Biopsych Homework 1

Incoming synapses are primarily found on:

dendrites and cell bodies.

Some dendrites contain additional short outgrowths. What are these outgrowths called?

dendritic spines

What is the result if a stimulus shifts the potential inside a neuron from the resting potential to a potential slightly closer to zero?

depolarization

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

depolarization of the membrane

In the brain, an arrangement of endothelial cells:

does not allow most molecules to pass because the cells are so tightly packed.

T / F Glial Cells can have action potentials.

false

The membrane of a neuron is composed of ____ with ____ embedded in them.

fat molecules; proteins

Nodes of Ranvier are:

gaps in the myelin of axons.

Radial glia:

guide the migration of neurons during embryonic development.

What is the result if a stimulus shifts the potential inside a neuron from the resting potential to a more negative potential?

hyperpolarization

Of the following, the most important consideration in developing a drug that will act in the brain is:

if the drug will cross the blood-brain barrier.

Which of the following actions would depolarize a neuron?

increasing membrane permeability to sodium

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.

into, into

What would a neuron in the pons be called that receives information only from other cells in the pons and sends information only to other cells in the pons?

intrinsic

Molecules that can cross the blood-brain barrier are usually:

molecules which can dissolve in the fats of the capillary walls.

What disease is related to the destruction of central nervous system myelin sheaths?

multiple sclerosis

The resting potential is mainly the result of?

negatively charged proteins inside the cell

The two kinds of cells in the nervous system are?

neurons and glia

Santiago Ramon y Cajal demonstrated that:

neurons are separate from one another.

When the potential across a membrane reaches threshold, the sodium channels:

open to let sodium enter the cell rapidly.

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.

out of, into

Voltage-activated channels are channels for which a change in the voltage across the membrane alters their:

permeability.

When the neuronal membrane is at rest, the sodium channels:

prohibit any movement of potassium ions.

At the peak of the action potential, the electrical gradient of potassium:

pushes potassium out of the cell.

The presence of an all-or-none law suggests that neurons can only convey different messages by changing their:

rate or pattern of action potentials.

Compared to passive transport, the major disadvantage of active transport is that it:

requires expenditure of energy.

What is the difference in voltage called that typically exists between the inside and the outside of a neuron?

resting potential

Allowing only certain people to cross the street, and only at certain times, is comparable to a neuron's _____ with respect to ions crossing the membrane.

selective permeability

Which of the following is most likely to cross the cell membrane by simple diffusion?

small, uncharged molecules

Which of the following molecules would be able to passively cross the blood-brain barrier?

small, uncharged molecules

What is the approximate resting potential of the inside of a neuron's membrane, relative to the outside?

-70 millivolts

T / F Additional stimulation beyond the threshold of excitation will result in a greater depolarization of the membrane during an action potential.

False

What are microglia?

Glial cells whose function resemble the immune system cells

____ is the main source of nutrition for vertebrate neurons.

Glucose

What type of glial cells myelinate axons in the brain and spinal cord?

Oligodendrocytes

Which type of glia builds myelin sheaths around axons in the periphery of the body?

Schwann cells.

What happens to the ion gates when the membrane of a neuron starts to be depolarized?

Sodium gates open.

Stimulus A depolarizes a neuron just barely above the threshold. Stimulus B depolarizes a neuron to 10 mV beyond threshold. What can we expect to happen?

Stimulus A and stimulus B will produce the same response in the neurons.

After the peak of an action potential, what prevents sodium ions from continuing to enter the cell?

The sodium gates in the membrane close.

Which of the following is a characteristic of glial cells in the human brain?

They are more numerous than neurons.

Which of the following is NOT true of astrocytes?

They make up the myelin sheaths in the periphery of the body.

T / F An afferent axon brings information into a structure.

True

T / F Astrocytes remove waste material created when neurons die and control the amount of blood flow to each brain area.

True

The all-or-none law states that:

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

Chemicals than cannot flow freely across a cell membrane enter a neuron through:

specialized protein Channels

Ribosomes are the part of a cell that:

synthesizes new proteins.

A neuron's sodium gates are firmly closed and the membrane cannot produce an action potential during:

the absolute refractory period.

Concentration gradients lead to what kind of movements?

the movement of ions to areas of their lowest concentrations

What is the point from which an axon releases chemicals into the synapse?

the presynaptic terminal

During the relative refractory period:

the sodium gates are reverting to their usual state.

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

the threshold of excitation

To what does saltatory conduction refer?

the transmission of an impulse along a myelinated axon

The sodium-potassium pump, repeatedly transports ____ sodium ions out of the cell while drawing ____ potassium ions into it.

three; two

The presence of myelin and the diameter of the axon:

affect the speed of an action potential

What does myelin cover?

all vertebrate axons and some invertebrate axons

When a membrane is at rest, what attracts potassium ions to the inside of the cell?

an electrical gradient

Dendrites ____.

are branching fibers that get narrower near their ends

Which type of glia release chemicals that modify the activity of neighboring neurons?

astrocytes.

In a myelinated axon, where are sodium gates abundant?

at the nodes of Ranvier

The information sender of the neuron, conveying an impulse toward either other neurons or a gland or muscle is called the:

axon.

Neurons typically have one ____, but many ____.

axon; dendrites

Local anesthetic drugs, such as Novocain, work by:

blocking the sodium gates.

When a membrane is at rest, what attracts sodium ions to the inside of the cell?

both an electrical gradient and a concentration gradient