Lecture 12: Neural Tissue 2

Question 1

Ependymal Cells

Answer 1

Produce and circulate,
Line ventricles and central canal,
Produce cerebrospinal fluid,
CNS

Question 2

Astrocytes

Answer 2

Maintain the blood-brain barrier,
Provide structural framework for the neurons of the CNS,
CNS

Question 3

Astrocytes Act As _______ For Substances Entering The CSF/Interstitial Fluid

Answer 3

Gatekeepers

Question 4

How Do Astrocytes Act As Gatekeepers?

Answer 4

Each ‘foot’ wraps around a capillary in CNS and act as gatekeepers of CNS bloodstream

Question 5

Ventricle

Answer 5

Fluid filled

Question 6

Oligodendrocytes

Answer 6

Extensions wrap around neuron axons, usually more than one,

CNS

Question 7

Microglia

Answer 7

“Garbage trucks”
Engulf (phagocytize) cellular debris, waste products and infective organisms,
CNS

Question 8

Satellite Cells

Answer 8

Similar to astrocytes,
Surround neuron cell bodies in ganglia,
Regulate the environments around neurons,
PNS

Question 9

Schwanns Cells

Answer 9

Similar to oligodendrocytes,
Myelinate sections of a single axon or
Surround sections of many unmyelinated axons,
PNS

Question 10

Temporary Crushing Injury To An Axon Results In _______

Answer 10

An unexcitable axon for days to weeks

Question 11

Sustained Crushing Or Severing Of An Axon Results In _____

Answer 11

Death of an axon distal to the injury

Question 12

Wallerian Degeneration

Answer 12

Axon distal to injury site degenerates and macrophages clean up debris,
Schwann cells help form a path for new axon growth,
Axon may or may not grow back

Question 13

Resting Potential For A Neuron

Answer 13

-70mV,

Net negative charge inside the cell

Question 14

Sodium Goes

Answer 14

In

Question 15

Potassium Goes

Answer 15

Out

Question 16

Passive Channels

Answer 16

Protein channels that are always open,
‘Leaky’,
Na+ and K+

Question 17

Gated Channels

Answer 17

Active channels,
Chemically-gated,
Voltage-gated,
Mechanically-gated

Question 18

Chemically-Gated Channels

Answer 18

Open or close when they bind specific chemicals (dendrites and cell body),
Have chemical receptors,
Gates opened by neurotransmitters

Question 19

Voltage-Gated Channels

Answer 19

Open or close in response to changes in transmembrane potential (axon),
Change in membrane voltage,
Activation gate opens at -60mV,
Inactivation closes at 30mV

Question 20

Mechanically-Gated Channels

Answer 20

Open or close in response to physical distortion,
Touch receiving neurons,
Pressure opens channel, allowing A.P. and/or depolarization

Question 21

Graded Potentials

Answer 21

Local change in transmembrane potential,
Produced from any stimulus that opens gated ion channels,
May or may not result in action potential,
Causes depolarization or hyperpolarization

Question 22

Hyperpolarize

Answer 22

Open more K+ channels to make more - because it is +,

Shifting negative

Question 23

Depolarize

Answer 23

Open Na+ channels,

Shifting positive

Question 24

Action Potentials

Answer 24

Propagated changes in transmembrane potential that spread across an excitable membrane

Question 25

Once Threshold Is Reached At ______, An Action Potential Occurs

Answer 25

Axon hillock

Question 26

Steps Of Action Potential (5)

Answer 26

1. Depolarization to threshold
2. Opening of activation gates on voltage-gated sodium channels
3. Na+ inactivation gates close and K+ channels open at +30mV
4. K+ channels start closing at -70mV
5. Hyperpolarization to -90mV and then return to resting potential

Question 27

How Does Returning To Resting Potential Happen?

Answer 27

It occurs through the action of passive channels and the Na+/K+ exchange pump (Na+/K+ ATPase pump)

Question 28

How Many Action Potentials Can A Neuron Undergo Per Second?

Answer 28

1000

Question 29

Refractory Period

Answer 29

Period of time during an action potential, when another action potential cannot or is unlikely to occur

Question 30

Absolute Refractory Period

Answer 30

Voltage-gated sodium channels are either open or are inactivated,
No action potential possible

Question 31

Relative Refractory Period

Answer 31

Sodium channels are in normal resting state, but potassium channels are open or membrane is hyperpolarized,
Action potential is possible but requires a larger stimulus because it is harder to reach threshold

Question 32

Propagation Of Action Potentials

Answer 32

Movement of an action potential along the length of an axon

Question 33

Continuous Propagation

Answer 33

Occurs in unmyelinated axons,

Action potential spreads from ‘segment’ to ‘segment’ down length of axon,

Question 34

Saltatory Propagation

Answer 34

Occurs in myelinated axons,

Depolarization of action potential occurs only at nodes

Question 35

Propagation Speed Is Determined By…

Answer 35

Myelination status and the diameter of an axon

Question 36

Larger Axon Diameter =

Answer 36

Much faster propagation speed,

Less resistance for sodium in axoplasm

Question 37

Type A Fibers

Answer 37

Largest diameter, myelinated,
Carry sensory information about position, balance, light touch, pressure, and motor information to skeletal muscles,
Carries most important info because it is fastest

Question 38

Typer B Fibers

Answer 38

Smaller diameter, myelinated,

Question 39

Type C Fibers

Answer 39

Smallest diameter, unmyelinated

Question 40

Type B & C Fiber Functions

Answer 40

Carry sensory information about general touch, temperature and motor information to smooth and cardiac muscle and glads