Ch. 3 Nervous System Cells

golgi method

by Camillo Golgi, silver staining technique that allows us to see neurons in tissue

Golgi thought that the nervous system was

a network of interconnected fibers: a “nerve net”

neuron doctrine

neurons are the units of brain function

Santiago Ramon y Cajal

contradicted the nerve net with the neuron doctrine; believed that individual nerve cells transmit signals, and are not continuously linked with other cells

brainbow

individual cells can be visualized with bioluminescent proteins, which offers a way to trace where each neuron sends its processes and how it connects with other neurons

what are the 2 types of cells found in the nervous system?

neurons and glia

how many individual neurons does the human brain consist of?

approximately 86 billion individual neurons

membrane

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

nucleus

structure that contains the chromosomes and genes

mitochondrion

structure that performs metabolic activities and provides energy that the cells require

ribosomes

sites at which the cell synthesizes new protein molecules

endoplasmic reticulum

network of thin tubes that transport newly synthesized proteins to their location

nuclear and cell membrane

individual membranes that surround the cell and the nucleus

intracellular fluid

where the cell’s internal structures are suspended

tubule

tiny tube that transports molecules and helps give the cell its shape

axon

extension that transmits information from cell body to other cells

Golgi body

membranous structure that packages protein molecules for transport

lysosomes

sacs containing enzymes that break down wastes

microfilaments

threadlike fibers making up much of the cell’s “skeleton”

basic neuron types

bipolar (interneuron), unipolar (sensory neuron), multipolar (motoneuron), pyramidal cell

soma

cell body

dendrites

branching extensions, collect information from other cells

T/F? a neuron has only one axon, but most have many dendrites

true

dendritic spines

protrusion from a dendrite that greatly increases its surface area and is the usual point of contact with axons of other cells

axon hillock

juncture of soma and axon, where the action potential begins

terminal button

knob at the tip of an axon that conveys information to other neurons

what is another name for a terminal button?

an end foot

synapse

gap between 2 neurons; usually between an end foot of an axon of one neuron and a dendritic spine of another neuron

presynaptic terminal

the endpoint of an axon where the release of chemicals occurs to facilitate communication with other nearby neurons

postsynaptic neuron

receives a chemical transmission from a nearby neuron

information flow in a neuron

dendrite, cell body, axon, terminal

sensory neurons

carry information from the sensory receptors in or on the body to the spinal cord

interneurons (association neurons)

associate sensory and motor activity within the CNS

motor neurons

send signals from the brain and spinal cord to muscles

what are the 5 types of glial cells?

ependymal, astrocyte, microglial, oligodendroglial, and Schwann

ependymal cell

small ovoid; moves cerebrospinal fluid (CSF)

astrocyte

star shaped; contributes to neuronal nutrition, support, and repair; contributes to forming blood-brain barrier and to healing scarring after injury

microglial cell

small; derived from blood; defensive function to remove dead tissue

oligodendroglial cell

forms myelin around CNS axons in brain and spinal cord

Schwann cell

wraps around peripheral nerves to form myelin

astrocytes help move nutrients between

vessels and neurons

glial cells in myelin

glial coating that surrounds axons

glial cells in multiple sclerosis (MS)

nervous system disorder associated with loss of myelin

glial cells in paralysis

loss of sensation and movement due to nervous system injury

glial cells in CNS

repair does not take place; regrowth may be inhibited

glial cells in PNS

microglia and Schwann cells help repair neurons