63 terms

Neurons and Glia

Neurons and Glia
STUDY
PLAY

Terms in this set (...)

nervous system is made up of two types of cells
neurons and glia
neuron
A cell of the nervous system
that is specialized for information
processing and communication.
glia
Cells in the nervous system that support the activities of neurons.
organelle
A small structure within a cell that carries out a specific function.
cell body / soma
The
main mass of a neuron, containing
the nucleus and many organelles.
axon
The branch of a neuron
usually responsible for carrying
signals to other neurons.
dendrites
The branch of a
neuron that generally receives
information from other neurons.
Neuron Membranes
The primary task of any cell membrane is to form a boundary
between the cell and its external environment. The neural membrane must separate the intracellular fluid of the cell's interior from the extracellular fluid surrounding the neuron.
intracellular fluid
The fluid inside a cell.
extracellular fluid
The fluid surrounding a cell.
permeability
A property of
a substance that determines
the extent to which other
substances may pass through it.
neural cytoskeleton
The neural cytoskeleton provides structural support that maintains the shape of the neuron
The Neural Membrane
Membrane is a bi-layer composed largely of phospholipids and other lipids studded with proteins and other large molecules
Ion Channels
Allow ions to diffuse down concentration gradient
Selective permeability to certain ions
Don't require additional energy
Ion Pumps
Actively move ions against concentration gradient
Create ion concentration gradients
Require Energy
voltage-dependent channels
Ion channels have the ability to open and close in response to stimuli in their immediate vicinity. Some ion channels, known as voltage-dependent channels, open and close in response to the electrical status of adjacent areas of membrane. These channels form an important part of our discussion of electrical signaling within the neuron
Ligand-gated channels
open when they come in contact with specific
chemicals. These chemicals are typically our naturally occurring chemical messengers but can be drugs from artificial sources as well
synapse
The junction between two neurons at which
information is transferred from one to another.
sodium-potassium pump
An
ion pump that uses energy to
transfer three sodium ions to
the extracellular fluid for every
two potassium ions retrieved
from the extracellular fluid.
calcium pump
A protein
structure embedded in the neural
membrane that uses energy to
move calcium ions out of the cell.
neurotransmitter
A chemical
messenger that transfers
information across a synapse.
cytoskeleton
A network of filaments
that provides the internal
structure of a neuron.
cytoskeleton made up of
microtubule
neurofilament
microfilament
microtubule
The largest fiber in the cell cytoskeleton, responsible for the transport of neurotransmitters and other products to and from the cell body.
neurofilament
A neural fiber
found in the cell cytoskeleton that is
responsible for structural support.
microfilament
The smallest fiber found in the cell cytoskeleton
that may participate in the changing of the length and
shape of axons and dendrites.
anterograde transport
Movement
of materials from the cell body
of a neuron to the axon terminal
along the microtubules.
retrograde transport
Movement
of material from the axon terminal
back to the cell body via the
cell's system of microtubules.
Tau Phosphorylation Leads to Cell Death
In Alzheimer's disease, the tau levels become elevated
(Baas & Qiang, 2005). In response, an affected neuron adds molecules of phosphate
to the tau protein, which causes it to disconnect from the microtubules. As shown in
■ Figure 3.4, the disconnected tau begins to form tangles, hindering the cell's ability
to signal and maintain its structure. The neuron folds in on itself and collapses
Structural Features of Neurons
Cell body (soma) contains nucleus and other organelles


DENDRITES
AXONS
Dendrites
branches that serve as locations at which information from other neurons is received
spines
Axons
are responsible for carrying neural messages to other neurons
Vary in diameter and length
Many covered by myelin
nucleus
The substructure
within a cell body that
contains the cell's DNA.
nucleolus
A
substructure within a cell nucleus
where ribosomes are produced.
ribosome
An organelle in the cell body
involved with protein synthesis.
endoplasmic reticulum
An organelle in the cell body that
participates in protein synthesis.
Golgi apparatus
An
organelle in the cell body that
packages proteins in vesicles.
mitochondria
Organelles
that provide energy to the cell
by transforming pyruvic acid
and oxygen into molecules of
adenosine triphosphate (ATP).
synaptic gap
The tiny fluidfilled
space between neurons
forming a synapse.
dendritic spine
A knob on the dendrite that provides additional
membrane area for the formation of synapses with other neurons.
myelin sheath
The fatty insulating material covering some
axons that boosts the speed and
efficiency of electrical signaling.
axon hillock
The cone-shaped segment of axon located at the
junction of the axon and cell body that is specialized for the
generation of action potentials.
local circuit neuron
neuron
that communicates with neurons
in its immediate vicinity.
projection neuron
A neuron
with a very long axon that
communicates with neurons in
distant areas of the nervous system.
collaterals.
The ends of many axons are divided into branches, known as collaterals. As a result, a neuron with only one axon may still communicate with a large number of other cells.
axon terminal
The swelling
at the tip of an axon collateral
specialized for the release of
neurotransmitter substances.
Synaptic vesicles
The axon terminal contains large numbers of both mitochondria and synaptic vesicles that contain chemical messengers. Synaptic vesicles are made from the same
double-lipid molecule structure as the cell membrane and are approximately 50 nm in diameter.
node of Ranvier
The uncovered section of
axon membrane between two
adjacent segments of myelin.
use of myelin
There are a number of important advantages to myelin. First of all, as mentioned earlier, myelin allows human axons to be smaller in diameter without sacrificing transmission speed. Space is a precious commodity in the nervous system. The smaller the diameter of our axons, the more neural tissue we can pack into our skulls, and the more information we can process. In addition, myelin reduces
the energy requirements of neurons by decreasing the amount of work done by sodium-potassium pumps. Myelin segments wrap so tightly around axons that there is little to no extracellular fluid between the myelin and the axon membrane.
mroe uses of myelin
As a result, there is no need for ion channels under a myelin sheath. The only places on a myelinated axon that have large numbers of ion channels are the axon hillock and the nodes of Ranvier. In contrast, an unmyelinated axon has ion channels along its entire length. During signaling, therefore, fewer ions move through the ion channels of a myelinated axon membrane than through an unmyelinated axon membrane of the same length. Because the sodium-potassium pumps work to restore ions to their pre-signaling locations, less of this work needs to be done in a
myelinated axon.
Structural Variations in Neurons
Unipolar
Bipolar
Multipolar
Unipolar
Single branch extending from the cell body
. Bipolar
Two branches extending from the neural cell body: one axon and one dendrite
Multipolar
Many branches extending from the cell body; usually one axon and many dendrites
multipolar neurons Where are they found?
msot common
Sensory neurons
are specialized to receive information from the outside
world. Our senses of vision, hearing, touch, taste, and smell all depend on specialized
receptor neurons. These neurons can translate many types of information, such as light
or sound waves, into neural signals that the nervous system can process.
Motor neurons
transmit commands from the central nervous system (the brain and spinal cord)
directly to muscles and glands.
interneurons
The vast majority of neurons are known as interneurons.
Interneurons are not specialized for either sensory or motor functions but act as
bridges between the sensory and motor systems.
macroglia
Large glial cells, including astrocytes, oligodendrocytes, and
Schwann cells
microglia
Tiny, mobile glial
cells that migrate to areas of
damage and digest debris.
astrocyte
A
large, star shaped glial cell of
the central nervous system,
responsible for structural support,
isolation of the synapse, control
of the extracellular chemical
environment at the synapse,
and possibly communication.
oligodendrocyte
A glial cell that
forms the myelin on central
nervous system axons.
Schwann cell
A glial cell
that forms the myelin on axons in
the peripheral nervous system.