Chapter 48/49

Question 1

Neurons

Answer 1

Nerve cells that transfer information within the body

Question 2

Neurons have two types of signals to communicate:

Answer 2

• Electrical signals (long-distance)

- Chemical signals (short-distance) AKA neurotransmitters

Question 3

Most of a neuron’s organelles are in the _.

Answer 3

Cell body

Question 4

Most neurons have _, highly branched extensions that receive signals from other neurons.

Answer 4

Dendrites

Question 5

Axon

Answer 5

Typically a much longer extension that transmits signals to other cells

Question 6

Synapse

Answer 6

A junction between the axon and another cell

Question 7

Information is transmitted from a _ cell (a neuron) to a _ cell (a neuron, muscle, or gland cell).

Answer 7

Presynaptic; postsynaptic

Question 8

Most neurons are nourished or insulated by cells called _ or _ cells.

Answer 8

Glia; glial

Question 9

_ have numerous functions to nourish, support, and regulate neurons.

Answer 9

Glia (or glial cells)

Question 10

Astrocytes

Answer 10

Form tight junctions in capillaries of the CNS, resulting in a blood-brain barrier which restricts the entry of most substances into the brain

Question 11

Nervous systems process information in three steps:

Answer 11

1) Sensory input
2) Integration
3) Motor output

Question 12

Sensors detect external stimuli and internal conditions and transmit information along _ neurons (step 1).

Answer 12

Sensory

Question 13

Sensory information is sent to the brain or ganglia (in lower eukaryotes), where _ integrate the information (step 2).

Answer 13

Interneurons

Question 14

Motor output leaves the brain or ganglia via _ neurons, which trigger muscle or gland activity (step 3).

Answer 14

Motor

Question 15

Many animals have a complex nervous system that consists of:

Answer 15

• A central nervous system (CNS)

- A peripheral nervous system (PNS)

Question 16

Central nervous system (CNS)

Answer 16

Where integration takes place; this includes the brain and a nerve cord (spinal cord)

Question 17

Peripheral nervous system (PNS)

Answer 17

Carries information into and out of the CNS

Question 18

The neurons of the PNS, when bundles together, form _.

Answer 18

Nerves

Question 19

Ion pumps and ion channels establish the _ of a neuron.

Answer 19

Resting potential

Question 20

Every cell has a voltage (difference in electrical charge) across its plasma membrane called a _.

Answer 20

Membrane potential

Question 21

The _ is the membrane potential of a neuron not sending signals.

Answer 21

Resting potential

Question 22

Changes in membrane potential act as _, transmitting and processing information.

Answer 22

Signals

Question 23

In a mammalian neuron at resting potential, the concentration of K+ is highest _ the cell, while the concentration of Na+ is highest _ the cell.

Answer 23

Inside; outside

Question 24

_ pumps use the energy of ATP to maintain these K+ and Na+ gradients across the plasma membrane.

Answer 24

Sodium-potassium

Question 25

These concentration gradients represent chemical _ that gets converted to electrical potential when ion channels open.

Answer 25

Potential energy

Question 26

When gated K+ channels open, K+ diffuses out, making the inside of the cell more negative. This is _, an increase in magnitude of the membrane potential.

Answer 26

Hyperpolarization

Question 27

Opening other types of ion channels triggers a _, a reduction in the magnitude of the membrane potential.

Answer 27

Depolarization

Question 28

If a depolarization shifts the membrane potential sufficiently, it results in a massive change in membrane voltage called an _.

Answer 28

Action potential

Question 29

Action potential

Answer 29

Signal conducted by axons

Question 30

Action potentials have a _ magnitude, are all-or-none, and transmit signals over long distances.

Answer 30

Constant

Question 31

In vertebrates, axons are insulated by a _, which causes an action potential's speed to increase.

Answer 31

Myelin sheath

Question 32

The speed of an action potential increases with the axon's _.

Answer 32

Diameter

Question 33

Myelin sheaths are made by glia (oligodendrocytes in the CNS, and _ cells in the PNS).

Answer 33

Schwann

Question 34

Action potentials are formed only at _, gaps in the myelin sheath where voltage-gated Na+ channels are found.

Answer 34

Nodes of Ranvier

Question 35

Action potentials in myelinated axons _ between the nodes of Ranvier.

Answer 35

Jump

Question 36

At electrical synapses, the current flows from one neuron to another through _.

Answer 36

Gap junctions

Question 37

At _ synapses, a chemical neurotransmitter carries information between neurons.

Answer 37

Chemical

Question 38

Most synapses are _ synapses.

Answer 38

Chemical

Question 39

The synaptic terminal of one axon passes information across the synapse in the form of chemical messengers called _.

Answer 39

Neurotransmitters

Question 40

Acetylcholine (ACH)

Answer 40

A common neurotransmitter in animals

Question 41

Acetylcholine is involved in:

Answer 41

* Muscle stimulation - Memory formation - Learning

Question 42

A number of _ disrupt acetylcholine neurotransmission (this leads to neurodegenerative diseases).

Answer 42

Toxins

Question 43

Acetylcholine is just one of more than _ known neurotransmitters.

Answer 43

100

Question 44

Neurotransmitters (other than acetylcholine) fall into four classes:

Answer 44

- Amino acids - Biogenic amines - Neuropeptides - Gases

Question 45

The human brain contains about 100 billion neurons, organized into _ more complex than the most powerful supercomputers.

Answer 45

Circuits

Question 46

What do powerful imaging techniques allow researchers to do?

Answer 46

Monitor multiple areas of the brain while the subject performs various tasks

Question 47

Nervous systems consist of circuits of _ and supporting cells.

Answer 47

Neurons

Question 48

The simplest animals with nervous systems, the cnidarians, have neurons arranged in _.

Answer 48

Nerve nets

Question 49

Nerve net

Answer 49

A series of interconnected nerve cells

Question 50

More complex animals have _, in which the axons of multiple neurons are bundled together.

Answer 50

Nerves

Question 51

Nerves

Answer 51

Channel and organize information flow through the nervous system

Question 52

Bilaterally symmetrical animals exhibit _, the clustering of sensory organs at the front end of the body (head).

Answer 52

Cephalization

Question 53

The simplest cephalized animals, flatworms, have:

Answer 53

- A central nervous system (CNS), with a brain and longitudinal nerve cords, and - A peripheral nervous system (PNS), with neurons carrying information into and out of the CNS