
Q

what is an agonist?

A

mimic/facilitate actions of NT

120
Q

what is an antagonist?

A

oppose/block actions of NT

NESC 3670: Genes, Brain & Behaviour (12 decks)

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