Section 7

Question 1

True or False:

Graded potentials are transient changes in the membrane potential. GPs travel only as mall distance from their point of origin and as they move, they decay in size.

Answer 1

True

Question 2

Postsynaptic membrane graded voltage potentials (activated ligand gated channels) occur at the:

Answer 2

1. Spinal cord in dendrites
2. Spinal ganglia in dendrites
3. NMJ in the motor end plate

Question 3

Positive or depolarizing graded potentials

Answer 3

EPSPs

Question 4

Negative or hyper polarizing graded potentials

Answer 4

IPSPs

Question 5

Occurs when successive discharges of neurotransmitter from 2 or more (different) presynaptic anon terminals cause successive postsynaptic potentials (EPSPs and/or IPSPs) to overlap or summate

Answer 5

Spatial summation

Question 6

Occurs with successive discharge of neurotransmitter from the same presynaptic axon terminal that results in successive postsynaptic potentials (EPSPs and/or IPSPs) that overlap or summate when they occur at sufficiently high frequency

Answer 6

Temporal summation

Question 7

True or False:

Axon membrane’s permeability to Na+ in the activated region is 10 x greater than permeability in the resting region

Answer 7

False; its several 1000 times greater

Question 8

True or False:

Membranes have the ability to move action potentials in either direction.

Answer 8

True

Question 9

Share movement without ionic current flow through the membrane; initially depolarizes inactive membrane

Answer 9

Capacitive current

Question 10

Currents in non-myelinated nerve axon; intracellular current flows from the active region through the intracellular fluid to the inactive region; when the - charge is replaced by a + charge, the + charge inside repels the + charge outside, which is replaced by a - charge on the outside

Answer 10

Eddy currents

Question 11

Ions or charges move across the membrane

Answer 11

Ionic current

Question 12

The current that changes the amount of charge on the membrane

Answer 12

Capacitive current

Question 13

___ current is responsible for depolarization, while ___ current is responsible for repolarization.

Answer 13

Na+; K+

Question 14

Summarize 3 steps of an action potential

Answer 14

1. Capacitive current initially depolarizes membrane (opens voltage gated channels)
2. Na+ channels open and close quickly; Na+ flows down its concentration gradient with a large driving force (upstroke of an action potential)
3. K+ channels open slowly for delayed increase K+ current (downstroke of an action potential)

Question 15

Action potential propagation in myelinated axons; nerve impulse leaps along the axon during conduction from node to node

Answer 15

Saltatory conduction

Question 16

Where are charges found in myelinated axons?

Answer 16

At the nodes of Ranvier

Question 17

True or False:

Nodes of Ranvier are spaced farther apart in smaller diameter axons than in small diameter axons.

Answer 17

False; nodes are space farther in larger diameter axons, which allows for even greater conduction velocity

Question 18

Period where no matter how large the stimulus is, an AP cannot be produced - Na+ channels completely closed

Answer 18

Absolute refractory period

Question 19

Period where a very large stimulus can produce an AP - some Na+ channels are still closed; K+ channels wide open

Answer 19

Relative refractory period

Question 20

Period where a very small stimulus can produce an AP; membrane is slightly depolarized and Na+ channels are ready to open

Answer 20

Supernormal period

Question 21

Graded potentials are _______ to stimulus strength

Answer 21

Proportional

Question 22

State the 4 steps of how capacitive current works.

Answer 22

1. Na+ current moves from active to inactive region of membrane inside the cell
2. Positive charge displaces negative charge in the inactive region
3. positive charge on the outside membrane is repel off by the positive charge on the inside membrane; initially exciting the membrane with the removal of the positive charge
4. Replacement of the positive charge with a negative on the outside membrane is capacitive current

Question 23

What is the Hodgkin Cycle?

Answer 23

Upstroke of an AP (occurs at each point along the membrane); membrane depolarization, incr. Na+ conductance, Na+ influx

Question 24

Occurs at the leading edge of the traveling nerve impulse activating resting membrane

Answer 24

Hodgkin cycle

Question 25

AP regenerates along each segment of the axon by the removal of a + charge stored on the outside of the resting membrane and the influx of Na+ (a moving Hodgkin Cycle)

Answer 25

AP propagation