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OT 5003 - Applied Neuroscience and Occupations > Chapter 5 - Physical and Electrical Properties of Cells in the Nervous System > Flashcards

Chapter 5 - Physical and Electrical Properties of Cells in the Nervous System Flashcards

1
Q

What are the 4 main components of a neuron?

A

Soma, Dendrites, Axon, and Presynaptic Terminals

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2
Q

Soma

A

The cell body. It maintains the cell and keeps it functioning.

(e.g. synthesizes proteins used as neurotransmitters)

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3
Q

Dendrites

A

Branchlike extensions that serve as the main input sites for the cell.

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4
Q

Axon

A

The output unit of the cell, specialized to send information to other neurons, muscle cells, or glands.

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5
Q

Presynaptic Terminals

A

Transmitting elements of the neuron

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6
Q

Neurons transmit information about their activity via neurotransmitters from the ___________ to the ___________.

A

Presynaptic terminals, synaptic cleft

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7
Q

____________ is the space between neurons, and serves as the site for interneuronal communication,

A

Synaptic cleft

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8
Q

Axoplasm

A

The cytoplasm within an axon

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9
Q

Axoplasmic transport

A

Mechanism for transporting neurotransmitters substances within an axon

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10
Q

What are the two directions involved in axoplasmic transport?

A

Anterograde and Retrograde

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11
Q

Anterograde

A

From the SOMA toward the PRESYNAPTIC TERMINAL

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12
Q

Retrograde

A

From the SYNAPSE back to the SOMA

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13
Q

What causes axoplasmic transport to slow down in speed?

A

Aging and also in neurodegenerative diseases such as Alzheimer’s, Huntington’s, ALS, etc.

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14
Q

In vertebrates, what are the 2 groups of cells that are classified based on number of processes arising from the soma?

A

Bipolar and Multipolar cells

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15
Q

Bipolar cells

A

Have two primary processes that extend from the cell body. The dendritic root divides into multiple dendritic branches, and the axon projects to form its presynaptic terminals.

Example: the retinal bipolar cell in the eye

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16
Q

Multipolar cells

A

Most common cells in the vertebrate nervous system with a variety of shapes and organizations.

  • Have multiple dendrites arising from many regions of the cell body and a single axon.
  • They are specialized to receive and accommodate huge amounts of synaptic input to their dendrites.

Example: spinal motor neuron, which projects from the spinal cord to innervate skeletal muscle fibers.

“Typical spinal motor cell receives approximately 8,000 synapses on its dendrites and 2,000 synapses on the cell body itself”

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17
Q

What are the subclass of bipolar cells? Describe it.

A

Pseudounipolar cells appear to have a single projection from the cell body that divides into two axonal roots. They also have TWO AXONS and NO TRUE DENDRITES.

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18
Q

Neurons function via rapid changes in the ______________ across the cell membrane.

A

electrical potential

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19
Q

What is electrical potential?

A

The distribution of ions across a membrane which creates a difference in the electrical charge on each side of the cell membrane

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20
Q

Membrane channels

A

Openings that allow ions to flow across the membrane. May be opened and closed. When open, ions diffuse through the membrane.

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21
Q

Leak channels

A

A small number of ions leak at a slow, continuous rate

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22
Q

Gated channels

A

Open in response to a stimulus and close when the stimulus is removed

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23
Q

What are the two types of membrane channels?

A

Leak and gated channels

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24
Q

What are the 3 types of gated channels?

A

Modality-gated, ligand-gated, voltage-gated channels

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25
Q

Modality-gated channels

A

Open in response to mechanical forces, temperature changes, or chemicals

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26
Q

Ligand-gated channels

A

Open in response to a neurotransmitter binding to the surface of a channel receptor on a postsynaptic cell membrane

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27
Q

Voltage-gated channels

A

Open in response to changes in the electrical potential across the cell membrane

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28
Q

What are the three types of electrical potentials in neurons that are essential for transmitting information?

A

Resting membrane, local, and action potential

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29
Q

What is resting membrane potential?

A

The electrical potential across the membrane that exists when a neuron is at rest (i.e. not transmitting information)

Unequal distribution of the ionic charge across the membrane is essential for the neurons to be excitable.

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30
Q

Steady-state condition

A

No net flow of ions across the membrane

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31
Q

Cell at its resting membrane potential will have no _______.

A

Net change in the total distribution of ions across the two sides, although individual ions may move across through leak channels.

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32
Q

What two forces determine ion distribution across the plasma membrane?

A

Concentration gradient (chemical concentration) and electrical gradient (charged ion distribution)

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33
Q

What controls the movement of ions?

A

Opposing chemical and electrical forces

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34
Q

When does equilibrium occur?

A

When there is no net movement ions across the membrane

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35
Q

How is electrochemical gradient maintained?

A
  • Anions trapped inside the neuron that are too large to diffuse through the channels
  • Passive diffusion of ions through leak channels
  • Na+/K+ pump
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36
Q

What is the Na+/K+ pump?

A
  • Uses energy from ATP to move ions across the membrane against their electrochemical gradient
  • Carries two K+ into the cell and three Na+ out of the cell with each cycle
  • As long as the cell has ATP, an unequal distribution of K+ and Na+ can exist across the membrane
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37
Q

When sudden, brief changes in membrane potential occur, the membrane can become __________ or ___________.

A

Depolarized, hyperpolarized

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38
Q

Depolarized

A

The potential becomes LESS NEGATIVE than the resting potential

INCREASES the likelihood that the neuron will generate a transmittable electrical signal and is excitatory

39
Q

Hyperpolarized

A

The potential becomes MORE NEGATIVE than the resting potential

DECREASES the neuron’s ability to generate an electrical signal, and is inhibitory

40
Q

Changes in membrane potential can result in _________ and __________.

A

Local potentials, action potentials

41
Q

Change in membrane potential occurs when…

A

ion channels open to selectively allow specific ions to pass.

42
Q

Sensory neurons

A

receiving sites are the sensory receptors

43
Q

Motor and interneurons

A

receiving sites are on postsynaptic membranes (often dendrites)

44
Q

The information causes the membrane to become _______ or _________.

A

depolarized, hyperpolarized

45
Q

Local potential

A

Initial change in membrane potential at receiving site

46
Q

Spreads passively…

A

only a short distance along the membrane

47
Q

Peripheral receptors have…

A

modality-gated channels

48
Q

Local receptor potentials

A

generated when the peripheral receptors of a sensory neuron are stretched, compressed, deformed, or exposed to thermal or chemical agents

49
Q

Local synaptic potentials

A

generated in motor neurons and interneurons when they are stimulated by input from other neurons

50
Q

Local potentials generally travel __ to __ mm.

Amplitude (strength) _______ with distance traveled.

A

1, 2

decreases

51
Q

Strength can be increased and potentials integrated via _______ and ________ summation.

A

Temporal, spatial

52
Q

Temporal summation

A

combined effect of a series of small potential changes that occur within milliseconds of each other

53
Q

Spatial summation

A

potentials generated in different regions of the neuron are added together

54
Q

A significant change in membrane potential can result from…

A

summation of multiple local potentials

55
Q

If summation of multiple local potentials causes the membrane potential to depolarize to a certain threshold an ________ is generated.

A

action potential

56
Q

Action potential

A

Brief, large depolarization in electrical potential that is repeatedly regenerated

57
Q

Action potential is all-or-none

A
  • Every time sufficient stimuli are provided so that threshold is reached, an action potential will be produced.
  • Stronger stimuli produce action potentials of the same voltage and duration as the minimally sufficient stimuli
58
Q

A large, depolarizing signal is actively propagated by…

A

repeated generation of a signal.

Information is transmitted longer distances than local (receptor or synaptic) potentials

Meaning of the signal is determined by the neural pathway

59
Q

Threshold stimulus intensity

A

stimulus intensity sufficient to produce an action potential

60
Q

Action potential is produced by a sequence of 3 events. List them.

A
  • Rapid depolarization (voltage-gated Na+ channels open)
  • Decrease in Na+ conduction (Na+ channels closed)
  • Rapid repolarization (voltage-gated K+ channels open)
61
Q

15 mV depolarization is typically sufficient to trigger an action potential.

A

Change in membrane potential -70 mV to -55 mV.

62
Q

Refractory period

A

Period of hyperpolarization

  • membrane potential is even more negative than during rest
  • difficult to initiate a subsequent action potential
63
Q

Refractory period is defined by the…

A

ion channels

64
Q

What adaptations make action potential progression faster?

A

increased diameter of the axon and myelination

65
Q

What is the water and hose analogy?

A

A wider hose will pour more water in less time. Tape (myelination) around a leaky hose will concentrate the flow.

66
Q

Myelin

A

A sheath containing fat that surrounds an axon

67
Q

What does myelin provide?

A

Insulation

68
Q

What does myelin prevent?

A

current flow across the axonal membrane

69
Q

What does myelin increase?

A

The speed of action potential propagation and the distance a current can passively spread

70
Q

What type of myelin leads to faster conduction?

A

Thicker

71
Q

Nodes of Ranvier

A
  • small patches on myelinated axons that lack myelin
  • distributed every 1 to 2 mm along the myelinated axon and contain high densities of Na+ and K+ channels
  • allow ion flow across the membrane
72
Q

Saltatory conduction

A

quick node-to-node jumping of action potential down a myelinated axon

73
Q

Saltatory conduction

A

quick node-to-node jumping of action potential down a myelinated axon

74
Q

Afferent neurons

A

carry information TOWARD the CNS

75
Q

Efferent neurons

A

carry commands FROM THE CNS outward (to muscles and glands)

76
Q

Interneurons

A

transmit impulses between other neurons

process information locally or convey information short distances; largest class of neurons

77
Q

Convergence

A

multiple inputs from a variety of cells terminate on a single neuron

78
Q

Divergence

A

single neuron with many branches that terminate on a multitude of cells

79
Q

________ and ________ contribute to the distribution of information through the nervous system.

A

Convergence, divergence

80
Q

Glial cells

A

cells that form a critical support network for neurons; also transmit information

81
Q

Glial cells are categorized by size and function

A

Microglia (small)

Macroglia (large)

82
Q

Microglial cells

A
  • act as the CNS immune system
  • activated during CNS development and following injury, infection, or disease
  • proteins in dying cells attract microglia to the site; microglia clean up and remove debris
83
Q

Macroglial cells are classified into 3 groups

A

Astrocytes, oligodendrocytes, schwann cells

84
Q

Astrocytes

A

Star-shaped cells

Act as scavengers, taking up extra K+ ions in the extracellular environment, removing chemical transmitters from synaptic clefts, and cleaning up other debris in the extracellular space

85
Q

Oligodendrocytes and Schwann cells form __________.

A

myelin sheaths

86
Q

Oligodendrocytes myelinate neurons in the _______ and Schwann cells myelinate neurons in the ________.

A

CNS, PNS

87
Q

Peripheral neuropathy

A
  • Any pathologic change involving peripheral nerves
  • Often involves destruction of the myelin surrounding the largest, most myelinated sensory and motor fibers
  • Results in disrupted proprioception (awareness of limb position) and weakness
88
Q

Guillain-Barre Syndrome

A

• Involves acute inflammation and demyelination of peripheral sensory and motor fibers
• Typically occurs after a mild infection; in 2/3 of cases it is preceded by an intestinal infection that activates the
immune system causing production of an antibody that mistakenly cross reacts with the myelin sheath
• Weakness is typically greater than sensory loss; may have pain or hypersensitivity to touch
• Patients may have difficulty with chewing, swallowing, speaking, and facial expressions if cranial nerves affected; weakness of respiratory muscles may require
ICU/ ventilator (25%)
• Onset is rapid, but followed by plateau then gradual recovery; recovery is usually complete
• Treatment may include plasmapheresis and
intravenous immunoglobulin therapy; PT and OT are often recommended

89
Q

Multiple Sclerosis

A
  • Immune system produces antibodies that attack oligodendrocytes, producing plaques in the white matter of the CNS
  • Signs and symptoms: weakness, lack of coordination, impaired vision, double vision, impaired sensation, and slurred speech; disruption of memory and emotions also possible
  • Diagnosis is difficult; MS usually manifests with one sign that may completely resolve
  • Onset common between 20 and 40 years of age; women 3x more frequently affected
  • 4 types of MS, named according to the course of disease progression:
  • Relapsing/remitting
  • Secondary progressive
  • Primary progressive
  • Progressive relapsing
90
Q

Neural stem cells

A

Immature and undifferentiated cells, precursors to both neurons and glial cells

91
Q

Characteristics of neural stem cells include the ability to:

A
  • self-renew, differentiate into most types of neurons and glial cells
  • populate developing and degenerating regions of the CNS
92
Q

Neural stem cells in the healthy mature brain are involved in forming ________ and _________.

A

memories, learning new tasks

excitement too over the possible rehabilitation implications

93
Q

Which of the following is NOT true about action potentials?

They are followed by a period of inability to fire.
They are larger in response to stronger stimuli.
They travel faster in larger axons.
They travel faster in myelinated axons.

A

They are larger in response to stronger stimuli.

94
Q

Oligodendrocytes are found in the ________ while Schwann cells are found in the ________.

Central nervous system; autonomic nervous system.
Central nervous system; peripheral nervous system.
Peripheral nervous system; autonomic nervous system.
Peripheral nervous system; central nervous system.

A

Central nervous system; peripheral nervous system.

OT 5003 - Applied Neuroscience and Occupations (1 decks)

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