Cells of the Nervous System

Question 1

Neurons

Answer 1

receive information and transmit it to other cells.

Question 2

Glia

Answer 2

serve many functions in the nervous system

outnumber neurons in the cerebral cortex, but neurons outnumber glia in several other brain areas such as cerebellum

Question 3

Santiago Ramón y Cajal

Answer 3

detailed drawings of the nervous system are still considered definitive today

used Golgi’s methods but applied them to infant brains, in which the cells are smaller and therefore easier to examine on a single slide

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

Question 4

Camillo Golgi

Answer 4

stain nerve cells with silver salts

Question 5

membrane

Answer 5

surface of a cell structure that separates the inside of the cell from the outside environment

Most chem- icals cannot cross the membrane, but protein channels in the membrane permit a controlled flow of water, oxygen, sodium, potassium, calcium, chloride, and other important chemicals

Question 6

nucleus

Answer 6

the structure that contains the chromosomes

Question 7

mitochondrion

Answer 7

the structure that performs metabolic activities, providing the energy that the cell uses for all activities.

Question 8

Ribosomes

Answer 8

the sites within a cell that synthesize new protein molecules. Proteins provide building materials for the cell and facilitate chemical reactions.

Some ribosomes float freely within the cell, but others are attached to the endoplasmic reticulum,

Question 9

endoplasmic reticulum

Answer 9

a network of thin tubes that trans- port newly synthesized proteins to other locations

Question 10

motor neuron

Answer 10

soma in the spinal cord, receives excitation through its dendrites and conducts impulses along its axon to a muscle

Question 11

sensory neuron

Answer 11

spe- cialized at one end to be highly sensitive to a particular type of stimulation, such as light, sound, or touch

Tiny branches lead directly from the receptors into the axon, and the cell’s soma is located on a little stalk off the main trunk

Question 12

Dendrites

Answer 12

branching fibers that get narrower near their ends

surface is lined with specialized synaptic receptors, at which the dendrite receives information from other neurons

greater the surface area of a dendrite, the more information it can receive

Question 13

dendritic spines

Answer 13

short outgrowths that increase the surface area available for synapses

Question 14

cell body, or soma

Answer 14

contains the nucleus, ribosomes, and mitochondria

Question 15

axon

Answer 15

thin fiber of constant diameter.

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

can have many branches, but there is only one axon

Question 16

myelin sheath

Answer 16

insulating material of an axon

Question 17

nodes of Ranvier

Answer 17

interruptions in the myelin sheath on an axon

Question 18

presynaptic terminal

Answer 18

also known as an end bulb or bouton (French for “button”).

At that point the axon releases chemicals that cross through the junction between that neuron and another cell.

Question 19

afferent axon

Answer 19

brings information into a structure

Question 20

efferent axon

Answer 20

carries information away from a structure

Question 21

interneuron or intrinsic neuron

Answer 21

a cell’s dendrites and axon are entirely contained within a single structure

eg, in thalamus

Question 22

Types of Glial Cells

Answer 22

astrocytes
microglia
Oligodendrocytes
Radial glia

Question 23

astrocytes

Answer 23

star shaped, wrap around the synapses of functionally related axons,

shields it from chemicals circulating in the surround

by taking up the ions and transmitters released by axons and then releasing them back, an astrocyte helps synchronize closely related neurons, enabling their axons to send messages in waves

dilate the blood vessels to bring more nutrients into brain areas that have heightened activity

Question 24

microglia

Answer 24

act as part of the immune system, removing viruses and fungi from the brain

Question 25

Oligodendrocytes

Answer 25

build the myelin sheaths that surround and insulate certain vertebrate axons in the brain and spinal cord

Question 26

Schwann cells

Answer 26

build the myelin sheaths that surround and insulate certain vertebrate axons in the periphery of the body

Question 27

Radial glia

Answer 27

guide the migration of neurons and their axons and dendrites during embryonic development.

most radial glia differentiate into neurons, and a smaller number differentiate into astrocytes and oligodendrocytes after embryonic development

Question 28

blood–brain barrie

Answer 28

mechanism that excludes most chemicals from the vertebrate brain

small, uncharged molecules such as oxygen and carbon dioxide cross through cell walls freely

molecules that dissolve in the fats of the membrane cross easily

include vitamins A and D and all the drugs that affect the brain—from antidepressants and other psychiatric drugs to illegal drugs such as heroin

Water crosses through special protein channels in the wall of the endothelial cells

Question 29

active transport

Answer 29

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

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

Question 30

endothelial cells

Answer 30

form the walls of the capillaries

in blood-brain barrier, they are joined much tighter than in normal capillaries, disallowing objects to pass