Ch. 1

Nodes of Ranvier are ____. a. gaps in the myelin of axons b. also known as myelin sheath c. spiny outgrowths on dendrites d. responsible for cell metabolism

a. gaps in the myelin of axons

Neurons differ most strongly from other body cells in their ____. a. temperature b. shape c. osmotic pressure d. mitochondria

b. shape

Protein channels allow ____ molecules to cross the cell membrane. a. large charged b. small charged c. large uncharged d. small uncharged

b. small charged

What occurs when depolarization is less than the cell's threshold? a. Sodium is prevented from crossing the membrane. b. Potassium is prevented from crossing the membrane. c. Sodium crosses the membrane only slightly more than usual. d. The cell will still produce an action potential.

c. Sodium crosses the membrane only slightly more than usual.

Under which conditions would the sodium-potassium pump likely be far less effective in creating a concentration gradient? a. if dendrites were generally longer than axons b. if the glia-to-neuron ratio were higher c. if selective permeability of the membrane did not exist d. if it were an active transport system that required energy

c. if selective permeability of the membrane did not exist

In the normal course of an action potential, ____. a. sodium channel remain open for long periods of time b. the concentration of sodium equalizes across the membrane c. sodium remains much more concentrated outside than inside the neuron d. subthreshold stimulation intensifies the action potential

c. sodium remains much more concentrated outside than inside the neuron

After the peak of an action potential, what prevents sodium ions from continuing to enter the cell? a. There is no longer a concentration gradient for sodium. b. The sodium-potassium pump greatly increases its rate of activity. c. All the available sodium ions have already entered the cell. d. The sodium gates in the membrane close.

d. The sodium gates in the membrane close.

Which action would depolarize a neuron? a. decreasing membrane permeability to calcium b. increasing membrane permeability to potassium c. decreasing membrane permeability to sodium d. increasing membrane permeability to sodium

d. increasing membrane permeability to sodium

The concentration gradient for potassium tends to ____. a. draw potassium into the cell b. push chloride out of the cell c. push sodium out of the cell d. push potassium out of the cell

d. push potassium out of the cell

The idea that a neuron's membrane is polarized refers to a difference in electrical potential between ____. a. the axons and the dendrites b. the axon hillock and the cell body c. sodium ions and potassium ions d. the inside and the outside of the membrane

d. the inside and the outside of the membrane

When the potential across a membrane reaches threshold, the sodium channels ____. a. open to let sodium enter the cell rapidly b. close to prevent sodium from entering the cell c. open to let sodium exit the cell rapidly d. close to prevent sodium from exiting the cell

a. open to let sodium enter the cell rapidly

An axon has many branches, each of which swells at its tip. These are known as ____. a. presynaptic terminals b. efferent axons c. afferent axons d. intrinsic neurons

a. presynaptic terminals

What is the main source of nutrition for vertebrate neurons? a. fats b. glucose c. sodium d. complex carbohydrates

b. glucose

What do neurons have that other cells do not? a. a plasma membrane b. large, branching extensions c. protein channels d. an endoplasmic reticulum

b. large, branching extensions

When a neuron is at rest, what is primarily responsible for moving potassium ions into the cell? a. concentration gradient b. an electrical gradient c. the sodium-potassium pump d. both the sodium-potassium pump and electrical gradient

d. both the sodium-potassium pump and electrical gradient

Electrical gradients lead to the ____. a. general movement of ions into the neuron b. general movement of ions out of the neuron c. movement of ions to areas having the same electrical charges d. movement of ions to areas having opposite electrical charges

d. movement of ions to areas having opposite electrical charges

What structure is composed of two layers of fat molecules that are free to flow around one another? a. the endoplasmic reticulum b. a ribosome c. a mitochondrion d. the membrane

d. the membrane

The neuron will produce an action potential only if the depolarization exceeds the ____. a. Threshold of excitation b. the resting potential c. hyperpolarization d. the refractory period

a. Threshold of excitation

What causes potassium ions to leave the axon just after the peak of the action potential? a. a continuing concentration gradient and the opening of the potassium gates b. an increase in the concentration gradient across the membrane c. an increased tendency of the sodium-potassium pump to push potassium out d. binding of potassium ions to proteins that leave at this time

a. a continuing concentration gradient and the opening of the potassium gates

The all-or-none law states that ____. a. a neuron produces an action potential of maximal strength, or none at all b. all neurons fire or none at all c. all neurons in a pathway fire at the same time, or none do d. all ions move in the same direction, or none do

a. a neuron produces an action potential of maximal strength, or none at all

When a membrane is at rest, what attracts potassium ions to the inside of the cell? a. an electrical gradient b. a concentration gradient c. both an electrical gradient and a concentration gradient d. neither an electrical gradient nor a concentration gradient

a. an electrical gradient

A presynaptic terminal is also known as ____. a. an end bulb b. a node of Ranvier c. myelin d. a spine

a. an end bulb

Which action will produce a hyperpolarization of a neuron? a. applying a negative charge inside the neuron with a microelectrode b. applying a positive charge inside the neuron with a microelectrode c. increasing the membrane's permeability to sodium d. decreasing the membrane's permeability to potassium

a. applying a negative charge inside the neuron with a microelectrode

Which type of glia release chemicals that modify the activity of neighboring neurons? a. astrocytes b. Schwann cells c. oligodendrocytes d. radial glia

a. astrocytes

Which type of glia remove waste material in the nervous system? a. astrocytes b. Schwann cells c. oligodendrocytes d. radial glia

a. astrocytes

The net effect of each cycle of the sodium-potassium pump is to ____. a. decrease the number of positively charged ions within the cell b. increase the number of positively charged ions within the cell c. decrease the number of positively charged ions outside the cell d. increase the number of negatively charged ions within the cell

a. decrease the number of positively charged ions within the cell

Radial glia ____. a. guide the migration of neurons during embryonic development b. synchronize the activity of axons c. wrap around the presynaptic terminals of several axons d. build the myelin sheaths that surround and insulate certain axons

a. guide the migration of neurons during embryonic development

When a neuron's membrane is at rest, the concentration gradient tends to move sodium ____ the cell and the electrical gradient tends to move it ____ the cell. a. into; into b. into; out of c. out of; into d. out of; out of

a. into; into

Korsakoff's syndrome ____. a. is marked by severe memory impairments b. results from too much thiamine c. results from lack of oxygen to the brain d. is due to a breakdown of the blood-brain barrier

a. is marked by severe memory impairments

The resting potential is mainly the result of ____. a. negatively charged proteins inside the cell b. positively charged proteins inside the cell c. negatively charged proteins outside the cell d. positively charged proteins outside the cell

a. negatively charged proteins inside the cell

The action potential of a neuron depends mostly on what movement of ions? a. sodium ions entering the cell b. sodium ions leaving the cell c. potassium ions entering the cell d. potassium ions leaving the cell

a. sodium ions entering the cell

Which type of glia builds myelin sheaths around axons in the periphery of the body? a. astrocytes b. Schwann cells c. oligodendrocytes d. radial glia

b. Schwann cells

Dendrites ____. a. contain the nucleus, ribosomes, and other structures found in most cells b. are branching fibers that get narrower near their ends c. are thin fibers of constant diameter d. are an insulating material that cover an axon

b. are branching fibers that get narrower near their ends

Ordinarily, stimulation of a neuron takes place ____. a. through hyperpolarization b. at the synapse c. in the mitochondria d. in the endoplasmic reticulum

b. at the synapse

When the neuronal membrane is at rest, the potassium channels ____. a. permit potassium ions to pass quickly and easily b. permit potassium ions to pass slowly c. prohibit any movement of potassium ions d. help to open up the sodium channels

b. permit potassium ions to pass slowly

During the relative refractory period, the ____. a. sodium gates are firmly closed b. sodium gates are reverting to their usual state c. sodium gates are wide open d. potassium gates are firmly closed

b. sodium gates are reverting to their usual state

Which of the following is an advantage of having a resting potential? a. The toxic effects of sodium are minimized inside the cell. b. No energy is required to maintain it. c. The cell is prepared to respond quickly to a stimulus. d. All of the ions are maintained in equal concentrations throughout the cytoplasm.

c. The cell is prepared to respond quickly to a stimulus.

As compared to dendrites, axons usually ____. a. form the information-receiving pole of the neuron b. are shorter in length c. are covered with myelin d. taper in diameter toward their periphery

c. are covered with myelin

As a general rule, axons convey information ____. a. toward dendrites of their own cell b. toward their own cell body c. away from their own cell body d. to surrounding glia

c. away from their own cell body

The major disadvantage of a blood-brain barrier is that ____. a. many chemicals can easily diffuse into the brain b. so much glucose is required to maintain it c. certain required chemicals must be actively transported d. viruses cannot escape

c. certain required chemicals must be actively transported

The concentration gradient refers to the ____. a. fact that the concentration of ions is greater on the inside of a neuron b. fact that the concentration of ions is greater on the outside of a neuron c. difference in distribution for various ions between the inside and outside of the membrane d. negatively charged proteins inside the cell

c. difference in distribution for various ions between the inside and outside of the membrane

What type of neuron in the pons receives information only from other cells in the pons and sends information only to other cells in the pons? a. afferent b. efferent c. intrinsic d. inter-synaptic

c. intrinsic

At the peak of the action potential, the electrical gradient of potassium ____. a. is the same as during the resting potential b. pulls sodium into the cell c. pushes potassium out of the cell d. pulls potassium into the cell

c. pushes potassium out of the cell

The speed of an action potential down an unmyelinated axon is best described as ____. a. the speed of electricity, regardless of the size of the axon b. less than 1 meter per second, regardless of the size of the axon c. faster in thin axons than in thick ones d. faster in thick axons than in thin ones

d. faster in thick axons than in thin ones

Molecules that can cross the blood-brain barrier are usually ____. a. large, uncharged molecules, such as lactose b. large, charged molecules c. neurotransmitters, such as dopamine d. molecules that can dissolve in the fats of the capillary walls

d. molecules that can dissolve in the fats of the capillary walls

The resting potential of a neuron refers to the ____. a. net positive charge on the inside of the neuron b. ions which rest in one place in the cell c. movement of ions to the outside of the neuron d. net negative charge on the inside of the neuron

d. net negative charge on the inside of the neuron

Local anesthetic drugs attach to the sodium channels of the membrane, which ____. a. allows sodium ions to enter and stop action potential b. prevents potassium ions from entering and stopping action potential c. allows potassium ions to enter and stop action potential d. prevents sodium ions from entering and stopping action potential

d. prevents sodium ions from entering and stopping action potential

What will most affect the speed of an action potential? a. the strength of the stimulus b. the time since the last action potential c. the length of the axon d. the resistance of the membrane

d. the resistance of the membrane

What is one major cause for the resting potential of a neuron's membrane? a. a difference in size between axons and dendrites b. a high permeability of the membrane to water molecules c. the refractory period of the membrane d. the sodium-potassium pump

d. the sodium-potassium pump

Why does the brain need thiamine? a. to enable glucose to cross the blood-brain barrier b. as a source of fuel in case there is not enough glucose c. as a building block for making proteins d. to enable it to metabolize glucose

d. to enable it to metabolize glucose