Lecture 3

Question 1

sensory stimulus

Answer 1

activation of cutaneous mechanoreceptors by skin deformation

Question 2

neural code

Answer 2

action potential, post-synaptic potential

Question 3

interpretation/action

Answer 3

flexor withdrawal reflec

Question 4

extracellular and cytosolic fluid

Answer 4

-neurons are in an extracellular milieu that is water-based
-ions: atoms or molecules with a net electrical charge

Question 5

the concentration gradient is the product of:

Answer 5

1. the imermeability of the plasma membrane to the movement of ions
2. the presence of proteins that maintain actively the gradient of concentration
3. the presence of proteins that allow ions to passively cross the membrane (into or out of the cell)

Question 6

ion channels

Answer 6

control of resting and action potentials

Question 7

receptors-channels

Answer 7

neurotransmitters and post-synaptic potentials

Question 8

metabotropic receptors

Answer 8

neurotransmitters and neuromodulators

Question 9

ion pumps

Answer 9

-producers of electrochemical gradients
-formed by transmembrane proteins
-catalyze ATP for energy (active transport)
-push ions against the concentration gradient (from more diluted to concentrated)
-produces the ion concentration gradients (neuronal signaling)

Question 10

proteins-channels

Answer 10

-voltage dependent
-polar R groups
-non polar R groups
-transmembrane domains
-ion selectivity
-mechanism of activation (gating)

Question 11

Na/K ATPase ion exchange pump

Answer 11

-catalyze ATP into ADP
-drives 3 Na+ out, brings 2 K+ in
-forms a concentration gradient of more Na outside and more K inside

Question 12

K+ equilibrium potential

Answer 12

-80mV

Question 13

Na+ equilibrium potential

Answer 13

62mV

Question 14

Ca2+ equilibrium potential

Answer 14

123mV

Question 15

Cl- equilibrium potential

Answer 15

-65mV

Question 16

diffusion

Answer 16

-dissolved ions redistribute in a homogenous manner
-ions diffuse along their concentration gradient when the channels are permeables to ions and there is a concentration gradient across the membrane

Question 17

electrical potential (V)

Answer 17

-pressure exerted on ions
-influences the movement of ions

Question 18

electric current (I)

Answer 18

movement of ions according to Ohm’s law:
V=R x I or I=V x G

Question 19

electric conductance (G)

Answer 19

= ease by which I can flow through

Question 20

resistance (R)

Answer 20

capacity to block I
R=1/G

Question 21

equilibrium potential

Answer 21

-each ion has a potential at which the net ionic flow is 0
-I.e. membrane potential at which the movement of the inside (i) to the outside (o) is the same as in the other direction
-difference in electrical potential that counters the diffusive force due to the concentration gradient

Question 22

is the membrane potential determined solely by the concentrations of K+?

Answer 22

No

Question 23

structure of K+ channels

Answer 23

-4 transmembrane subunits
-hairpin pore endows selectivity and permeability to K+ ions
-mutations of K+ channels (hereditary neurological disorders –> epilepsy)