lecture 4 & 5

Question 1

graded potentials

Answer 1

variable strength and used for short-distance communication

Question 2

action potentials

Answer 2

very brief, large depolarizations. Rapid signaling over long distances

Question 3

depolarization

Answer 3

the membrane potential becomes less negative

Question 4

overshoot

Answer 4

peak of the action potential where the membrane potential is above 0 and the inside of the cell is more positive than the outside

Question 5

repolarization

Answer 5

the membrane potential returns toward the resting membrane potential following either depolarization or hyperpolarization

Question 6

hyperpolarization

Answer 6

becomes more negative than the resting membrane potential. Prevents a neuron receiving another stimulus at this time

Question 7

importance of membrane potential changes

Answer 7

this is the way body uses for communication. Such as action potentials in neurons and muscles

Question 8

reason why graded potentials lose strength as they move out of the cell?

Answer 8

• current leak: open leak channels in the soma the release positive ions decreasing the strength of depolarization
• cytoplasmic resistance: the cytoplasm provides resistance to the flow of electricity

Question 9

depolarization

Answer 9

• Na+ channels open, moves into the cell, membrane potential becomes more positive

Question 10

hyperpolarization

Answer 10

-stimulus opens K+ or Cl- channels, K+ moves out of the cell, cell becomes more negative
-can prevent an action potential because drops below membrane potential thus impossible to get to threshold potential

Question 11

in graded potentional, the magnitude of the of the voltage change is…

Answer 11

proportional to the strength of the stimulus

Question 12

Types of graded potentials: Receptor potentials

Answer 12

• occur in specialized sensory receptor cells
• result from transduction process (conversion of an energy stimulus into an electrical potential)
• due to the opening either mechanical or ligand gated channels

Question 13

Types of graded potentials: Post synaptic potentials

Answer 13

• occur in neurons
• depolarizing potentials are called EPSP and hyperpolarizing potentials are called IPSP

Question 14

excitatory postsynaptic potentials (EPSP)

Answer 14

• increase likelihood of postsynaptic action potential occuring
• opens mixed cation channels (K+ and Na+). results in depolarization

Question 15

inhibitory postsynaptic potentials (IPSP)

Answer 15

• decrease the likelihood of a post synaptic potential from ocurring
• opens K+ or Cl- channels causing hyperpolarization

Question 16

Types of graded potentials: endplate potentials (EPP)

Answer 16

• occur is skeletal muscle cells
• similar to ESPS

Question 17

action potentials

Answer 17

• large depolarization: travel from a neuron’s trigger zone to the end of its axon
• constant amplitude
• do not decrease in strength with distance
• all or none
• caused by voltage gated channels and

Question 18

the total number of neurotransmitters released at the axon terminal

Answer 18

directly related to the total number of action potentials

Question 19

voltage clamp technique

Answer 19

• Hodgkin and Huxley used this technique with ion substitution in giant squid axons

Question 20

potassium leak channel and sodium potassium leak channel maintain

Answer 20

resting membrane potential

Question 21

the voltage gated sodium channels and the voltage gated potassium channels are involved in

Answer 21

progression of an action potential along the membrane

Question 22

voltage gated Na+ channels

Answer 22

• activation gate opens rapidly
• the inactivation gate is slower to close

Question 23

voltage gated K+ channels

Answer 23

• diversity of channels
• slow to open and close
• channels open and close upon changes in the transmembrane potential
• important for repolarization and hyperpolarization
• don’t have inactivation gate

Question 24

Positive feedback loop

Answer 24

• Na+ entry
• loop stops when the Na+ channel inactivation gate closes

Question 25

negative feedback loop

Answer 25

- depolarization of membrane due to Na+ influx - K+ voltage gated channels open - repolarization of membrane potential

Question 26

local current flow for propogation of action potentials

Answer 26

- short distance - unmyelinated

Question 27

saltatory conduction

Answer 27

- myelinated - the nodes of ranvier have voltage gated Na+ channels - action potential in one node depolarizes and travels to the next

Question 28

the net result of saltatory conduction

Answer 28

-faster conduction -energy efficient

Question 29

larger neurons conduct

Answer 29

action potentials faster

Question 30

multiple slerosis

Answer 30

- demyelinating disease - optic nerve affected - creates leak channels between the nodes for saltatory conduction

Question 31

Guillain-Barrer syndrome (PNS)

Answer 31

- auto immunue, triggered by infection, creates antibody against its myelin - demyelinating disease - creates leak channels between the nodes for saltatory conduction

Question 32

absolute refractory period (ARP)

Answer 32

- Na+ channels are inactivated thus another stimulus will not lead to a second action potential

Question 33

relative refractory period (RRP)

Answer 33

a stronger than normal stimulus is needed to elicit an action potential

Question 34

the refractory period prevents

Answer 34

backward conduction