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Pob 1 > Lecture 25 Neurons > Flashcards

Lecture 25 Neurons Flashcards

1
Q

Rundown of nervous system

A

● The nervous system transmits information between specific locations
● The information conveyed depends on a
signal’s pathway, not the type of signal
● Nerve signal transmission is very fast

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2
Q

Neuron structure

A

The neuron is a cell that exemplifies the close fit between form and function 7

● Cell body - Most of organelles
● Dendrites, highly branched
extensions that receive signals from other neurons
● The axon is often a much longer
extension that transmits signals to other cells at synapses
● The cone-shaped base of an axon
is called the axon hillock

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3
Q

Structural diversity of neurons

A

sensory neurons, interneurons, motor neurons

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4
Q

Sensory neurons

A

transmit information about external stimuli such as light, touch, or smell

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5
Q

Interneurons

A

integrate (analyze and interpret) the
information

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6
Q

Motor neurons

A

transmit signals to muscle cells,
causing them to contract

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7
Q

Synapse

A

is a junction between an axon and another cell

Synapse passes info through neurotransmitters (short distance: chemical)

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8
Q

neurotransmitters

A

The synaptic terminal of one axon passes
information across the synapse in the form of chemical messengers

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9
Q

Transmitting a signal (long distance)

A

silde 10

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10
Q

Complex nervous system: Organisation

A

● Central nervous system (CNS),
where integration takes place;
○ brain or simpler clusters called
ganglia
○ spinal cord
● Peripheral nervous system (PNS),
which carries information into and out
of the CNS
● Neurons of both the CNS and PNS
require supporting cells called glial
cells, or glia

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11
Q

Central nervous system (CNS)

A

where integration takes place;
○ brain or simpler clusters called ganglia
○ spinal cord

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12
Q

Peripheral nervous system (PNS)

A

which carries information into and out
of the CNS
● Neurons of both the CNS and PNS
require supporting cells called glial
cells, or glia

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13
Q

Membrane potential

A

Every cell has a voltage (difference in electrical charge) across its plasma
membrane

Changes in membrane potential can be graded or action potentials

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14
Q

resting potential

A

is the membrane potential of a
neuron not sending signals

Changes in membrane potential can be graded or action potentials

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15
Q

The plasma membrane is decorated with
proteins

A

slide 13

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16
Q

3 major ways to transport molecules across membranes

A
  1. Facilitated diffusion
  2. Active transport
  3. Bulk transport (exocytosis and endocytosis)
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17
Q

Facilitated diffusion: channels

A

Facilitated diffusion does not require energy
A channel, or a carrier protein, allows passive diffusion to occur through the protein

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18
Q

Active transport

A

● But cells aren’t simply at equilibrium with their environment!
● E.g. different concentrations of Na+
and K+ ions inside and outside the cell.
● These “electrochemical gradients”are necessary for the transmission of nerve impulses.

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19
Q

Active transport: the Na+/K+ pump

A

● Transport “up” the concentration gradient for each ion.
● Requires energy (hydrolysis of ATP)
● Phosphorylation / dephosphorylation drive conformational change

how the electrochemical gradient is maintained

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20
Q

What is Active transport

A

moves substances against their concentration gradients

Active transport requires energy, usually in the form of ATP.

Active transport allows cells to maintain concentration gradients that differ from their surroundings.

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21
Q

Membrane potential

A

slide 19

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22
Q

Formation of the Resting Potential

A

● In most neurons, the concentration of K+ is higher inside the cell, while the concentration of Na+ is higher outside the cell.
● Sodium-potassium pumps use the energy of ATP to maintain these K+ and Na+ gradients across the plasma membrane.
● These concentration gradients represent chemical potential energy.

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23
Q

Sodium-potassium pump

A
  1. Cytoplasmic Na+binds to the sodium- potassium pump. The affinity for Na+
    is high when the protein has this
    shape.
    2.Na+ binding stimulates phosphorylation by ATP.
    3.Phosphorylation leads to a change in
    protein shape, reducing its affinity for Na+, which is released outside.
    4.The new shape has a high affinity for K+
    , which binds on the extracellular side and triggers release of the phosphate group.
    5.Loss of the phosphate group restores the protein’s original shape, which has
    a lower affinity for K+
    6.K 6 + is released; affinity for Na+
    is high again, and the cycle
    repeats

(slide 21 and 22 and 23)

cycle on slide 24

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24
Q

IMPORTANT sodium potassium pump

A

slide 25

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25
Q

Facilitated diffusion: channels

A

Facilitated diffusion does not require energy

A channel, or a carrier protein, allows passive diffusion to occur through the protein

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26
Q

The diffusion of solutes across a membrane

A

The condition in which no net ionic flux
occurs across a membrane because
concentration gradient is in exact balance.

(slide 28)

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27
Q

The diffusion of ions across a membrane

A

The condition in which no net ionic flux
occurs across a membrane because
concentration gradients and opposing
transmembrane potentials are in exact
balance.

(slide 29)

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28
Q

Membrane selectively permeable to K+

A

slide 30 and 31

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29
Q

Ion channels

A

slide 32

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30
Q

Ion Channel diversity

A

Nongated channels, voltage-gated channels, chemically-gated channels

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31
Q

Nongated channels

A

Nongated channels are responsible for the resting membrane potential

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32
Q

Voltage-gated channels

A

Voltage-gated channels are responsible for generation and propagation of the action potential, the outgoing signal from the neuron

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33
Q

Chemically-gated Channels

A

Chemically-gated channels are responsible for synaptic potentials, the incoming signals to the neuron

34
Q

Ion channels

A

slide 35 (nongated channels)

35
Q

Ion channels with a K+ channel

A

slide 36 (nongated channels)

36
Q

Ion channels; Resting potential dominated by K+

A

slide 37 (nongated channels)

37
Q

Neuronal resting potential: -70

A

slide 38 (nongated channels)

38
Q

The cell changes its potential

A

slide 39 (nongated channels)

39
Q

Resting potential

A

slide 40 (nongated channels)

40
Q

Voltage-gated ion channel

A

slide 42
gate closed: no ions flow across membrane
gate open: ions flow through channel

41
Q

What triggers Depolarization

A

opening other types of ions channels

(voltage-gated channels)

42
Q

Depolarizatoin

A

a reduction in the magnitude of the membrane potential

For example, depolarization occurs if gated Na+ channels open and Na+ diffuses into the cell

(voltage-gated channels)

43
Q

Graded potentials

A

are changes in polarization where the magnitude of the change varies with the strength of the stimulus

(voltage-gated channels)

44
Q

Action potential

A

If a depolarization shifts the membrane
potential sufficiently, it results in a
massive change in membrane voltage

(voltage-gated channels)

45
Q

Threshold

A

Action potentials have a constant
magnitude, are all-or-none, and transmit
signals over long distances.

They arise because some ion channels
are voltage-gated, opening or closing
when the membrane potential passes a
certain level

(voltage-gated channels)

46
Q

Voltage-gated ion channel

A

slide 47 and 48

(voltage-gated channels)

47
Q

Resting Stage

A

slide 49

(voltage-gated channels)

48
Q

Stimulation

A

slide 50

(voltage-gated channels)

49
Q

Depolarisation

A

slide 51

(voltage-gated channels)

50
Q

Repolarisation

A

slide 52

(voltage-gated channels)

51
Q

Hyperpolarisation

A

slide 53

(voltage-gated channels)

52
Q

Hyperpolarization

A

When gated K+ channels open, K+
diffuses out, making the inside of the cell more negative

an increasing in magnitude of the membrane potential

(voltage-gated channels)

53
Q

Action potentials “travel” along the axon

A

slide 57

(voltage-gated channels)

54
Q

Conduction of Action Potentials

A

● At the site where the action potential is generated (usually the axon hillock), an electrical current depolarizes the neighboring region of the axon
membrane.
● Action potentials travel in only one direction: toward the synaptic terminals.
● Inactivated Na+
channels behind the zone of
depolarization prevent the action potential from traveling backwards.

(voltage-gated channels)

55
Q

Action potentials “travel” along the axon

A

slide 59

(voltage-gated channels)

56
Q

Conduction of an action potential

A

slide 60

(voltage-gated channels)

57
Q

Conduction of an action potential

A

slide 61

(voltage-gated channels)

58
Q

Conduction of an action potential

A

slide 62

(voltage-gated channels)

59
Q

Conduction of an action potential

A

slide 63

(voltage-gated channels)

60
Q

Myelinated axons

A

● The electrical insulation that surrounds vertebrate axons is called a myelin
sheath
● Produced by glia: oligodendrocytes in the CNS and Schwann cells in the
PNS.
● During development, these specialized glia wrap axons in many layers of
membrane.
● The membranes forming these layers are mostly lipid, which is a poor
conductor of electrical current and thus a good insulator

(voltage-gated channels)

61
Q

Myelin sheath

A

the electrical insulation that surrounds vertebrate axons

(voltage-gated channels)

62
Q

What is produced by glia in the CNS

A

oligodendrocytes

(voltage-gated channels)

63
Q

What is produced by glia in the PNS

A

Schwann cells

(voltage-gated channels)

64
Q

Transmitting a signal: Synapse

A

slide 65
(voltage-gated channels)

65
Q

Transmitting a signal: Synapse

A

electrical synapses and chemical synapses

(voltage-gated channels)

66
Q

electrical synapses

A

the electrical current flows from one neuron to another through gap junctions

(voltage-gated channels)

67
Q

chemical synapses

A

a chemical neurotransmitter carries information between neurons.
● Most synapses are chemical synapses

(voltage-gated channels)

68
Q

A chemical synapse: neurotransmitter release

A

slide 67 and 68

(voltage-gated channels)

69
Q

Action potential causes the release of the neurotransmitter

A

● The presynaptic neuron synthesizes and packages the neurotransmitter in synaptic vesicles located in the synaptic terminal.
● The neurotransmitter diffuses across the synaptic cleft and is received by the postsynaptic cell.

(voltage-gated channels)

70
Q

single neurotransmitter

A

may bind specifically to more than a dozen different receptors.

A single neurotransmitter could excite postsynaptic cells expressing one receptor and inhibit postsynaptic cells expressing a different receptor.

(voltage-gated channels)

71
Q

Generation of Postsynaptic Potentials

A

● Direct synaptic transmission involves binding of neurotransmitters to ligand-gated ion channels in the postsynaptic cell.
● Neurotransmitter binding causes ion channels to open, generating a postsynaptic potential.

(chemically-gated channels)

72
Q

A chemical synapse: communication!

A

slide 73
(chemically-gated channels)

73
Q

Metabotropic receptor

A

● In some synapses, a neurotransmitter binds to a receptor that is metabotropic
● In this case, movement of ions through a channel depends on one or more metabolic steps
(chemically-gated channels)

74
Q

Postsynaptic potentials

A

Excitatory postsynaptic potentials (EPSPs) and Inhibitory postsynaptic potentials (IPSPs)
(chemically-gated channels)

75
Q

Excitatory postsynaptic potentials (EPSPs)

A

are depolarizations that bring the membrane potential toward threshold
(chemically-gated channels)

76
Q

Inhibitory postsynaptic potentials (IPSPs)

A

are hyperpolarizations that move the membrane potential farther from threshold
(chemically-gated channels)

77
Q

Temporal Summation

A

slide 76
(chemically-gated channels)

78
Q

Spatial Summation

A

slide 77
(chemically-gated channels)

79
Q

Termination of Neurotransmitter Signaling

A

After a response is triggered, the chemical synapse returns to its resting state.

The neurotransmitter molecules are cleared from the synaptic cleft.

Two mechanisms of terminating
neurotransmission
(chemically-gated channels)

80
Q

Nerve gas sarin

A

Blocking this process can have severe effects. The nerve gas sarin triggers paralysis and death due to inhibition of the enzyme that breaks down the neurotransmitter controlling skeletal
muscles.
(chemically-gated channels)

81
Q

The connection among neurons make neuronal circuits

A

slide 80
(chemically-gated channels)

82
Q

Flow of information

A

slide 81
(chemically-gated channels)

Pob 1 (10 decks)

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