RAT #3

Question 1

Sensory neurons are also called ____ neurons because they transmit information toward the central nervous system

Answer 1

Afferent

Question 2

The amplitude of the peak of the action potential depends on ________.

Answer 2

The relative sizes of the electrochemical gradients for Na+ and K+ and the differences in Na+ and K+ permeability.›

Question 3

The resting membrane potential depends directly or indirectly on _________.

Answer 3

1. The conc. gradients of ions across the cell membrane and the ion permeability of the cell membrane.
2. The conc. gradients of ions across the cell membrane
3. The conc. gradients of ions across the cell membrane and the Na+/K+ ATPase
4. The Na+/K+ ATPase
5. The ion permeability of the cell membrane

Question 4

The resting membrane potential of a cell is produced by ion movements through _______

Answer 4

Potassium leak channels and sodium leak channels

Question 5

Refractory periods contribute to which of the following properties of action potentials?

Answer 5

Directionality, all or none, and coding of stimulus strength by frequency

Question 6

Outside the central nervous system, clusters of neuron cell bodies are called _________, and axons travel together in bundles called ______.

Answer 6

Ganglia; nerves

Question 7

The positive feedback look during the depolarization phase of the action potential is “turned off” during repolarization because _______

Answer 7

Na+ channels inactivate and K+ channels open

Question 8

In sodium channels at the resting membrane potential, ________.

Answer 8

The activation gate is closed and the inactivation gate is open

Question 9

The types of channels that can be found in excitable cells such as neurons include ____

Answer 9

Voltage gated, ligand gated, and leak.

Question 10

In myelinated axons, _______

Answer 10

1. Some current leaks across the membrane between nodes
2. Action potentials propagate by electronic conduction
3. Currents must reach the next node before the membrane potential falls below threshold

Question 11

Put the following events of the action potential in the correct order, starting with depolarization:

a. Na+ permeability> K+ permeability
b. K+ permeability> NA+ permeability
c. Vm approaches EK+
d. Vm approaches ENa+

Vm - membrane potential
E = equilibrium potential

Answer 11

a, d, b, c

Question 12

In contrast to almost all other cell types in the body, neurons _____

Answer 12

Can change their membrane potential and the permeability of their plasma membranes

Question 13

Action potentials propagate down the axon ______.

Answer 13

Like a row of falling dominoes, by current flow through the intra and extracellular fluid around sequential areas of axonal membrane, and by current flow through electronic conduction

Question 14

In neurons that generate many action potentials, why dont the ion gradients across the neurons cell membrane dissipate

Answer 14

The Na+/K+ ATPase helps reestablish the gradients by actively transporting these ions back across the neuronal membrane and even though the membrane potential can change dramatically, very few ions actually move across the neuronal membrane during each action potential.

Question 15

If the Na+/K+ ATPase were turned off, the membrane potential would eventually become equal to __________.

Answer 15

zero mV

Question 16

Normal concentration gradient of Cl-

Answer 16

Higher outside the cell than inside

Question 17

Normal concentration gradient of Ca2+

Answer 17

Lower inside the cell than the outside of the cell

Question 18

Normal concentration gradient of Na+

Answer 18

Lower inside the cell than outside the cell

Question 19

Normal concentration gradient of K+

Answer 19

Higher inside the cell than outside of the cell

Question 20

Normal concentration gradient of protein

Answer 20

Higher inside the cell than outside of the cell

Question 21

Equilibrium potential of Na+

Answer 21

+60mV

-when a sodium ion channel is opened sodium will moved into the cell until the cell reaches +60mV

Question 22

Equilibrium potential of K+

Answer 22

• 90 mV

- when a potassium channel is open potassium will exit the cell until it reaches -90mV

Question 23

Equilibrium potential of Ca2+

Answer 23

+122 mV

-when a calcium channel is open calcium will move into the cell until it reaches +122 mV

Question 24

Equilibrium potential of Cl-

Answer 24

• 63mV

- When a chloride channel is open chloride will move into the cell until it reaches -63 mV

Question 25

The movement of ____ into the cytosol of axon terminals is directly linked to exocytosis of neurotransmitter molecules into the synaptic cleft

Answer 25

Ca++

Question 26

If a resting neuron’s membranes receive a drug that makes them more permeable to sodium:

Answer 26

They will undergo a graded depolarization, likely to be followed by an action potential.

Question 27

What would be an example of a neuron with the slowest conduction velocity for action potentials

Answer 27

A thin, non-myelinated neuron

Question 28

What correctly describes the activity of the voltage-gated-K+-channels during an action potential

Answer 28

The opening of these channels causes the depolarization phase of the action potential

Question 29

The “decision point” for action potentials in a neuron is the

Answer 29

Axon hillock

Question 30

Which of these is present at higher concentration in the cytosol than in the interstitial fluid?
Na+, K+, Cl-, Ca++

Answer 30

K+

Question 31

What is a characteristic of action potentials?

Answer 31

They are an all-or-none sequence of depolarization and reploarization

Question 32

Neurotransmitters are typically released ____ into a synapse

Answer 32

From the pre-synaptic membrane of neurons

Question 33

Action potentials

Answer 33

Generally occur along axons of neurons
All or nothing event
Propagation of an action potential is dependent on the movement of Na+ through voltage-gated sodium channels to depolarize the neuron and the movement of K+ through voltage-gated potassium channels to repolarize the neuron

Question 34

Threshold

Answer 34

When depolarization reaches a point of no return

Question 35

Graded potentials

Answer 35

Small, variable changes in membrane potential that occur in the dendritic region when ligands or mechanically gated ion channels open.
When a GP is strong enough it will initiate an action potential

Question 36

Depolarization

Answer 36

Small amount of a positively charged ion enters the cell, Na+
-when the resting membrane potential becomes less negative (positive)

Question 37

Repolarization

Answer 37

Potassium exits the cell causing the membrane potential to become more negative until it reaches -70 mV

Question 38

Hyperpolarization

Answer 38

Sometimes the potassium channels are slow to close which results in the membrane potential dipping lower than -70mV

Question 39

Sodium potassium ATPase

Answer 39

Maintains the concentration gradient of Na+ and K+
-transporter pumps 3 Na+ out of the cell and 2 K+ into the cell per 1 ATP molecule consumed. This keeps the normal concentration gradient of Na+ low inside the cell and high outside of the cell. As well as keeps K+ high inside the cell and low outside the cell.

Question 40

Flow of information between neurons and along a single neuron

Answer 40

Most of the info received by a neuron occurs at the dendritic region where a signal, typically in the form of a ligand (hormone/neurotransmitters) or mechanical stimulation. The axonal region delivers the info in the form of action potentials that travel down the axon. Finally the axon terminal releases that info in the form of a neurotransmitter which exits via a vesicle due to calcium entering the region.

Question 41

Describe how afferent sensory neurons fit into a homeostasis loop

Answer 41

A controlled variable is monitored by sensors when something goes wrong error signals are sent to the central nervous system (the integrating center) via afferent neurons. The central nervous system sends out correcting signals via efferent neurons to effector tissues which work to correct the problem

Question 42

What type of receptors are on the postsynaptic membrane of the parasympathetic neurons? What binds to these receptors?

Answer 42

Nicotinic cholinergic; acetylcholine

Question 43

What type of receptors are on the postsynaptic membrane of the sympathetic nervous system? What binds to these receptors?

Answer 43

Nicotinic cholinergic; acetylcholine

Question 44

What signal is released from the post ganglionic neuron of the parasympathetic nervous system? and what are the receptors called? where are they located?

Answer 44

Acetylcholine; muscarinic cholinergic; heart (cause a decrease in HR)

Question 45

What signal is released from the post ganglionic neuron of the sympathetic nervous system? and what are the receptors called? where are they located?

Answer 45

Norepinephrine; adrenergic; heart (increase HR)

Question 46

Explain how the autonomic nervous system exerts antagonistic control over the heart.

Answer 46

The autonomic nervous system exerts antagonistic control over the heart because the sympathetic branch increases HR while the parasympathetic branch decreases heart rate (2 different signals)

Question 47

Explain how the sympathetic nervous system can cause both vasodilation and vasoconstriction.

Answer 47

Beta-adrenergic receptors cause vasodilation
Alpha-adrenergic receptors cause vasoconstriction

*When EPI binds to either. Lots of EPI at beta = lots of vasodilation less = less dilation
Lots of EPI at alpha = lots of vasoconstriction “”

Question 48

What does alpha-conotoxin do?

Answer 48

Inhibit nicotinic acetylcholine receptors at nerves and muscles

Question 49

What does δ conotoxin do?

Answer 49

Inhibit the inactivation of voltage-dependent sodium channels

Question 50

What does κ conotoxin do?

Answer 50

Inhibit potassium channels

Question 51

What does μ conotoxin do?

Answer 51

Inhibits voltage-dependent sodium channels in muscles

Question 52

Which of the following would be the most useful to treat symptoms of methamphetamine intoxication?

• An agonist of the dopamine receptor
• An antagonist of the dopamine receptor
• An inhibitor of the DAT channel (preventing re-uptake of dopamine)
• Caffeine
• None of the above

Answer 52

B
-The dopamine transporter normally transports dopamine back into the axon terminal, Amphetamines reverse the direction of dopamine movement so more dopamine stays in the synapse