1-04 The Cells Of The Nervous System

Front 1

Objective

Identify the parts of an animal cell and the role played by each.

Back 1

The cell membrane separates the inside of the cell from its surroundings; the nucleus contains the chromosomes; and the mitochondria are responsible for metabolic activity.

Front 2

Objective

Identify the parts of a neuron and the role played by each.

Back 2

The dendrites receive electrical signals from other neurons; the cell body contains the nucleus, ribosomes (where new proteins are synthesized), mitochondria, and other life-supporting structures; and the axon—a neuron only has one—sends electrical signals to other neurons.

Front 3

Objective

Discuss the different kinds of glial cells and the function of each.

Back 3

The astrocytes assist axon in the release of chemical messengers called neurotransmitters; they also help remove the waste materials that are generated when a neuron dies; and they help control the amount of blood flow to a brain area. Microgila act as part of the brain’s immune system, helping to remove waste materials from the brain, as well as viruses, fungi and other microbes. Oligodendrocytes help build the myelin sheath that insulates the axons of neurons in the brain and spinal cord, whereas Schwann cells help build the myelin sheath that insulates axons in the peripheral nervous system. Radial glia help guide the migration of neurons in the nervous system, as well as the growth of axons and dendrites during embryonic development.

Front 4

Objective

Identify the cells of the brain that can and cannot divide.

Back 4

Generally, neurons cannot divide, although there has been some evidence in recent years that new neurons may be generated in certain situations. New glial cells are constantly being generated to replace the old ones that die off.

Front 5

Objective

Explain why the blood-brain barrier exists and how it works.

Back 5

The blood-brain barrier exists in order to allow nutrients into the brain and to keep toxins out. This is how it works: The walls of the capillaries that enter the brain are made up of endothelial cells that are joined together very tightly. The gaps between these cells are so small that they allow virtually nothing to get through them.

There are two ways that molecules can pass through this blood-brain barrier. The first way is through passive transport. Only small uncharged molecules such as oxygen or carbon dioxide can pass freely, or fat-soluble molecules such as vitamin A or D that can dissolve in the fats that make up the membrane of the capillary wall. Even water molecules have to pass through special channels.

A second way that molecules can get through the blood-brain barrier is through a mechanism called active transport, in which specific proteins in the membrane grab them up and pump them from the blood into the brain. Molecules that enter the brain in this manner include glucose, amino acids, most vitamins, and hormones.

Front 6

Objective

Explain why the brain depends so heavily on glucose as a fuel.

Back 6

Besides being a good energy source, glucose is just the right size to be able to get through the blood-brain barrier.

Front 7

neuron

Back 7

Cells that send and receive information in the form of electrochemical signals

Front 8

membrane

Back 8

The outer part of a cell that separates the inside of the cell from its surroundings

Front 9

nucleus

Back 9

The part of the cell that contains the chromosomes

Front 10

mitochondrion

Back 10

A structure that creates energy for the cell

Front 11

ribosome

Back 11

The part of the cell where new proteins are synthesized

Front 12

endoplasmic reticulum

Back 12

A network of thin tubes in the cell that are lined with ribosomes and that transport new proteins to the parts of the cell where they are needed

Front 13

motor neuron

Back 13

A neuron that sends a signal to a muscle or gland cells; motor neurons control the movement of muscles in the body

Front 14

sensory neuron

Back 14

A neuron that is sensitive to a specific type of stimulation, such as light in the eye or mechanical vibrations in the ear

Front 15

dendrites

Back 15

The part of the neuron that receives electrochemical signals from other neurons

Front 16

dendritic spines

Back 16

Short outgrowths along the dendrite that help increase its surface area so that it can receive more signals

Front 17

cell body (or soma)

Back 17

The part of the cell that contains the nucleus

Front 18

axon

Back 18

The part of the neuron that sends electrochemical signals to other neurons

Front 19

myelin sheath

Back 19

A fatty deposit that coats the axon and that provides electrical insulation

Front 20

presynaptic terminal

Back 20

The tip of the axon from which chemical messengers called neurotransmitters are released

Front 21

afferent axon

Back 21

The axon of a neuron that delivers an electrical signal into a structure

Front 22

efferent axon

Back 22

The axon of a neuron that takes information away from a structure

Front 23

interneuron

Back 23

A neuron whose axons and dendrites are all confined within a specific structure

Front 24

blood-brain barrier

Back 24

The structures that keep many chemicals out of the brain

Front 25

active transport

Back 25

A protein-mediated process that requires energy in order to pump molecules from the blood into the brain

Front 26

glucose

Back 26

A simple sugar that serves as the primary energy source for neurons

Front 27

thiamine

Back 27

Also known as vitamin B1, this chemical substance is necessary for glucose metabolism