Lesson 13

Question 1

electrical potential

Answer 1

difference in concentration of charged particles between two points

Question 2

current

Answer 2

flow of charged particles from one point to another

Question 3

resting membrane potential (RMP)

Answer 3

charge difference across plasma membrane

Question 4

leak channels

Answer 4

membrane channels that are always open; are specific for one ion

Question 5

gated channels

Answer 5

channels that are normally closed, but can be stimulated to open; specific to its ion

Question 6

chemically-gated channel

Answer 6

binding of a chemical (hormone, neurotransmitter) causes the channel to open
- found on neuron cell body, dendrites

Question 7

voltage-gated channel

Answer 7

channel opens due to a change in the membrane potential
- found on neuronal axon, skeletal/cardiac muscle

Question 8

mechanically-gated channel

Answer 8

channel opens due to physical stress/deformation on the cells plasma membrane
- found on sensory receptors (touch)

Question 9

three states of a gated channel

Answer 9

1. closed - but capable of opening
2. open - aka activated
3. inactivated - ions cannot pass through, channel is not closed but ‘gated off’ by an inactivation gate

Question 10

resting membrane potential results from these three things

Answer 10

1. diffusion of ions down their concentration gradients through the membrane
2. selective permeability of the membrane, allowing some inos to pass more easily than others
3. electrical attraction of cations and anion to each other

Question 11

what ion has the greatest influence on resting membrane potential?

Answer 11

potassium K+

Question 12

Is sodium or potassium more abundant in the ECF?

Answer 12

sodium

Question 13

What can sensory neurons be triggered by? (4)

Answer 13

chemicals, light, heat, or mechanical forces

Question 14

characteristics of local potentials: graded

Answer 14

vary in magnitude with stimulus strength
- stronger stimuli will cause gated channels to remain open longer

Question 15

characteristics of local potentials: decremental

Answer 15

get weaker the farther they spread from the point of stimulation

Question 16

characteristics of local potentials: reversible

Answer 16

if stimulation ceases, membrane voltage quickly returns to normal resting potential

Question 17

depolarization

Answer 17

is excitatory, makes a neuron more likely to fire an action potential

Question 18

hyperpolarization

Answer 18

is inhibitory, makes a neuron less likely to produce an action potential

Question 19

action potential

Answer 19

rapid up-and-down change in voltage produce by the coordinated opening and closing of voltage-gated ion channels

Question 20

seven steps of an action potential

Answer 20

1. local potential spreads to the axon hillock (must reach threshold potential)
2. voltage-gated Na+ channels open quickly; depolarizing the cell
3. when voltage reaches +35 mV, Na+ channels inactivate
4. the voltage gated K+ channels are fully open, and K+ flows out of the cell membrane repolarizing it
5. K+ continues to exit and produces a negative overshoot, aka hyperpolarization
6. membrane potential returns back to normal as Na+ leaks into the cell
7. cell is at resting potential

Question 21

all-or-none law

Answer 21

if threshold is reached (-55mV), a neuron fires to maximum voltage; if threshold is not reached, it does not fire

Question 22

characteristics of local potentials: nondecremental

Answer 22

does not get weaker with distance, the action potential is ‘regenerated’ as it travels along the axon

Question 23

characteristics of local potentials: irreversible

Answer 23

once starts, an action potential travels all the way down the axon and cannot be stopped

Question 24

refractory period

Answer 24

period of resistance to stimulation; has two phases

Question 25

absolute refractory period

Answer 25

no stimulus of any strength will trigger another action potential

Question 26

relative refractory period

Answer 26

an unusually strong stimulus is needed to trigger a new action potential

Question 27

unmyelinated axons have ______ along their entire length

Answer 27

voltage-gated channels

Question 28

continuous conduction

Answer 28

chain-reaction continuing down an axon

Question 29

why can action potentials only be generated at the nodes of axons?

Answer 29

the voltage-gated ion channels are concentrated here

Question 30

the speed at which a nerve signal travels down an axon depends on two factors…

Answer 30

1. diameter of the neuron
2. presence or absence of myelin

Question 31

type A neuronal fibers

Answer 31

• myelinated, large diameter axons
• fast, carries info quickly
• high speed (120m/sec)

Question 32

type B neuronal fibers

Answer 32

• myelinated, medium diameter axons
• carries intermediate info
• medium speed (18m/sec)

Question 33

type C neuronal fibers

Answer 33

• unmyelinated, small diameter axons
• carries flow info
• slow speed (1m/s)