Bio 1 - Bio 1

Question 1

Neurons receive information and transmit it to what

Answer 1

other cells.

Question 2

Glia serve many

Answer 2

functions that are difficult to summarize,

Question 3

Cajal’s research demonstrated

Answer 3

that nerve cells remain separate instead of merging into one another.

Question 4

The surface of a cell is its

Answer 4

membrane (or plasma membrane),

Question 5

Except for mammalian red blood cells, all animal cells have a

Answer 5

nucleus, the structure that contains the chromosomes.

Question 6

mitochondrion (plural: mitochondria) is the structure that performs

Answer 6

metabolic activities, providing the energy that the cell uses for all activities

Question 7

Ribosomes are the sites at which

Answer 7

the cell synthesizes new protein molecules

Question 8

endoplasmic reticulum,

Answer 8

a network of thin tubes that transport newly synthesized proteins to other locations.

Question 9

motor neuron, with its soma in the spinal cord, receives excitation through its

Answer 9

dendrites and conducts impulses along its axon to a muscle.

Question 10

A sensory neuron is specialized at one end to be highly sensitive to a

Answer 10

particular type of stimulation, such as light, sound, or touch.

Question 11

Dendrites are

Answer 11

branching fibers that get narrower near their ends.

Question 12

Many dendrites contain

Answer 12

dendritic spines, short outgrowths that increase the surface area available for synapses

Question 13

The cell body, or soma (Greek for “body”; plural: somata), contains

Answer 13

the nucleus, ribosomes, and mitochondria.

Question 14

The axon is a

Answer 14

thin fiber of constant diameter. (The term axon comes from a Greek word meaning “axis.”)

Question 15

The axon conveys

Answer 15

an impulse toward other neurons, an organ, or a muscle

Question 16

An axon has many branches, each of which

Answer 16

swells at its tip, forming a presynaptic terminal, also known as an end bulb or bouton (French for “button”). At that point the axon releases chemicals that cross through the junction between one neuron and the next.

Question 17

An afferent axon

Answer 17

brings information into a structure;

Question 18

an efferent axon carries

Answer 18

information away from a structure.

Question 19

If a cell’s dendrites and axon are entirely contained within a single structure, the cell is an

Answer 19

interneuron or intrinsic neuron

Question 20

Neurons vary enormously in

Answer 20

size, shape, and function

Question 21

Glia lia (or neuroglia), the other components of the nervous system, perform many

Answer 21

functions.

Question 22

Glia are smaller but more

Answer 22

numerous than neurons

Question 23

The star-shaped

Answer 23

astrocytes wrap

Question 24

astrocytes wrap around the

Answer 24

presynaptic terminals of a group of functionally related axons, as shown in Figure 1.10.

Question 25

tripartite synapse,

Answer 25

the tip of an axon releases chemicals that cause the neighboring astrocyte to release chemicals of its own, thus magnifying or modifying the message to the next neuron (Ben Achour & Pascual, 2012). However, the evidence for this idea is based on some uncertain assumptions, and it remains controversial

Question 26

Tiny cells called microglia act as part of the

Answer 26

immune system, removing waste material, viruses, and fungi from the brain.

Question 27

Oligodendrocytes (OL-i-go-DEN-druh-sites) in the brain and spinal cord and Schwann cells in the periphery of the body build the

Answer 27

myelin sheaths that surround and insulate certain vertebrate axons.

Question 28

Radial glia guide the migration of

Answer 28

neurons and their axons and dendrites during embryonic development.

Question 29

vertebrate brain does not replace

Answer 29

damaged neurons

Question 30

including oxygen and carbon dioxide, cross freely. Water crosses through special protein channels in the wall of the

Answer 30

endothelial cells (Amiry-Moghaddam & Ottersen, 2003).

Question 31

Also, molecules that dissolve in the fats of the membrane cross easily. Examples include

Answer 31

vitamins A and D and all the drugs that affect the brain

Question 32

Active transport, a

Answer 32

protein-mediated process that expends energy to pump chemicals from the blood into the brain.

Question 33

Chemicals that are actively transported into the brain include

Answer 33

glucose (the brain’s main fuel), amino acids (the building blocks of proteins), purines, choline, a few vitamins, iron, and certain hormones, thiamine.

Question 34

Prolonged thiamine deficiency, common in

Answer 34

chronic alcoholism, leads to death of neurons and a condition called Korsakoff’s syndrome,

Question 35

Instead of conducting an electrical impulse, the axon regenerates

Answer 35

an impulse at each point.

Question 36

touch on your shoulder reaches your brain

Answer 36

sooner than will a touch on your toes, although you will not ordinarily notice the difference

Question 37

vision, however, your brain does need to know whether

Answer 37

one stimulus began slightly before or after another one. If two adjacent spots on your retina

Question 38

electrical gradient, also known as

Answer 38

polarization—a difference in electrical charge between the inside and outside of the cell.

Question 39

The neuron inside the membrane has a slightly

Answer 39

negative electrical potential with respect to the outside, mainly because of negatively charged proteins inside the cell.

Question 40

This difference in voltage is called the

Answer 40

resting potential.

Question 41

membrane is selectively permeable. That is, some

Answer 41

chemicals pass through it more freely than others do.

Question 42

membrane is selectively permeable. That is, some chemicals pass through it more freely than others do.

Answer 42

Oxygen, carbon dioxide, urea, and water cross freely through channels that are always open. Several biologically important ions, including sodium, potassium, calcium, and chloride, cross through membrane channels (or gates) that are sometimes open and sometimes closed,

Question 43

When the membrane is at rest, the sodium and potassium channels are

Answer 43

closed, permitting almost no flow of sodium and only a small flow of potassium.

Question 44

Certain types of stimulation can open these channels, permitting freer flow of both ions. The sodium–potassium pump, a protein complex, repeatedly transports

Answer 44

three sodium ions out of the cell while drawing two potassium ions into it. The sodium–potassium pump is an active transport that requires energy. As a result of the sodium–potassium pump, sodium ions are more than 10 times more concentrated outside the membrane than inside, and potassium ions are similarly more concentrated inside than outside.

Question 45

The sodium–potassium pump is effective only because of the

Answer 45

selective permeability of the membrane,

Question 46

selective permeability of the membrane,which prevents the sodium ions that were pumped out of the neuron from

Answer 46

leaking right back in again.

Question 47

When sodium ions are pumped out, they stay out. However, some of the potassium ions in the neuron slowly

Answer 47

leak out, carrying a positive charge with them. That leakage increases the electrical gradient across the membrane, as shown in

Question 48

concentration gradient,

Answer 48

the difference in distribution of ions across the membrane. Sodium is more concentrated outside than inside, so just by the laws of probability, sodium is more likely to enter the cell than to leave it.

Question 49

Sodium ions are more concentrated

Answer 49

outside the neuron, and

Question 50

potassium ions more concentrated

Answer 50

inside.

Question 51

Protein and chloride ions (not shown) bear negative charges inside the cell. At rest, almost no sodium ions cross the membrane except by the sodium–potassium pump. Potassium tends to flow into the cell because of an electrical gradient but tends to flow out because of the concentration gradient. However, potassium gates retard the flow of potassium when the membrane is

Answer 51

at rest.

Question 52

The sodium–potassium pump continues pulling potassium into the cell, so it always remains

Answer 52

a little extra concentrated inside.

Question 53

If we now use another electrode to apply a negative charge, we can further increase the negative charge inside the neuron. The change is called

Answer 53

hyperpolarization, which means increased polarization.

Question 54

Now let’s apply a current to depolarize the neuron—that is,

Answer 54

reduce its polarization toward zero

Question 55

Stimulation beyond the threshold of excitation produces a massive

Answer 55

depolarization of the membrane.

Question 56

When the potential reaches the threshold, the membrane opens its

Answer 56

sodium channels and permits sodium ions to flow into the cell. The potential shoots up far beyond the strength of the stimulus

Question 57

The chemical events behind the action potential may seem complex, but they make sense if you remember three principles:

Answer 57

1.At the start, sodium ions are mostly outside the neuron, and potassium ions are mostly inside. 2.When the membrane is depolarized, sodium and potassium channels in the membrane open. 3.At the peak of the action potential, the sodium channels close.

Question 58

A protein that allows sodium to cross is called a

Answer 58

sodium channel, one that allows potassium to cross is a potassium channel, and so forth.

Question 59

The ones regulating sodium and potassium are

Answer 59

voltage-gated channels.

Question 60

Local anesthetic drugs, such as Novocain and Xylocaine, attach to the

Answer 60

sodium channels of the membrane, preventing sodium ions from entering, and thereby stopping action potentials (

Question 61

all-or-none law is

Answer 61

that the amplitude and velocity of an action potential are independent of the intensity of the stimulus that initiated it, provided that the stimulus reaches the threshold

Question 62

Thicker axons convey action potentials at

Answer 62

greater velocities.

Question 63

Thicker axons can also convey more

Answer 63

action potentials per second. The ability to do so is important for certain kinds of sensory information

Question 64

The nervous system uses both kinds of coding. For example, a taste axon shows

Answer 64

one rhythm of responses for sweet tastes and a different rhythm for bitter tastes

Question 65

Immediately after an action potential, the cell is in a

Answer 65

refractory period during which it resists the production of further action potentials.

Question 66

In the first part of this period after the action potentional,

Answer 66

the absolute refractory period, the membrane cannot produce an action potential, regardless of the stimulation.

Question 67

During the second part after the action potential,

Answer 67

the relative refractory period, a stronger-than-usual stimulus is necessary to initiate an action potential.

Question 68

The refractory period depends on two facts:

Answer 68

The sodium channels are closed, and potassium is flowing out of the cell at a faster-than-usual rate.

Question 69

propagation of the action potential describes the

Answer 69

transmission of an action potential down an axon.

Question 70

myelin,

Answer 70

an insulating material composed of fats and proteins.

Question 71

The jumping of action potentials from node to node is referred to as

Answer 71

saltatory conduction,

Question 72

We therefore call them local neurons.

Answer 72

Because they do not have an axon, they do not follow the all-or-none law. When a local neuron receives information from other neurons, it has a graded potential, a membrane potential that varies in magnitude in proportion to the intensity of the stimulus.

Question 73

The four ways to examine brain function

Answer 73

1.Examine the effects of brain damage. After damage or temporary inactivation, what aspects of behavior are impaired? 2.Examine the effects of stimulating a brain area. Ideally, if damaging some area impairs a behavior, stimulating that area should enhance the behavior. 3.Record brain activity during behavior. We might record changes in brain activity during fighting, sleeping, finding food, solving a problem, or any other behavior. 4.Correlate brain anatomy with behavior. Do people with some unusual behavior also have unusual brains? If so, in what way?