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1

what is a neuron

-specialized animal cell that purpose is to send, receive, and conduct signals

2

Name another cell type in the nervous system?

glial cells : provide structural support and electrical insulation neurons

3

define membrane potential

-the electrical charge difference across a cell membrane
-store up source of electrical energy

4

resting membrane potential

-when a neuron is not being excited or inhibited

-approximately -70mV
-inside more negatively charged than the outside

5

what maintains the resting membrane potential

-70 mV

6

voltage-gated channels

-an ion channel that opens or closes according to the value of the membrane potential (changes in nearby transmembrane voltage)

7

ligand-gated channels

-an ion channel that opens or closes in response to the binding of a specific chemical (Neurotransmitter) or physical stimuli

8

non-gated ion channels

-unregulated ion channels that are always open

-always allow the associated ion to pass through

9

describe the differential ion concentrations in the neuron at rest....is the membrane potential positive or negative at rest

-more negative at rest
-Na+ outside
-K+ inside
-more Cl- outside

10

describe the driving forces (electrical and chemical) on Na+ and K+ rest (i.e. how would the ions move if a channel opened)

-Na+= chemical and electrical forces IN

-K+= chemical OUT; electrical IN

11

purpose of Na+ K+ pump

-helps maintain differential concentrations of Na+ and K+ ions

-balances the ions by pumping Na+ out and K+ in

12

depolarization

-making a membrane potential less negative

-Na+

13

hyperpolarization

-making a membrane potential more negative

-closer to the firing threshold.

-K+

14

what happens during an action potential (STEPS)

1. membrane is at rest
2. depolarizing stimulus make the inside less negative and more likely to fire
3. depolarization causes Na+ to rush IN making the cell more positive
4. K+ channels open, K+ rushes OUT
5. Na+ inside causes sodium influx causing Na+ channels to close (no more Na+ enters cell)
6. inside more positive so K+ channels open and cause outflow of K+
7. outflow of K+ causes the membrane to return to rest
8. Na+ K+ pump resets and re-establishes resting membrane potential: K+ channels close, Na+ channels reset, extra K+ outside diffuses away

15

all-or-none law

-an action potential either occurs or does not occur

-once triggered, it travels without getting smaller to the end

16

how is the threshold of excitation of an action potential reached

-with enough excitatory postsynaptic potentials (EPSPs)

-if enough Na+ ions have entered the cell with the neurotransmitter binding then they add up until it reaches a threshold causing an axon Potential to be generated at the axon hillock

17

how can action potentials represent continuous information when action potentials fire in an all-or-none fashion

-variation of firing when on or off

18

absolute refractory period

-time when impossible to initiate another action potential
-Na+ channels are inactivated

-impossible to fire another action potential, because ions are in the wrong place

19

relative refractory period

-time when it takes a stronger stimulus to initiate an action potential
-during overshoot hyperpolarization
-harder to fire AP, takes more stimulation

20

absolute and refractory period similarities

-prevent the backwards movement of APs and limit the range of firing

-keeps it moving in one direction
-from the axon hillock, to the axon terminals

21

why does an action potential tend to move in one direction in the neuron

refractory period : keeps it moving in one direction

22

how does myelin affect the conduction of action potentials

-allows AP to happen only at the Nodes of Ranvier

-causes information to travel faster

23

define saltatory conduction

-conduction of action potentials by myelinated axons

-action potential appears to jump from one node of Ranvier to the next
-faster conduction

24

synaptic transmission

the process by which presynaptic neuron communicates with the postsynaptic neuron

-the sending of neurotransmitter between neurons to keep the message going

25

2 types of synaptic transmission

-chemical synapse: slower, but signal strength maintained

-electrical synapse/gap junctions: faster, but signal can degrade

26

what are dendritic spines, and what is their purpose

-"tree" branches off the soma
-RECEIVE INFORMATION from the terminal buttons of other neurons

27

describe the process of chemical synaptic transmission *

-AP reaches the terminal, causes Ca2+ channels to open
-Ca2+ flows into cell
-fusion pore widens and Ca2+ causes vesicles to bind with cell membrane (Ca2+ ions attach to the receptors of the vesicles of the neurotransmitter)

-release of neurotransmitter by exocytosis into the synaptic cleft

-transmitter binds with receptor and neurotransmitter to leave terminal button into the synaptic cleft

28

ionotropic receptor *

-contains a binding site for a neurotransmitter and is also an ion channel that opens when a molecule of thee neurotransmitter attaches to the bonding site

29

metabotropic receptor *

-contains a binding site for a neurotransmitter; activates an enzyme that begins a series of events that opens an ion channel elsewhere

30

EPSP *

-DEPOLARIZATION, EXCITATORY

-often result from Na+ or Ca2+ going into the cell