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