AP1: MLP Chapter 11

15.a)

(Image 5)

33.c) At threshold, axons will _______.

Likely generate an action potential if refractory periods have elapsed.

35.a) Which of the following is described correctly?

Schwann cells provide the myelination in the peripheral nervous system.

31.b) Which of the following occurs during depolarization?

Sodium flows into the cell.

31.a) Which of the following occurs first in the generation of an action potential?

The membrane depolarizes.

28.a) Which of the following occurred in the presence of tetrodotoxin?

The number of action potentials decreased.

27.a) A nerve is _______.

a bundle of axons

30.d) When the stimulus voltage is increased, _______.

a greater-than-threshold depolarization results and sodium permeability into the cell increases to overcome the potassium exiting.

18.e) Which of the following describes a change from the resting membrane potential?

a receptor potential, a synaptic potential or an action potential

11.a) Which areas of this neuron would be classified as receptive regions? (Image 4)

both A and B • The dendrites and soma of the cell receive signals from other neurons

34.c) Increasing the amount of myelination _______.

decreases the time between action potentials

28.c) In the presence of lidocaine, the action potential was NOT affected at R1 because _______.

lidocaine was applied downstream of R1

35.d) The nodes of Ranvier are _______.

locations on the axon where the myelin sheath is absent

18.d) The typical concentration of sodium is _______.

lower than potassium intracellularly.

33.d) Longer stimuli will allow for _______.

more action potentials to occur, the absolute refractory period to finish and the relative refractory period to finish

28.d) The effects of lidocaine and tetrodotoxin were _______.

similar, but tetrodotoxin had a greater effect

12.a) Which of these materials or structures would be found in greatest amounts or numbers at E? (Image 4)

vesicles containing neurotransmitter • Neurotransmitters are released by secretion from the ends of axonal terminals.

27.c) In this simulation, ___________________ will be used to stimulate the axon.

voltage

29.a) An action potential requires _______.

voltage-gated sodium channels to open and sodium to flow with its electrochemical gradient

8.a) Destruction of which of the neuroglial cell types leads to the disease multiple sclerosis (MS)? (Image 3)

A • The defects in nerve transmission associated with MS are caused by a loss of myelin within the CNS.

5.a) Which of the neuroglial cell types shown form myelin sheaths within the CNS? (Image 3)

A • These cells form myelin sheaths within the white matter of the CNS. (Oligodendrocytes)

28.b) Which of the following occurred in the presence of tetrodotoxin?

An action potential was always seen at R1.

3.a) Which of the cell types shown helps determine capillary permeability? (Image 3)

B • Extensions from these cells wrap capillaries and provide extra control over which materials enter or leave the intercellular fluid of the CNS.(Astrocytes)

20.a) At which point of the illustrated action potential would voltage-gated Na+ channels be mostly open but voltage-gated K+ channels be mostly closed? (Image 7)

B • Voltage-gated Na+ channels open when the membrane potential reaches threshold. Voltage-gated K+ channels would be mostly open near C.

13.a) In which area of the neuron is an action potential initially generated? (Image 4)

C • Graded potentials originating in the dendrites and cell body are integrated (summated) at the axon hillock (C). Membrane potentials above threshold at the hillock will open voltage-gated Na+ channels found in the "trigger zone," producing an action potential that proceeds down the axon.

14.a) Which of the following membrane regions would have significant numbers of voltage-gated ion channels? (Image 4)

C and D • Voltage-gated Na+ and K+ channels allow for the triggering of an action potential at the axon hillock (C) and its propagation down the axon (D).

34.a) Which fibers generate the smallest value for conduction velocity?

C fibers

23.a) At which of the points along the illustrated action potential can a second action potential be produced, but only with a stimulus significantly greater than the one that produced the first? (Image 7)

D • Point D would be considered within the relative refractory period. A significantly strong stimulus may create enough depolarization to return the membrane to threshold. An important consequence of this design is that greater stimulus intensity will result in an increase in nerve impulse frequency.

4.a) Which of the cell types shown is most associated with the production and flow of cerebrospinal fluid (CSF)? (Image 3)

D • These cells line central cavities of the CNS and, in certain places, produce CSF. The cilia of these cells help circulate the CSF that nourishes and cushions the brain and spinal cord. (Ependymal cells)

9.a) What is the structure at A? (Image 4)

Dendrite • A indicates the dendrites of the neuron.

6.a) Which of the neuroglial cell types shown are found in the peripheral nervous system (PNS)? (Image 3)

E • The cell shown in E wraps and insulates the soma of neurons within ganglia in the PNS. (Satellite cells)

1.a)

Image #1

2.a)

Image #2

26.d) If an increase in extracellular potassium hyperpolarizes a neuron, which of the following would be correct?

It would change the membrane potential to a more negative value.

10.a) What structural classification describes this neuron? (Image 4)

Mulipolar • The neuron shown has a many processes (axon and dendrites) that emerge from the cell body. Such neurons typically function as motor neurons or interneurons.

21.a) Which of the following correctly states the direction followed by the specified ions when their voltage-gated channels open? (Image 7)

Na+ ions move into the axon; K+ ions move out. • Na+ ions move into the axon and K+ ions move out according to their concentration gradients.

17.b) What effect did decreasing the extracellular sodium have on the resting membrane potential?

Only a small change occurred, because the resting neuron is not very permeable to sodium

7.a) Name the glial cell at F. (Image 3)

Schwann Cell • Schwann cells carry out myelination of the peripheral nervous system (PNS). • While satellite cells are found in the peripheral nervous system, they do not myelinate. Rather, they are found surrounding the nucleus.

30.a) Why does the threshold increase when the interval between the stimuli decreases?

Some sodium channels have been inactivated and cannot be reopened immediately.

18.a) Which of the following statements about receptor potentials is FALSE?

The receptor potential is carried by neuroglia

17.a) What effect did increasing the extracellular potassium have on the resting membrane potential?

The resting membrane potential became less negative.

25.a) Local anesthetics block voltage-gated Na+ channels, but they do not block mechanically gated ion channels. Sensory receptors for touch (and pressure) respond to physical deformation of the receptors, resulting in the opening of specific mechanically gated ion channels. Why does injection of a local anesthetic into a finger still cause a loss of the sensation of touch from the finger?

Touch stimulation of this sensory receptor will open the mechanically gated ion channels, but action potentials are still not initiated because propagation of an action potential requires the opening of voltage-gated Na+ channels. • Propagation (spreading) of an action potential from the cell body to the axon hillock and eventually the axon terminals (synaptic knobs) requires the sequential opening of mechanically and voltage-gated ion channels. When the sequence is interrupted, the message cannot spread to the sensory regions of the central nervous system, causing numbness.

31.c) Which of the following occurs during repolarization?

Voltage-gated potassium channels open and some voltage-gated sodium channels inactivate. Potassium flows out of the cell.

30.c) When the interval between the stimuli decreases, _______.

a second action potential is generated until the interval reaches the absolute refractory period

36.a) A weak, subthreshold stimulus will result in _______.

a small depolarization at the receiving end of the neuron

22.a) Which of the following mechanisms is most significant in returning Na+ and K+ concentrations to resting ionic conditions (from point D to point E)? (Image 7)

active transport by the Na+-K+ pump • Maintenance (and restoration) of the resting ion concentrations depends on the Na+-K+ pump. Once gated ion channels are closed, the combined action of the pump and ion leakage (particularly that of K+) establishes a resting membrane potential in a typical neuron of around âˆ'70 mV.

37.c) A depolarizing synaptic potential is also known as _______.

an excitatory postsynaptic potential

30.b) During the relative refractory period, _______.

another action potential can be generated provided the stimulus is large enough.

36.d) An excitatory postsynaptic potential occurs _______.

at the receiving end of the interneuron

18.c) The conducting region of the neuron is the _______.

axon

27.d) We describe the regeneration of the action potential down the membrane of the axon of the neuron as _______.

conduction or propagation

29.b) To reach threshold, the amount of sodium _______.

entering the cell must overcome the potassium exiting

26.c) An axon that is more negative than the resting membrane potential is said to be _______.

hyperpolarized

32.b) Increase in stimulus intensity _______.

increases the frequency of action potentials

33.b) In this activity, which of the following will increase the stimulus intensity?

increasing the duration of the stimulus

32.a) The time interval between action potentials is called the _______.

interspike interval

35.b) The rate with which an action potential travels along an axon _______.

is called the conduction velocity and is measured in meters/sec

17.c) The channels that provide for the movement of potassium in the resting neuron are _______.

leakage

31.d) Which of the following allow the movement of potassium through the neuronal membrane?

leakage channels and voltage-gated potassium channels

29.d) Which of the following is used to block pain?

lidocaine

35.c) Which of the following describes a B fiber?

medium diameter, lightly myelinated

18.b) Which of the following is NOT a functional region of a neuron?

medullary region

37.b) A suprathreshold stimulus results in _______.

more action potentials

26.b) Increasing the voltage resulted in which of the following?

no change to the action potential

37.a) A single action potential is described as _______.

not graded

24.a) In multiple sclerosis, the cells that are the target of an autoimmune attack are the _________.

oligodendrocytes • Oligodendrocytes are a type of neuroglial cell that function to form the myelin sheath around the axons of neurons within the central nervous system

37.d) The stimulus for graded potentials includes _______.

sensory stimuli and neurotransmitter

17.d) Establishing the resting membrane potential requires energy through the use of the _______.

sodium-potassium pump

29.c) Which of the following blocks voltage-gated sodium channels?

tetrodotoxin and lidocaine

36.c) Increasing the strength of the stimulus applied to the sensory receptor increased _______.

the frequency of action potentials in the sensory neuron, the amount of neurotransmitter released at the axon terminal of the sensory neuron and the frequency of action potentials in the interneuron

34.b) The time interval for conduction would be shortest with

the largest and most heavily myelinated axons

36.b) Which stimulus was at or above threshold?

the moderate and strong stimuli

33.a) When the stimulus intensity increases, _______.

the number of action potentials increases

32.c) The frequency of action potentials is _______.

the reciprocal of the interspike interval, and measured in hertz

34.d) In this activity, the stimulus voltage used was _______.

the same for all of the axons and suprathreshold for all of the axons

32.d) During the relative refractory period, _______.

the stimulus must be above threshold to generate an action potential

19.a) What change in a neuron is being measured in the graph? (Image 7)

the voltage measured across the axon membrane at a specific point as an action potential travels past • It is important to recognize that an identical event will begin in the adjacent area of the axon membrane as the action potential observed here decays.

26.a) The minimum voltage that is required to generate an action potential is called the _______.

threshold voltage

27.b) The region on the neuron where action potentials are generated is called the ______.

trigger zone

16.a)

(Image 6)