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Neurobiology > Unit 1 > Flashcards

Unit 1 Flashcards

1
Q

What is the neuron doctrine?

A

Ramon y Cajal: nerve cells are discrete entities

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2
Q

What are the four major parts of a neuron?

A

soma, axon, dendrite and synapses

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3
Q

What are the 4 types of glial cells

A
  1. Astrocytes
  2. Oligodendrocytes
  3. Microglial cells
  4. Glial stem cells
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4
Q

what are the types of the component neurons in neural circuits?

A

Afferent neurons, efferent neurons and interneurons

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5
Q

What are the components of the CNS and PNS?

A

CNS: Brain and spinal chord
PNS: sensory ganglia and nerves, sensory receptors, somatic motor division, and visceral or autonomic motor division

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6
Q

Neurons constitute ______ which constitute _______.

A

Neurons constitute neural circuits which constitute neural systems.

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7
Q

Neural circuits

A

neurons organized into ensembles to process specific kinds of information

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8
Q

Who coined the term “synapse”?

A

Charles Sherrington

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9
Q

What are two major cell types in the nervous system?

A

Nerve cells (neurons) and supporting glial cells

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10
Q

Input v Output in neuron

A

input: dendrite
output: axon

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11
Q

Synaptic Cleft:

A

extracellular space between pre and post synaptic elements

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12
Q

What happens with the function of a neuron with multiple, highly branched dendrites and one axon?

A

It integrates information from many neurons

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13
Q

Astrocytes

A

Maintain appropriate chemical environment for neuronal signaling, including the blood brain barrier

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14
Q

Oligodendrocytes

A

lay down a laminated, lipid rich wrapping called myelin around some CNS axons

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15
Q

What is myelin provided by in the PNS

A

schwann cells

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16
Q

Microglial cells

A

derived from hematopoietic precursor cells
- share many features with macrophages and are primarily scavenger cells that remove myelin and cellular debris from injury sites or normal cell turnover
Reside in the CNS

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17
Q

Glial stem cells

A

retain capacity to proliferate and generate additional precursors or differentiated glia and sometimes neurons

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18
Q

Neuropil

A

dense tangle of dendrites, axon terminals, and glial cell processes
- the regions between nerve cell bodies where most synaptic connectivity occurs

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19
Q

Afferent neurons

A

nerve cell that carry form periphery TOWARD brain or spinal chord

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20
Q

Efferent neurons

A

nerve cells that carry info AWAY from brain or spinal chord

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21
Q

Interneurons

A

** Only in CNS
Participate in local aspects of a circuit

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22
Q

Sensory systems

A

acquire and process information from environment

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23
Q

Motor systems

A

response to information by generating movements and other behavior

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24
Q

Associational systems

A

in between; mediate the most complex brain functions

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25
Q

Ganglia

A

nerve cell bodies that reside in the PNS

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26
Q

Nerves

A

bundles of peripheral axons

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27
Q

How are nerve cells in the CNS arranged?

A

Nuclei and cortex

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28
Q

Cortex:

A

sheet like array of nerve cells

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29
Q

Tracts

A

gathering of CNS axons

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30
Q

Commissures

A

tracts that cross the midline of the brain
- how left and right brain communicate with each other

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31
Q

Gray matter

A

any accumulation of cell bodies and neuropil in the brain and spinal chord

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32
Q

White matter

A

axon tracts and commissures in the CNS

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33
Q

Why is white matter lighter than the gray matter?

A

White matter is richer in myelin, which reflects more light than gray matter

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34
Q

Name some sensory ganglia and nerves

A

cranial nerve ganglia, dorsal root ganglia (spinal ganglia), cranial nerves, and spinal nerves

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35
Q

what do autonomic ganglia and nerves innervate

A

cells that innervate smooth muscles, cardiac muscle, and glands

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36
Q

enteric nervous system

A

small ganglia and neurons throughout the wall of the gut; control gastric motility and secretion

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37
Q

Parts of CNS

A

Brain: cerebral hemispheres, diencephalon, cerebellum, and brainstem

Spinal chord

motor neuron cell bodies

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38
Q

Parts of PNS

A

-Sensory ganglia and nerves
-sensory receptors
-somatic motor division (ONLY MOTOR NERVES NOT NEURON CELL BODIES)
-Visceral and autonomic motor division

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39
Q

What are some effectors in the nervous system?

A

smooth, skeletal, and cardiac muscles, and glands.

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40
Q

Define action potential

A

all or nothing change in the electrical potential across the nerve cell membrane that conveys information from one point to another

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41
Q

Define synaptic transmission

A

the information encoded by action potentials is passed on at synapses to a target cell

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42
Q

Synaptic vesicles

A

the secretory organelles in the presynaptic terminals of chemical synapses, filled with NT molecules

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43
Q

How is current determined?

A

by the number of electrons passing through a cross section of a conductor in one second

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44
Q

What is current measured in?

A

amperes (amps; A)

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45
Q

What is voltage

A

the force required to make current flow through a conductor

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46
Q

another name for voltage

A

potential

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47
Q

Movement of positive of negative charges to generate:

A

electrical currents

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48
Q

Separate positive and negative charges to generate:

A

electrical potentials

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49
Q

Why are electrical potentials generated?

A

1) differences in the concentrations of specific ions across neuronal membrane (ion concentration gradients)
2) membranes are selectively permeable to certain ions (selective permeability)

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50
Q

Neurons use ____ to produce electrical signals

A

ion movements

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51
Q

What are active transporters?

A

Actively move ions into or out of cells against their concentration gradient to establish ion concentration gradients

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52
Q

What are ion channels?

A

Creates the selective permeability for membrane and allow only certain kind of ions to cross the membrane in the direction of their concentration gradients **Passive movement

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53
Q

Channels and transporters work _____ each other to generate _____

A

against; resting potential, action potentials, synaptic and receptor potentials that trigger action potentials

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54
Q

Electrochemical equilibrium

A

a state in which the electrical effect causes diffusion in one direction and the concentration effect causes diffusion of equal magnitude in the opposite direction

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55
Q

Electrophysiological recordings

A

measures the electrical activity of a neuron

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56
Q

Extracellular recordings

A

an electrode is places near the neuron of interest to detect its activity
**Only detects temporal patterns of several action potentials but not the smaller, graded changed in electrical signals (only spikes)

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57
Q

Intracellular recording

A

the electrode is places inside the neuron of interest
**detects smaller, graded changes of electrical potential

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58
Q

What are the major functional features of neurons and how do neurons transmit signals within the circuit?

A
  • specialized for intracellular communication
  • moment to moment electrical signaling
  • neurons send electrical signals through long distance through the action potential
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59
Q

How do neurons move ions across their membrane?

A

through ion movements
- active transporters and ion channels

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60
Q

What are the differences in how ions move across their membrane

A

active transporters: actively move selected ions against concentration gradient and create ion concentration gradients

ion channels: allow ions to diffuse down concentration gradient and are selectively permeable to certain ions

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61
Q

Neurons can generate electrical potentials across their membrane because…

A

1.ion concentration gradients
2. selective permeability

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62
Q

How do we measure electrical signals of neurons?

A

Through extracellular and intracellular recordings

63
Q

What does intracellular recording detect

A

resting membrane potential
receptor potential
synpatic potential
wave form of single action potential

64
Q

What is the resting potential

A

no action potential firing
-around -70 mV but can range from -40 to -90 mv

65
Q

What are the different types of neuronal electrical signals and what are the differences among them?

A

Receptor potential
Synaptic potential
Action potential

66
Q

Define receptor potential

A

shape of Pacinian corpuscle changed - Na+ chennel open

67
Q

Synaptic potential

A

NT binds to post synaptic receptors

cation channel open

68
Q

What is electrochemical equilibrium

A

balance between chemical force and electrical force

69
Q

What is the equilibrium potential and how do we calculate it

A

electrical potential generated across the membrane at electrochemical equilibrium

Calculate it through the Nernst Equation

70
Q

What is the Nernst equation

A

V = 58log [ion] outside / [ion]inside

relation of equilibrium potential to the concentration gradient

71
Q

Goldman Equation

A

equilibrium potential when the membrane is permeable to several different ions

72
Q

How does resting or action potential depend on relative permeability of the membrane to K+ and Na+?

A

at resting state: K+ is more permeable than Na+

during AP: Na+ permeability increases and becomes more permeable than K+

73
Q

What did Hodgkin and Katz conclude?

A
  1. the membrane of the resting neuron is more permeable to K+ than to other ions
  2. There is more K+ inside the neuron than outside
74
Q

How is the resting membrane potential of a squid giant axon determined

A

by the K+ concentration gradient and the selective permeability of it

75
Q

What causes the membrane potential of a neuron to depolarize during an action potential?

A

increase Na+ permeability

76
Q

Hodgkin anf Katz showed that the action potential arises because…

A

the neuronal membrane becomes temporarily permeable to Na+

77
Q

Describe rising and overshoot phase of action potential:

A

membrane becomes extraordinarily permeable to Na+
- causes membrane potential to depolarize

78
Q

Describe falling phase of AP

A

membrane potential rapidly repolarizes due to inactivation of Na+ permeability and increase in K+ permeability

79
Q

Describe undershoot phase of AP

A

membrane potential is transiently hyperpolarized bc K+ permeability becomes even greater at rest

80
Q

Why is the resting potential of a cell negative?

A

at rest there is an excess K+ inside the cell and the membrane is permeably chiefly to K+

81
Q

In a two compartment model of a cell with a K+ permeable membrane, at equilibrium potential, there is _______ flux of K+ ions

A

no net

82
Q

How does membrane permeability of K+ and Na+ change during an AP?

A

Pk exceeds Pna at rest; Pna temporarily increases during the AP

83
Q

What is the voltage clamp method?

A

allows experimenters to control membrane potential and simultaneously measure the permeability changes

84
Q

Current clamp method

A

records the membrane potential by injecting current into a cell through the recording electrode

85
Q

What can the voltage clamp method measure?

A

membrane potential at any desired level

86
Q

Define inward current

A

positive charge entering the cell (graph going below 0)

Negative ions moving out of the cell

Depolarization if on voltage trace

87
Q

Define outward current

A

positive charge moving OUT of the cell (above 0)

Hyperpolarization on voltage trace

88
Q

What are the two types of membrane permeabilities activated by changes in membrane potential during generation of an action potential?

A
89
Q

Describe the time- dependent membrane conductance changes underlying the action potential

A

Na+ and k+ require for to activate

** K+ conductance has a pronounced time delay

90
Q

What are the four phases of an action potential

A
  • Rising and overshoot phase
  • Falling phase
  • Undershoot
  • Refractory period
91
Q

Describe the voltage- dependent membrane conductance changes underlying the action potential

A

The speed of both activation and inactivation increasing at more depolarizing potentials

92
Q

What does depolarization cause Na conduction to do

A

Depolarization = Na+ conductance to activate AND inactivate over time

**K conductance does NOT inactivate like this

93
Q

Explain rising and overshoot phase

A

selective increase in voltage dependent Na+ conductance is responsible for action potential initiation

94
Q

Explain falling phase

A

depolarization slowly activates voltage dependent K+ conductance

causes K+ to leave cell and repolarize membrane potential

95
Q

Explain undershoot phase

A

K+ becomes temporarily higher

hyperpolarization – more negative

96
Q

What does hyperpolarization cause?

A

the voltage dependent K+ conductance to turn off

97
Q

explain refractory period

A

**follows an action potential

a new action potential cannot be fired

98
Q

Leak channels:

A

constantly open K+ channel

*not voltage dependent

99
Q

Why is there a refractory period following an action potential?

A

(1) slow time course of turning off the K+ conductance
(2) persistence of Na+ conduction inactivation

100
Q

Why do action potentials have a treshold?

A

so Na+ entering the neuron is exactly equal to the K+ current that is flowing out from the leak K+ channel

101
Q

What kind of a feedback loop is an action potential?

A

positive feedback

102
Q

Action potentials serve as a _____ that allows neurons to transmit signals over ______ distances

A

booster system; long

103
Q

What does refractoriness prevent?

A

backward propagation

104
Q

Why does myelination increase conduction velocity?

A

by insulating the axonal membrane to increase passive current flow and saltatory conduction

causes saltatory conduction

105
Q

What can the patch clamp method measure

A

currents flowing through single channels

106
Q

Define macroscopic currents

A

current flowing through large number of channels

107
Q

Define microscopic currents

A

current flowing through single channeld

108
Q

What are functional properties of single Na+

A

-inward
-inactivated during depolarization
-voltage dependent
- open probability increases when depolarized

109
Q

What are functional properties of single K+

A
  • outward
  • not inactivated during depolarization
110
Q

How can ion channels be classified?

A

ion selectivity and gating mechanisms

111
Q

name two gating mechanisms of ion channels

A
  • Non gated or leak channels
  • voltage gated channels
  • ligand gated channels
  • mechanically gated channels
  • temperature gated channels
112
Q

which ions are used in non gated or leak channels?

A

Na, K, Cl
*small current going back and forth to maintain homeostasis

113
Q

ions used in voltage gated channels

A

H, Na, K, Ca, Cl

114
Q

extracellular ligands

A

**most common

many are NT: ACh, NMDA, AMPA, glycine, GABA, 5-HT

115
Q

intracellular ligands

A

secondary messengers: Ca, cGMP, cAMP, or cyclic- nucleotide-gated channels

116
Q

extraordinary ligand

A

light/photons

117
Q

what is the least common gating mechanism?

A

mechanically - gated channels

118
Q

how do ion channels generate diversity

A
  1. different selectivity and gating mechanisms
  2. alternative splicing of ion channels genes
  3. changing a single amino acid
  4. posttranslational modifications
  5. channels are often made up of subunits encoded by different genes
119
Q

what are channelopathies

A

genetic diseases result from small but critical mutations in ion channel genes ex cystic fibrosis

120
Q

Cystic fibrosis

A

mutatiosn in conductance regulator (CFTR) gene encoding a Cl- channel

121
Q

What are the molecular properties of different voltage gated ion channels?

A

Na and Ca channels: 6 repeating membrane spanning motif

122
Q

What are the two classes of neuronal transporters and what are their differences?

A

ATPase pump: acquire energy directly from hydrolysis of ATP

Ion exchangers and co-transporters: don’t use ATP but use electrochemical gradient of other ions as an energy source

123
Q

Why is Na+/K+ pump electrogenic

A

pump generates an electrical current that can hyperpolarize the membrane potential by causing a net loss of one positively charged ion from inside of the cell during each round of pumping

124
Q

Which which toxin can be used to block Na/K pump?

A

tetrodotoxin and tetraethylammonium ion

125
Q

TTX

A

tetrodotoxin

selective Na+ channel blocker blocks early current

126
Q

TEA

A

Tetraethylammonium ion

selective K+ channel blocker blocks late current

127
Q

What are structural and functional properties of the electrical synapse?

A

current flows through connexons, which as specialized membrane channels that connetc two cells at gap junction

minority but in all nervous systems

permit direct, passive flow of current

function:
(1) synchronize electrical activity among population of neurons
(2) coordinate intracellular electrical signaling and metabolism of coupled cells

128
Q

What are major differences between electrical and chemical synapses

A

enable cell to cell communication via the secretion of neurotransmitters

129
Q

Describe the sequence of events involves in signal transmission at chemical synapses

A
  1. action potential arrives at axon terminal
  2. voltage gated ca channels open
  3. ca enters the presynaptic neuron
  4. ca signals to NT vescicles
  5. Vescicles move to the membrane and dock
  6. NT released via exocytosis i
  7. NT bind to receptors
  8. Signal initiated in post synaptic cell
130
Q

What are co-transmitters

A

when more than one transmitter is present within a nerve terminal

131
Q

What are two majoe categories of neurotransmitters?

A

small molecule neurotransmitters and neuropeptides

132
Q

What are the criteria that define a nuerotransmitter

A
  1. substance must be present within the presynaptic neuron

2.substance must be released in response to presynaptic depolarization and release MUST be Ca dependent

  1. specific receptors for the substance must be present on the post synaptic cell
133
Q

What is the role of Ca in synaptic transmission

A

causes NT to be released

134
Q

What are the conclusions from Bernars Katz experiments that defines quantal release of NT?

A

**studied transmissions at the NMJ

conclusion: NT is released in multi-molecular packets (quanta)

135
Q

What are EPP and MEPP

A

End plate potential and Mini end plate potential

136
Q

End plate potential

A

a transient depolarization at the postsynaptic muscle fiber elicited by an AP from the presynaptic motor neuron

137
Q

Miniature end plate potential

A

spontaneous changes in muscle cell membrane without stimulation from the presynaptic motor neuron

138
Q

How is the fused vesicle membrane
retrieved after transmitter release?

A

with SNARES

139
Q

What are the two types of neurotransmitter receptors

A

ionotropic receptors and metabotropic receptors

140
Q

Ionotropic receptors

A

ligand gates ion channels

combine transmitter-binding and channel functions into a single molecular activity

141
Q

Metabotropic receptors

A

g -coupled receptors

movement of ions through a channel depends on intervening metabolic steps
**NO CHANNEL as a part of the receptor structure

142
Q

Explain reversal potential

A

direction of EPC reverses or the membrane potential at which there is no net flow of ions

143
Q

What are PSC

A

post synaptic current

currents generated from opening of ion channel by transmitter binding to postsynaptic receptor in chemical synapse

144
Q

What is PSC called in NMJ

A

EPC

145
Q

What are PSP

A

changes of postsynaptic membrane potential due to PSC in chemical synapse

146
Q

Relationship between PSC and PSP

A
147
Q

How do you use the reversal potential to determine the direction of the PSC and polarity?

A
  • channels depolarizing when postsynaptic membrane is more negative

-channels hyperpolarizing when post synaptic membrane is more positive than reversal potential

148
Q

What are EPSP and IPSP

A

excitatory and inhibitory post synaptic potentials

149
Q

How do you determine whether a postsynaptic response is excitatory or inhibitory

A

type of channel and concentration of permanent ions inside and outside the cell

149
Q

How to determine PSC

A

PSC = Vm - Erev

150
Q

Erev > threshold

A

excitation

151
Q

Erev < threshold

A

inhibition

152
Q

What is the summation of synaptic potentials?

A
  • PSP at brain synapses are smaller than PSP at NMJ
    CNS neurons are typically innervated by thousands of neurons and PSPs produced by each active synapse can sum together in time and in space to determine the behavior of the postsynaptic neuron

Neurobiology (3 decks)

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