CHAPTER3 Flashcards
Tetrodotoxin
an extremely powerful poison that puffer (fugu) fish contain with no known antidote
what make tetrodotoxin lethal?
like similar poisons, it prevents the transmission of action potentials
action potentials
the electrical signals by which neurons communicate quickly over long distances
what do motor neurons do?
command the muscles to contract or relax
what do your eyes and ears do?
carry signals about external events by responding to physical stimuli such as light patterns and sound waves
the brain has the consistency of ________
slightly hardened mashed potatoes
Santiago Ramon y cajal
used new techniques to stain and visualize brain tissue
- he realize that the brain is built of billions of discrete cells
what is the most important type of cell in your nervous system?
neuron
how many neurons does the human brain contain?
100 billion neurons
components of a neuron
they have a membrane, nucleus, and specials organelles
- they produce traffic and secrete chemicals
what does the membrane of a neuron do?
seperates the cell’s components from environment outside the cell
neurons have ____ that are inserted into the membranes, and these ____ allow the cells to interact with it’s outside environment
proteins
what property do neurons posses that distinguishes them?
- because of the particular proteins on their surfaces,
they can transmit electrical signals quickly over long distances
neurons 4 zones of importance
- dendrites
- soma or cell body
- axon / nerve fiber
dendrites
long, branching extensions from the cell body
soma
greek for body
a typical soma spans about _____ micrometers
10-25
the key feature of the soma is the cell’s _______, which is the control centre of the cell’s that regulates cell activity, including gene expression
nucleus
dendrites are specialized for ________________
collecting information from thousands of tiny chemical signals that they receive all along their extent
the soma plays a key role in ______ the signals coming in from the dendrites
integrating
axon
an extension that reaches long distances beyond the soma that is essentially capable to conduct signals rapidly across long distances
which three ways does the axon differ from dendrites?
1) there is only one axon coming from a neuron, whereas there can be many dendritic extensions
2) axons tend to remain constant in diameter all along their length
3) axons tend to be much longer than dendrites, dendritic trees rarely extend more than 3 millimeters, whereas azons carrying signals from your spinal chord to your big toe (sciatic nerve) run the entire length of your leg
in giraffes, ______ are several meterslong and run the entire span of the neck!
axons
a typical axon will branch robustly at its ends, typically splitting into about _______ axon terminals
10,000
which 4 zones of importance do axon terminals consist of?
1)
where are axon terminals typically found?
in close proximity to the dendrites and somas of other cells, and such junctions are called synapses
what does the synapse do?
links axons to other neruons (in the central nervous system) or to a neuron, muscle or gland (in the peripheral nervous system)
en passant synapses
synapses that exist along the axon itself
the typical synapse connects an _______ to a _____ or ____
axon
dendrite or soma
there are also synapses that can join axon to ____ or dendrite to _____, although these are more rare.
axon to axon
dendrite to dendrite
in the three year old brain, the amount of synapses is estimated to be a ____
quadrillion
an adult brain contains somewhere between ____ and ____ trillion synapses, in a total volume of about 1,200 cubic centimeters
100 and 500
there are _____ of these tiny connections (synapses) in a cubic milimeter of cerebral cortex for a typical college student
several billion
collecting: _____
integrating: _____
conducting: _____
outputting information: ______
dendrites
soma
axon
axon terminals
what can you use to classify neurons?
function shape
sensory neurons
neurons that directly respond to signals from outside environment
motor neurons
direct output to muscles or glands; final step for signals to exit the nervous system and effect change in the body or environment
afferent neurons: _______
incoming sensory neurons
efferent neurons: _______
outgoing motor neurons
in mammals, the vast majority of neurons can not be classified as either afferent or efferent - instead they are _____ between the sensation of a ____ at one end and the _____ at another end
interneurons
signal
action
primitive animals, such as _____, have neurons that contain both sensory and motor qualities in the same cell
- this combination is NOT found in more advanced species
jellyfish
multipolar neurons (most common)
neurons with multiple dendrites
bipolar neurons
composed of a single dendrite on one end and a single axon on the other end
_____ neurons are often found in sensory neruons such as the retina and inner ear
bipolar
monopolar neurons
neurons with only a single extension that leaves the soma and branches into two directions
one end of monopolar neurons ________ while the other end _______
recieves the information
serves for output
_______ neurons are typically found in sensory neruons that signal touch and pain
monopolar
all neurons are _____, which means they do not divide like many other cells in the body
postmitotic
greek word for glue
gila
gila
cells that play several roles including providing ways to speed up the signalling from neurons, regulating concentrations of extracellular chemicals, and determining the extent to which networks of neurons can modify their connections
ogliodendrocytes
1/4 of the forms of gila: large cells whose main fucntion is to wrap a layer of “insulation” around axons - known as myelination (similar to the way that a copper wire is wrapped in rubber)
a single ogliodendrocyte wraps the axon of up to ___ different neurons and are found only in the _______; the function of myelination is accomplished in the _________, by a second type of glial cell, the ________ cells
50
central nervous system
peripheral nervous system
schwann cells
schwann cells
similar in function to ogliodendrocytes, but they wrap myelin only around a single axon
nodes of ranvier
the gaps between myelinated segments
short segments like stringed sausages
myelination:
no myelination:
axons in cortex
subcortical and peripheral axons
astro
cyte
greek for star
greek for cell
astrocyte
3/4 of the glial cells, perform critical functions in maintaining the chemicals outside the neruons, the repair of injury in the central nervous system, the contribution of nutrients, the regulation of local blood flow to a region & the release of chemical signals
microglia
4/4 type of glial cell, makes up 20% of glial cell population, these small cells are the front line of immune defense in the central nervous system: they are constantly on the move, searching for any infectious agents that might damage neural tissue. When they detect a foreign body they consume it and destroy it to prevent disease and inflamination
