lecture 6

Question 1

ions

Answer 1

ions- electrically charged particles
anions- negatively charged ex. Cl
cations- positively charged ex. Na, K

Question 2

concentration gradient

Answer 2

differences in concentration of a substrate b/w 2 regions

- substances diffuse from high to low

Question 3

voltage gradient

Answer 3

difference in charge b/w 2 regions

- ions move from high charge to low charge

Question 4

resting potential

Answer 4

stored energy in electrical charge across membrane in absence of stimulation
cells have negative intra and positive extra
around -70 mV

Question 5

which 4 ions produce resting potential (3 main)

Answer 5

Na, K, large anions and some Cl

Question 6

how is the resting potential maintained

Answer 6

through an active process of gates, channels and pumps

Question 7

large protein anions

Answer 7

made inside the cell, cannot leave

• negative charge isnt large enough to produce resting potential
• cells need to balance negative charge

Question 8

potassium

Answer 8

balance large anions

- high concentration inside cell, K is drawn outwards

Question 9

Na

Answer 9

high concentration outside
gate is mostly closed so no entry of Na allowed
- blocked by voltage gated channels

Question 10

resting potential summary

Answer 10

large anions cannot leave, make inside -
concentration gradient pushes K out through channels
gated channels prevent Na from entering
Na/K pumps eject Na and inject K

Question 11

graded potentials

Answer 11

small voltage fluctuations across the cell membrane

- happen if concentration of any ions changes

Question 12

2 types of graded potentials

Answer 12

1. hyperpolarization- increase in electrical charge
   becomes more negative due to inward flow of Cl or outward flow of K
2. depolarization- decrease in electrical charge
   becomes more positive due to inward flow of Na

Question 13

action potential

Answer 13

large brief reversal in polarity of axon for approx 1ms

- reverses to become positive then returns to negative

Question 14

basic mechanism for action potential

Answer 14

voltage sensitive ion channels open or close at specific membrane voltages
- Na channels open quick and close quick
k channels open after and close slowly

Question 15

refractory periods

Answer 15

absolute- tip of AP, can be no AP generated

relative- during hyperpolarization, requires a strong depolarizaiton to initiate another AP

Question 16

nerve impulse

Answer 16

propagation of AP on the membrane of an axon

- how neurons signal

Question 17

why dont impulses travel backwards

Answer 17

refractory periods

Question 18

all or none law

Answer 18

size and shape of AP remains constant along the axon

Question 19

myelin

Answer 19

produced by oligodendroglia in CNS and schwann cells in PNS

• wrap around to produce insulating sheath
• AP cannot occur under sheath

Question 20

node of ranvier

Answer 20

gaps in sheath rich in ion channels

Question 21

saltatory conduction

Answer 21

propagation of AP at successive nodes of ranvier

- makes nerve impulses metabolically cheaper and much faster