chapter 2: transmission

Question 1

polarized

Answer 1

more negative on inside than outside

Question 2

ions

Answer 2

electrically charged molecules

Question 3

anions are ___ charged

Answer 3

negative

Question 4

cations are ___ charged

Answer 4

positive, includes Na and K which are vital for action potential

Question 5

resting potential

Answer 5

non-excited state, balance between the ions inside and outside the cell, -70 millivolts

Question 6

how does the cell maintain a resting state?

Answer 6

properties of the cell membrane & forces of ionic movement

Question 7

ion channels

Answer 7

proteins that span the membrane and allow specific ions to pass through. allow neurons to have selective permeability

Question 8

ion pumps

Answer 8

work alongside ion channels and are much more precise

Question 9

sodium-potassium pumps

Answer 9

pumps three Na ions out for every two K ions pumped in

Question 10

diffusion

Answer 10

ions flow according to a concentration gradient from high to low

Question 11

electrostatic pressure

Answer 11

opposites attract (positively charged ions are attracted to negative spaces and vice versa)

Question 12

equilibrium potential

Answer 12

electrical charge that balances two opposing forces; flow of K outside is balanced by flow of K inside

Question 13

action potential

Answer 13

surge of electricity that causes chemical release; mechanism of communication

Question 14

depolarization

Answer 14

movement towards a positive potential

Question 15

graded potential

Answer 15

small transient voltage charges that build to cause action potential

Question 16

what is the threshold needed for an action potential to occur

Answer 16

-55 mv

Question 17

step 1. resting state

Answer 17

K+ movement in and out of cell, NA+ is non-permeable

Question 18

step 2. depolarization

Answer 18

all Na+ voltage-gated channels open, and Na+ rushes in. K+ channels close

Question 19

step 3. absolute refractory

Answer 19

no action potential can be produced; charge is above 0

Question 20

step 4. repolarization

Answer 20

the cell becomes polarized again

Question 21

step 5. relative refractory

Answer 21

only very strong stimulation can produce an action potential

Question 22

step 6. hyperpolarization

Answer 22

increase in membrane potential where it becomes more negative

Question 23

propagation

Answer 23

creates many more action potentials down the axon

Question 24

why do action potentials only go one direction?

Answer 24

because of the refractory state of the membrane after a depolarization

Question 25

2 types of conduction

Answer 25

continuous and saltatory

Question 26

continuous

Answer 26

unmyelinated & slower

Question 27

saltatory

Answer 27

myelinated & faster

Question 28

advantages of saltatory

Answer 28

less energy required to maintain ionic balance insulation increases conduction velocity no extracellular fluid between myelin sheath and axon myelin provides buffer from negative ions

Question 29

what two factors affect speed of propagation

Answer 29

myelin & size of axon (larger diameter = faster AP)

Question 30

signal propagation

Answer 30

AP depolarized adjacent regions in axon

Question 31

what are the two types of signal conduction

Answer 31

continuous & myelinated

Question 32

what happens when action potential reaches the end of an axon?

Answer 32

a neurotransmitter is released into the synapse

Question 33

how do neurotransmitters move

Answer 33

from the axon on the presynaptic cell towards the target neuron, the postsynaptic cell

Question 34

receptors

Answer 34

proteins present on the cell membrane; presynaptic neurotransmitters bind to post synaptic receptors

Question 35

ligands

Answer 35

molecules that fit into receptors and activate/block them; usually neurotransmitters but can be drugs

Question 36

postsynaptic potentials

Answer 36

brief changes in membrane potential of the postsynaptic cell in response to a neurotransmitter; causes excitation or inhibition

Question 37

2 types of postsynaptic potentials

Answer 37

EPSP and IPSP

Question 38

EPSP

Answer 38

brief depolarization of a neuron membrane in response to stimulation; Na

Question 39

IPSP

Answer 39

brief hyperpolarization of a neuron membrane in response to stimultion; Cl

Question 40

does a single EPSP or IPSP cause an action potential in the postsynaptic cell?

Answer 40

no; it causes graded potential

Question 41

spatial summation

Answer 41

integration of events happening at different places on the axon hillock; location matters

Question 42

temporal summation

Answer 42

integration of events happening in quick succession; timing matters

Question 43

what determines an IPSP or EPSP?

Answer 43

neurotransmitter and receptor

Question 44

degradation

Answer 44

rapid breakdown and inactivation of transmitter by an enzyme

Question 45

acetylcholinesterase (AChE)

Answer 45

breaks down ACh and recycles

Question 46

reuptake

Answer 46

transmitter is cleared from the synapse by being absorbed into presynaptic axon terminal

Question 47

transporters

Answer 47

special receptors that bring the transmitter back inside

Question 48

autoreceptors

Answer 48

presynaptic receptors that decrease neurotransmission release; "kill switch"

Question 49

steps of synaptic transmission

Answer 49

1. action potential arrives at presynaptic axon terminal 2. voltage-gated calcium channels in the terminal membrane open, allowing calcium ions to enter. 3. Ca ions cause synaptic vesicles filled with neurotransmitter to fuse with the presynaptic membrane and rupture, releasing transmitter into synaptic cleft 4. transmitters bind to postsynaptic receptor molecules, opening ion channels and leading to EPSP or IPSP 5. EPSPs or IPSPs spread toward the postsynaptic axon hillock; if the threshold is reached, AP occurs 6. synaptic transmission is rapidly stopped 7. transmitter may activate presynaptic receptors that decrease transmitter release