Exam 2

Question 1

During action potential, which of the following is true about the voltage gated K+ channels?

a) they are triggered to open at voltages near the resting membrane potential
b) They are triggered to open when the membrane reaches threshold potential
c) They are triggered to open at voltages below the resting membran potential
d) none of the above

Answer 1

b) They are triggered to open when the membrane reaches threshold potential

Question 2

In a neuromuscular junction, the muscle is the

a) presynaptic cell
b) postsynaptic cell
c) synaptic cell
d) signaling cell

Answer 2

b) postsynaptic cell

Question 3

Most neurons show ______, such that one end of the neuron receives a signal and the other end sends a signal

a) functionality
b) polarity
c) specificity
d) none of the above

Answer 3

b) polarity

Question 4

When a cell ____, the charge difference between the intracellular and extracellular fluids decreases.

a) depolarizes
b) hyperpolarizes
c) both of the above
d) none of the above

Answer 4

a) depolarizes

Question 5

The area of the axon covered with myelin and found between the nodes of Ranvier is known as an _______.

a) interconnectio
b) interspace
c) internode
d) synaptic cleff

Answer 5

c) internode

Question 6

In the neuromuscular junction, nicotinic acetylcholine (ACh) receptors are ________ ion channels

a) voltage gated
b) ligand gated
c) leakage
d) none of the above

Answer 6

b) ligand gated

Question 7

Cardiac muscle cells take much longer to repolarize. The main reason for this is that the voltage sensitive ________ channels stay open for a much longer period.

a) sodium
b) calcium
c) potassium
d) chloride

Answer 7

b) calcium

Question 8

In skeletal muscle, motor neurons release acetylcholine into the neuromuscular junction which generates depolarization at the ___________.

a) motor end plate
b) sensory end plate
c) axon terminals of the motor neuron
d) none of the above

Answer 8

a) motor end plate

Question 9

Assume that an EPSP is being generated on the dendritic membrane. Which will occur?

a) specific sodium channels will open
b) specific potassium channels will open
c) a single type of channel will open, permitting simultaneous flow of sodium and potassium
d) sodium channels will open first and then close as potassium channels open

Answer 9

c) a single type of channel will open, permitting simultaneous flow of sodium and potassium

Question 10

Inhibition of acetylcholinesterase blocks neurotransmission at the neuromuscular junction because:

a) ACh is no longer released by the presynaptic neuron
b) ACh synthesis in theprysynaptic neuron is blocked
c) ACh is not degraded, hence prolonged depolarization is enforced on the postsynaptic cell
d) ACh is blocked from attachin to the postsynaptic ACh receptors

Answer 10

c) ACh is not degraded, hence prolonged depolarizatio is enforced on the postsynaptic cell

Question 11

An IPSP is inhibitory because:

a) it hyperpolarizes the postsynaptic neuron
b) it reduces the amount of neurotransmitter released by the presynaptic neuron
c) it prevents calcium ion entry into the presynaptic neuron
d) all of the above

Answer 11

a) it hyperpolarizes the postsynaptic neuron

Question 12

Cardiac muscle uses a process called _____ Ca2+ release to link/couple dihydropyridine receptors and ryanodine receptors activation

a) Ca2+ induced
b) Na+ induced
c) depolarization induced
d) repolarization induced

Answer 12

a) Ca2+ induced

Question 13

What mechanism causes the voltage gated Na+ channels to close during an action potential?

a) the activation gate is voltage sensitive and closes when Na+ intracellular
b) the activation gate is sensitive to K+ and closes when its intracellular concentrations drop
c) The inactivatin gate has a time-dependent closure
d) The inactivatin gate voltage sensitive and closes when Na+ intracellular concentrations drop

Answer 13

c) the inactivation gate has a time dependent closure

Question 14

Which of the following statements is true of graded potentials?

a) they travel over long distances
b) they vary in strength
c) they travel without decrement
d) all of the above

Answer 14

b) they vary in strength

Question 15

Action potentials can be conducted into the muscle along invaginations of the sarcolemma known as the:

a) sarcoplasmic reticulum
b) T-tubules
c) terminal cisternae
d) sarcotubules

Answer 15

b) T-tubules

Question 16

Conduction of action potentials along a myelinated axon is termed saltatory conduction because the actin potential:

a) is dependent on the K+ ion
b) appears to leap or jump from node to node
c) moves very slowly down the axon
d) all of the above

Answer 16

b) appears to leap or jump from node to node

Question 17

Skeletal myofibers depolarize and repolarize very quickly, typically within about ______ of the time required to complete a contraction-relaxation cycle

a) 55%
b) 25%
c) 15%
d) 5%

Answer 17

d) 5%

Question 18

Axons are found in the _______ region of a neuron.

a) signal reception
b) signal integration
c) signal conduction
d) signal transmission

Answer 18

b) signal integration

Question 19

Whatis the correct relationship between graded potentials and action potentials?

a) graded potentials are used to generate action potentials
b) action potentials are used to generate graded potentials
c) graded potentials and action potentials are two terms for the same phenomenon
d) all graded potentials increase the likelihood of an actin potential

Answer 19

a) graded potentials are used to generate action potentials

Question 20

Which of the following potentials will be most likely to generate an action potential?

a) a subthreshold potential
b) a suprathreshold potential
c) a hyperpolarizing potential
d) an inhibitory potential

Answer 20

b) a suprathreshold potential

Question 21

Action potentials are able to travel over long distances without decaying because

a) the axons are perfectly insulated, so no current is able t leak out
b) the action potential uses completely different ions than graded potentials
c) one action potential generates the next one in an adjacent area of membrane
d) all of the above

Answer 21

c) one actin potential generates the next one in an adjacent area of membrane

Question 22

During the absolute refractory period, what is the state of the gates of the sodium channel?

a) both activation and inactivation gates are close
b) both activation and inactivatin gates are open
c) the activaton gate is open and the inactivatin gate is closed
d) the activatin gate is closed and the inactivatin gate is open

Answer 22

a) both activation and inactivation gates are close

Question 23

What role does Ca2+ play in synaptic transmission?

a) Ca2+ is released into the synapse, transmitting a signal to the axon terminal of the presynaptic cell
b) Ca2+ causes the release of vesicles from the postsynaptic cell
c) Ca2+ causes the release of vesicles from the presynaptic cell
d) none of the above

Answer 23

c) Ca2+ causes the release of vesicles from the presynaptic cell

Question 24

During synaptic transmissin:

a) the frequency of the action potential is directly correlated with neurotransmitter release
b) the frequency of the actin potential is inversely correlated with neurotransmitter release
c) the frequency of the actin potential has no effect on neurotransmitter release
d) none of the above

Answer 24

a) the frequency of the action potential is directly correlated with neurotransmitter release

Question 25

Inhibitory postsynaptic potentials could result from opening _______ or ______ chemically-gated channels: a) potassium; chloride b) sodium; potassium c) calcium; calcium d) none of the above

Answer 25

a) potassium; chloride

Question 26

T or F: Action potentials are often described as all-or-none phenomena because once an action potential has been initiated, it always proceeds to its conclusion

Answer 26

True

Question 27

T or F: During the relative refractory period of an action potential, it is impossible to generate a new action potential

Answer 27

False

Question 28

T or F: Sarin and many organophosphate pesticides function by increasing the amount of acetylcholine release

Answer 28

True

Question 29

T or F: Neurogenic muscle cells can depolarize and contract on their own, as opposed to myogenic muscle cells which require neural innervation

Answer 29

False

Question 30

T or F: The effective refractory period is the same for all types of striated muscles

Answer 30

False

Question 31

T or F: The resting membrane potential which exists across the plasma membranes of neurons occurs because there is a buildup of posititve charges inside the membrane and negative charges outside the membrane

Answer 31

False

Question 32

T or F: When a graded otential arrives at the axon hillock before an earlier graded potential has died out , the two potentials can be added in a process known as spatial summation

Answer 32

True

Question 33

T or F: In neurons, the absolute refractory period coincides with the depolarization and repolarization phases of action potential

Answer 33

True

Question 34

T or F: The axon hillock acts as a decision point for the neuron

Answer 34

True

Question 35

T or F: The action potential uses changes in its amplitude to carry information about the strength of a signal

Answer 35

False

Question 36

T or F: Depolarizatio is the first step in vertebrate striated muscle excitation

Answer 36

True

Question 37

T or F: Once a skeletal muscle membrane repolarizes, a second action potential can induce another contractin even if the muscle has not yet relaed from the previous contraction

Answer 37

True

Question 38

T or F: Muscles that elevate cytoplasmic calcium concentration using intracellulare stores such as most types of mammalian striated muscle, use the sarcoplasmic reticulum calcium ATPase, or SERCA, to pump calcium out of the cell

Answer 38

False

Question 39

T or F: Natural action potentials are bidirectional signals

Answer 39

False

Question 40

T or F: The axon hillock joins the cell body (soma) to the axon

Answer 40

True