For Final Exam

Front 1

what is the difference between graded potential and action potential?

Back 1

graded: confined to small area; potential change of variable amplitude and duration; it has no threshold or refractory period
action: brief all or none; has threshold and refractory period

Front 2

Describe where in the cell are the majority of the ions located: K, Na, and Cl.

Back 2

K is greater intracellulary

Na and Cl greater extracellularly

Front 3

What is a process? What is a soma?

Back 3

processes are long extentions of the neurons such as dendrites and axons.

soma are the cell body that contain the nucleus and the ribosomes

Front 4

describe the functions of the dendrites and axons. what type of potentials do they mostly undergo?

Back 4

dendrites receive input from neurotransmitters, then undergo graded potential.

axons undergo action potentials to deliver information; involved in output

Front 5

what part of the neuron is where most signals are generated? where is it located?

Back 5

initial segment; located between cell body and axon.

Front 6

what accounts for the different functions of the various parts of the nerve cell?

Back 6

regional distribution of various membrane-bound channels and pumps

Front 7

describe how myelin sheaths are formed in the CNS and PNS and what is its role.

Back 7

in CNS: myelin-foring cells called oligodendrocytes, each may branch to form myelin on many axons

in PNS: individual cells that form individual myelin sheath at regular intervals called Schwann Cells

the presence of myelin allows nerve impulses to be conducted more rapidly

Front 8

what are nodes of ranvier?

Back 8

regularly spaced gaps in the myelin sheath around an axon or nerve fiber.

Front 9

what part of the neuron, myelinated or unmyelinated is where the action potenial is conduced? why is this so?

Back 9

unmyelinated: nodes of ranvier because contains clusters of Na and K ion channels

Front 10

Describe the anatomy of an afferent neuron and its location within CNS/PNS.

Back 10

contains sensory receptors in PNS; axon and cell body also in PNS

the central process is the only part of afferent neuron in CNS

LACK DENDRITES

Front 11

Describe the anatomy of interneueron and its location with CNS/PNS.

Back 11

it lies entirely within CNS

Front 12

Describe the anatomy of an efferent neuron and its location within CNS/PNS.

Back 12

cell bodys of efferent neurons within CNS

axon/axon terminal with PNS

Front 13

what physical structures constitute the CNS and PNS

Back 13

CNS: brain and spinal cord

PNS: afferent and efferent neurson

Front 14

what is axonal transport? what does it depend on?

Back 14

process involving intracellular filaments by which materials are moved from one end of axon to another

depends on scaffolding of microtubule rails running the length of the axon and specialized types of motor proteins

Front 15

what is anterograde axonal transport and what protein is involved?

Back 15

transport from cell body toward axon terminal;
move nutrients, molecules, enzymes, vesicles with neurotransmitters

kinesin protein

Front 16

what is reterograde transport and what protein is involved?

Back 16

from axon terminal to cell body; carry recycled membrane vesicles and growth factors

involves dynein

Front 17

what are neurotrophic factors?

Back 17

growth factors for neural tissue.

Front 18

what the criteria for axon repair?

Back 18

if axon is outside of CNS and there is no damage to cell body

Front 19

what are glial cells?

Back 19

surround soma, axon, and dendrites of neurons and physically and metabolically support neurons.

Front 20

give examples of glial cells in CNS and function.

Back 20

1. oligodendrocytes: form myelin covering of CNS axons
2. astrocytes: regulated composition of extracellular fluid; stimulate formation of tight jxns to form blood-brain barrier; sustain neurons metabolically
3.microglial: specialized macrophage like cells that perform immune function in CNS
4.ependymal cells: regulated production and flow of cerebrospinal fluid

Front 21

are lipids conductors or insulators? why?

Back 21

insulators:
contain very few qed groups and cannot carry current, therefore regions of high electrical resistance

Front 22

what is the resting membrane potential?

Back 22

voltage difference between inside and outside of cell in absence of excitatory or inhibitory stimulation.

Front 23

what the two factors that influence the magnitude of the resting membrane potential?

Back 23

1. difference in specific ion concentration in intra/extrcellular fluids
2. difference in membrane permeabilites to the different ions.

Front 24

what is the equilibrium potential?

Back 24

the membrane potential at which the concentration gradient force is equal to the voltage gradient. they are equal but opposite. THERE IS NO NET MOVEMENT.

Front 25

when a neuron is at rest, which ion is still more likely to diffue? why?

Back 25

K+ because some of its channels are still open, therefore allowing it to diffuse down the concentration gradient

Front 26

give three examples of graded potential.

Back 26

1.synaptic potential: produced in postsynaptic neuron in response to presynaptic signals; may be inhibitory or excitatory.
2.receptor potential:produced at peripheral endings of afferent neurons in response to stimuli
3.pacemaker potential: spontaneous or rhythmical behaviors such as breathing, heartbeats

Front 27

complete the sentences:
1. graded potentials may be...
2. the size of graded potentials is proportional to ...
3. graded potentials decay as...

Back 27

1. excitatory/inhibitor
2. size of stimulus
3. they move over distance

Front 28

what is summation?

Back 28

addition of depolarization events; a graded potential occurs before previous one has died down

Front 29

what types of channels do graded potentials and action potentials rely on?

Back 29

graded potentials: leaky K+ channels and Na/K pump

axn potential: voltage-gated

Front 30

what type of cells are capable of generating axn potentials and graded potentials?

Back 30

axn: nerve, muslce

graded: all

Front 31

axn potential: step 1
1. describe resting potential
2. how does stimulus initate axn potential?

Back 31

1. close to K eq. potential because there are more open K channels
2. opening of voltage-gated Na channels, which leads to depolarization; ENTRY of Na

Front 32

axn potential: step 2
what period is reached in this step?

Back 32

membrane reaches critical threshold period; depolarization because POSITIVE feedback loop

Front 33

axn potential: step 3
Na ions still entering cell. what is happening? what are the charges inside and outside cell?

Back 33

Na entry causes depolarization which opens more voltage-gated Na channels which causes more depolarization. this process is representated as upstroke of membrane potential and OVERSHOOTS so membrane is positive inside and negative outside.

Front 34

axn potential: step 4
1. what is the peak value of axn potential?
2. what breaks the cycle and is one contributor of repolarization?
3. what also causes repolarization

Back 34

1. Na equilibrium potential
2. inactivation gates of Na channels
3. voltage gated K channels, which are slower to open, finally open, causing K to EXIT, moving membrane potential closer to the negative K equilibrium potential

Front 35

axn potential: step 5
1. the return of membrane to negative potential causes what to happen?
2. what is the cause of hyperpolarization?

Back 35

1. voltage-gated Na channels go from inactivated to closed state and K channels return to closing state.
2. slow closing of K voltage gated channels; K permeability remains above resting levels and the membrane is transiently hyperpolarized toward the K equilibrium potential

Front 36

axn potential: step 6
what happens when voltage-gated K channels finally close?

Back 36

the resting membrane potential is restored.

Front 37

what prevents cellular accumulation of Na and loss of K?

Back 37

continuous axn of Na/K pump

Front 38

how do local anesthetics work?

Back 38

block voltage gated Na channels, therefore channels cannot open and no axn potential is generated.
inhibit Na influx

Front 39

what happens during absolute refractory period? why?

Back 39

nothing... a second stimulus cannot produce another axn potential during this period.

Na channels are either open or inactivated and another axn potential cannot be generated until the Na channels have closed.

Front 40

what happens during relative refractory period? when and why?

Back 40

a second axn potential may be generated ONLY if stimulus is greater than usual.

occurs during period AFTER hyperpolarization.

some but not all Na channels have returned to resting state and some K channels that repolarized membrane are still open

Front 41

what determines the direction of the axn potential propagation?

Back 41

refractory periods because membrane area that just underwent axn potential is in refractory state and therefore axn potential can only proceed in one direction

Front 42

why are axn potentials propagated and not graded potentials?

Back 42

in the axon there are great numbers of voltage gated Na channes therefore small changes in current flow will open many channels and easily reach threshold potential

Front 43

describe factors that determine the velocity of propagation.

Back 43

1.fiber diameter: larger is faster b/c larger fibers offer less resistance and more ions flow
2. myelination: present=faster b/c less leakage and jumping also produces faster progagation

Front 44

what is the phenotype of multiple sclerosis? what effects does this have?

Back 44

loss of myelin slows or block propagation of impulses, which results in poor coordination, lack of sensation, and partial paralysis