U5 Lecture 36

Question 1

what are the steps of propagation of the action potential

Answer 1

1. entry of Na+ produces a local current

2. entry of Na+ in the new region of membrane produces a local current that spreads to adjacent areas

Question 2

what does the ‘local current’ do after produced by entrance of Na+

Answer 2

it spreads laterally to depolarize adjacent areas of membrane

Question 3

what happens if the adjacent membrane area is depolarized to threshold

Answer 3

it starts a new cycle of action potentials in this new region of membrane

Question 4

what happens if the new adjacent membrane is depolarized to threshold

Answer 4

it starts a new cycle of action potentials in this new new region of membrane

Question 5

what are the two factors of velocity of propagation

Answer 5

1. size (diameter of axon)

2. myelination

Question 6

size:____ is faster

Answer 6

bigger

Question 7

what happens to resistance to current flow in axoplasm as diameter increases

Answer 7

it decreases

Question 8

what is myelination

Answer 8

certain glial cells (oligodendrocytes and schwann cells form insulating layer (‘sheath’) around axons

Question 9

what are the steps in saltatory conduction

Answer 9

1. Na channels at node open
2. electronic conduction
3. channels at next node open
4. electronic conduction
5. next node begins to activate

Question 10

what is demyelination

Answer 10

disruption of myelin sheath

Question 11

what are examples of demyelination in the CNS and PNS

Answer 11

central-multiple sclerosis

peripheral- guillan barre

Question 12

what happens in the absence of myelin insulation

Answer 12

electrotonic conduction fails to reach and depolarize next node- action potential fails

Question 13

how is an electrical signal transmitted from one excitable cell to another

Answer 13

synaptic transmission

Question 14

what is synaptic transmission

Answer 14

same general events that occur during neuromuscular transmission

Question 15

post synaptic electrical events (graded potentials) are…

Answer 15

1. depolarizing

or 2. hyperpolarizing

Question 16

what does depolarizing mean

Answer 16

( if Na+ enters)

excitatory post synaptic potential EPSP

Question 17

what does hyperpolarizing mean

Answer 17

(if K+ leaves, or Cl-enters)

-inhibitory post-synaptic potential IPSP

Question 18

what is spatial summation

Answer 18

signals from many pre synaptic neurons that add up at the trigger zone

Question 19

what is temporal summation

Answer 19

increased frequency of action potentials from one pre synaptic neuron