neural conduction (1.5)

Question 1

membrane potential

Answer 1

the difference in the electrical potential (charge) between the inside and outside of the cell

Question 2

neuron resting membrane potential

Answer 2

-70 mV (polarized)

Question 3

salty banana

Answer 3

sodium outside of neuron, potassium on inside

Question 4

factors contributing to even distribution of ions (2)

Answer 4

random motion: particles move down their concentration gradient
electrostatic pressure: like charges repel and opposites attract; K+ held inside by negative membrane potential, while Na+ channels are closed

Question 5

concentration gradient

Answer 5

move from areas of high concentration to areas of low concentration

Question 6

equilibrium potential

Answer 6

the membrane potential at which there is no net flow of an ion (concentration and electrical gradients are equal and opposite)

Question 7

factors contributing to uneven distribution of ions (2)

Answer 7

selective membrane permeability: only allows certain ions in (like one-away traffic)
sodium-potassium lumps: take sodium from inside the cell and expels them; goes against concentration gradient

Question 8

net equilibrium potential of K, Na, and Cl

Answer 8

K: -100 mV (bistable channels —> free will)
Na: +40 mV (goes out, not in —> sodium-potassium pumps)
Cl: -70 mV (no chloride channels though)

Question 9

dominant ion

Answer 9

potassium (K)

Question 10

depolarizations vs hyperpolarizations

Answer 10

depolarizations: EPSPs (excitatory postsynaptic potentials) that make the membrane potential more negative (2 mV high); increase likelihood that neuron will fire
hyperpolarizations: IPSPs (inhibitory postsynaptic potentials) that make the membrane potential more negative (2 mV down); decrease the likelihood that neuron will fire

Question 11

postsynaptic potentials are graded, rapid, and decremental

Answer 11

graded: amplitude proportional to intensity of stimulus
rapid: instantaneous like a new tube of toothpaste
decremental: get smaller as they travel towards the soma (leaky)

Question 12

threshold of activation/excitation

Answer 12

about -60 mV; must be reached near axon hillock (between cell body and axon); when hit, the cell fires an action potential

Question 13

spatial vs temporal summation

Answer 13

spatial summation: integration of events happening at different places (more common)
temporal summation: integration of events happening at different times

Question 14

action potential

Answer 14

a short-lasting event in which the membrane potential of a cell rapidly rises and falls (not graded)

Question 15

all-or-none

Answer 15

APs occur to their full extent or not at all (sodium tries to bring electric potential up, potassium tries to bring it down)

Question 16

refractory period (definition, absolute, relative)

Answer 16

refractory period: time during which the cell resists generating new APs
absolute: 1 ms; impossible to initiate an AP because voltage-gated Na+ channels are closed
relative: 2-4 ms: AP is possible for a stronger than normal stimulus (voltage-gated K+ channels still opened)

Question 17

how the conduction of APs differ from that of PSPs (3)

Answer 17

not graded: all-or-none
slow: channels open and close (keep duration and speed separate)
nondecremental: always the same size

Question 18

orthodromic vs antidromic conduction

Answer 18

orthodromic conduction: in the natural direction (cell body to terminal buttons)
antidromic conduction: towards the cell body (travels along the axon)

Question 19

nodes of Ranvier and saltatory conduction

Answer 19

nodes of Ranvier: the gaps between the adjacent myelin segments (AP conducted passively)
saltatory conduction: in myelinated axons; APs “hop” from one node of Ranvier to the next (myelination increases speed)