Chapter 3

Question 1

Foot+Tack response pathway

Answer 1

pinch skin-sensory neuron (into dorsal root)-spinal cord (CNS)-brain-spinal cord (out of ventral root)-motor neuron-mechanical/motor response

Question 2

Cytosol and Extracellular fluid

Answer 2

key ingredient (polar water molecule is solvent)

Question 3

Ions

Answer 3

contain spheres of hydration when ionized

Question 4

lipids

Answer 4

hydrophobic and contribute or resting and action potentials (dont dissolve in water due to even electrical charge)

Question 5

proteins/structure

Answer 5

enzymes, cytoskeletal elements, receptors, special transmembrane proteins (that control resting and action potentials)

R-group+alpha carbon+amino acid tails (peptide bonds form polypeptides)

Question 6

four levels of protein structures

Answer 6

primary
secondary
tertiary
quaternary

Question 7

Channel Proteins

Answer 7

contain polar R groups and nonpolar R groups across phospholipid bilayer (subunits make the whole); purpose is ion selectivity and gating

Question 8

Ion pumps

Answer 8

formed by membrane spanning proteins, ATP using, neuronal signaling

Question 9

Diffusion

Answer 9

Ionic flow down concentration gradient; channels permeable to specific ions, concentration gradient is across the membrane

Question 10

electrical conductance (g)

Answer 10

g=1/R

Question 11

Resistance (R)

Answer 11

R=1/g

Question 12

Electrical current flow across a membrane

Answer 12

Ohm’s law: Current=(conductance)(potential)

I=gV

Question 13

resting potential

Answer 13

Inside (-ve)vs relative outside (+ve); -65mV

Question 14

Equilibrium potential (Eion)

Answer 14

equilibrium reached when K+ channels inserted into the phospholipid bilayer; electrical potential difference that exactly balances ionic concentration gradient

Question 15

Equilibrium potentials (4 important notes)

Answer 15

1. Large changes in Vmemb=miniscule changes in ionic concentrations
2. Net difference in electrical change inside and outside of membrane surface
3. Rate of movement of ions across membrane is proportional to Vmemb-Eion
4. if Concentration difference is known: equilibrium potential can be calculated

Question 16

nernst equation

Answer 16

used to calculate the exact value of equilibrium potential for EACH ION separately in mV: Considers: 1.charge of ion 2. Temperature 3. Ratio of the external and internal ion concentrations

Question 17

K+ (ratio of out:in/Eion)

Answer 17

1:20/-80mV

Question 18

Na+(ratio of out:in/Eion)

Answer 18

10:1/62mV

Question 19

Ca2+(ratio of out:in/Eion)

Answer 19

10 000:1/123mV

Question 20

Cl-(ratio of out:in/Eion)

Answer 20

11.5:1/-65mV

Question 21

At rest, which ions are more concentrated outside, which ions are more concentrated inside?

Answer 21

outside: sodium, calcium, chloride
inside: potassium

Question 22

Sodium potassium pump

Answer 22

enzyme breaks down ATP when Na+ is present

Question 23

Calcium pump

Answer 23

actively transports Ca2+ out of cytosol

Question 24

Goldman equation

Answer 24

takes into account permeability of membrane to different ions

Question 25

determinant of membrane potential

Answer 25

membrane permeability determines membrane potential (since neurons are permeable to more than one type of ion)

Question 26

Key determinant in resting membrane potential

Answer 26

Potassium channels

Question 27

potassium channels(Lily and Yuh Nung Jan)

Answer 27

Shaker potassium channel

Question 28

Mackinnon (2003 nobel prize)

Answer 28

neurological disorders due to mutations of specific potassium channels are inherited

Question 29

How many subunits in potassium channels?

Answer 29

4

Question 30

channel selectivity in potassium channels

Answer 30

K+ ions

Question 31

Why is Resting membrane potential close to Ek

Answer 31

Because it is mostly permeable to K+, membrane potential is sensitive to extracellular K+

Question 32

What happens when an increase of extracellular K+ ions/what regulates external potassium concentration?

Answer 32

depolarizes membrane potential/blood brain barrier and potassium spatial buffering (astrocyte)

Question 33

Sodium potassium pump

Answer 33

works against the concentration gradient: 3 potassium back in for 2 sodium back out to restore the large K+ concentration gradient