Chapter 8

Question 1

3 types of neurons

Answer 1

sensory interneuron motor neuron

Question 2

anaxonic neuron

Answer 2

a bunch of afferent processes, but no axon typically CNS interneurons

Question 3

bipolar neuron

Answer 3

processes –> cell body–> axon typically a sensory neuron

Question 4

pseudounipolar neuron

Answer 4

one single elongate process, with the cell body situated on one side typically a sensory neuron

Question 5

multipolar neuron

Answer 5

“typical” neuron that you think of a bunch of dendrites –> cell body –> axon typically a motor neuron

Question 6

node of ranvier

Answer 6

in between area of connecting schwann cells covered in myelin sheath.

Question 7

cell body

Answer 7

soma

Question 8

dendritic spines

Answer 8

specialized little processes that increase dendritic surface area, increases communication ability of the neuron. a micro-anatomical feature

Question 9

axonal growth cone

Answer 9

during embryogeneis, axons seek out targets and grow out. also involved in neural-regeneration should damage and re-growth occur responds to growth factors extracellular matrix molecules and membrane proteins

Question 10

axon hillock

Answer 10

region where the cell body meets the axon

Question 11

Glial cells in CNS

Answer 11

ependymal cells astrocytes microglia oligodendrocytes

Question 12

Glial cells in PNS

Answer 12

Schwann cells satellite cells

Question 13

Ependymal cells

Answer 13

create barriers between compartments source of natural stem cells

Question 14

astrocytes

Answer 14

Highly branded glial cell make up large portion of the brain communicate w/each other via gap junctions for rapid communication source of neural stem cells take up K, water and NTs secrete neurotropic factors *help form the blood brain barrier* provide substrates for ATP production if there is a nerve injury, will start forming scar tissue, interferes with regeneration and repair

Question 15

Microglia

Answer 15

modified immune cells- not actually nerve cells act as scavengers when activated, remove damaged cells and foreign invaders

Question 16

oligodendrocytes

Answer 16

form myelin sheets branch to myelinate several axons

Question 17

schwann cells

Answer 17

form myelin sheets one schwann cell associates with one axon secrete neurotropic factors

Question 18

satellite cells

Answer 18

support cell bodies located in ganglia essentially non-myelinating schwann cells

Question 19

Multiple sclerosis

Answer 19

de-myelination, exposing naked nerve fiber autoimmune, in part. affects skeletal muscle, but there are also bladder and bowel dysfunction, respiratory issue, parathesia, optic disturbances, depression, paranoia, mental changes phenotype varies greatly

Question 20

ganglia

Answer 20

nerve cell bodies located outside of CNS

Question 21

nerve regeneration in CNS

Answer 21

can’t happen b/c of astrocyte inhibition

Question 22

conductance

Answer 22

ease of which an ion flows through a channel

Question 23

voltage gated ion channels

Answer 23

respond in change to cells membrane potential Na and K channels along the axon

Question 24

current

Answer 24

I the flow of electrical charge caries by an ion direction depends on the electrochemical gradient of the ion

• K+ : moves into the cell
• Na+, Cl- and Ca2+ : move out of the cell

Question 25

electrical signal created by

Answer 25

the net flow of ions across the membrane, depolarizing or hyper polarizing the cell

Question 26

current flow (I) follows ohms law

Answer 26

I= V / R I is directly proportional to the voltage difference and inversely proportional to the resistance

Question 27

axonal transport

Answer 27

moves proteins and organelles between cell body and axon terminal

Question 28

Slow axonal transport

Answer 28

rate of protein being synthesized and being moved along mt transport is slow

Question 29

fast axonal transport

Answer 29

can be bi-directional, vessels can be used again.

Question 30

synapse development

Answer 30

depends on neurotrophic factors

Question 31

resting membrane potential of a neuron

Answer 31

~-70mV

Question 32

the major contributor to the resting membrane potential

Answer 32

K

the resting membrane is more permeable to K, and there is more K inside the cell

Question 33

Nearnst equation

Answer 33

describes the membrane potential that would result if the membrane were permeable to only one ion

E ion(in mV) = 61 / Z x log [ion] out/ [ion] in

•Z is the electrical charge on the ion (1+ for K+)

Question 34

Predicted E K+ = -90mV

Answer 34

actual E K+ is -70mV

why not the same?

other ions must be contributing to the membrane potential

•neurons at rest are slightly permeable to Na+

(Na+ leaks in)

Question 35

•Goldman-Hodgkin-Katz equation (GHK)

Answer 35

•Calculates the membrane potential that results from all ions that can cross the membrane
•
•Accounts for membrane permeability of each ion

For mammalian cells:

Na+, K+ and Cl- have largest effect on resting membrane potential

each ion’s contribution is inversely proportional to its ability to cross the membrane

Dependent on:
•the combined contributions of concentration gradient ([out]/[in]) (add these together)

• membrane permeability (P ion) for each ion
• If a membrane is not permeable to an ion, it drops out of the equation (eg Ca2+)

Question 36

if a membrane becomes more permeable to Na+

Answer 36

will get membrane depolarization

Question 37

if a membrane becomes more permeable to K+

Answer 37

will get membrane hyperpolerization

Question 38

4 major types of gated channels in neurons:

Answer 38

. Na+ channels

2. K+ channels
3. Ca2+ channels
4. Cl- channels

Question 39

Conductance

Answer 39

ease at which an ion flows through a channel

•varies with the gating state and the protein isoform
•
•eg: K+ leak channels are open most of the time; others open or close in response to stimuli

Question 40

mechanically gated ion channels

Answer 40

found in sensory neurons, open in response to physical forces such as pressure or stretch

Question 41

chemically gated ion channels

Answer 41

respond to a variety of ligands, such as ECF neurotransmitters, ICF signal molecules

Question 42

voltage gated ion channels

Answer 42

respond to changes in the cell’s membrane potential

eg: Na+ and K+ channels along the axon

Question 43

biological electricity resistance comes from 2 sources

Answer 43

Rm: resistance of the cell membrane

Ri: internal resistance of the cytoplasm

(and the diameter of the cell)

Rm and Ri together comprise the length constant for a given neuron

Question 44

graded potentials

Answer 44

•Variable strength signals
•
•travel short distances
•
•lose strength as they travel through the cell
•
•used for short distance communication
•
•if strong enough, can initiate an action potential

Question 45

Action potentials

Answer 45

•Very brief, large depolarizations
•
•Travel for long distances through a neuron without losing strength
•
•Rapid signaling over long distances

Question 46

___ follows an action potential

Answer 46

refractory period

No RF, would lose gradients, signals would not be coordinated

The membrane cannot be excited to get an AP at the RF

The excitability factor steadily increases in the RF period

Question 47

Current flow

Answer 47

the depolarized section has + on inside and – on outside

Nonpolarized area of cell is – on inside and + on outside

action potential is UNIDIRECTIONAL

Question 48

trigger zone

Answer 48

the area where Na channels are open and Na enters the cell

Question 49

Saltatory conduction

Answer 49

Action potentials appear to jump from one node of Ranvier to the next.

Only the nodes have voltage-gated Na+ channels

Demyelinating diseases reduce or block conduction when current leaks out of

the previously insulated regions between the nodes.

Question 50

NT termination

Answer 50

NTs returned to axon terminals for reuse or transported to glial cells

enzymes inactivate NTs

or NTs diffuse out of synaptic cleft