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From Flashcardlet > BMS 108 Ch. 7 Nervous System Part 1 > Flashcards

BMS 108 Ch. 7 Nervous System Part 1 Flashcards

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0
Q

What are the two kinds of cells that make up the nervous system?

A

neurons and glial cells

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1
Q

What are the two structural divisions of the Nervous System?

A
  1. Central Nervous System

2. Peripheral Nervous System

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2
Q

What are the functional units of the nervous system?

A

neurons

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3
Q

What do glial cells do?

A

Help maintain homeostasis and “help neurons”.

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4
Q

Glial cells are ___ times more common than neurons.

A

5

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5
Q

What are neurons?

A

Electrically excitable cells that gather and transmit information.

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6
Q

What are the three ways in which neurons gather and transmit information?

A
  1. Responding to stimuli (from other neurons or external inputs) “transduction”
  2. Producing and sending electrical impulses
  3. Releasing chemical messages
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7
Q

What are the two types of axons?

A

Myelinated and unmyelinated

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8
Q

What does myelin do?

A

electrically insulates the axon

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9
Q

What are the gaps inbetween myelin on a myelinated axon called?

A

Nodes of Ranvier

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10
Q

What glial cells are responsible for myelinating axons in the CNS?

A

Oligodendrocytes

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11
Q

Do oligodendrocytes myelinate just one axon?

A

No

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12
Q

What glial cell myelinates axons in the PNS?

A

Schwann cells

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13
Q

What are the glial cells in the CNS? in the PNS?

A

Astrocytes, oligodendrocytes, microglial cells, ependymal cells; Schwann cells and satellite cells

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14
Q

Why are some axons myelinated?

A

To increase conduction velocity

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15
Q

What are the reasons not to myelinate an axon?

A
  • Myelin costs energy to produce

- Some very small unmyelinated fibers are actually faster than they would be if we myelinated them

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16
Q

In addition to myelin, what is another way to speed up electrical velocity?

A

Increased diameter of the axon

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17
Q

What is white matter?

A

Portion of the nervous system with myelinated axons

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18
Q

What is gray matter?

A

Portion of the nervous system with unmyelinated axons

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19
Q

What is the difference between a neuron, a nerve and a tract?

A

A neuron is 1 nerve cell; a nerve is a bundle of axons in the PNS; a tract is a bundle of axons in the CNS

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20
Q

How does an axon regenerated in the PNS?

A
  • Schwann cells survive and form a regeneration tube.

- Tube releases chemicals (neurotropins) that attract growing axon

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21
Q

Can axons regenerate in the CNS?

A

Limited

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22
Q

Why is regeneration in the CNS limited?

A

Oligodendrocytes produce proteins that inhibit regrowth and form glial scar tissue that blocks regrowth.

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23
Q

Axons can be both _____ and _______.

A

long; short

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24
Q

What are the four special transport systems for axons?

A
  1. Axoplasmic flow
  2. Axonal transport
  3. Anterograde transport
  4. Retrograde transport
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25
Q

What is Axoplasmic flow?

A

Moves soluble compounds toward nerve endings away from the cell body (slow, nonspecific)

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26
Q

What is Axonal Transport?

A

Moves large and insoluble compounds bidirectionally along microtubules, uses cytoskeleton (fast, specific).

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27
Q

What is Anterograde Transport?

A

Moves materials away from the cell body.

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28
Q

What is Retrograde Transport?

A

Moves materials toward the cell body.

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29
Q

What are the three structural classifications of neurons?

A
  1. pseudounipolar (unipolar)
  2. bipolar
  3. multipolar
30
Q

What is a pseudounipolar neuron?

A

Neuron with a cell body that sits aside one long axon (collects sensory information)

31
Q

What is a bipolar neuron?

A

A neuron with 2 processes coming off the cell body - 1 dendrite and 1 axon.

32
Q

What is a multipolar neuron?

A

A neuron with many dendrites and 1 axon

33
Q

Which structural neuron type is most common?

A

Multipolar

34
Q

What are the three FUNCTIONAL classifications of neurons?

A
  1. Afferent (Sensory)
  2. Efferent (Motor)
  3. Association (Interneurons)
35
Q

What is the most common type of glial cell?

A

Astrocytes

36
Q

What are the 5 functions of Astrocytes?

A
  1. Buffering K+ levels
  2. Recycling neurotransmitters
  3. Regulating adult neurogenesis
  4. Releasing transmitters that regulate neuronal activity
  5. Regulate BBB (Blood Brain Barrier)
37
Q

What is the Blood Brain Barrier?

A

A selective barrier formed by tight capillaries in the brain and astrocytes.

38
Q

What is Equilibrium Potential?

A

Describes voltage across cell membrane if ONLY 1 TYPE of ion could diffuse.

39
Q

What does the Nernst Equation calculate?

A

Gives the membrane voltage needed to stop an ion from flowing down its concentration gradient.

40
Q

The Nernst Equation calculates the equilibrium potential of ____ ion.

A

each

41
Q

What does the equilibrium potential depend on?

A

The ration of ion concentrations inside and outside the cell membrane.

42
Q

According to the Nernst Equation, the greater the concentration gradient, the greater the ________ _______.

A

driving force

43
Q

What is the Nernst Equation?

A

Equilibrium Potential (E sub x) = 61 log [X sub out]
__ _________
z [X sub in]

z= valence (charge) of the ion
E sub x = a voltage expressed in mV

44
Q

What is Resting Membrane Potential?

A

The membrane voltage of a cell not producing impulses (-70mV on average)

45
Q

What does RMP depend on?

A
  1. ion concentration inside and outside the cell
  2. permeability of each ion*

*affected most by K+ because it is most permeable. If the cell were ONLY permeable to K+, RMP would be -90mV

46
Q

In addition to high K+ permeability, RMP is also affected by slight ____ permeability.

A

Na+

47
Q

What is the result of Na+ permeability on RMP?

A

Some Na+ diffusion into the cell makes it’s RMP -70mV instead of the -90mV if it was just permeable to K+

48
Q

How many mV does the Na+/K+ Pump add to the RMP of a cell?

A

-3mV

49
Q

Does the Na+/K+ Pump require ATP?

A

Yes

50
Q

The Na+/K+ Pump is electrogenic. What does that mean?

A

Electrogenic means that there are not an equal amount of ions entering and leaving the cell. In the Na+/K+ Pump, this is because for every 2 K+ taken in, 3 Na+ are pushed out.

51
Q

Excitable cells can __________ their RMP quickly.

A

discharge

52
Q

What is an Action Potential?

A

A large, fast change in membrane permeability that generates and conducts an electrical impulse.

53
Q

What are the three basic types of membrane potential changes?

A
  1. Depolarization
  2. Hyperpolarization
  3. Repolarization
54
Q

What is depolarization?

A

Occurs when membrane potential becomes more positive than RMP.

55
Q

What is hyperpolarization?

A

Occurs when membrane potential becomes more negative than RMP.

56
Q

What is repolarization?

A

Occurs when membrane potential returns to RMP.

57
Q

Movement of ions = ?

A

Electrical activity

58
Q

How do MP changes occur?

A

Governed by ion flow through membrane channels

59
Q

K+ _________ __________ are always open.

A

leak channels

60
Q

Closed channels have ___________ ________ that can be opened.

A

molecular gates

61
Q

What kind of ion channel is opened by depolarization?

A

Voltage-gated (VG) channels

62
Q

K+ can flow via both _____ _______ and ________ _______ _______.

A

leakage channels; voltage-gated channels

63
Q

VG K+ channels are ________ in resting cells.

A

closed

64
Q

Na+ channels are also _______ ________ and closed in resting cells.

A

voltage-gated

65
Q

If a cell were only permeable to Na+, what would be the RMP of the cell?

A

+66mV

66
Q

The voltage-gated channels are opened by __________ which changes the MP to _______.

A

depolarization; -50mV

67
Q

What kind of channels open if a cell becomes adequately depolarized? (reaches threshold) What value (in MP) is threshold?

A

Voltage-gated Na+ channels; -50mV

68
Q

What is another name for the rising phase of an action potential?

A

depolarization

69
Q

What is another name for the falling phase of an action potential?

A

repolarization

70
Q

Describe the mechanism of an action potential.

A
  • Depolarization and repolarization occur via diffusion (protein carriers/ion channels)
  • Does not require ATP
  • After an AP, Na+/K+ pump extrudes Na+, recovers K+
  • After AP, permeability goes back to “rest” (high K+ via leak channels, low Na+)
71
Q

Near the peak of an AP why does potassium leave the cell?

A

When the MP changes to +30mV after a massive influx of Na+, which cause both an electrical and chemical drive for potassium to leave the cell.

72
Q

What causes the MP “overshoot” of RMP on the falling phase of AP?

A

Excess K+ channels open

73
Q

What kind of primary active transport helps return the cell to RMP following the overshoot?

A

The Na+/K+ pump

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