Chapter 12 Neural Tissue

Question 1

3 Requirements for Transmembrane Potential

Answer 1

Concentration gradient of ions (Na, K)
Selectively permeable through channels
Maintains charge difference across membrane

Question 2

Transmembrane Potential

Answer 2

Cytosol - higher K, lower Na
Extracellular fluid (ECF) higher Na, lower K

Question 3

Passive Forces Acting Across the Membrane

Answer 3

Chemical gradients

Electrical gradients

Question 4

Chemical gradients

Answer 4

Concentration gradients of ions (Na, K)

K diffuses out of cell, Na diffuses into cell

Question 5

Electrical Gradients

Answer 5

Separate charges of positive and negative ions
Membrane is more permeable to K than Na
Result in potential difference

Question 6

Sodium-potassium pump

Answer 6

3 Na out, 2 K in, leaving charge -1 inside cell

Question 7

Channels

Answer 7

ions can leak in or out

Question 8

Electrical Current

Answer 8

movement of charges to eliminate potential difference (cations and anions will move together- attraction)

Question 9

Resistance

Answer 9

amount of current a membrane restricts (how easy ions cross the membrane)
High resistance - low current

Question 10

Equilibrium Potential

Answer 10

transmembrane potential at which there is no net movement of a particular ion across the cell membrane

Question 11

Transmembrane Potential

Answer 11

charge difference across a cellular membrane

Question 12

Membrane permeability to Na and K determines transmembrane potential

Answer 12

Passive channels (leak channels)
always open, permeability changes with conditions
Active channels (gated channels)
open and close in response to stimuli
THESE ARE NOT PUMPS!

Question 13

Conditions of active channels

Answer 13

closed (capable of opening)
open (activated)
inactivated (incapable of opening)

Question 14

3 classes of gate channels in active channels

Answer 14

chemical, voltage, mechanical

Question 15

Chemically gated channels

Answer 15

open in presence of specific chemical binding site

Example: receptors bind acetylcholine at neuromuscular junction

Question 16

Voltage gated channels

Answer 16

characteristic of excitable membrane, found in neural axons, skeletal muscle sarcolemma, cardiac muscle