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BIOL 155 MIDTERM > Nervous System > Flashcards

Nervous System Flashcards

1
Q

What are the three main components of the nervous system?

A
  1. CNS: inside vertebrae and cranial bones
  2. PNS: outside the skull and spine— directly connected to the CNS
  3. ENS: associated with the digestive tract— indirectly connected to the CNS
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2
Q

What are the two classes of cells that nervous tissue consists of? What are their function?

A

Neurons: transmit information
Neuralgia: which play supporting roles— protect and maintain neurons

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3
Q

What are the three functional classifications fo neurons?

A
  1. Sensory neurons
  2. Interneurons
  3. Motor/effector neurons
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4
Q

What do sensory neurons do?

A

Take information from the environment or non-neurons and transmit it to neurons

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5
Q

What do interneurons do?

A

Receive and transmit signals between other neurons

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6
Q

What do Motor/effector neurons do?

A

Receive information from other neurons and transmit it to non-neuronal cells (i.e.muscles)

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7
Q

What are the four types of glial cells in the nervous system?

A
  • ependymal cells
  • microfilm
  • myelinating cells
  • Astrocytes and satellite cells
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8
Q

What are ependymal cells? What is their function?

A
  • Simple cuboidal epithelium that lines cavities in the CNS called ventricles
  • secrete CSF
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9
Q

What are Microglia? What is their function?

A

Descendants of WBC’s, perform immune functions and also help modify connection between neurons

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10
Q

What are Schwann cells (PNS)/Oligodendrocytes (CNS)?

A

Wrap around axons and produce a myelin sheath (electrical insulation)

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11
Q

What are satellite cells (PNS) and astrocytes (CNS)?

A
  • Cells that provide physiological support for neurons, helping maintain their extracellular environment
  • attach to dendrites
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12
Q

Can axons in the PNS regrow?

A

Yes

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13
Q

Can axons in the CNS regrow?

A

No— glia prevent the axon from regrowing through physical and chemical barriers

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14
Q

What is the advantage that the CNS could get by not allowing new neurons to grow?

A

— neurons are very specialized and need specific chemicals to regrow

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15
Q

How are Na+ and K+ gradients maintained?

A

Primary active transport, Na-K-ATPase pump

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16
Q

How is the Cl- gradient is maintained?

A

Secondary active transport (co-transport with K+)

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17
Q

What do leak channels do?

A
  • allow for ionic permeability at rest

- always open, even at rest

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18
Q

What allows ions to move through ion channels

A

their electrochemical gradient

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19
Q

What chemical has the most leak channels?

A

Potassium

20
Q

What is the equilibrium potential?

A

A transmembrane potential where electrical forces are exactly the right size to balance out the force from that ion’s concentration gradient

21
Q

What is the equilibrium potential for K+?

A

-90

22
Q

What is the equilibrium potential for Na+?

A

+70

23
Q

What is the equilibrium potential for Cl-?

A

-70

24
Q

What determines how much an ion will contribute to the potential?

A

How permeable it is

25
Q

How can a membrane channel change?

A

Shifts according to which ions are most permeable at a given time

26
Q

A sensory neuron has an RMP of -70mV, and a myofibre at rest has an RMP of -90mV. What leak channels are present in each cell?

A
  1. Sensory neuron: Cl-

2. Myofibre neuron: K+

27
Q

If a stimulus from the environment triggers the sensory neuron to open ion channels in its dendrites that are equally permeable to both Na+ and K+, what will happen to the membrane potential?

A

It will stay at about -70mV

28
Q

What are the three kinds of gated ion channels?

A
  1. Voltage
  2. Ligand
  3. Mechanical
29
Q

Where are ligand and voltage gated channels found in a neuron? What kind of potential do they produce?

A
  • ligand gated Na+ channel on dendrites— graded potential
  • voltage gated Na+ and K+ channels on the axon
  • voltage gated Ca2+ channels at the axon terminals
30
Q

What is a (post)synaptic potential?

A

A change in membrane potential that comes from the neurotransmitter released by another neuron

31
Q

What an example of hyperpolarization?

A

An NT opens ion channels that are only permeable to K+

32
Q

What affects the size of a graded potential?

A
  • how many open channels there are

- the concentration of neurotransmitter released

33
Q

Why is there only a small change in the membrane potential when ligand gated Cl- channels open?

A

The equilibrium channel of Cl is very close to the the RMP

34
Q

What do mechanically gated ion channels do?

A
  • produce a graded potential called a receptor potential
35
Q

How are graded potentials generated?

A
  • different ion channels

- generated locally by the stimulation that triggers the channel to open

36
Q

Where is the threshold potential?

A

-55mV

37
Q

How many gates do voltage gated sodium channels have?

A

2:
1) activation gate: opens rapidly in response to the depolarization
2) inactivation gate: starts open, then closes (and stays closed until the membrane gets back near to RMP or even more negative)

38
Q

When does a voltage gated K channel open? How quickly does it open?

A

Right when the neuron crosses threshold; very slowly (K starts moving out of the cell and repolarizing around the time that sodium channels are closing)

39
Q

Why does the potential go BELOW threshold when it is repolarizing?

A
  • the K channels stay open for a short amount of time after repolarization
  • there are more voltage gated channels than leak channels so K keeps moving out of the cell
40
Q

What kind of feedback contributes to action potential?

A

Both positive and negative:

  • positive: sodium channels depolarize the membrane and make more channels open
  • negative: k channels repolarize/hyperpolarize and makes more channels close
41
Q

What is the AP absolute and relative refractory period?

A

Absolute: cannot get another action potential once the membrane reaches threshold
Relative: Hyperpolarization causes a period of time where the cell is too polarizated to get to threshold

42
Q

Depolarization spreads both directions, but the AP is only generated distally— why?

A

The sodium inactivation gates are still closed

43
Q

What is myelin made out of?

A

Fat and protein

44
Q

What is a node? What do they do?

A
  • The 1-2mm long section between internodes that has no myelin wrapping
  • section where VG channels and leak channels are
45
Q

Why is myelin insulating?

A

It prevents ions form escaping through leak channels and therefor enhances the spread of potentials

46
Q

What is conduction speed?

A

The time it takes an action potential to travel a given distance along an axon

47
Q

Why do myelinated axons use less ATP?

A

pumps use ATP, unmyelinated axons need more action potentials

BIOL 155 MIDTERM (8 decks)

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