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A&P > Exam 2: Myelin & Synapses > Flashcards

Exam 2: Myelin & Synapses Flashcards

1
Q

What is the name of the “insulation” that is found on neurons?

A

Myelin sheath

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2
Q

What is myelin derived from?

A

Sphingomyelin in the cell wall

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3
Q

What type of cells create myelin?

A

Glial cells = supporting cells in the nervous system
Specific Examples:
CNS: Oligodendrocytes
PNS: Schwann Cells

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4
Q

T/F Myelin slows down action potentials

A

False

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5
Q

Explain how Schwann cells work

A

Schwann cells grow and wrap themselves in a spiral around a neuron. Each layer that is wrapped around becomes increasingly compact with water being squeezed out more and more. Water becomes fully pushed out of the cell and it becomes a good insulator. You are left with a lipid compound that provides protection, speed, and efficiency.

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6
Q

How do signals move when there is a myelin sheath present?

A

Signals “jump” in steps underneath the myelin sheath

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7
Q

What are the openings between myelination called?

A

Nodes

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8
Q

What do nodes contain?

A

Fast Na+ channels

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9
Q

If you want to block myelinated neurons in anesthesia, what do you need to do?

A

Give more anesthetic to block all of the dense sodium channels found within the nodes

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10
Q

T/F Having more sodium channels at the nodes means that the cell has an overall higher amount of sodium channels than cells without nodes.

A

False; Just because you have a dense amount of sodium channels at the nodes does not mean you have more sodium channels overall

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11
Q

What is saltatory conduction?

A

Movement of the action potential from one node to the next

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12
Q

What does the myelin coating make the nerve more resistant to?

A

Crush injuries

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13
Q

T/F When we lose myelination within our CNS it is difficult to replace

A

True

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14
Q

What happens when we lose myelin in our optic nerve?

A

Our vision becomes cloudy, delayed, and we might lose peripheral vision

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15
Q

What are 3 examples of demyelinating diseases?

A
  1. MS
  2. Optic Neuritits
  3. Guillain-Barre Syndrome
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16
Q

What causes demyelinating diseases?

A

Genetics
Infection
Autoimmune hyperreactivity
Polyneuropathies

17
Q

What is something easy to repopulate in cell walls?

A

Na/K pumps

18
Q

What happens if there are fast sodium channels further down the line with only a long stretch of sodium-potassium pumps?

A

Sodium will be pumped out of the cell and there won’t be any to continue to the next node and continue signaling correctly

19
Q

What is it called when one cell wants to talk to another?

A

Synapse

20
Q

Where do direct electrical synapses occur?

A

Gap junctions

21
Q

What is a connexon and what is it comprised of?

A

A connexon is a conduit that allows for ionic current to pass from one cell to another; A connexion is comprised of 6 connexin proteins and bound to the connexon in an adjacent pair

22
Q

What can move through gap junctions?

A

Small ions via simple diffusion (Na; Ca can also move but it is larger and clunky so it doesn’t fit as well as Na)

23
Q

Are electrical synapses fast or slow overall? In the heart?

A

Overall they can be very fast; the heart purposefully has a lower number of gap junctions in very specific places to purposefully slow down

24
Q

What are chemical synapses?

A

Electrical signals that are related cell to cell via a chemical intermediary

25
Q

What is the downside to chemical synapses?

A

They take longer to get the message across since they don’t work bidirectionally

26
Q

T/F The response of cells in chemical synapses depends on what receptors are on the target cell and what receptors they are tied to

A

True

27
Q

Is ACh excitatory or inhibitory in the heart?

A

Inhibitory

28
Q

Is ACh excitatory or inhibitory in the skeletal muscle?

A

Excitatory

29
Q

What do sending cells have on them?

A

Presynaptic Terminal

30
Q

What do receiving ends of the cells have on them?

A

Postsynaptic terminal

31
Q

What letter is used for myelinated neurons?

A

A

32
Q

What letter is used for non-myelinated neurons?

A

C

33
Q

What letter is used for lightly myelinated neurons?

A

B

34
Q

What is the largest size of neuron fibers?

A

20 micrometers

35
Q

What is the smallest size of neuron fibers?

A

0.5 micrometers

36
Q

If we want something sent quickly, do we send it on a larger of smaller fiber?

A

Larger

37
Q

What do A-fibers subdivide into?

A

Alpha, Beta, Delta, and Gamma fibers

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