L6 Graded Potentials

Question 1

Which cells are excitable?

Answer 1

Nerves and muscles

Can undergo rapid changes in their membrane

Can change their resting potentials into electrical signals

Question 2

Resting Vm

Answer 2

Voltage across plasma membrane in a cell with no changes in membrane permeability

Question 3

Neural communication is based on

Answer 3

Rapid change in membrane permeability to ions

Question 4

Direction of synapse

Answer 4

Unidirectional

Dendrites to cell body down axon to dendrites of other neuron

Question 5

Graded potential is

Answer 5

Change in potential when a neuron releases neurotransmitter onto the dendrites/cell body of another neuron

Question 6

Signal that travels down axon is known as

Answer 6

The action potential

Question 7

Vm at rest is

Answer 7

Negative =polarized

Question 8

If Vm becomes less negative

Answer 8

More positive

Less polarized/depolarized

Question 9

If depolarized plasma membrane returns to negative Vm is

Answer 9

Repolarized (more negative)

Question 10

If plasma membrane becomes more negative the Vm rest

Answer 10

Hyperpolarized

Question 11

Step 1 of graded potentials

3

Answer 11

Resting membrane exposed to chemical stimulus (signal comes in from presynaptic to postsynaptic neuron)

Chemically gated channels open

Membrane potential changes

Question 12

A graded potential that depolarizes the membrane potential makes the neuron

Answer 12

More pos

More likely to fire

Question 13

A graded potential that hyperpolarizes the membrane potential makes the neuron

Answer 13

More neg

Less likely to signal

Question 14

Graded potential step 2

Answer 14

Movement of ions through channel produces local current

Depolarizes or hyperpolarizes nearby regions of cell membrane

Change in potential is proportional to stimulus
Farther away from source=less graded potentials

Question 15

Summarize graded potential

3

Answer 15

Vary with size of stimulus

Decays with distance

May be depolarizing or hyperpolarizing

Question 16

Graded potentials depend on what and what are the two kinds?

Answer 16

Permeability changes induced by neurotransmitter of postsynaptic neuron

Excitatory postsynaptic potential- EPSP
Inhibitory postsynaptic potential- IPSP

Question 17

EPSP causes what

Answer 17

Depolarization

More likely to fire

Na+ or Ca2+

Question 18

IPSP causes what

Answer 18

Hyperpolarization

Less likely to fire

Cl- or K+

Question 19

Summation of postsynaptic potentials

Answer 19

One neuron may receive input from 1000s of other neurons simultaneously

Whether it fires depends on whether net input is excitatory or inhibitory

Question 20

For a neuron to fire it has to reach what voltage?

Answer 20

-50mV

Roughly +15mV change (-70 to -55)

Question 21

Typically EPSP has a voltage of

Answer 21

0.5mV (lasts 20msec)

Question 22

A typical neuron would need how many EPSPs to reach threshold?

Answer 22

30

Question 23

Temporal summation

Answer 23

Single synapses receives many EPSPs in short period of time

1 neuron firing many times rapidly

Question 24

Spatial summation

Answer 24

Single synapse receives many EPSPs from many presynaptic cells

Question 25

Magnitude of graded postsynaptic potential (GPSP) depends on

Answer 25

Sum of activity in all presynaptic inputs

Only if EPSP is reinforced by other supporting signals through summation will info be passed on

Question 26

Interaction of EPSPs and IPSPs allows

Answer 26

A fine degree of discrimination and control in determining what info will be passed on