Chapter 1: Nerve Cells and Nerve Impulses

Which action would depolarize a neuron?

increasing membrane permeability to sodium

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 1.2

Glial cells ____. a: are less numerous than neurons in the human brain b: transmit information over long distances within the central nervous system c: occupy about ten times more space in the brain than do neurons d: are smaller but more numerous than neurons in the human brain

d: are smaller but more numerous than neurons in the human brain 1.1

In what direction does a local neuron transmit information? a. through its dendrites to cell body to axon b. through its axon to cell body to dendrites c. only toward the cell body d. equally well in any direction

d: equally well in any direction

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 1.1

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 1.1

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

What occurs when depolarization is less than the cell's threshold?

sodium crosses the membrane only slightly more than usual

A membrane produces an action potential whenever the potential across it reaches what level?

The threshold of excitation

Voltage-activated channels are channels for which a change in the voltage across the membrane alters their ____. a. permeability b. length c. number d. threshold

a: permeability

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

b: shape 1.1

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 1.1

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: jopen to let sodium enter the cell rapidly 1.2

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 1.2

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 1.1

What leads to Korsakoff's syndrome? a: thiamine deficiency due to chronic alcoholism b: glucose deficiency due to chronic alcoholism c: viruses that manage to cross the blood brain barrier d: glial cells that over reproduce and increase pressure in the brain

a: thiamine deficiency due to chronic alcoholism 1.1

Ordinarily, stimulation of a neuron takes place ____.

at the synapse

The membrane of a neuron is composed of ____ with ____ embedded in them. a: carbohydrates; purines b: fat molecules; proteins c: proteins; neurotransmitters d: benzene molecules; carbohydrates

b: fat molecules; proteins 1.2

The function of a myelin sheath is to ____. a. prevent action potentials from traveling in the wrong direction b. increase the velocity of transmission along an axon c. increase the magnitude of an action potential d. provide a store of nutrients for the neuron

b: increase the vilocity of transmission along an axon

Which event will increase the concentration gradient of sodium? a: decreasing permeability to potassium ions b: increasing activity of the sodium potassium pump c: increasing membrane permeability to sodium ions d: increasing membrane permeability to chloride ions

b: increasing activity of the sodium potassium pump 1.2

Chemicals are released by axons ____. a: into the presynaptic terminal b: into the junction between neurons c: through the efferent terminals d: to the mitochondria

b: into the junction between neurons 1.1

Gaps in the insulating material that surrounds axons are known as _____. a: interpeduncular nuclei b: nodes of Ranvier c: myelin synapses d: presynaptic terminals

b: nodes of Ranvier 1.1

A drug will prevent an action potential if it ____. a. lowers the threshold of the membrane b. blocks the movement of potassium across the membrane c. blocks the movement of sodium across the membrane d. increases the movement of sodium across the membrane

c: blocks the movement of sodium across the membrane 1.2

When a membrane is at rest, what attracts sodium ions to the inside of the cell? a: electrical gradient b: concentration gradient c: both d: neither

c: both 1.2

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 1.1

Glial cells whose function most closely resembles that of the immune system are called ____. a: oligodendrocytes b: Schwann cells c: microglia d: radial glia

c: microglia 1.1

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 1.1

Glucose enters the brain via which type of transport? a: indirect transport b: direct transport c: passive transport d: active transport

d: active transport 1.1

Water, oxygen, and _____ most freely flow across a cell membrane. a: calcium b: positively charged ions c: magnesium d: carbon dioxide

d: carbon dioxide 1.1

Ribosomes are the part of a cell that _____. a: performs metabolic activities b: breaks down harmful chemicals c: transports proteins d: synthesizes new proteins

d: synthesizes new proteins 1.1

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 1.2

What action tends to open the sodium gates across a neuron's membrane?

depolarization of the membrane

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

a: a concentration gradient 1.2

Which of the following describes the transmission of information in a local neuron? a. The signal decreases in strength as it travels. b. The signal increases in strength as it travels. c. The signal strength remains constant as it travels. d. Local neurons do not transmit any information.

a: the signal decreases in strength as it travels 1.2

What type of glia helps to synchronize the activity of axons? a: oligodendrocytes b: astrocytes c: radial glia d: Schwann cells

b: astrocytes 1.1

Neurons typically have one ____, but many ____. a: dendrite; axons b: axon; dendrites c: cell body; axons d: dendrite; cell bodies

b: axon; dendrites 1.1

The primary feature of a neuron that prevents the action potential from traveling back from where it just passed is the ____. a. concentration gradient b. refractory period c. sodium potassium pump d. phospholipid bilayer

b: refractory period 1.2

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

b: small charged 1.1

What term describes the difference in voltage that typically exists between the inside and the outside of a neuron? a: concentration gradient b: generator potential c: resting potential d: shock gradient

c: resting potential

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 is one major cause for the resting potential of a neuron's membrane? 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

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 1.1

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 1.2

The surface of a dendrite is lined with specialized junctions through which the dendrite receives information from other neurons. What are these junctions called? a: synaptic receptors b: axons c: synaptic hillocks d: glia

a: synaptic receptors 1.1

The branching fibers that form the information-receiving pole of the nerve cells are called _____. a: motor neurons b: dendrites c: sensory neurons d: axons

b: dendrites 1.1

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 1.2

If all of a neuron's dendrites or axons were contained within the spinal cord, it would be considered a (n) ____ neuron. a: efferent b: afferent c: intrinsic d: Purkinje

c: intrinsic 1.1

In the normal course of an action potential, ____.

sodium remains much more concentrated outside than inside the neuron

Which scientific work did Cajal apply to his study of infant brains? a: Charles Sherrington's study of reflexes. b: Camillo Golgi's cell staining method. c: Perves & Hadley's dye injection method. d: Galileo's invention of the telescope.

a: Charles Sherrington's study of reflexes. 1.1

The two basic kinds of cells in the nervous system are _____. a: neurons and glia b: dendrites and axons c: ribosomes and lysosomes d: neurons and axons

a: neurons and glia 1.1

The tree-like branches of a neuron that receive information from other neurons are called _____. a: axons b: dendrites c: soma d: myelin

b: dendrites 1.1

What is the approximate resting potential of the inside of a neuron's membrane, relative to the outside? a: -70 millivolts b: +10 millivolts c: 0 millivolts d: +90 millivolts

a: -70 millivolts 1.2

____ in the brain and spinal cord and ____ in the periphery are specialized types of glia that build the myelin sheaths that surround neurons. a: Oligodendrocytes; Schwann cells b: Schwann cells; oligodendrocytes c: microglia; oligodendrocytes d: radial glia; Schwann cells

a: Oligodendrocytes; Schwann cells 1.1

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 1.2

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 1.2

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 1.1

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

a: astrocytes 1.1

At what point do the sodium gates begin to close, shutting out further entry of sodium into the cell? a. at the peak of the action potential b. when the threshold is reached c. at the end of the relative refractory period d. when the concentration gradient for sodium is eliminated

a: at the peak of the action potential 1.2

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 of the cell d: increase the number of negatively charged ions within the cell

a: decrease the number of positively charged ions within the cell 1.2

If you were to accidentally touch a hot stove with your hand, you would quickly pull your hand away. The information carried to the muscles in your arm to make them contract was carried by ____. a: efferent neurons b: afferent neurons c: intrinsic neurons d: sensory neurons

a: efferent neurons 1.1

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

a: electrical gradient 1.2

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 1.1

Many dendrites contain short outgrowths called spines that _____. a: increase the surface area available for synapses b: increase the speed of transmission c: eliminate cell waste products d: increase the symmetry of the cell

a: increase the surface area available for synapses 1.1

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 1.2

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 1.1

The endoplasmic reticulum is a _____. a: network of thin tubes that transport newly synthesized proteins b: site where the cell synthesizes new protein molecules c: structure that separates the inside of the cell from the outside d: structure that contains the chromosomes

a: network of thin tubes that transport newly synthesized proteins 1.1

What type of glial cells myelinate axons in the brain and spinal cord? a: oligodendrocytes b: Schwann cells c: radial glia d: astrocytes

a: oligodendrocytes 1.1

Which action will produce a hyperpolarization of a neuron?

applying a negative charge inside the neuron with a microelectrode

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 1.1

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 1.1

A drug that blocks the sodium gates of a neuron's membrane will ____. a. decrease the threshold b. block the action potential c. cause repeated action potentials d. eliminate the refractory period

b: block the action potential 1.2

What mechanism prevents or slows some chemicals from entering the brain, while allowing others to enter? a: a threshold b: a blood-brain barrier c: an endoplasmic wall d: a differential-drug inhibitor

b: blood-brain barrier 1.1

The cell membrane is composed of two layers of _____. a: protein b: fat c: carbohydrate d: plasma

b: fat 1.1

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

b: glucose 1.1

Santiago Ramon y Cajal demonstrated that _____. a: at rest, the neuron has a negative charge inside its membrane. b: neurons are separate from one another. c: neurons communicate at specialized junctions called synapses. d: action potentials follow the all or none law.

b: neurons are separate from one another. 1.1

Which of the following describes selective permeability? a: ions can only travel in certain directions across the membrane b: only certain molecules are allowed to cross the membrane freely c: only certain types of stimulation will result in an action potential d: all molecules must pass through designated channels

b: only certain molecules are allowed to cross the membrane freely 1.2

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 1.2

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 1.2

When the neuronal membrane is at rest, the sodium channels ____. a: permit sodium ions to pass quickly and easily b: are at equilibrium with potassium channels c: are closed, so there is almost no flow of sodium d: allow sodium to leak out as steady, continuous drip

c: are closed, so there is almost no flow of sodium 1.2

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 the outside of the membrane 1.2

. According to the all-or-none law, ____. a. all neurons produce an action potential at the same time or none at all b. all of the extracellular sodium enters the axon, or none at all c. once an axon reaches threshold, the amplitude and velocity of an action potential are nearly equal each time d. neurons are either active all the time or not at all

c: once an axon reaches threshold, the amplitude and velocity of an action potential are nearly equal each time 1.2

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 mantained in equal concentrations thoughout the cytoplam

c: the cell is prepared to respond quickly to a stimulus

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

d: both sodium-potassium pump and electrical gradient 1.2

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 1.2

What happens to a virus that manages to cross the blood-brain barrier and enter the brain? a: it is quickly destroyed by natural killer cells b: it gets trapped in a neuron, and then both are destroyed by natural killer cells c: it gets trapped in a glial cell, and then both are destroyed by natural killer cells d: it remains there and may cause negative effects several years later

d: it remains there and may cause negative effects several years later 1.1

Why do neurons rely so heavily on glucose as their source of nutrition? a: neurons lack the enzymes necessary to metabolize other fuels. b: glucose is the only fuel that can be used even in the absence of vitamins c: glucose is not used extensively by other parts of the body d: other fuels do not readily cross the blood-brain barrier

d: other fuels do not readily cross the blood-brain barrier 1.1

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 1.2

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 1.2

What occurs when a stimulus shifts the potential inside a neuron from the resting potential to a more negative potential?

hyperpolarization

The action potential of a neuron depends mostly on what movement of ions?

sodium ions entering the cell

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 1.1

The insulating material that covers many vertebrate axons is called the _____. a: dendrite b: myelin sheath c: cell body or soma d: presynaptic terminal

b: myelin sheath 1.1

The structure that contains a cell's chromosomes is called the _____. a: endoplasmic reticulum b: nucleus c: mitochondrion d: ribosome

b: nucleus 1.1

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 1.1

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 1.1

When a neuron's membrane is at rest, the concentration gradient tends to move potassium ____ 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

c: out of; into

Small, charged molecules can cross the cell membrane through _____. a: diffusion b: ribosomes c: mitochondria d: protein channels

d: protein channels 1.1

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 1.2

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 1.2